Or are they just for high rpm horsepower? Would stock manifolds be better to maximize low rpm torque than headers?
As much trouble as headers are (especially to install in a big car), I think you're better off staying with manifolds.
Bucket of worms. Headers provide great flow, but don't dampen noise like cast iron does. They also flow enough that you will need to re-jet your carburetor for good low-end performance. What do you want from your car? Small tube headers may provide what you want, to a point. You are going to have to wait for more answers and ask more questions before you get to where you need to be in terms of information.
I cant find anybody or any threads where someone has tried to build the 350 specifically for low rpm torque 0-60 runs. It has a long stroke but there is just no interest it seems. Id like to see 450 torque at 2400 rpm and hp at whateer it ends up at. So far I have learned that smaller passageways and higher air flow velocity makes low rpm torque along with long stroke and high vacuum. high lift short duration. Everything just the opposite of high rpm hp engines. but would automatic or manual trans be better for low end torque to the rear wheels?
You want something similar to Steve Caruso's setup. Although he still runs cast iron exhaust manifolds due to class restrictions he still makes great power. If you used headers and a slightly higher stall and jet/rework carb I'm sure you can get a strong setup.a deep gear in rear will help too.
With the cubes limited to 350 CID the best way to get increased off the line acceleration is with a better gear ratio in the rear end. The stock camshaft and engine setup is pretty good for low RPM torque and there is not too much you can do to increase the low RPM torque except for some very careful head porting, high compression ratio, and a custom cam. If it were me and this was my goal to get the heavy car quick from a stop to 60 then I would use a 4.11 gear with a good possi unit, 200R4 trans, and stock engine. If I still wanted more I would raise the compression to about 10.5:1, use a custom camshaft, and wait for the new TA heads as they will give gains all across the board I am sure. A spread bore carb (Q jet) is better than the square bore (holley) for fuel mileage but the holley has better part throttle power due to the larger primaries... I found the 2 barrel carb setup better in the low RPM than the 4 barrel Q jet for this same reason... Headers will help almost the whole RPM range I would be willing to bet, how much though is dependent on too many variable to predict. For the auto vs manual trans I would give the money to the auto trans on getting the power to the tires smoother. With a good torque converter you can get extra torque multiplication and low slip % so it is the best of both worlds. Also with a lockup converter you can have 100% lockup on the highway even with a high stall converter.
I remember you Gary, you want to build a daily driver sbb 350 and try to get better mpg. Why don't you just ask that? There is a thread where a guy is building a sbb for a jeep with nothing but low end torque as his goal. He actually found a crower level 1 cam on ebay that he is going to use for his build.(the level 1 is no longer available) So yes people do build them that way. A better way to go would be with good flowing heads with the cam as the limiting factor(like the LS engines do it). If your budget is big enough for a set of the new TA aluminum heads and a TA dual plane intake(the single plane would be fine if you plan on running EFI of some sort) you can build a great low end torque cruiser. Even with cast iron factory heads you could still do a sbb 350 torque engine. A custom roller cam would be the way to go to get you close to your 450 lbs ft goal, good flowing heads will also help. A custom roller cam with around 192* duration @ .050" intake and 208* duration @ .050" exhaust with a more aggressive ramp rate that can be had with a roller with a .525 + lift on something like a 116 lobe separation should be great for low end tire shredding torque. :TU: Cam specs off the top of my head, but should be close to what you are looking for. A cam like this and good flowing heads and a lighter rotating assembly and 9:1 to 9.5:1 compression(depending on what heads you have should get you close to your goal. A shop that grinds custom cams could get you closer to the exact specs you would need with flow numbers of heads, compression ratio, vehicle weight, trans type and rear gear ratio.(I would need that info also to dial in those specs) The heads are important that they flow well so the cylinders can fill faster and more efficiently at lower RPM with the custom cam so you could reach your goal. Headers and dual ex. would be needed as well but smaller tube headers like the 1 5/8 diameter with a 2 1/2 dual system. And actually manual transmissions take less power from the engine than an automatic, but a auto O/D trans with a lockup converter is a good way to go as well.(whatever you prefer auto or manual can make your goal) The 65 Impala below in my signature has headers, and a roller cam that has .550" int. and .546 ex. lift, it has 202* int. and 212* ex. duration @ .050" with 113 lsa. That cam spins the tires(275-60-R15 drag radials) in second gear of the 700R4 from a dead stop with only a 3.07:1 rear gear ratio, when they are aired up all the way on the street not at the strip. And to top it off I get around 25 miles per gallon on the freeway with it! I never could understand putting a huge cam in an engine just because "I like the way it sounds when its idling". Bigger isn't always better because that "little cam" gets me across the finish line at the quarter mile track in a 4,500 lb car with me in it in 13.26 seconds @ 102 mph.(best run to date) I should be in the 12s when I lighten the car by around 300 lbs when I replace the repaired frame that has around 300 to 400 lbs of angle iron welded to the frame.(I have a frame already, just have to make the time to install it!) GL Derek
The biggest low end torque gain is from the cam and as you stated short duration combined with high lift. One of the parameters for low end torque is the early closing intake valve. The not so obvious is the high lift and it relation to low end torque and that has to do with creating higher port velocity. The object is to transfer the kinetic energy from the piston to the air charge in the intake system. The 350 piston has it's max velocity at 74.8* before and after TDC. The goal is to get the curtain area that is under the head of the intake valve at some lift point to at least equal the smallest cross sectional area of the intake port by the time the piston is at max velocity. In other words the intake valve is lifted high enough so it is not the main restriction to flow at the time the piston is at it's highest velocity. On a stock 350 head that is around .380" intake valve lift. With the stock cam at .400" lift that puts the 380" lift point after 100* ATDC where the piston is slowing down. As an example, If the valve lift is just increased to .450", the .380" lift point is moved much closer to the max piston velocity point at 74.8* ATDC and the velocity in the intake system is increased. A roller cam would allow even higher ramp rates. Combine that with long tube small diameter headers and head work that increases flow without increasing the cross sectional area of the port and you should have plenty of low end torque. Then add a high helix roots or a twin screw supercharger and ....
