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) ! |
nditiz1 |
Aug 1 2020, 09:44 AM
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#2
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Senior Member Group: Members Posts: 1,177 Joined: 26-May 15 From: Mount Airy, Maryland Member No.: 18,763 Region Association: MidAtlantic Region |
I calculated 8.5:1 via CB performances website. Other than that it looks good. I'm not sure what higher deck height does other than give you more clearance to drop down. Someone with better engine knowledge can chime in. I just know you don't want to go too low especially with flat top pistons. I think the min on flat top is somewhere around .036 in.
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