408 Stroker

[Killer6]

Holy I guess. That’d be a handful for sure. The biggest goal I have is that I want the car to go into the high 12’s maybe and be a fun street beast at the same time. The 318 is just too slow.

With a stroker, You won't even need that much cam to do that easily. As stated, it ain't gonna cost any more to stroke a 360 than a 318, go with the bigger bore.
And when AJ say's "just a lil math", for Him ^^^^^the above post is just a little, LOL!! You've been warned!!

 

[autoxcuda]

A good cast crank stroker kit would work fine. Lots of them running out there in the 500hp range. I like a forged piston in the kit.

It doesn't take much to get an A into the 12's. Maybe 330hp. A nice 425-450HP stroker in a good chassis should run EASY high 11's. ET is ALL about the hook, not HP.

Yep.

I've got the Scat cast crank, icon forged -20cc dish piston, I-beam rod, balanced rotating kit. 9.7:1 compression with 64cc heads (measured) is about max with 91 pump gas.

I run a comp XE274-S cam. But a comp XE275HL hydraulic with stock rockers would be very similar and working with a budget. Don't need a big cam. Dont need rpm to make power... So then don't need big valve springs...so don't need trick rockers. Factory steel adjustable rockers would work too and be very durable. I run the valve springs that come with the Edelbrock heads.

Scat balence job has been fine and it's a smooth running motor. Peak HP is under 6,000 rpm.

Built it in 2011. Been to many track days and flog on it. Driven down in LA traffic on 90+ degree days. Driven 80 mile trips to track. Runs errands around town stoplight to stoplight. Cruise at 3400 rpm on freeway with my overalll gearing.

 

[AJ/FormS]

I vote 360 cuz it hits more targets more often and most of the time will be happy with cheap gas, and will last waaay longer, not having to run race-gears.

But if you like the rumpidy rump of a big cam, or the feeling of I-did-it-with-a-318, well,just,do it with a 318!
Post 25 is biased towards your goal of hitting high twelves.
In practice,You wouldn't have to run 4.56s ALL the time.They just hit a lot of targets, and help the engine put down more average horsepower during the run, and that is how low-ET is made.
Instead of 4.56s you could run more transmission gears;the important thing is to be running a finaldrive gear that puts your engine thru the traps at an optimum rpm and so that there are no more gears left. This is most important with a small engine running a big cam, cuz the powerband is real small; so you have to keep it on the pipe.
So if 4.56s is the optimum final drive gear, then you can do that with the 4.56s and direct in the trans, OR you could do it with 3.23s and a 1.40 trans gear. The result is still 3.23x 1.4=4.52 close enough. The problem is that the 1.40 gear comes in a 4 speed box and you're only gonna use 3 gears, so you may still trap near 106, but the ET won't be there, cuz the engine wasn't on the pipe long enough or early enough. The best solution for a small engine is more gears.
But there is none for our Mopars, and that is why the 360 (or bigger) is preferred for a dual-purpose machine.
But if there was a 5 speed, with say a 1.30 4th gear, then you could run 3.55s, a very nice street gear. And so 3.55 x 1.30 =4.62 again close enough. This theoretical 5 speed might have a low gear of say 3.57 giving you a starter gear of 3.57 x 3.55=12.7 a really nice race gear. If the other 2 gears were appropriately spaced, you would have a dynomite trans, and a 1:1 5th gear would then make 3.55s hiway doable. So the ideal 5speed for your 318 might look like 3.57-2.32-1.67-1.30-1.00 and the splits are .65-.72-.78-.77. Everybody with a 318 needs something like this. You could run a smaller cam and on a tighter LSA and with less compression, and still hit the targets.
OK here comes my secret, the way I did it;
The Mopar 3.09 overdrive box and a GVOD, used as a splitter.The ratios are
3.09-2.41-1.67-1.30-1.00-.78od-.54od........splitter gears in red.
the Splits are .78-.69-.78-.77-.78-.73 and of course you now have double overdrive and 7 useable gears. So you can run any rear gear you want. Now you can run those 4.56s with impunity. and you can use5 ratios to hit 106, and still have two ratios to cruise with; one for up to 60 mph and the other will hit 85 at 2600.
The splits are so tight that your 318 will be on the pipe from 20 mph and all the way thru the traps. That means it will be putting down an average horsepower almost equal to it's maximum output. That means it will trap at a higher mph than expected, and that means it will ET better than 12.9.
The converse is, to still trap at 106, you can build your teener with a little less power, and that means, more fun around town.
Is the Mopar/GVOD ideal? no. There are some idiosyncrasies to overcome, chief of which is the very wide splits when not gear-splitting.
OK , so that OD box is no friend of a big-cammed small-displacement engine.... until you put some race gears in the back, and put second gear where you need it. Running it as a 3 plus1, the ratios are
3.09-1.67-1.00-.73,and the splits are .54-.60-.73.
ouch! Notice the 1-2 split is 54%. That means that whatever you rev it to in first, the revs will fall to 54% of it. So consider how you might normally drive the car. Typicaly with my 367, I rev it up to about 2800 in first, then granny pull second, and I have 3.55s. If you do that with 3.55s and a hot 318, the Rs will fall to .54 x2800=1512 and your teener will about drop dead, cuz there's no torque to pull itself outta that hole. 2800 is about 20mph. And it gets worse. Your hot teener won't get back on the torque until 50 mph (3600 in second), so you will have 30 mph there where the engine is in the dead-zone. Now, that was with a hot-cammed 318. See what I mean about that tranny being no friend to a small-displacenent hot-cammed engine?
But you want to run 4.56s to ET well in the quarter.
So how's that gonna work? Well firstly is that race starter gear of 4.56 x 3.09= 14.09, which sounds like a crazy gear right? And it is You'll barely be moving and then it's time to shift. ( I ran this combo with 4.30s and behind my 367). Spo where's the torque start with that hot 318? Let's guess she's awake at 3200. So if that's correct you will have to rev first up to 3200/.54=5930 to stay on it, hang on, that's 34mph. That will be an easy pull for just going to the 7-11. We don't need to get that crazy.Plus at 34mph,the load is very light.
So let's say we shift at 20mph; that would be 3500rpm, so that's doable. Now going into second the Rs will be 54% of 3500, so1890. Now you see the problem.
The hot-teener won't have much power there, and it doesn't have a Torque Convertor to help you,so you are granny driving. But guess what, your second gear is now the same as second gear would be with the standard A833 box and 1.67x4.56/1.92=3.97 rear gear, so you are no worse off than that guy.........until you hit third gear, then your back in the basement Say you take that gear to 3500 again, now doing 37mph. After the shift you will be doing .60 x 3500 =2100 and you're back in the basement.
See what I mean?
I ended up running 4.88s and sacrificing first gear entirely. And I had a small cam in my 367; a [email protected], and Plenty of compression at 10.9Scr.
So once again, by itself this box is horrible for hot-cammed,small displacement engine.
page 1 end.
To be continued in another post,lol,

