10.5 to 1 pistons in a 283

[Philip M.]

I am building a 270 horse 283 and I was curious what the experince has been with using 10.5 to 1 pistons instead of the stock 9.5 to1 pistons if you did so did you find it somewhat more powerful did it run hotter did it detonate and ping with bad gas
I have everything to go the correct cam the correct heads and im tempted to up the compression and hopefully burn the gas a little better I wonder about all that carburation and im thinking this could help (maybe not) but the pistons are nearly the same price after all the expense it might be nice to have a little more power im thinking it could create at least 20 more horsepower
thanks to anyone who replys
Philip Mc lachlen member 54904

[George J.]

Re: 10.5 to 1 pistons in a 283

Phil,
You may want to read Duke's presentation which is posted at the top of the Technical Discussion Board. He talks about compression ratios with respect to different engine combinations.

George

[Joe R.]

Re: 10.5 to 1 pistons in a 283

Phillip,

I would recommend carefully reading Duke's fine seminar material (especially slide 9):

https://www.ncrs.org/seminars/tuningseminar.pdf

There is a lot more to setting the compression ratio than just the pistons. You also need to read Duke's article on managing your compression ratio (CR). It was in the Corvette Restorer, but I'm not sure which issue. You may be a new enough member that you didn't get that issue. I have an electronic copy, I will post it or send it to you if Duke says it's OK to do so. I agree with you, you want the CR to be as high as possible to avoid leaving HP on the table. But you also don't want to detonate.

If you want more 10 percent more horsepower and torque, you might want to consider having your heads reworked and flow tested. That'll also buy you a few hundred extra revs. After that, you probably should get your engine dyno tested to verify the results.

Joe

[Gene M.]

Re: 10.5 to 1 pistons in a 283

Philip,
If you have everything at the tolerance limits you may get to 10.5 to 1 compression. Generally with tolerance variations it will be some what less. My estimate is 10 at best. CC the heads and mill to minimum and have pistons flush with the deck and a thin shim gasket are required for max compression ratio. But it will be more than what you take out. Cam selection wil add/subtract compression.