opinions welcome on build.

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mechanicmark

mechanicmark

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As stated, would you go 3.79" or 4.00" stroke crank. 340 .030 over, plate honed. Edelbrock/Hughes 2.08" cnc'd heads will be used with 71 cc chambers. Flat top pistons. Pro-Flow 4 e.f.i system. Mechanical Flat tappet cam will be used. Auto trans. high stall and 3.91 rear gears for a hot street/strip 72 Demon. Lets not have a cylinder head discussion. Thanks, Mark!
 
If you use the 3.79 stroke and a 6.250 rod you can use an off the shelf 4.000 stroke piston.

I'm not a fan of 4.000 stroke anything with a production style head. I'm not even a fan of that stroke with a W2 head.

But that's just me. I'm not impressed with low speed tractor engines for a muscle car.
 
4” crank, TF 190 heads, pistons to suit.

For about 10.5cr(with the TF heads.....60cc?).....pistons .005 down the hole, .040 gasket, you’ll need a piston with about an 18cc inverted dome/valve relief volume.
 
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I have a 367, with far more power than the street chassis can handle. I'm very happy with the stock stroke.

Plus with those 71cc aluminum chambers, you almost need some cubes to take advantage of the higher cylinder pressures possible, and then you can reduce either the stall or the rear gear;maybe both.

But honestly for street use,I think those 3.91s need to be revisited, cuz at 60 mph your Rs will be ~7500 in first or ~4450 in second, so neither of which are much good, performance wise,at 60 mph.But I guess, with a stroker it wouldn't much matter cuz unless you spend a big wad on the suspension, it all goes up in tiresmoke anyway.
Just my opinion
 
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yellow rose said:
If you use the 3.79 stroke and a 6.250 rod you can use an off the shelf 4.000 stroke piston.

I'm not a fan of 4.000 stroke anything with a production style head. I'm not even a fan of that stroke with a W2 head.

But that's just me. I'm not impressed with low speed tractor engines for a muscle car.
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Thanks, I was not aware of that. Good info. I am looking at 7k plus rpm. Or what ever it will be going thru traps.
 
what PRH said
.200 stroke difference is going to make no difference on how it revs in a street car
street cars need all the mid range they can get- so the cu inches do make a difference
the top end power is determined by the heads and will be similar
do you have a source on 6.250 rods in the same ballpark with 4" stroke rods
that said get the rods as long as possible if you have a same price choice as the pistons will be lighter
with the pistons down .005 I'd run the .028 gasket
If you have to buy a crank why not go BIG?
 
The main reason to got with a stroker is to bring the rpm down.

if was full race you could stick with stock stroke, cause you don’t have to worry about compromising gear, stall and streetablity. If was a serious street strip I’d think about going with 3.79 if your willing to gear it any other use I’d go with the 4.
 
mechanicmark said:
I am looking at 7k plus rpm. Or what ever it will be going thru traps.
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IMO, I think you're putting the cart before the horse.
IMO I think you need to rethink street/strip ....... because a 7000 rpm engine with 3.91s is often a lousy street combo, as shown in post 7. Cuz if you can tame your traction issues, then; 7500 is too high for street in first gear, and 4450 is too low in second. I can almost guarantee you a 5speed hot 318 is gonna embarrass you from zero to sixty mph, cuz your 7000 engine ain't coming up on the cam until near 70 mph, might go thru the power peak at 6700/90, which is probably about right for a stroker in the Eighth. Then on the shift the Rs will fall to 4600 still at 90mph,but it won't hit the power-peak again until about 125/130 mph, which is a really really long pull from 90. And of course, it takes about 480hp to go 125@3200# So again wrong gear.
So, I mean, you could make 3.91s work, but really they would be wrong for both a streeter and a racer with a 7000 rpm engine, IMO. Ima thinking she'll want a lot more gear and an overdrive.
For a streeter;
You like 3.91s? The math says 60 will be ~4440@5% slip and 27" tires.
I suggest a power-peak around 4500, no more than 4800 for that. And for low-ET, a really big stroker, with exceptional traction,lol. Now you can go thru the power peak twice on the way to 60 and annihilate just about anything.
A better idea,IMO, is a power peak of say 5000, stretched to 5200@60mph, and the math spits out...... 4.56s which will put down ~17% more road torque than the 3.91s so your engine can have about 17% less power for the same ET @60 mph... or 17% less cubes, so a 350 cuber versus a 408 say. I mean just roughly.
I'd like to say that to 60mph,the 350 with 4.56s and a 5000power peak is gonna waste the 408 with 3.91s and a 6700 powerpeak but my calculator can't prove it.
But what I can tell you is a Hi-Compression 360 based combo with a 5200power peak, 4.30s and overdrive, is a helluva street combo.
IDK anything about a racer,except more cubes will get you more speed; this is where strokers shine.
When I put 3.55s and a 4-gear behind my 367, it immediately went 106/12.9 @3650 pounds;with zero tuning on 245/60-14s... That was fast enough for me so just one run and I went home.

For a streeter it's not always about the power; but rather having the power at the right MPH. The feeling I get drifting/sliding around a corner at near full lock steering with the tires howling and the engine screaming... is incomparable. It can be done with a big engine and small gears or it can be done with a smaller engine and a lil more gear.

Overdrive makes optimizing the gears to the 1/4strip, so much easier.
 
