CSL DART
1971 DART SWINGER
Thank you very much!
Broad question from a rookie
- Thread starter CSL DART
- Start date
-
ir3333
Well-Known Member
How do you guys just come up with a 400 hp figure?
Rumble nailed it....post exactly how you are going to be using your project and how you
would like it too perform.There are a lot of experienced builders on here.
...Listen to the guys that say "this is what i used, and this is how it performed"
Too many guys build a 1/4 mile car and end up very unhappy driving it on the street.
Rumble nailed it....post exactly how you are going to be using your project and how you
would like it too perform.There are a lot of experienced builders on here.
...Listen to the guys that say "this is what i used, and this is how it performed"
Too many guys build a 1/4 mile car and end up very unhappy driving it on the street.
The link for the gear vendors overdrive is a interesting thought. I’m not a fan of the price or the gimmick of gear splitting. Your call. But an overdrive is always a decent idea. It helps reduce cam size and engine stress while adding drivability and mileage.
Tell me (us) at what rpm do you think it is OK to be on the Hwy. with? What’s screaming rpm?
CSL DART
1971 DART SWINGER
I'm so damn new lol! I'll be honest, I didn't even know about the whole overdrive option on transmissions until some of you guys shed some light on it with your responses. Actually sounds like a great way to have the best of both worlds! I'd be lying if I tried to give you a specific rpm range on the freeway, but I just don't want the car to sound like it's contemplating blowing up when I'm doing 75 mph lol! The 360 I have in the car right now is nice, but it just doesn't sound happy above 70mph.
CSL DART
1971 DART SWINGER
I'm already on it Just ordered a Haynes service and repair manual too...First post... reading is Fun-D-Mental...
CSL DART
1971 DART SWINGER
Thanks, I'll keep your advice in mind. I'm definitely not gonna be "that guy" with a quarter mile car. I want to build a sturdy car to drive on the street and freeway as often as possible.
Yes! The oversrive option is a good one but a little bit of a pain in the ***. As far as a Mopar trans goes your best bet IMO would be the A-500. It is based off of the 904 and it does require some tunnel mods.
But the OD ratio is .69. This should be multiples by the gear ratio for the new OD ratio. Or final drive. Let me illustrate;
355 gears X’s .69 OD ratio equals 2.45 final drive. Great for 200 PMH assaults.
But;
4.56’s = 3.14
4.10’s = 2.82.
Get some fat tires!
FWIW, the author of that transmission book is a member here.
But the OD ratio is .69. This should be multiples by the gear ratio for the new OD ratio. Or final drive. Let me illustrate;
355 gears X’s .69 OD ratio equals 2.45 final drive. Great for 200 PMH assaults.
But;
4.56’s = 3.14
4.10’s = 2.82.
Get some fat tires!
FWIW, the author of that transmission book is a member here.
Dartnut
Don't hate me because i'm beautiful
IMHO, forget the Haynes manual and buy a Factory Service Manual for your car.
That would be money well spent, as well as the other two you ordered.
The Haynes manual is okay if you have nothing else at all, but the FSM is the way to go for precise information, pictures, etc.
So, what do you want to know about broads?
That would be money well spent, as well as the other two you ordered.
The Haynes manual is okay if you have nothing else at all, but the FSM is the way to go for precise information, pictures, etc.
So, what do you want to know about broads?
Ehhhh, the Hanyes is OK for some general information and help. It’s not a bad thing to have. It has some info that is a “Nice to know” stuff. The FSM has is the King book(s) to have.
CSL DART
1971 DART SWINGER
I understand thanks! I guess the question I keep wondering is: is the anything I should keep in mind that might be different because the original engine looks like it was a 225, and the 360 appears to be a late seventies engine with some obvious changes. I'm on vacation this week so I'm going to be pulling more numbers off the parts to zero in on what I actually have. I understand that the casting numbers are located in a couple different locations (driver side front of the block, driver side bottom of the block) I pulled both of those already and am going to look on the oil filter side for the others. The numbers under the driver side head were hard to read and didn't make sense when I looked in the front of my year one catalog! The number below verified an LA 360 but only narrowed it down between 75-92. Also want to pull the numbers off the Holly 4bbl, not sure what the cfm is on it. It has a Weiand I take manifold (not sure what version yet). Also has exhaust manifolds off 340. No headers, but it has H pipe dual exhaust with turn downs. I like the muscle car sound of the H pipe over the crossover exhaust I'll be out in my garage all day today lol! Have a good one and thanks for all your help and advice
CSL DART
1971 DART SWINGER
Thank you! I will try to order one as soon as possible
Dartnut
Don't hate me because i'm beautiful
Good choice.
