Setting deck height for 9:1 compression |
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Setting deck height for 9:1 compression |
Chad911sc |
Dec 11 2024, 04:46 PM
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#1
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Newbie Group: Members Posts: 21 Joined: 24-September 24 From: Florida Member No.: 28,374 Region Association: South East States |
I have my short block built and I’m ready to set my deck height. It’s 96mm bore with stock 71mm factory crank. This is a 2.0 2056 build. I have a Web 86a cam calling for approx 9:1 compression. I have 60cc heads with 3cc valve reliefs on my flat top pistons. If I plug all this into the calculator, I get 8.3:1 for my compression ratio if I set the deck height to .040 inch
After I set up the piston on the rod and bolt down the cylinder to the block, I get .053 inch from the piston to the top of the cylinder. My question is, what is the best way to proceed to get the 9:1 ratio with at least .040 inch total deck height. I am thinking that if I take off 6 total cc’s from the head, that will leave me with 54cc heads with the 3cc valve pocket = total 57cc’s. Bringing me now to the correct 9:1 compression ratio with the .040 inch deck height. If I am in the right ballpark, this means I need to have my heads fly cut….correct?? If this is correct, how do I go about calculating how many thousands of an inch do I need to have removed by the machine shop to remove 6cc from the head? I obviously will need to remove at least .013 inch total deck height get to my .040 goal, and that’s with no shims or head gaskets being used. Thanks for your time, Chad |
Chad911sc |
Dec 16 2024, 02:39 PM
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#2
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Newbie Group: Members Posts: 21 Joined: 24-September 24 From: Florida Member No.: 28,374 Region Association: South East States |
Thanks for all the replies!
Wish I would have seen that Raby video before starting this build. Now I’m leaning on taking it back apart and sending it off to European Motorworks for the suggested work. There is no one I would trust in the Orlando area to do this type of machining on type 4’s. After lapping in those registers of mine, I put the pistons and cylinders on #1 and #2 and rechecked my deck height on both cylinders. They were both at .053 before the lapping and now they both measure in at .050 thousands. So that means I removed a total of .003 from the deck (IMG:style_emoticons/default/mad.gif) itself. After watching the Raby video it seems like that is nothing according to him on the 2.0 case. When I lay the piece of glass on the top of the deck and try to put even my .00015 feeler gauge into any spot on the deck between the glass and the deck surface, it will no fit. That middle spot on the register of the 2.0 is considerably thinner than the 1.7, but if it’s flat after only taking off .003 then I still should be good?? Right? I definitely want to do it right the first time and be done with it. So if I need to break it back apart, I will. So what do you guys think? (IMG:style_emoticons/default/confused24.gif) And just a side note….Thanks again Ian for making those wonderful videos! Without those I wouldn’t have even attempted this build. It’s been a fun journey so far and I’m ready to get her back in the car, but if it takes longer, I’m ok with it. |
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