 

[RAMM]

A good cast crank stroker kit would work fine. Lots of them running out there in the 500hp range. I like a forged piston in the kit.

It doesn't take much to get an A into the 12's. Maybe 330hp. A nice 425-450HP stroker in a good chassis should run EASY high 11's. ET is ALL about the hook, not HP.

Listen to crackedback,AJ/FormS and Moper if he has chimed in. I like to over-engineer so commenting from experience I would go against the grain and build a solid 380-400 hp STOCK stroke 360. Stick some Speed-pro flat tops H116CP pistons on stock rods with ARP bolts or Scat I-beams-balance and use a Lunati Voodoo 10200703 cam with stock rockers. I have made close to 430 HP/440 tq (365) with this and J heads (1.94/1.6 231 cfm @ .450") There you go, save your money say no to 4" strokes. J.Rob

 

[crackedback]

Listen to crackedback,AJ/FormS and Moper if he has chimed in. I like to over-engineer so commenting from experience I would go against the grain and build a solid 380-400 hp STOCK stroke 360. Stick some Speed-pro flat tops H116CP pistons on stock rods with ARP bolts or Scat I-beams-balance and use a Lunati Voodoo 10200703 cam with stock rockers. I have made close to 430 HP/440 tq (365) with this and J heads (1.94/1.6 231 cfm @ .450") There you go, save your money say no to 4" strokes. J.Rob

LOL I was going to mention the 703 camshaft. Seen that dinky stick make 480hp in a 408 with mildly ported ede heads.

My friends 3300# demon with a 340ish hp 360 (xe268H, headers, LD340, 2500 converter) ran around 107+ in the 1/4 with a bad tune up. Leaving super soft from the line.

The 360 is more than capable and would save a few bucks over a stroker kit.

 

[darten1972]

I vote 360 cuz it hits more targets more often and most of the time will be happy with cheap gas, and will last waaay longer, not having to run race-gears.

But if you like the rumpidy rump of a big cam, or the feeling of I-did-it-with-a-318, well,just,do it with a 318!
Post 25 is biased towards your goal of hitting high twelves.
In practice,You wouldn't have to run 4.56s ALL the time.They just hit a lot of targets, and help the engine put down more average horsepower during the run, and that is how low-ET is made.
Instead of 4.56s you could run more transmission gears;the important thing is to be running a finaldrive gear that puts your engine thru the traps at an optimum rpm and so that there are no more gears left. This is most important with a small engine running a big cam, cuz the powerband is real small; so you have to keep it on the pipe.
So if 4.56s is the optimum final drive gear, then you can do that with the 4.56s and direct in the trans, OR you could do it with 3.23s and a 1.40 trans gear. The result is still 3.23x 1.4=4.52 close enough. The problem is that the 1.40 gear comes in a 4 speed box and you're only gonna use 3 gears, so you may still trap near 106, but the ET won't be there, cuz the engine wasn't on the pipe long enough or early enough. The best solution for a small engine is more gears.
But there is none for our Mopars, and that is why the 360 (or bigger) is preferred for a dual-purpose machine.
But if there was a 5 speed, with say a 1.30 4th gear, then you could run 3.55s, a very nice street gear. And so 3.55 x 1.30 =4.62 again close enough. This theoretical 5 speed might have a low gear of say 3.57 giving you a starter gear of 3.57 x 3.55=12.7 a really nice race gear. If the other 2 gears were appropriately spaced, you would have a dynomite trans, and a 1:1 5th gear would then make 3.55s hiway doable. So the ideal 5speed for your 318 might look like 3.57-2.32-1.67-1.30-1.00 and the splits are .65-.72-.78-.77. Everybody with a 318 needs something like this. You could run a smaller cam and on a tighter LSA and with less compression, and still hit the targets.
OK here comes my secret, the way I did it;
The Mopar 3.09 overdrive box and a GVOD, used as a splitter.
the ratios are 3.09-2.41-1.67-1.30-1.00-.78od-.54od........splitter gears in red.
the Splits are .78-.69-.78-.77-.78-.73 and of course you now have double overdrive and 7 useable gears. So you can run any rear gear you want. Now you can run those 4.56s with impunity. and you can use5 ratios to hit 106, and still have two ratios to cruise with; one for up to 60 mph and the other will hit 85 at 2600.
The splits are so tight that your 318 will be on the pipe from 20 mph and all the way thru the traps. That means it will be putting down an average horsepower almost equal to it's maximum output. That means it will trap at a higher mph than expected, and that means it will ET better than 12.9.
The converse is, to still trap at 106, you can build your teener with a little less power, and that means, more fun around town.
Is the Mopar/GVOD ideal? no. There are some idiosyncrasies to overcome, chief of which is the very wide splits when not gear-splitting.