You're talking about the FSM not the broad, right?
CSL DART
1971 DART SWINGER
I'll be honest, I'm not entirely sure. I haven't ordered anything yet. When I looked at 1971 it just showed a Dodge service manual for the year. Is there something more specific I can find? I started reading building max performance for Mopar small blocks by Larry Shepard and realized quickly how far behind the curve I am compared to most guys on this site. Holy s**t!! I'm just gonna try not to get discouraged and keep reading
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,947
- Reaction score
- 12,298
These are very telling comments. And IMO the 408 will fill the multi-use tall-order.
But so will a stout 360 with an overdrive.
or a turbocharged 318.
The big questions are budget, skill level, and willingness to cut the car up a tad.
There are several of us on here who have built combos that are very similar to what you are talking about, and IMO, the overdrive is the winner. If you have Some skills and time and a bit of money, this will make the rest of the combo relatively easy to achieve,even with just a 360. And if you build it right, you can even put fuel-mileage on the table, so you can afford to drive it all the time.
And this goes back to what Rumble said.
NO worries about being behind the curve. The curve is always changing and keeping up requires the ear to the ground while turning the wrench at the same time.
You’ll catch up. First things first, read the books. Learn what you need to know for YOURSELF & your project needs and then carry on from there.
No worries!
Best thing you can do is become an expert on YOUR CAR!
You’ll catch up. First things first, read the books. Learn what you need to know for YOURSELF & your project needs and then carry on from there.
No worries!
Best thing you can do is become an expert on YOUR CAR!
Oh, I haven’t seen a FSM for a specific car. They normally cover a group. Like 75-79 B bodies. The share so many parts it’s silly but the FSM will also sperate by specific model if need be.
I have one for my Dodge Magnum. 78-79. That’s a busy set of books.
I have one for my Dodge Magnum. 78-79. That’s a busy set of books.
CSL DART
1971 DART SWINGER
Thanks for the advice! I'm 49 and I feel like the only dumb son of a ***** that has never built an engine lol! This is my 4th Dart I've owned, but the only work I really did was on the random things that would typically go wrong on old cars. As far as getting to know my own car I'm getting slightly frustrated trying to match the casting numbers on the block. I've seen clearly that it's a 360, but narrowing down the specific year has proven a challenge. The numbers on the front driver side front below the head are difficult to read clearly and haven't corresponded with any of the casting information I've been able to find. The number below on the driver side are clear but the information I found just says it's an LA block 75-92. The number on the oil filter side is 5-28-79. Is it possibly a 79? The previous owner said he thought it was a 77'. Plus I can't even get access to the transmission to pull the numbers, but I'm pretty sure it's a 904. The carburetor looks to be a Holley 770 avenger. Haven't ran the numbers off the intake manifold but it's a Weiand. It has reasonable hp already, but I can't help wanting more lol! I think the exhaust manifolds came off a 340, but I'm thinking about tti headers with an H pipe instead of the newer crossover exhaust, because I love the muscle car sound of the H pipe..
Here's what gearing does. This is a dyno of a 360 380hp create engine.
Say your gonna floor it at 20 mph.
If you had 3.73 rear gear with a 2.74 1st gear
Vs 4.36 with 2.74 1st gear. At 20 mph the 3.73 will be at 2500 rpm and 4.36 will be at 3000 rpm. If you look at the dyno graph with the 3.73 your acceleration will start with 181 hp and the 4.36 will be pulling from 230 hp.
That a huge 50hp difference.
The 4.36 gears will always be higher up in the hp curve compared to the 3.73 making the 4.36 quicker until you run out of rpm.
Now if you add a 4" stroke to the otherwise same as 380hp combo. It would basically have the same hp curve but 500 rpm lower.
So 230 hp would now be at 2500 rpm.
So a 360 with 4.36 gears at 20 mph and 408 with 3.73 at 20 mph will both now be pulling from 230 hp.
So basically you got to gear it so your into your engines powerband or stroke your engine to lower your powerband to work with less gear.
CSL DART
1971 DART SWINGER
Thanks for the information, I've understand the concept of higher gears creating more bottom end and running higher rpm's as you get to highway speed for years, but I definitely lack the knowledge that you have and I appreciate the detailed explanation. At this point (still lots of time to decide), the overdrive option sounds decent to me to have the best of both worlds.... thanks again
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,947
- Reaction score
- 12,298
OK, I'm up for talking TM (Torque Multiplication).
