Thinking out loud - 1911, Found my deck height. All good? |
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Thinking out loud - 1911, Found my deck height. All good? |
jaredmcginness |
Jul 4 2020, 10:03 AM
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#1
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... Group: Members Posts: 502 Joined: 12-June 19 From: Baltimore Member No.: 23,209 Region Association: MidAtlantic Region |
See update and actual numbers on the added reply.
Sorry for the novel!! Hey guys, I'm building a 1911. I want to make sure that I have my thoughts in the right place. -96 Bore x 66 stroke. Fresh rebuilt 1.7 heads with a 105mm fly cut register. Stock valves -Running a .495 lift cam, lifters to match, HD springs + counter bore .630 (IIRC) extended. I need to CC my heads first, get the volume, then determine my deck height and compression ratio? Stock 1.7 heads are 50cc. I assume mine will end up a tad larger, maybe 52cc. (will the fly cut alter the size?) But I might be off. Is 8.5:1 a good target ratio? Ive read a few threads and this seems to be the middle ground compression. A good target DH is .045-.065? With a minimum of 0.040 to avoid contact. A few examples - per a CR calculator: 50cc, 0.065 = 8.7:1 50cc, 0.045 = 9.2:1 53cc, 0.065 = 8.4:1 53cc, 0.045 = 8.8:1 This in mind, depending on my head volume it should be easy to narrow down where I need to be. Am I on the right track? New to this and been digging into some old books. Whats a good compression ratio, that should be safe for a mild carbed (dual 36) motor and mild cam. Want this thing to last more than a summer! I dont really have a target CR, because I dont know the difference of a few decimal points! Happy 4th (IMG:style_emoticons/default/beerchug.gif) ! |
jaredmcginness |
Aug 1 2020, 08:33 AM
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#2
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... Group: Members Posts: 502 Joined: 12-June 19 From: Baltimore Member No.: 23,209 Region Association: MidAtlantic Region |
Hey guys,
To update this, I just CC’d my heads and got the deck height numbers, does this all check out? Target CR 8.5:1. 96x66 1911 -Heads CC’d at 49.5. Let’s call it 50cc. -Deck Height came out to .076 -No shim -Calculated CR = 8.6:1 This sounds like a decent and safe bump. Is my desk height too high? Seems reasonable, but I know 0.045 is a solid target. Not looking for a high compression build. Just a strong cruiser. Thanks! |
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