To be continued, gotta go to work

Thanks for the incredible reply. Wow. Lots of Good info there. Thanks again.

 

[AJ/FormS]

Listen to crackedback,AJ/FormS and Moper if he has chimed in. I like to over-engineer so commenting from experience I would go against the grain and build a solid 380-400 hp STOCK stroke 360. Stick some Speed-pro flat tops H116CP pistons on stock rods with ARP bolts or Scat I-beams-balance and use a Lunati Voodoo 10200703 cam with stock rockers. I have made close to 430 HP/440 tq (365) with this and J heads (1.94/1.6 231 cfm @ .450") There you go, save your money say no to 4" strokes. J.Rob

I totally concur with build as it is more or less what I have, concept wise.

 

[darten1972]

Listen to crackedback,AJ/FormS and Moper if he has chimed in. I like to over-engineer so commenting from experience I would go against the grain and build a solid 380-400 hp STOCK stroke 360. Stick some Speed-pro flat tops H116CP pistons on stock rods with ARP bolts or Scat I-beams-balance and use a Lunati Voodoo 10200703 cam with stock rockers. I have made close to 430 HP/440 tq (365) with this and J heads (1.94/1.6 231 cfm @ .450") There you go, save your money say no to 4" strokes. J.Rob

Those are very impressive numbers. This sounds incredibly affordable. I already have a Air Gap intake and 1 5/8 Doug’s long tubes. My heads actually only have the 1.88/1.60 valves with stock non adjust rockers. In your opinion I should probably look for a set of heads? As far as bore goes maybe 30 over to make the hole round again? Anything I should do to the block? Thanks for this info.

 

[AJ/FormS]

Part 2
So what to do? That box by itself is good for a low-rpm, hi-torque engine. When you add the GVOD and split gears, it becomes an incredible experience. It works best NOW, with a hi-torque bigger engine to keep the rpms down, and one that has a maybe slightly narrower than usual powerband,and who cares how fast it runs cuz it will just be so much fun. At least that's the attitude I took.
So, this combo liked my 367/230cam. It has enough cubes to pull itself outta the hole when just grannying about, and I geared it for the 1/8 in 1.30 gear, that's 4 ratios to get there. And let the quarter be what it would to be. She went 93(eighth) that day.
And that brings us to the second glitch with that combo. With a teener,anytime you want to do some spirited driving, you will HAVE to split-shift. And as fun as that is for a few weeks, it does get old. And here's why; The GVOD shifts like lightning.....when it shifts. The problem is that it's a hydraulic unit, and it gets it's power from the driveshaft. So when you start off from zero mph, there is no pressure. So you have to wait for the pressure to come up. With 3.55s this takes a while. With 4.30s it was fast enough. The next thing is, it doesn't shift the second you push the button; rather there is a fraction of time and then BAM!, and I mean BAM!!. It shifts so fast,you will hardly see the gap in the rubber on the road. And power-shifting at WOT, there is no shock absorption so it tends to break parts. It used to bark the 295 tires at 80mph on the shift.
And the third; You cannot backshift the unit under power. You can downshift the mainbox at any time, but to outshift the CVOD you must clutch it and wait for the shift. And there is no telling when the shift has taken place cuz to wire it for splitshifting, you throw out the little computer it comes with. So you have to learn to anticipate that outshift.
And the fourth; if you back up the car with the unit engaged, you will almost surely kill the unit. That little mistake on my part, less than 2 seconds,cost me 2400USd plus shipping both ways. OUCH!
So I wired up some lights right under my tach, to tell me when the GVOD was energized, and when the trans was in reverse, and I always look there before letting out the clutch,lol.
So there are some caveats.

 

[AJ/FormS]

