grx45

I am trying to calculate the the compression ratio of my 355 chevy gen I small block. I know all the basics like cylinder head size pistons and rotating assembly etc. The piece of information I am missing is if the block was decked or not. Had a bad experience with the machine shop i dealt with and the receipts and paper work on clear on if it was deck or how much it was. Is there a way to measure this with out pulling the motor and taking off the cylinder heads?

watajob

iTrader: (29)

No. And, I'm no expert but, if I understand this correctly, the most important measurement is how far the piston is down the hole at TDC.

1gary

Yep.Your right.A clue if a block was decked is if the numbers stamped on the deck on the passenger side in front of the head are gone,then it was cut.How much can only be told by your machine shop or by removing the head and measuring it.Really just to be told by the machine shop isn't enough.Standard re-builder's pistons have a very poor pin height for performance use.Too far down in the hole that is.Sometimes you can clean off the tops of the pistons,which you would do anyways to measure it,and pick up a part number and size of the top of the pistons.Then trace that number to get from the source getting what pin height they are.SCR's/DCR's and quench are dependent on that.

AlkyIROC

Do your calculations for compression ratio using 0.006" and 0.030" as a deck height. Your final answer should fall between those limits. At least it will give you a ballpark compression ratio range.

cosmick

My first 350 came out weak because my replacement pistons were only 1.54" instead of 1.56", so my deck-down was around 0.045", plus my MrGasket set came with 0.051"-thick head gaskets. That may be a worst-case scenario, but still safer than a decked block with really thin gaskets.

Ingram78

Throw some boost at it! Lol
No, seriously it probly don't have enuff quench for boost to be AS effective.