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What would be a good set of pistons for a 289 with 60 cc combustion chambers that would get the compression ratio at 9.0 to 8.5? Using the calculators it seems it should be flat tops with 5 cc reliefs. It seems that when you look at each brand they always state the comp. much higher. Using the calculator the only measurment i am not sure of is deck clearance. I used .010.

Just wondering what pistons others are using. Not for a race motor but would like 250 to 300 horsepower.
 

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You also have to look at the pin height (distance from top of piston to the center of the wrist pin) since that distance varies with different manufacturers. It is that distance that determines deck clearance (distance piston is below the deck at TDC), Of course, you have to also know your deck height.

Factory deck height for a 289/302 is 8.206". If your block has ever been through a rebuild before, they will generally deck it to square and remove a few thousandths.
289s have a slightly longer rod than a 302. 289s are 5.155 and 302s are 5.090.
The pin height (aka compression height) from the pin to the top of the piston varied between years. 289s and early 302s used a 1.600, 73-76 used 1.605 and 77-up used 1.616.

I went through all of this maddening math when I was searching for a piston for my 351W-based 393W stroker. At the time there was no stroker 'kit' offered that gave me my desired 9.5:1 compression ratio - they went from 8.5:1 and the next step was 10.7:1. I pored over the various manufacturer's websites and found what I wanted. Pin height, pin diameter, bore size, piston dish, etc. It was a lot of work!

You also have to ask yourself what is the intended use of the motor. What grade of gas will you use. Those questions will determine which type of piston you should use-- Cast, Hyper or Forged.

I did some searching on my own - given your parameters, and found several likely choices. Mind you, this was a 'quick and dirty' search and is NOT guaranteed to be 100% error free. Silv-o-lite Hyper 3101H, Sealed Power Z273 cast, and Keith Black KB115 or KB311 hypers look like they will work BUT DON'T TAKE MY WORD FOR IT!!!!
 

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Discussion Starter #3
Comp.jpg Cougrrcj. Yep I am going through the same pain staking math like you did. The Keith Black pistons are the ones i came up with too. Also looks like i got the same #'s you listed so research was good. Check out this web link if i do it right, and the #'s I came up with.

http://www.kb-silvolite.com/calc.php
 
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