Page 3
And now for the final secret, and the one you might like.
Heave that pos od box as far as you can.
Get yourself a 3.09/direct box from a 65 FormulaS or equivalent. The ratios are
3.09-1.92-1.40-1.00. This is a great box for everything except the hiway with 4.56s.
The secret is to put the GVOD on that old hummer. The ratios now are
3.09-2.41-1.92-1.50-1.40-1.09-1.00-.78od. GV in red again. In practice, you never use 1.50/1.40 back to back, nor 1.09/1.00. It's always one or the other. the rpm difference at 6500 is less than 600.
So, how do I use this box? Let's go to the track first.
I use 3.09-2.41-1.92-1.50 in the eighth and gear it to run thru the traps at 6460. That would be 3.73s. The starter is a sane 3.73 x 3.09=11.53. The splits are .78-.80-.78; how do you like that, I pulled the main stick just once!, and she trapped in second-over.
But you like the quarter, so I'd set it up to trap in 1.09 gear. Depending where exactly your hot teener power-peaked, let's say 5800 and you wanna trap at 6000 max, this would require 4.10s now.Wow, things are looking up! Ok so the ratios to use are;
3.09-2.41-1.92-1.40-1.09... hyup you're seeing 5 ratios, this teener is gonna rock!!, and the splits are .78-.80-.73-.78, pretty sweet, and the starter is 4.1 x 3.09=12.67. So this is 5 ratios with just 2 pulls on the stick, including the sometimes tricky 2-3. This is awesome!
Now how about around town? Well it shifts like any other box,you just never use the od until you hit the hiway. I drive it like this 3.09-1.91-1.40-1.09-.78od.. That gives me a short 4th and a bigger drop into od.
How about granny driving? Again I like to short shift the 1-2 cuz I have a BIG 367,lol. But say you took a bunch of cam outta that teener, cuz it's now running off the charts with 5 gears in the quarter, and to go 12.9 you no longer need a monster cam. I mean that makes sense to me. Why have a 337 hp teener that only spends 20 miles a year at the track;if that,right?
Ok so let's say you're down to a 268cam and hi-flow heads, plus a matching compression ratio, and all the usual bolt-ons. This teener is now making torque. So you can shift at say 3300, Hyup 3300 isn't outrageous. So 3300 with 4.10s and a 3.09 low is 21mph;perfect. So you pull the stick and on the 1-2 shift,the Rs fall to 2050. Sounds a lil low, but the teener is now pulling harder,a lot harder than with that race-cam it had before.So now you buzz it up to 3300 again,now doing 34mph, and on the 2-3 shift,the Rs drop to 2406. That's pretty good. And buzzing 3rd up to 3300 will get you 46mph, and at the shift into 3-od, the Rs fall to 2574, which you then drive up to 65 and pull the stick for the last time, and the Rs fall to 2580. That all sounds pretty good now.
Spirited driving? Well you'll want to keep the Rs between about 4000 and 5500. In second, this would be 40 and 55. Anywhere in that zone and she'll be rocking. Too fast for ya? Get it into first-over and that will be 32mph to 45mph, sound Ok to you? Hah! I knew it would.
Ok but guess what; Second gear with 4.10s will get you 60@5870. How U likey dat? That would be first gear, and first-over,and second, and three ratios all used up. You make that hook and you are gonna show a lotta bigger boys, taillights. If you can't make it hook, no worries, spinning to 60 is still a lot of fun......as long as the car goes where you point it, and only where you point it, cuz getting crossed up at over 50 is usually a write-off. Even 30 will do a lotta damage.
When my son asked to take the Cuda to prom-night, we had a little talk before I gave him the keys.
IIRC there were just 4 rules;1)Before you stand on it,And I know you want to, and that's what it was built for, but; you pick your spots; don't let your buddies push you around. 2)Bring it back with at least enough gas to drive it to a filling station, 3)and bring it back when you say you will;If you can't, you call me I don't care what time of night or from where.I'm not interested in calling every hospital in a 100 mile radius. 4) And if you break it you fix it.
After he brought it back as per the rules, I had to add another one; 5) if your buddies smell like ashtrays, they're not allowed in. I hate cigarette smoke;almost more than anything.
So the point is this; make sure your car goes where you point it; but if it does get outta shape, make sure it can stop!
Oh yeah, my 367 is pretty tame, but it's way more than I need to go 12.9 in the quarter. Is it fun? Heck ya. Is it dangerous? Well my 17 year old son managed to bring it home on the morning after the prom,as promised, unscathed. And she's never been crashed since I built her in 1999.
I could be just as happy with a warmed up teener; this transmission combo is dynomite.
And you get it free right here on FABO.
Done.lol

 

[AJ/FormS]

What compression ratio and cam are you currently running, and why do you feel it's slow?
I mean a 72 swinger is still pretty light.
My 1970 was 3200flat, in spring of 71, with P/S and P/b and rally suspension, all pure stock.340/A833/3.55s. Together, me and the car scaled at 3330.
So it can't be that.lol

 

[rumblefish360]

Geez-us Christmas AJ. Can you nut shell anything. Does it have to be a bible every time you reply?

 

[darten1972]

What compression ratio and cam are you currently running, and why do you feel it's slow?
I mean a 72 swinger is still pretty light.
My 1970 was 3200flat, in spring of 71, with P/S and P/b and rally suspension, all pure stock.340/A833/3.55s. Together, me and the car scaled at 3330.
So it can't be that.lol

Currently running a 340 purple shaft cam with a 20 overbore with the 360 heads and airgap. I had a Huges whiplash cam in it for a couple of weeks but it had a tick in it from day one. Found out that it took one of the lobes out of it. Must have been a break in issue? Not sure. I’m just flat tired of this motor. I want more torque and responsiveness. I bought a new street demon 625 carb which works ok. I’ve had the car for 24 years and after the fresh rebuild of the entire car I’m just sick of this little motor. It did run 14.4 @ 92 Mp/h on street tires many years ago so it’s not a sloth. Just need more go go.

 

[doogievlg]

Currently running a 340 purple shaft cam with a 20 overbore with the 360 heads and airgap. I had a Huges whiplash cam in it for a couple of weeks but it had a tick in it from day one. Found out that it took one of the lobes out of it. Must have been a break in issue? Not sure. I’m just flat tired of this motor. I want more torque and responsiveness. I bought a new street demon 625 carb which works ok. I’ve had the car for 24 years and after the fresh rebuild of the entire car I’m just sick of this little motor. It did run 14.4 @ 92 Mp/h on street tires many years ago so it’s not a sloth. Just need more go go.

What gear is in the car? You may have already said but I couldn’t find it.

A small block with a decent cam, rpm intake, and headers should have a higher mph than that. Something else may be going on.

 

[AJ/FormS]

Currently running a 340 purple shaft cam with a 20 overbore with the 360 heads and airgap. I had a Huges whiplash cam in it for a couple of weeks but it had a tick in it from day one. Found out that it took one of the lobes out of it. Must have been a break in issue? Not sure. I’m just flat tired of this motor. I want more torque and responsiveness. I bought a new street demon 625 carb which works ok. I’ve had the car for 24 years and after the fresh rebuild of the entire car I’m just sick of this little motor. It did run 14.4 @ 92 Mp/h on street tires many years ago so it’s not a sloth. Just need more go go.