Say that you have a regular automatic,with ratios of 2.45-1.45-1.00 and a popular rear gear like a 3.23.
Your TM will thus be the trans gear selected times the rear gear.
and say you had a tired 318 or something.
Now say this engine has 120ftlbs of torque available at 2200rpm. This torque will be multiplied by the TC,briefly, then reduced somewhat by powerloss in the trans and rear gears, and the whatever is left over,can be multiplied by the TM ratios to come out as available torque for acceleration purposes.
So lets take that 120 and estimate 15% loss in the powertrain and the gross it up to road-torque.
I get 120x .85x2.45x3.23=807ftlbs available for take-off in first gear. No smoke and not at all impressive. The TC might deliver a 10% boost on the hit but it decays rapidly as the vehicle moves ahead, and so I will ignore it for this exercise.
Ok so this sucks for performance.
So the first thing we need to do is find more power. Out goes the 2200 and in comes a 2500. Let's say this engine can deliver 180ftlbs at 2500. Ok so the math is 180x.85x3.23x2.45=1210 ftlbs. Ok so now we have enough to chirp the tires, and on a good day maybe spin them for a short ways, but mostly still not impressive.
Now lets look at cruising. 3.23s will get you 80mph=3340 with 26" tires,at zero-slip, so more likely is 3400@2% slip.That's quite a bit of revs.But guess what, 2.94s will only bring it down to 3100, and 2.76s to 2900.
> So let's say you want the 2.76s. What's that gonna do to your take off? Well, still with the 2800 and 180 numbers, I get 180x.85x2.76x2.45=1035ftlbs. ouch, back into the doghouse we go.
Okso,we need more power, out goes the 2500 and in comes a 3200. Now that little engine is making say 220, and the new numbers are 220x.85x2.76x2.45=1265, and tire chirping is again a reality.
But you wanna smoke the tires
So you install an engine that makes 35% more torque at 2500 or 240ftlbs and away you go. Now you find out that the 2500 and 2.76s get you 80=2850, and 240x.85x2.76x2.45=1380......but it's not quite enough,to satisfy you; so you hop it up and get 280@2500. This then gets you 280 x.85x2.76x2.45=1610 and that is now plenty of torque to smoke any street tire you can fit in the stock tubs.
So this is how it works, trading TM and TCs around and playing the numbers game. I purposely chose an imaginary engine with imaginary numbers so I could control the results with math.
> But let's say you had an overdrive trans with ratios of 2.74-1.54-1.00-.69od ....................... With this you can bias your cruise rpm against first gear TM at take off
Let's go back to that 180flb@2800 engine and give this combo
180x.85x2.74x3.91=1639 ftlbs, sweet, and 80=2850@2% slip. That's pretty sweet. So................180@2800 is like a 318
But you have a 360, with a long stroke,and say you pumped her up a bit so lets try it with 3.73 gears, and say 280ftlbs at 2800. And the math is 280 x .85x2.74x3.73=2430 tire-frying ftlbs, and 80mph =2700@2% slip.
> But let's say you took a bit of cam out of her and geared her down one more time and went back to a 2500TC; It might look like 250x.85x2.74x3.55=2070ftlbs, still plenty, and now 80=2580.
By taking cam out of her it now works with the wide-ratio trans, but more importantly, this cam has a longer power-extraction period and less overlap, and so you picked up say 2 mpgs, and this affects not your cruise torque nor your take-off, and only slightly slows your zero to 60mph ET.
I love playing these games.
Now lets compare3.55s with and without the overdrive
without, take off is 1848, and 80=3750
and with .69od, take-off is 2070 while 80=2580
That's a pretty good balance....IMO.
Now I gotta remind you that all the numbers I used are fictitious,lol. I made 'em up for the exercise.
But I just gotta say;IMO, 250 ftlbs at 2500 to 2800rpm,is easy-peasy for a lo-po 360.
Oh, I see I'm late to the party ,lol
Say that you have a regular automatic,with ratios of 2.45-1.45-1.00 and a popular rear gear like a 3.23.
Your TM will thus be the trans gear selected times the rear gear.
and say you had a tired 318 or something.
Now say this engine has 120ftlbs of torque available at 2200rpm. This torque will be multiplied by the TC,briefly, then reduced somewhat by powerloss in the trans and rear gears, and the whatever is left over,can be multiplied by the TM ratios to come out as available torque for acceleration purposes.