As you can see with the below simulator dyno info the stock 350 would gain a ton of torque with a roller cam and this one is not optimized for low RPM torque it is more of a best of both worlds street cam. I sold this to a member but it may be available as he never used it and it is still new with lifters etc. About 370 hp @5500 rpms and 400 ft of tq About 440 hp @6000 rpms and 440 ft of tq About 450 hp @ 5500 rpms and 460 ft of tq, a gain of about 10 hp and 20 ft of tq. over build #2
I thought you might show up and tell him what I was trying to say.:Brow: LOL! Its like you're in my head.:grin: Hey Paul, always enjoy reading your posts, nice info right there.:TU: I mentioned a higher lift because I recommended ported heads or wait for the TA aluminum heads. And the importance of having the head's flow mapped out to help the cam designer design a better cam. I was also thinking that some added stroke along with some added bore would also help out quite a bit as well. Doing a 370 stroker is fairly easy with a sbb with a set of nascar take out rods and a set of AutoTec pistons. External balancing would be ok with a build like this because 6,000 RPM would probably be about maxed out and beyond the power band. This would be a SWEET street build!:eek2: Derek
If you wait for the new heads, they should be closed chamber design so you can zero deck the pistons and have an effective squish area which will allow a higher compression ratio before detonation.
Yeah, wish TA wasn't so tight lipped on chamber CC and design, there would probably be more people building 350s to be ready to buy the heads when they're done.o No: Derek
Mike told me today that the CC will be close to stock as we predicted but they will let us know more soon as the head development goes forward.
So what do you think, about 60cc? I think around 60cc - 64cc would be better if it is a closed chamber design so zeroed deck flat top pistons with 2 valve reliefs can be used without being a million to one compression. Would be around 10.3(64cc) to 10.8(60cc) to one with zero deck flat tops. Ideally if they machined the cambers they could offer different chamber cc from 50cc as cast to maybe up to 68cc machined? Seeing how we only have one shot at aluminum sbb heads. I still think a stage 2 exhaust port design would be the way to go though, even with a sbc port and bolt pattern so sbc headers would fit. Would be great for making low end torque and high end HP.(wanted to be relevant to the original posters post) :Brow: Derek
Looking at it from a broad perspective they will want to keep the CC between 50 and 65 so that people can bolt them onto their engines without requiring a different piston to be used. Ideally it will be a closed chamber head so that we have some quench, however this is up to TA and whomever is helping them develop the heads. I think we are just going to have to wait and see how it works out however we know we can mill the heads to lower the CC so it would be a pretty safe bet to build an engine for a 50 CC head. I know what you mean about the larger than stock CC being better so that we could zero deck a flat top piston but I do not see it happening. I am pretty sure we will need a dish in the piston to keep the compression ratio down. The key will be the quench pad on the piston to match the closed part of the head, if it is indeed a closed chamber head... There really is so much we do not know yet about the 350 heads, but I am just thankful we are getting them and letting TA do their thing... I trust they will work great, but like you said it would be nice to know how to order pistons.... I am going to take a chance and do my best to get the right pistons in my engine now ahead of time and go from there.
I just had a brainstorm, if TA made the heads so they can be made both ways stage 1 exhaust and with a little extra machining make them stage 2 exhaust, that would be great! Making them closed chambered they could come out with a new line of pistons, flat tops, domed and inverted dome. Instead of dished, deeper dished or v6 flat tops. LOL Derek
You got of a lot of bla bla bla here with no answer. 1 5/8 headers will work good and give you about 10-20 more horse and more torque. Put on a X-Pipe and 2 1/2 with duals. Get a flange kit just before the mufflers then you can drop the whole system off the car between the headers and the mufflers if you have to drop the trans. Headers always help.
Like anything else you have to properly tune the combination. If you are building for torque, you won't have higher RPM capability so the gain of the headers would be very minor to low end power. You would need to have something custom made with very small tube diameter. Off the shelf header offerings are very few options. Usually Sean's right on but would advise against the low gearing. Torque engines love taller gears. The 4.10s would make the car feel like it has more torque but overall drivability (highway use) would suffer too much. More compression is a good thing for torque, just don't go to the point you have to run race fuel as it will limit the fun you have with the car. Get a true 9.5 to 1 compression, Crower level 2 cam, leave the ports and valves stock, Q-jet, iron manifolds, stock or LOW rpm stall converter, and you are all set.