Well that's just a little too vague; which purple and exactly what compression ratio? If you don't know, then a cylinder pressure test could be helpful. I'm sorta seeing the common teener blues here, which is total lack of compression. But I'll wait for the numbers, before commenting.
But here's some food for thought, The biggest reason so many teen owners are disappointed,after a cam upgrade, is the lack of low-rpm grunt, which is directly related to the lack of compression, and not enough rear gear, and TC if an automatic . But that can and does happen with other SBMs to.
Going from 8/1 to 11/1 represents about 5.2% power gain so about 12 hp on your engine, which doesn't sound like much, but this is at peak power. The difference in torque at part throttle, and especially below 2500 rpm is almost profound. So if you have a 3000TC it's not an issue. But with a stick car that might be a difference of 16 or more crank-footpounds at, 15/20 mph depending on rear gear. In first gear, after TM, that could be over 40ftpounds at the pavement.And that is very significant. Don't let anyone tell you that 9/1 compression is enough. Without a qualifier, 9/1 means nothing. (although 9/1 in an otherwise stock teener would really wake it up),

The intake closing event and the Scr are intimately related.
For instance;If you've got a 292/108 in there,in at 104, with a 70* ICA, that cam would need a lot of compression to pull up the bottom end; like 10.8Scr,and the bottom end could still be softer than a stock 8.0Scr 318.There is no good way to get 10.8 on a teener with those heads; you would be looking at a total chamber volume of 67 cc.That's heads,deck,gasket and piston tops.
If your pistons are down in the holes, that could be your biggest problem. There may be other issues; like lack of stall and gear. If you put that top end and cam onto a 360, it will have similar problems.It still wants a 10.8Scr, but now in a 360 that takes 76.3cc, which is a lot more doable, but not with pistons down in the holes either.If you put all that stuff on a stock 8.0 360, it will be a worse slug than a stock 318, up to maybe 3000 rpm(guessing).
I had a 367 with that cam and 11.3Scr and the bottom was still too soft for me, and that was with a deep starter gear (manual trans). I didn't put a lot of miles on that cam, and then I sold it .That cam is best left for a race-track only environment.It pulled gangbusters after about 5300, and was still pulling at 7000.But the first 20/25mph were miserable. And really,7000 in first gear with 3.55s is already speeding almost everywhere in Manitoba. A power peak of 5300 would typically occur at 45 mph. That's like forever, when trying to catch a BB-car,lol.

At 3330 pounds; The 14.4 with street suspension translates to about 227 hp. the 94mph says 228. So it looks well sorted, if a bit anemic..

This post abbreviated for Rumble,lol.

 

[darten1972]

Sorry for the lack of info there. I don’t have the cam card as this is a very old build that was done by a shop many years ago. All I know is that’s a 340 spec purple shaft. What I do know is the bottom end is totally stock, 3:23 sure grip and a newly installed 2500 stall in the 904 tranny. That’s all I know. I should give the Teener a bit more credit than I do I guess. I’m just so used to it I want more. I’m thinking if I build my 360 with some decent pistons, some Edlebrock heads and maybe some roller gear it might make the Dart shake it’s tires a bit harder? I’d love to put a roller cam in it just to avoid the potential break in issues that I had before? Sorry but my knowledge base is very poor and I’m no mechanic. I’m really enjoying all the info you guys are sending me. It certainly will help me figure out my next move.

 

[AJ/FormS]

Sorry for the lack of info there. I don’t have the cam card as this is a very old build that was done by a shop many years ago. All I know is that’s a 340 spec purple shaft. What I do know is the bottom end is totally stock, 3:23 sure grip and a newly installed 2500 stall in the 904 tranny. That’s all I know. I should give the Teener a bit more credit than I do I guess. I’m just so used to it I want more. I’m thinking if I build my 360 with some decent pistons, some Edlebrock heads and maybe some roller gear it might make the Dart shake it’s tires a bit harder? I’d love to put a roller cam in it just to avoid the potential break in issues that I had before? Sorry but my knowledge base is very poor and I’m no mechanic. I’m really enjoying all the info you guys are sending me. It certainly will help me figure out my next move.

1) Well, that's too bad we can't know which purple, but there's enough information in this last post to know that your combo suffers from the triple failure of not enough compression, not enough stall, and not enough gear; ALL THREE.
Pretty much any "upgrade cam" to a 318, in an 8/1 stock bottom end, with uncut big-port heads will be soft on the bottom. Actually even the stock teener cam is already soft with the factory 2bbl heads,lol.

2) One thing comes to mind; you said a 340 Purple cam. The common factory 340 cam was a 268/276/114 .429 lift cam. You might already have a similar cam. The equivalent Purple 340 cam is P4452761 with specs of 268/272/110, and .450/.455 lift. But,you can't easily prove that.But you can easily check the cranking compression.
I highly recommend a compression test to see just how bad it is.
To make the 318 come alive, it will need cranking compression up near 165psi combined with a LeakDown no more than 4%. Your hot 318; hates 110,120,130,strongly dislikes 140,150 and probably 155 too.

