Originally Posted by 0trbo4myCHEVUICK
Went to the machine shop today and talked to the guy. He got in his book and said that with the pistons .025 in the hole I would be at 9:7 compression with a 58cc head. He doesent believe me about the pistons being .038 in the hole. He wants me to bring the block up there tomorrow morning so he can measure with his dial caliper. We will see what happens but man im still nervous about tearing the thing apart. Not only because of the labor but because It would be so hard to not change parts and that gets me into more money. I was perfectly on my pre-determined 3000 budget for the entire build. Decking the block only costs 100 bucks if I can handle tearing it down and not digging too deep into my pockets for upgrades. I know my pistons suck and I would like a steel crank but probably arp bolts would be the only thing I do..
If I was in the shoes of your machinist, I might
doubt those numbers, too.
The reason is the deck from the factory is supposed to be 9.025", give or take a thou or two. Rebuilder pistons are 0.020" 'shorter' in compression height (deeper in the hole) than stock production pistons.
So he's expecting to see either 0.025" in the hole- uncut deck and stock compression height pistons,
0.045" in the hole- uncut deck and rebuilder pistons (0.025" deck plus 0.020 compression height difference).
BUT! It's entirely possible to be exactly what you say it is. One way to end up at 0.038" in the hole is rebuilder pistons and the deck cut about 0.007". You can look at the deck and tell if it's been machined other than by the factory. One clue is if the suffix code is very shallow or missing altogether- if the block was decked 0.007", the suffix would definitely show it.