Fun with numbers ---->DCR!
06-02-2006, 10:51 AM
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Fun with numbers ---->DCR! I was reading the thread "10.2 too low for 396?" and it inspired me to get more familiar with my engine. When it was built by a local machine shop, they said CR was 10.8:1 and I said "OK" and that was it. I wish I had known more then. But anyway, I downloaded Pat Kelley's calculator and I've been using my cam card and it seems the only value I have left is piston to deck clearence. I dug through old receipts but can't find anything. I know the block wasn't decked and heads weren't supposed to be milled. So I've got 14cc dish pistons with stock 54cc chambers. I also have 5.85" rods. Can anyone help me get close?
06-02-2006, 12:40 PM
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Playing with the static CR, I came up with .029" below the deck for PTD clearence for 10.8:1. Would that be close with stock castings and an undecked block? I wish I had all these specs. 
06-03-2006, 10:08 PM
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OK a second more thorough look at my receipt says "cut deck" so the block has been decked. I thought surely it had been. The question is how much they decked it. The bigger question is how they arrived at 10.8:1 SCR with a decked block????? It's the only number that is unknown.
06-04-2006, 11:37 AM
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If you know everything else but the "deck height" you can figure out how they arrived at the 10.8SCR. Just start playing with the deck height figures in the calculator until you arrive at 10.8.
06-06-2006, 10:15 AM
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Yeah well that's what I did and I got a deck height of .029" which someone mentioned was a factory spec on a good day. So my ultimate conclusion was that if they had decked the block, there was no way they could arrive at a deck height of .029" after they had cut it. That would have made the deck like .040" or something out of the factory and I doubt mine would have been that bad off. I called them and the owner said they usually deck the blocks somewhere between .010" and .015" which sounded better to me. With the deck at .010", my SCR is 11.3:1 and with .015" it comes out to 11.17:1. I'm not sure why they said 10.8:1 cuz using Pat Kelley's calculator, my CR's came out over 11:1. The only value I didn't have was the deck and I got closer with the phone call so I'm gonna say they calculated something wrong. I had all my production numbers and my receipts so I'm more inclined to believe my new values.