3) IMO the 268Purple is about as big a cam as a street-318/automatic should go.
And this 268Purple WILL work(sortof) with the 2500TC, but it still won't like the 3.23s very much off the line, and not at all at the track cuz it's still a two-gear run. You need to use all three gears to ET well.
And wonder of wonders, this 268*cam wants a compression ratio of just 9.8, which is a total chamber volume of 74.4 cc. Since there may be 11cc in the deck clearance; with a thin gasket of 4.5cc, the heads will now need to be 58.5cc. While I suppose you could cut your J heads down to this, there are other ideas

4) Your current chamber size with factory uncut parts is probably around 92cc. To make the 268 cam happy, this needs to get down to 77.4; so you can see the problem, I think. I'd be surprised if the current combo could muster an 8.0Scr.And that coupled with a 60* ICA spells around 125 psi, and that would make the teener take off just a little stronger than a slanty, if it was married to a clutch.
The 2500TC will get it thru that dead-zone a little better, but then the 3.23gears keep the rpm too low for too long, and it just becomes a huge disappointment; I know exactly what you're going thru, having gone thru this many decades ago. The power didn't really come on until she was into the 4000s, and the valves floated at about 5500, and shutting down that early, while she's just waking up, makes for a disappointing run, to say the least. But it did have dynomite passing power, I'll give it that.

5) To get the total chamber volume down, I see three options:
Option 1; is small-chamber heads,on a zero deck block. The stock teener has pistons waaay below the decks, sometimes in the range of .050 to .060. This is about 11 to 12 cc. We have to get rid of that. But hang on; in conjunction with machining the decks .050 or more, you would also have to machine your J heads way down and when you bolt this all together, you will find out that the intake will now also have to be machined. And so that's a lot of set-ups and a lot of machining costs. AND having it all fit and not have leaks when you're done, is sortof a crapshoot.
6) Option 2; is pop-up pistons, with the current open chamber heads, and no machining.. The KB-399s are a good solution, and they will allow you to get the squish up into the effective zone, possibly allowing you to run one grade lower gas. And all the factory parts go together pretty good without any machining.The bonus of that is that if you blow it up, you don't have a ton of money in the machining which you can never get back.
7) Option 3;Some guys have put a small-main 3.58 stroke crank into the 318. This pops the stock pistons up, 1/2 the stroke difference higher, which is .133 inch.This could bring the stock pistons up out of the holes maybe as little as .076, depending on the year of the 318.I haven't done this, and I think the top ring might be a little close to the top, so you'd have to measure and be ready to spring for new pistons,again. You could make this work with open-chamber heads and the right head gasket. And the bonus outta this deal is, you get 345 cubes,(an extra 23 cubes over your current 322).

8) So there are three possible solutions if keeping the 318. Oh and to ET well,you'll still need some gears. But you won't absolutely need them for the street.
But you should know,that IMO the best solution is a taller piston,and that if you decide to install pistons, it will cost about the same whether you do it, to either your 318 or to a 360, and altho the 360 will have a fair bit stronger bottom end strictly due to the cube difference, you may still have to change the TC and for sure the gears, to take advantage of the new combo, at the track.

9) You can bandaid the teener as it is now,with something like 3.91s and a 3500TC and it will be waaay more fun to drive, but it won't change the trap speed much cuz you haven't changed the absolute power at all. Your average power will be up some with the 3.91s; but they are really not the right answer for the quarter. The engine will still not be in the power-zone going thru the traps with 3.91s, and it still is waaay late getting onto the power, the ET won't change much either. So the bandaids would just make it funner to drive.

10) Cheer up;I'll bet that with the 3.23s you were still in second gear running thru the traps.The math says around 5600.Which with a 268* cam isn't that far off the mark, but running the strip in just 2 gears, I'd have to say that 94mph is pretty good with that combo.

11) Parting shots
A) But if you put all your top end and cam into/onto a zero-deck 365, And assuming the heads aren't junk,she might go 106 easy enough..... and at 3330#, that is 320hp, and that could be 12.5 with SSsuspension, maybe just sneaking into the 12s with street suspension. You want faster/quicker? It gets expensive in a hurry! Get you some hi-flow heads and upsize the cam AND bringing the compression along with it, and you'll be in the mid twelves. Make it hook, and into the 11s you go.
B) But I just gotta say one thing; A 360 powered car that goes 12.9 with street suspension is plenty fun on the street. The cam is still small enough that the 360 can break Swinger-sized tires loose, with 3.55s, even in second gear, almost any time after 3500 rpm. Which, if you have a 3500TC......DOH....... is just about any time at all.
But you, set-up to run the Quarter, will be running at least 4.30s, so..........you're gonna have to spend more money; spinning ain't winning..
C) I stopped setting up for the Quarter, years ago;the gearing is just all wrong for a streeter. And I'm getting too old to be swapping chunks all the time. So I set up for doing the 1/8, and let the qtr be what it will be. I'm happy just knowing from the Eighth numbers, what the Qtr might be.(online calculators). A 106 qtr is about 85 in the Eighth. So perhaps set your car up to go 85 at about 300 or so rpm past peak power, in second gear and call it done. This will be about 3.23s for your assumed-to-be-268 Cam. This will get you about 5400; just a little low perhaps, but you already got 'em...... 3.55s would be 5900, and..... 3.73s are 6200.
And 3.23s are a good cruiser gear. And they're a perfect gear for going hammer down into first at 32 mph.That's an instant 3400, so who cares what the stall is, we got TM. Yeah the starter gear is a little soft at 7.91,but give that combo a workout while your tuning for the new compression ratio. Maybe you'll kick the 3.23s to the curb..... but maybe not; especially if you go 360,then leave them for a while.
Happy HotRodding!

