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compression test 113"

   
Old Dec 30, 2010 | 12:54 PM
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Default compression test 113"
About to do a compression test. Have a SE 113" kit. MVA heads, 4.060 cylinders, 10.5:1 pistons, 266 e cams. What PSI should I be seeing ?
 
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Old Dec 30, 2010 | 01:00 PM
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you can run the scenarios on big boyz website. They have a calculator in there that will give it to you. You will also need to know what year heads cc'd at.
 
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Old Dec 30, 2010 | 02:08 PM
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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.
 
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Old Dec 30, 2010 | 03:03 PM
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Originally Posted by leeinmemphis
you can run the scenarios on big boyz website. They have a calculator in there that will give it to you. You will also need to know what year heads cc'd at.

+ 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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Old Jan 3, 2011 | 02:21 PM
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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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Old Jan 3, 2011 | 05:14 PM
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I would be looking at installing compression releases. That seems like alot of compression. not a bad thing but you'll kill your battery quick.

Have you done anything with the crank shaft ?
 
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Old Jan 3, 2011 | 06:49 PM
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Have ACR's turns over fine.
 
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Old Jan 3, 2011 | 06:54 PM
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Creep, didnt this motor melt down?
 
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Old Jan 3, 2011 | 08:16 PM
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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
 
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Old Jan 3, 2011 | 08:22 PM
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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?
 
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