So my LT-1 has called it quits on me, and now is the time to build the engien I want. For the past 3 years I've been boggling setups in my mind, and I've decided on a FI setup. I've asked this question before, but no one seemed to give me the answer I was looking for. I'm looking to build a block that can support 16-20lbs of boost. Should I go for the 355 forged or 383 forged? Can I achiecve the same power wit hthe boosted 355 over the boosted 383?

 

Your biggest problem will be dropping your compression ratio to support 16-20psi. If you are planning on getting AFR heads with a huge chamber you can do a 383. If you are not going to go with aftermarket heads then you will have to do a 355. With the larger stroke in the 383 it leaves less room for a decent lenth rod and the dish to piston pin distance. The more distance the thicker the piston head the better. With the less piston dish the higher the compression and the less boost you can run, unless you get a larger combustion chamber in the head to make up for it.

Does this make sense??

 

It will come down to the heads, but I'm guessing with the 383 I can make more power with less boost. I don't plan on takign it over 10spi, I just want to make sure it can handle that and plenty more down the road.

 

Good post. But a little clarification. The same pistons WRT ring package and crown design are available for 3.48 and 3.75" strokes. However, it may be necessary to use a short rod with the 3.75" crank to use the piston you want. The problem with pistons really becomes an issue for a stroke longer than 3.75". But as you imply, all else being equal the CR will be higher with the longer stroke. Using typical specification, a 383 will have close to 0.6 higher compression than a 355. With LT1 heads the lowest you are going to get will still be close to 9:1. That's fine for 10psi and pump gas. But will start to be problematic with higher boost.

Rich