I'm thinking about using the ultra light aluminum racing piston's when I have my motor rebuilt, but I was told by someone that I would lose my low end torque because pontiac's are designed for the weight of the stock piston's?Any opinion's?
Light pistons are used in engines that rev up to very high RPMs. These engines usually are not built around low RPM torque. I don't think that piston weight alone would affect the torque made by the motor.
Pistons and rods don't make performance all on their own. Use the pistons - they are fine, but do not use Aluminum rods unless you are going to build a racing-only motor. And I don't mean "sometimes" race. Aluminum rods are replaced about every 250-400 runs, depending on the engine, and I am pretty sure they are not put into road-race cars (Of course, there are always exceptions.) If you are running in a street car, you can use cast rods that are properly set up for as much as 500 HP. Forged rods will take that up to well over 1000 when ground, polished, re-sized and heat treated.
Light pistons and aluminum rods reduce the inertia required to slow down the piston at the end of the stroke and reverse its direction. This allows the motor to spin up to higher RPMs. Most Pontiac heads have to be seriously worked to sustain decent flow in the RPM ranges we are talking about. Round port or E-heads, or some very, VERY well done D port heads ($$$) are required, along with some very serious cam and intake selections. A forged crank would be a very important consideration as well. This motor would have no bottom end torque, and wouldn't start pulling until well into the high 3000-4000 PRM range.
If you are dead set on running Aluminum rods, drop me an e-mail. ( quenton@celesco.com ). I have a set of never-ever used Mickey Thompson forged aluminum rods that I have had for over 20 years. They are still in the original wrappers, but the origianl box is pretty tattered. Years ago I had dreams to build a motor to use them. I had a set of AFR ported Ram Air 4 heads that I was going to use on that motor. Luckily, I never spent the money to build it. Instead, I spent it equally foolishly on a monster 455. I should have spent it on an awesome paint job and a mostly stock 455, and still had enough change to buy another car.
No,I'm not dead set on using them I plan on having a 400 h.o. built for my bird to run in the factory stock drag's.They go by n.h.r.a. rules there's a 68' ram air bird that run's in the race here in mich. that run's low to mid 12's I would like to be able to run with him and still be streetable.So do you think it would warrant me to use the alum. piston's or stay with stock?What about a aluminum flywheel?Now the ram air car is a automatic with 3:90 rear axle,mine being a 4-speed 3:55 rear axle.Any suggestion's?
All pistons are Aluminum - even the stock ones. The question is: Forged or Cast? We could have a good debate about this here ...
I believe that a street motor that is raced occasionally would benefit from forged pistons. There are a lot of folks who feel that some of the modern hypereutectic alloys are great as far as cast pistons are concerned, and will last just as well. Older-style forged pistons are a little noisy while the car warms up, but they are almost indestructable. I don't have any first-hand knowledge of the hyper's. I am sure one of the other guyts here does, though.
A Firebird is too heavy for an Aluminum flywheel. Stick with a steel or iron one. (IMHO)