 

[yellow rose]

Put a dial indicator on the retainer and Measure the lift. That will tell you what cam it is...if it's an MP cam

 

[darten1972]

1) Well, that's too bad we can't know which purple, but there's enough information in this last post to know that your combo suffers from the triple failure of not enough compression, not enough stall, and not enough gear; ALL THREE.
Pretty much any "upgrade cam" to a 318, in an 8/1 stock bottom end, with uncut big-port heads will be soft on the bottom. Actually even the stock teener cam is already soft with the factory 2bbl heads,lol.

2) One thing comes to mind; you said a 340 Purple cam. The common factory 340 cam was a 268/276/114 .429 lift cam. You might already have a similar cam. The equivalent Purple 340 cam is P4452761 with specs of 268/272/110, and .450/.455 lift. But,you can't easily prove that.But you can easily check the cranking compression.
I highly recommend a compression test to see just how bad it is.
To make the 318 come alive, it will need cranking compression up near 165psi combined with a LeakDown no more than 4%. Your hot 318; hates 110,120,130,strongly dislikes 140,150 and probably 155 too.

3) IMO the 268Purple is about as big a cam as a street-318/automatic should go.
And this 268Purple WILL work(sortof) with the 2500TC, but it still won't like the 3.23s very much off the line, and not at all at the track cuz it's still a two-gear run. You need to use all three gears to ET well.
And wonder of wonders, this 268*cam wants a compression ratio of just 9.8, which is a total chamber volume of 74.4 cc. Since there may be 11cc in the deck clearance; with a thin gasket of 4.5cc, the heads will now need to be 58.5cc. While I suppose you could cut your J heads down to this, there are other ideas

4) Your current chamber size with factory uncut parts is probably around 92cc. To make the 268 cam happy, this needs to get down to 77.4; so you can see the problem, I think. I'd be surprised if the current combo could muster an 8.0Scr.And that coupled with a 60* ICA spells around 125 psi, and that would make the teener take off just a little stronger than a slanty, if it was married to a clutch.
The 2500TC will get it thru that dead-zone a little better, but then the 3.23gears keep the rpm too low for too long, and it just becomes a huge disappointment; I know exactly what you're going thru, having gone thru this many decades ago. The power didn't really come on until she was into the 4000s, and the valves floated at about 5500, and shutting down that early, while she's just waking up, makes for a disappointing run, to say the least. But it did have dynomite passing power, I'll give it that.

5) To get the total chamber volume down, I see three options:
Option 1; is small-chamber heads,on a zero deck block. The stock teener has pistons waaay below the decks, sometimes in the range of .050 to .060. This is about 11 to 12 cc. We have to get rid of that. But hang on; in conjunction with machining the decks .050 or more, you would also have to machine your J heads way down and when you bolt this all together, you will find out that the intake will now also have to be machined. And so that's a lot of set-ups and a lot of machining costs. AND having it all fit and not have leaks when you're done, is sortof a crapshoot.
6) Option 2; is pop-up pistons, with the current open chamber heads, and no machining.. The KB-399s are a good solution, and they will allow you to get the squish up into the effective zone, possibly allowing you to run one grade lower gas. And all the factory parts go together pretty good without any machining.The bonus of that is that if you blow it up, you don't have a ton of money in the machining which you can never get back.
7) Option 3;Some guys have put a small-main 3.58 stroke crank into the 318. This pops the stock pistons up, 1/2 the stroke difference higher, which is .133 inch.This could bring the stock pistons up out of the holes maybe as little as .076, depending on the year of the 318.I haven't done this, and I think the top ring might be a little close to the top, so you'd have to measure and be ready to spring for new pistons,again. You could make this work with open-chamber heads and the right head gasket. And the bonus outta this deal is, you get 345 cubes,(an extra 23 cubes over your current 322).

8) So there are three possible solutions if keeping the 318. Oh and to ET well,you'll still need some gears. But you won't absolutely need them for the street.
But you should know,that IMO the best solution is a taller piston,and that if you decide to install pistons, it will cost about the same whether you do it, to either your 318 or to a 360, and altho the 360 will have a fair bit stronger bottom end strictly due to the cube difference, you may still have to change the TC and for sure the gears, to take advantage of the new combo, at the track.

9) You can bandaid the teener as it is now,with something like 3.91s and a 3500TC and it will be waaay more fun to drive, but it won't change the trap speed much cuz you haven't changed the absolute power at all. Your average power will be up some with the 3.91s; but they are really not the right answer for the quarter. The engine will still not be in the power-zone going thru the traps with 3.91s, and it still is waaay late getting onto the power, the ET won't change much either. So the bandaids would just make it funner to drive.

10) Cheer up;I'll bet that with the 3.23s you were still in second gear running thru the traps.The math says around 5600.Which with a 268* cam isn't that far off the mark, but running the strip in just 2 gears, I'd have to say that 94mph is pretty good with that combo.