So lets take that 120 and estimate 15% loss in the powertrain and the gross it up to road-torque.
I get 120x .85x2.45x3.23=807ftlbs available for take-off in first gear. No smoke and not at all impressive. The TC might deliver a 10% boost on the hit but it decays rapidly as the vehicle moves ahead, and so I will ignore it for this exercise.
Ok so this sucks for performance.
So the first thing we need to do is find more power. Out goes the 2200 and in comes a 2500. Let's say this engine can deliver 180ftlbs at 2500. Ok so the math is 180x.85x3.23x2.45=1210 ftlbs. Ok so now we have enough to chirp the tires, and on a good day maybe spin them for a short ways, but mostly still not impressive.
Now lets look at cruising. 3.23s will get you 80mph=3340 with 26" tires,at zero-slip, so more likely is 3400@2% slip.That's quite a bit of revs.But guess what, 2.94s will only bring it down to 3100, and 2.76s to 2900.
> So let's say you want the 2.76s. What's that gonna do to your take off? Well, still with the 2800 and 180 numbers, I get 180x.85x2.76x2.45=1035ftlbs. ouch, back into the doghouse we go.
Okso,we need more power, out goes the 2500 and in comes a 3200. Now that little engine is making say 220, and the new numbers are 220x.85x2.76x2.45=1265, and tire chirping is again a reality.
But you wanna smoke the tires
So you install an engine that makes 35% more torque at 2500 or 240ftlbs and away you go. Now you find out that the 2500 and 2.76s get you 80=2850, and 240x.85x2.76x2.45=1380......but it's not quite enough,to satisfy you; so you hop it up and get 280@2500. This then gets you 280 x.85x2.76x2.45=1610 and that is now plenty of torque to smoke any street tire you can fit in the stock tubs.
So this is how it works, trading TM and TCs around and playing the numbers game. I purposely chose an imaginary engine with imaginary numbers so I could control the results with math.
> But let's say you had an overdrive trans with ratios of 2.74-1.54-1.00-.69od ....................... With this you can bias your cruise rpm against first gear TM at take off
Let's go back to that 180flb@2800 engine and give this combo
180x.85x2.74x3.91=1639 ftlbs, sweet, and 80=2850@2% slip. That's pretty sweet. So................180@2800 is like a 318
But you have a 360, with a long stroke,and say you pumped her up a bit so lets try it with 3.73 gears, and say 280ftlbs at 2800. And the math is 280 x .85x2.74x3.73=2430 tire-frying ftlbs, and 80mph =2700@2% slip.
> But let's say you took a bit of cam out of her and geared her down one more time and went back to a 2500TC; It might look like 250x.85x2.74x3.55=2070ftlbs, still plenty, and now 80=2580.
By taking cam out of her it now works with the wide-ratio trans, but more importantly, this cam has a longer power-extraction period and less overlap, and so you picked up say 2 mpgs, and this affects not your cruise torque nor your take-off, and only slightly slows your zero to 60mph ET.
I love playing these games.
Now lets compare3.55s with and without the overdrive
without, take off is 1848, and 80=3750
and with .69od, take-off is 2070 while 80=2580
That's a pretty good balance....IMO.
Now I gotta remind you that all the numbers I used are fictitious,lol. I made 'em up for the exercise.
But I just gotta say;IMO, 250 ftlbs at 2500 to 2800rpm,is easy-peasy for a lo-po 360.
Oh, I see I'm late to the party ,lol
Last edited:
One thing you left out is converting to hp.
Say pulling down the road at at full power 409hp @ 5400 with 4.10 with 24" tires.
At 5400 the torque is 399 lbs-ft.
399 x 4.10 = 1636 lbs-ft to the tires which would be rotating 1317 rpm at the tire.
So 1636 x 1317/ 5252 = 409 hp obviously there would be drivetrain power loss.
If you changed the gears to 3.55, 1416 lbs-ft to the tires now but now rotating 1521 rpm still giving you 409hp at the wheel.
Torque is vastly different but still getting the same power to the ground. But obviously the mph at these two events will be vastly different.
The goal aint more torque but to get into your powerband. And for the 380hp create engine that would be mainly 4500-6000rpm and secondarily 3000-4500 rpm.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,947
- Reaction score
- 12,298
Ileftthatoutonourpose
cuitwasaTMexercise
cuitwasaTMexercise
Last edited:
-
