compression test 113"
HDF Community Team
Joined: Jun 2006
Posts: 12,763
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From: san antonio
Making a couple of assumptions, like 0.00" deck height; MVA chambers are 98cc per spec; OEM head gasket and pistons are SE 10.5 forged with dome volume of 11.5, you are looking at 10.7 static; 8.9 corrected and 184psi cranking at sea level.
If the assumptions are wrong; the number are wrong.
If the assumptions are wrong; the number are wrong.
Road Master
Joined: Oct 2009
Posts: 892
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From: in the wind
+ 1. I did that and it was real close. I got 180 at 7000 ft from the calculator and when I did the test It was at 174.
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Road Captain
Joined: May 2007
Posts: 648
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From: STRONG ISLAND
ok just finished comp test. front cylinder read 200psi through 5 cranks. rear cylinder first and second crank read 210psi then as battery startted to die dropped to 200psi. front plug was clean, rear plug had a lilttle oil on it. So where am I at right now?
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Road Captain
Joined: May 2007
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From: STRONG ISLAND
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Road Captain
Joined: May 2007
Posts: 648
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From: STRONG ISLAND
Oil went missing, fried rockers, one lifter was bad ( maybe unrelated ), but definetly oil depravation fried rockers. havent taken it apart yet. But builder said I had wear in cylinders thats why I did compression test. figured I would have lost some. Will no for sure what cylinders look like this week after tear down
Unofficial HDF Chaplain
Joined: Dec 2009
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From: san diego
what are you trying to diagnose? comp should be within 10% of each other, first of all, dramitic change indicates a problem. low comp,(100- 125, with those pistons) is an issue. too many varibles to compression, mileage, oil consumption, cam timing, excessive carbon deposits, again, why the test?