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mechanicmark said:
Thanks, I was not aware of that. Good info. I am looking at 7k plus rpm. Or what ever it will be going thru traps.
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mechanicmark said:
No rotating assembly yet y.r. I have the heads. The e.f.i will not tolerate a huge duration cam, there for, thinking some stroke. Mark.
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What cam are you going to use that will make power at 7k and still work with FI? Turning one 7k and making power at 7k are two different animals.
 
justinp61 said:
What cam are you going to use that will make power at 7k and still work with FI? Turning one 7k and making power at 7k are two different animals.
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Yeah, I didn't see the 7k deal. If that's the case then the 3.79 stroke is what you want and use a 6.250 Chevy Rod so you can use an off the shelf piston and get some Rod ratio back.

It's going to take good heads and intake work and some cam to MAKE power at 7000 with that stroke.
 
GEO said:
I'd personally pass on the solid lifter cam. Go hydraulic or hyd roller
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This is sarcasm? At 7000+ rpm? I would go 4 inch crank. If at a later date you are open/able to move up in head choice, you will have the bottom end for it. 7000+ rpm become pretty needy quickly. You will be happy with that head and a 4” crank again with room to grow head wise.
 
AJ/FormS said:
But honestly for street use,I think those 3.91s need to be revisited, cuz at 60 mph your Rs will be ~7500 in first or ~4450 in second, so neither of which are much good, performance wise,at 60 mph.But I guess, with a stroker it wouldn't much matter cuz unless you spend a big wad on the suspension, it all goes up in tiresmoke anyway.
Just my opinion
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Not sure I understand this. Who is going 60 mph in first and why is that relevant? Rpm at 60 in third, ok. The question he needs to answer is “is that RPM too high for me/my fuel budget/ or my valve train to live with” For me around town, go to coffee car 4:10’s are appropriate even considering c12 fuel. Any real time on the highway then 3:91’s or 3:73’s. Everyone has different tolerance level for rear gear. You don’t need to spend a ton of money on rear suspension to get it to work.
 
That's not to say that you can't rev your lil 367 to 7000 with just a 230* cam that peaks at maybe 5200...., I mean as a streeter with 3.55s,and a Commando box, and a gear splitter, mine is still spinning the tires at 7000@50 mph; and first-over is good to 60@6400,still spinning; while second is good for 60=5100 at just about peak hp, yes still spinning.
So if it's street-fun yur after, you don't need a lotta cubes, cheap BFGs can help make it happen.
At the track still with 3.55s, she turned 7000 all the way......
I mean traps at 93=6150 in second over, for the Eighth. Which might be 113@5440 in third-over. But if it was to go 115 then 115=5540
And 65mph cruising is 2240.
That's the best I could do, to hit as many bases as I could; namely 4 very close ratios in the Eighth, and altho I never tracked it, it would be 5 ratios (with one not quite as close) in the quarter.
To be truthful;with this new transmission combo, I wouldn't mind the next smaller cam and 3.23s. As a streeter it would be every bit as quick to 60 and with 65=2030 I could get that smaller cam back into the fuel-mileage game. I live 20 miles from the nearest big town and and 60 from the nearest big city, and nearly 150 from the track......
I'm just waiting for that 230* cam to expire; it's been in there since 2004.
 
furrystump said:
Not sure I understand this. Who is going 60 mph in first and why is that relevant? Rpm at 60 in third, ok. The question he needs to answer is “is that RPM too high for me/my fuel budget/ or my valve train to live with” For me around town, go to coffee car 4:10’s are appropriate even considering c12 fuel. Any real time on the highway then 3:91’s or 3:73’s. Everyone has different tolerance level for rear gear. You don’t need to spend a ton of money on rear suspension to get it to work.
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Ok wait I can see how what I wrote might be ambiguous. What I mean is that I'm not interested in drag racing, and I ain't interested in losing my license, so I'm a zero to 60 kindof guy. I mean I'll pay an imprudent fine which doesn't go on my license, but I won't be caught speeding for 85 in a 65; cuz up here the cops kindof frown on that and try to throw everything they can at you, and you end up walking for 5 years.
That means I optimize my gearing for max power at or near 60 mph, in second gear, cuz I know First is gonna be a throw-away gear on account of no traction. And I'm gonna hammer the brakes to not exceed65.
With that in mind, maybe what I wrote makes more sense.
 
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furrystump said:
Not sure I understand this. Who is going 60 mph in first and why is that relevant? Rpm at 60 in third, ok. The question he needs to answer is “is that RPM too high for me/my fuel budget/ or my valve train to live with” For me around town, go to coffee car 4:10’s are appropriate even considering c12 fuel. Any real time on the highway then 3:91’s or 3:73’s. Everyone has different tolerance level for rear gear. You don’t need to spend a ton of money on rear suspension to get it to work.
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Hes talking about getting max street fun, basically your gonna stretch it out in 1st then bang it into 2nd and let off shortly after that most times when playing around.

Like My car is terribly geared right now 2.94 and for me I have to drive it up to 40 mph then hammer it to get anything out of it. Hard to get it in it’s powerband to have fun and only get a few seconds of a full throttle run around town.
 
IMO; 3.91s are just wrong for a 7000 rpm streeter. So either the gears go, or the wicked cam,too-wicked-for-an-automatic-streeter, has to go. I don't know how to harness 430horsepower at 40 mph on 275s in a Demon, on the street. If it crosses 60mph in second at 4450, that 7000rpm engine ain't gonna be all that quick; you might as well have just a 223/230 cam and trap 60mph at peak-hp with that, it won't be hardly any slower, and your engine won't cost you an arm and a leg to build, nor any special maintenance, and that kind of engine drives forever on just oil changes. And best of all it takes full throttle right away even with a factory-stall TC, without detonating itself to death. It's just an all 'round more fun combo........ IMO
 
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