Tips on high torque 302?

[KAILUAZ]

Looking for carb/intake/cam advise for a autocross motor where I need more torque than top end. This will be run on short local parking lot autocross courses and some HPDE open track events. Just for fun, not points/competition.
Heres what I got: older 302 roller out of who knows what car or truck, stock heads, shortie Hooker headers, Flows with dumps. Stock T5, 8.8 with 4.10's.
Thoughts?

 

[85_SS_302_Coupe]

Run a duel plane intake, my choice would be either an Edelbrock Performer RPM Air Gap or more likely a Weiand Stealth (the Stealth is a great inake, runs from 1500rpm all the way to 6500rpm). Match it up with no more than a 600cfm Holley double pumper. As for heads you can use stock but if you can get some GT40P's they'd be great for a nice budget engine and would make great torque. You don't need to get crazy with the cam....even stock might be best for this since it'll give great throttle response and good bottom end. Everything else sounds good but i'd run full exhaust with tailpipes, as you'll make more torque with them than without (although it'll be a small difference, every little bit helps).


That probably will be sufficient for the engine since autox is more about corners/braking/accelerating than top speed. You'll likely spend more time tuning the suspension than you will the engine. On a setup this simple you can probably get away with even a box-stock Holley 600 and probably won't even need to jet it.

 

[87Mustang351]

what size carb are u running 85, my 750 DP seems to be too much for my 351.. i was thinking on swaping the jets to a 650

 

[85_SS_302_Coupe]

what size carb are u running 85, my 750 DP seems to be too much for my 351.. i was thinking on swaping the jets to a 650

I run a 650 which is still too big for my 302, it would be about right for a 351 though. You can jet down but you're still pulling too much air with the 750 so it'll be fighting itself to keep from running lean and you'll probably have some softer throttle response as a result. I actually bought my 650 for a 351 that i never ended up getting. If you're running big aftermarket heads and a cam to go with it, the 750 would be good for peak HP and for drag racing but you might still suffer on the bottom end.

A big portion of carb performance is air velocity. A carb that's too big is trying to pull in too much air that the heads and cam can't match, so the air coming in the engine is going to move much slower. The opposite of this would be a smaller carb like a 570cfm that they come with stock....they're awesome for bottom end but run out of breath at high RPMs. I've also read that Barry Grant 570s are excellent for mostly stock engines because they actually flow more than the advertised 570cfm....but i've never owned one. I figured the 600 is a nice middle ground between bottom and top end that won't run out of breath on the high side but should still be responsive down low.

 

[jrichker]

Best bet is an EFI setup with a long runner intake or a 1" intake manifold spacer, long tube exhaust and some Thumper heads. The idea is to keep intake and exhaust runners long for best low RPM power, and port volumes low and port velocities high. That gives immediate throttle response without having to wait for the RPM’s to wind up.

EFI intake runners are much longer than any carb intake and put the torque down in the RPM range that pulling out of a corner gives you. Plus there is no slosh factor to deal with in the carb fuel level.

 

[KAILUAZ]

Best bet is an EFI setup with a long runner intake or a 1" intake manifold spacer, long tube exhaust and some Thumper heads. The idea is to keep intake and exhaust runners long for best low RPM power, and port volumes low and port velocities high. That gives immediate throttle response without having to wait for the RPM’s to wind up.

EFI intake runners are much longer than any carb intake and put the torque down in the RPM range that pulling out of a corner gives you. Plus there is no slosh factor to deal with in the carb fuel level.

Yeah, but EFI is out of the question for this build. Thanks though.

 

[FastDriver]

Don't necessarily agree with your methods (low-end torque motor vs. hp with numerically high gearing), but I really think Jhricker is on it building a low-end torque motor. EFI is worth doing if you can swap it. For a budget build, I'd run ported E7s with long tubes and a cobra or ported stock intake and a stock cam. For low end torque you'd be hard pressed to do better.

 

[ninety15.0]

I also think the stock HO cam and ported stock heads are the best combo here. If you are hung up on staying carbed then i would stick a 600 CFM carb on there. The idea for good low end torque is high port velocity at low engine speeds....which equates to small ports. Big heads are out of the question and like others have said...run the smallest carb you can get away with

 

[samickguy15]

.

Slap on some E6SE heads for some good stock torque. They don't breath great, but they make good torque.

 

[ninety15.0]

I dont think putting E6's on there is a good idea. No sense in taking a step backwards in terms of performance. E7's are better heads all around

 

[65ShelbyClone]

Nobody mentioned putting a 331 kit under the stock heads and cam.....

Assuming 100% volumetric efficiency, a 4500rpm 302 could actually get away with a 450cfm carb. Since the stock heads and cam won't get you there, a 450 would have some headroom plus good throttle response and fuel/air mixing from the higher velocity.

Another option is a rootes blower.....

 

[KAILUAZ]

I guess I should figure out what heads I have on this thing. Where are the casting numbers? I have the intake off right now.
Thanks.

 

[KAILUAZ]

So the head casting numbers are E6SE, so I guess this engine is out of a 86 Thunderbird.

 

[65ShelbyClone]

It could have come from an '86 GT also. The E6s are not exactly revered in the performance arena, though.

I thought about this some more and the opposite end of the spectrum that serves the same purpose is a high revving engine with lots of power and short gears. However, a pile of torque will allow for fewer gear changes and that will save time around the course.

I guess it depends on how money you're willing to spend how much you're willing to do to the engine. A stroker with small heads will make tons of torque and decent power, but that's a grand just in parts.

 

[FastDriver]

I always shoot to make power throughout the rpm band with anything but a drag car. If it were me building the car and it were a race only car, I'd build a high comp 331 or 347 that I could spin to 7000 and would cam it to make peak power 6100-6200 rpm. That would give you a really really broad torque curve from about 3500 rpm up. Gear that with a TKO II and 4.10s and you would have useable gearing to stay in your power band from 20mph all the way up to 160.