So I'm using an onlie compression ratio calculator, instead of my math (Wallace racing). What I don't know if when it asks for deck height I make it .000 or if I make it a negative .035, as the pistion is out of the block that much. In calculating the dome volume, the .500 down is 90 cc. But, in reality, the pistion is actually only .465 down even though the dial indicator says it's .500 down. The difference is 11.7:1 or 13.03:1 and if I miss, I will wreck a set of pistons.

Maybe I should old school it and use my math but I thought the computer was easier.

Which way is it?

Thanks

For the online calculators, use -.035" for the deck height. Also, .500" down is .500" down. You are looking at it backwards. You measured the .500" from the deck, but in reality, the piston is down .535" from TDC.

That is what my math said too, but as I get older I don't trust it much.

That means I have ti mill the domes down a bit.

Thanks

i like this one better.
http://www.diamondracing.net/tools/

So Im not doing well . I have milled about .045 off the piston and yet I still have only removed very little for compression. I'm more than slightly pissed. I would apprciate you looking this over and tell me if im correct or have blown my mind.






Appreciate it.

If your piston is almost 1/2" in the hole, I fail to see why you're doing any machining. And should that measurement be right I'd like to see a picture of the dome on your piston..


You shouldn't have to calculate the dome, it should be on the build sheet, if you don't have it just call the manufacturer and give them the order number.

Your numbers don't jive, can you take pics?

I had to calculate the dome volume because the deck is PLUS .035 out of the hole. Had I measured the head gaskets I would have set it out at .050 and I had the piston maker leave the dome big so I could set the compression ratio where I wanted it. It's a battle trying to convince someone that you want a POSITIVE deck height.

I'm going to go out and re-do my measurements and calculate the C.R. one more time before any more milling.

Trying to sneak up on it because I'm not dure how many thousandants off of a radius equates to what CC I am removeing. Guess I should have paid more attention in school.

Why in the world do you want positive deck height?

Because I am using open chamber W-2 heads. On any O.C. Chrysler head like that they need a positive deck height unless you want to mill the piss out of the heads, making the decks so thin they won't hold a gasket.

I stopped a stroker project because I would need about a 12-14 cc dish, or run a quench of .080 or more.