Did you get my reply to your PM?

John

‘Zero deck’ simply means machining the decks so that they are even with the piston tops.  If using composition head gaskets, then there is some latitude in that you’d need to machine the decks approximately 0.020” just to get the heads where they sit back in the stock location again or they would be sitting that much too high without the machining.  Because of manufacturing variances when these blocks were originally machined, going back and remachining the decks insures that both decks will be at the same heights instead of lopsided or different from side to side and end to end which will then put each piston at the same deck clearance.

Besides machining the decks for a compression ratio increase, they are also machined more for maintaining minimum quench thus reducing the propensity for detonation if the quench area was overly large to begin with.  Domed pistons can push the compression ratio too high for the available pump fuel depending upon the head and piston combination being used.

no I never got a reply, I figured i had messed up and you didn't get my PM.

oh well...computers are nice but sometimes they're a bit frustrating

B

Sorry you didn't get the PM.  Maybe I did something wrong.  Anyway, I basically said the same thing Ted did, and added that I highly recommend doing it.

John

    if you want a "Zero deck height" it would be best to mock up the engine and measure the distance the pistons you are using are down in the hole, then deck accordingly.  Also find out if your machinist is using a surfacer that will square the block and get equal distance from the center line. It's not mandatory but the best way to go. Some guys just copy the old deck and they are not all square.

Paul.  First order of business is insure that all your rods are the same length and the crankshaft has the same stroke on each journal.  But beyond this, then simply dry assemble the shortblock and measure the distance each piston is in the hole at each TDC and have the block decked accordingly.  A short cut is to simply install the same rod and piston in each corner hole and take a deck measurement at each corner and cut the block based on these measurements.  As Tim mentions, very few blocks are ‘square’ on their decks as delivered from the factory so decking also helps to fix this.

The block is now at a deck height of 9.751"

Well, I'm still figuring out how to insert the image and have it show properly. Here's the executive summary; The outside corner by the number 8 cylinder was at 9.784", the opposite corner, inside #4, was 9.753", and the whole thing was ugly all over.