11) Parting shots
A) But if you put all your top end and cam into/onto a zero-deck 365, And assuming the heads aren't junk,she might go 106 easy enough..... and at 3330#, that is 320hp, and that could be 12.5 with SSsuspension, maybe just sneaking into the 12s with street suspension. You want faster/quicker? It gets expensive in a hurry! Get you some hi-flow heads and upsize the cam AND bringing the compression along with it, and you'll be in the mid twelves. Make it hook, and into the 11s you go.
B) But I just gotta say one thing; A 360 powered car that goes 12.9 with street suspension is plenty fun on the street. The cam is still small enough that the 360 can break Swinger-sized tires loose, with 3.55s, even in second gear, almost any time after 3500 rpm. Which, if you have a 3500TC......DOH....... is just about any time at all.
But you, set-up to run the Quarter, will be running at least 4.30s, so..........you're gonna have to spend more money; spinning ain't winning..
C) I stopped setting up for the Quarter, years ago;the gearing is just all wrong for a streeter. And I'm getting too old to be swapping chunks all the time. So I set up for doing the 1/8, and let the qtr be what it will be. I'm happy just knowing from the Eighth numbers, what the Qtr might be.(online calculators). A 106 qtr is about 85 in the Eighth. So perhaps set your car up to go 85 at about 300 or so rpm past peak power, in second gear and call it done. This will be about 3.23s for your assumed-to-be-268 Cam. This will get you about 5400; just a little low perhaps, but you already got 'em...... 3.55s would be 5900, and..... 3.73s are 6200.
And 3.23s are a good cruiser gear. And they're a perfect gear for going hammer down into first at 32 mph.That's an instant 3400, so who cares what the stall is, we got TM. Yeah the starter gear is a little soft at 7.91,but give that combo a workout while your tuning for the new compression ratio. Maybe you'll kick the 3.23s to the curb..... but maybe not; especially if you go 360,then leave them for a while.
Happy HotRodding!

Wow thanks so much for all the info. That’s a ton of material to put down in a post. Thanks again. Much appreciated

 

[spl440]

With the 360 you already have a factory stroker. All you need is more cam and compression and have at it.

 

[gregsdart]

First off, love the car! If it were mine, I would build the 408 shortblock, freshen the heads you have (J heads?) and run it till you can upgrade to the cam and heads you really want to run. Your original post said you would like a 408, and if you are like most of us, we always want more power. You might regret not going 408 down the road. There are ways to get what you want, it just might take some creativity to make it happen. My very first build I funded by buying and selling parts. I just didn't have the budget at that time to write a check so I got creative.
Starting with a 408 With the 3.23 gears and stock converter, it will run a lot better with all those extra cubes, for sure. The cam you have will put the torque where it will work best with those gears and converter too. Most of the street fun is in the lower rpms anyway.

 

[doogievlg]

You said you want to run 12s but what are your street goals for this engine. Are you going to be sitting in traffic in it? Just quick around town runs? Driving 100 miles to a car show?

 

[B3422w5]

Well that's just a little too vague; which purple and exactly what compression ratio? If you don't know, then a cylinder pressure test could be helpful. I'm sorta seeing the common teener blues here, which is total lack of compression. But I'll wait for the numbers, before commenting.
But here's some food for thought, The biggest reason so many teen owners are disappointed,after a cam upgrade, is the lack of low-rpm grunt, which is directly related to the lack of compression, and not enough rear gear, and TC if an automatic . But that can and does happen with other SBMs to.
Going from 8/1 to 11/1 represents about 5.2% power gain so about 12 hp on your engine, which doesn't sound like much, but this is at peak power. The difference in torque at part throttle, and especially below 2500 rpm is almost profound. So if you have a 3000TC it's not an issue. But with a stick car that might be a difference of 16 or more crank-footpounds at, 15/20 mph depending on rear gear. In first gear, after TM, that could be over 40ftpounds at the pavement.And that is very significant. Don't let anyone tell you that 9/1 compression is enough. Without a qualifier, 9/1 means nothing. (although 9/1 in an otherwise stock teener would really wake it up),

The intake closing event and the Scr are intimately related.
For instance;If you've got a 292/108 in there,in at 104, with a 70* ICA, that cam would need a lot of compression to pull up the bottom end; like 10.8Scr,and the bottom end could still be softer than a stock 8.0Scr 318.There is no good way to get 10.8 on a teener with those heads; you would be looking at a total chamber volume of 67 cc.That's heads,deck,gasket and piston tops.
If your pistons are down in the holes, that could be your biggest problem. There may be other issues; like lack of stall and gear. If you put that top end and cam onto a 360, it will have similar problems.It still wants a 10.8Scr, but now in a 360 that takes 76.3cc, which is a lot more doable, but not with pistons down in the holes either.If you put all that stuff on a stock 8.0 360, it will be a worse slug than a stock 318, up to maybe 3000 rpm(guessing).
I had a 367 with that cam and 11.3Scr and the bottom was still too soft for me, and that was with a deep starter gear (manual trans). I didn't put a lot of miles on that cam, and then I sold it .That cam is best left for a race-track only environment.It pulled gangbusters after about 5300, and was still pulling at 7000.But the first 20/25mph were miserable. And really,7000 in first gear with 3.55s is already speeding almost everywhere in Manitoba. A power peak of 5300 would typically occur at 45 mph. That's like forever, when trying to catch a BB-car,lol.

At 3330 pounds; The 14.4 with street suspension translates to about 227 hp. the 94mph says 228. So it looks well sorted, if a bit anemic..

This post abbreviated for Rumble,lol.

Your going to gain WAY more than 5.2% power increase going from 8 to 11 compression. You will actually pick up nearly that much with each single point increase.
Thermal effciency also increases dramatically.

 

[darten1972]

You said you want to run 12s but what are your street goals for this engine. Are you going to be sitting in traffic in it? Just quick around town runs? Driving 100 miles to a car show?

I want to have the option of driving it 100 miles if need be. I also want to flatten it from a dead stop and just lay rubber. I really would like to see 12’s but I need to be realistic at the same time.

 

[autoxcuda]

I want to have the option of driving it 100 miles if need be. I also want to flatten it from a dead stop and just lay rubber. I really would like to see 12’s but I need to be realistic at the same time.

Build a 408 with cast crank, I beam rods, Icon forged pistons, balanced assembly, that aforementioned vodoo hyd cam, stamped rockers, edelbrock heads, 9.5-9.8:1 compression, double pump carb, and your current intake and headers.

You'll be able to flatten it at any speed up to 30mph and lay rubber.