I have an '81 with the original engine (and I know it has original internals, except the cam).  I am laying plans bulking up the power output later this year.  Can anyone tell me if the factory pistons with be flat, partially dished (on the side of the combustion chamber) or fully dished?  If the latter, it would not have enough "quench" to optimize fuel mixing and atomization, so I might be looking at adding new pistons as well...  Thanks for any help.

I'd be willing to bet that both (the L-48 or the L-82) engines had dished pistons in '81. GM couldn't get a high comp. engine to pass emissions back then, so they had to go with no-compression I'd go ahead and plan on a set-o-mashers, if you're looking to pump it up.

I'd say dish as well.  As far as needing pistons well that depends if you plan on keeping your current heads.  There are some aftermarket heads out that are 54 or 58 cc.  If you have 76cc heads thats a 20 cc swing and that is a bunch.  20 cc is usually worth around 1.5 to 2 points of compression.

You want to keep two things in mind when doing your engine.  What type of fuel you want to run and is it widely available.  If you build an engine to run on 93 you might not be able to get it everywhere, and with today's increasing fuel costs you might not want to pay for 93 all the time.

 

regardless of whether they are dish or not..  you will probably need to replace them when you clean up the bores.. 

that 24 yr old engine will probably need to go .030 over anyway..

If you visit the website www.corvettefaq.com there is a fasinating article about achieving 400 plus hp from a 350 crate motor with flat top pistons and low compression. They performed a number of mods that did not require touching the bottom end at all. It is an 8 part article that is linked directly to the site above. The best part is the motor still runs on 92 octane pump gas.

It is great reading and might give you some great insite. They used all over the counter bolt on parts with almost no machine work to keep the costs down.

Have fun!

 

Bill