 Race engine piston to cyclinder clearance, How much is too little? |
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| Driver174 |
 Jun 17 2018, 11:07 AM
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#1
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Member  Group: Members Posts: 106 Joined: 2-February 17 From: Nevada Member No.: 20,806 Region Association: None 
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914-4 2.0L approx. 10.5:1, JE forged 2618 Aluminum pistons, Web 163/86b cam
JE clearance guidlines say to set clearance to .0035" along with a note "some applications may require more clearance". I had cyclinders bored 0.75 mm oversize with piston clearance of 0.0035", but am having second thoughts; maybe should of increased clearance to .0045. Engine will see road racing conditions, so will get run hard for 20-30 minutes or more during each race. Should I increase the piston clearance? I'm assembling the engine now so it's not too late to address. Thanks, Jim |
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| Driver174 |
Jun 19 2018, 12:19 PM
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#2
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Member Group: Members Posts: 106 Joined: 2-February 17 From: Nevada Member No.: 20,806 Region Association: None
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Any thoughts before I assemble this engine? I checked the clearance of each piston/bore, and am going to put largest of .0038” in # 3 position.
Thanks again, |
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| ChrisFoley |
Jun 20 2018, 06:39 AM
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#3
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I am Tangerine Racing Group: Members Posts: 7,909 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None
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Probably not too many engine builders looking in this forum on a regular basis, Jim.
I bet you would get some opinions if you posted the same topic in the Garage. |
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| wndsrfr |
Jun 20 2018, 07:57 AM
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#4
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Senior Member Group: Members Posts: 1,428 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region
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Len Hoffman...(HAM inc.)...advised me when I put JE's in my 2316....I advise you to PM him before you increase that clearance.....as I recall he said not to exceed .0025", so you're maybe past that already....
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| Krieger |
Jun 20 2018, 11:23 PM
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#5
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Advanced Member Group: Members Posts: 4,702 Joined: 24-May 04 From: Santa Rosa CA Member No.: 2,104 Region Association: None
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FWIW, I just finished building a 911 six. I used Wayne Dempsey's engine build book a he recommends 1.5mm clearance for intake and 2.0mm for exhaust.
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