theblur98ss

iTrader: (71)

Just curious if there's any up/downside to lowering compression one was or the other. It is better to have a large combustion chamber and solid piston or a dished piston with a smaller chamber....or does it even matter?

67Firebird455

iTrader: (27)

There will be agruing over this, due to "quench" yada yada yada... Technically it's supposed to be better having a flat piston and a larger de-shrouded chamber.

Steve Bryant

iTrader: (1)

What is your CR now?
What do you want to lower your CR to?
What are your plans for the engine?

Thanks,

Steve

Beaflag VonRathburg

iTrader: (176)

Oldie, but goodie

https://ls1tech.com/forums/showthrea...sh#post5749712

theblur98ss

iTrader: (71)

Here's my story in a nutshell. I have a 408 for a turbo project. I currently have 32cc pistons and 72cc heads giving me around 8.3:1 compression. I found a great set of heads for a good price that are 62cc. In my blind half assed guessing it made more sense to have a bigger combustion chamber but wasn't sure. Then new heads would put me right at 9:1 but I just wanted to double check everything.

Websy21

iTrader: (34)

not too sure but I would have left it with the 72cc heads at 8.3 CR myself

hammertime

iTrader: (1)

I've read that the surface area of a small chamber, small dish, combustion volume is less than that of a large chamber, domed piston, combustion volume. That being the case, the combustion event is spread out over a larger area, taking longer to complete, and in some cases requiring greater spark advance. Most people tend to agree this isn't as efficient.

That said, it's far easier to R&R the heads to change the compression than to swap pistons.