12:1 Compression

Finallall

Member
Ruggles Stage 1 guide says stock 3.0 flat pistons will give ya 12:1 compression in a stock 3.8. Anyone use them and did you have to modify anything to make it work (cut relief valves in the pistons)?

Thanks.
 
That's a lot of compression for a street motor. Are you planning to make it a track only car? You'd be happier getting the pistons made to get what you're after or you could use the 3.0 rods to get a better ratio and a lighter piston.
 
Well you have a few choices. If you get the 10:1 pistons for the buick 350 you'll have somewhere between 9.5 to 9.8 and it will give you about what you want. Now if you really want a good torque motor then find a set of 3.0 rods and have the pistons made. A little more money but the longer rods will reduce the height of the piston and the legnth gives you a better dwell time at the top and bottom of the travel for better cylinder charge. It will also give you a faster reving engine. Same idea as running a 6" rod in a SBC. If you have the pistons made then you can also have them made so you have them almost to the top of the cylinder for a better squish to reduce detonation and also have them fly cut for valve clearance.
 
Custom pistons cost money. I'm looking for the easy way out. Ultimately I would like the SBC 350 pistons but can't find them in 20 over. Only 30 over and I don't wanna bore the block over again. :frown:
 
Custom pistons cost money. I'm looking for the easy way out. Ultimately I would like the SBC 350 pistons but can't find them in 20 over. Only 30 over and I don't wanna bore the block over again. :frown:

OK, you need to rethink if you want to use a SBC piston. I've been looking for 2 years for one so I can run one in a 4 inch bore 4.1 and it's not available so the 3.8 has a bore of 3.8 inches and there is no one making a "pop" in piston from a Buick to a chevy. the only piston that's even close is a 305 and the PCH just won't work. IT'S A BUICK NOT A CHEVY!! THERE IS NO EASY WAY OUT!! If you want a car that will do everything then stop and sell what you have and get a Honda or Subaru. I'm not trying to be nasty but you need to a great deal of research on the Buick design and relize there is no easy or "cheap" way to go about it. The design is different than anyone else and the closest is not something we will discuss.
 
That's because they stopped making them about 6 months ago. Another way to go about it is to get a standard replacement 3.8 piston and cut .030 off both the block and heads and you'll get more compression. If you want anything other than a stock cast piston now you're going to have them made. No other options any more.
 
Sorry I meant to say Buick 350 pistons in 20 over. Ultimately I would like to have this piston Federal Mogul ZH522P20 - Speed-Pro Hypereutectic Pistons but it's never in stock. O well a 1 point increase in compression will only give you around 10 hp anyway so probably not worth the headache. I think 8.5 CR will be OK.

Hey thsose are the ones I have in my engine. But that was done like five years ago....:D

That sucks that they stopped making them. I wanted to build another 3.8 using the same pistons. :(
 
just save youy money and be patient.... i see N/A stage 2 pistons up for sale all the time... no good to most of these turbo guys, but just right for a hot N/A street motor.

A.j.
 
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