Compression ????
Thread Starter
Staging Lane
Joined: Dec 2005
Posts: 61
Likes: 0
From: reno
Compression ???? Ok so I rebuilt my motor after getting it back from the tuner and getting some low hp numbers. He said check compression and do leak down test ect…. Compression test was at 180lbs all around he said it should be about 210to 220 with my setup... so rebuilt it with new pistins rings bearings ect…
Compression after 100 miles is at 125lbs????? am I missing something?? hear is all my mods the block is a LM4 aluminum 5.3 bored out to 3.908
Stock ls6 crank rods and heads (243) with new head gasket to .45 thicknesses
Mahle pistons flat top with valve reliefs
Patriot gold springs comp Chromalloy push rods stock length
Ms3 cam
Fast 90/90
42LB injectors, SLP oil pump, headers ….
Car runs fine decent power and no strange noises or back fires .Anyone with any suggestions that could explain low compression readings…..
Compression after 100 miles is at 125lbs????? am I missing something?? hear is all my mods the block is a LM4 aluminum 5.3 bored out to 3.908
Stock ls6 crank rods and heads (243) with new head gasket to .45 thicknesses
Mahle pistons flat top with valve reliefs
Patriot gold springs comp Chromalloy push rods stock length
Ms3 cam
Fast 90/90
42LB injectors, SLP oil pump, headers ….
Car runs fine decent power and no strange noises or back fires .Anyone with any suggestions that could explain low compression readings…..
Thread Starter
Staging Lane
Joined: Dec 2005
Posts: 61
Likes: 0
From: reno
I also ran 1.85 rockers on the old setup for a few months then went back to stock... if i slightly bent my intake valves i know I will loose compression but would it back fire run bad???? just trying to find some answers thanks...
Thread Starter
Staging Lane
Joined: Dec 2005
Posts: 61
Likes: 0
From: reno
update.. did a compression test same thing went ahead and did a leak down test and sure enough air coming from intake side
time to pull the heads and change the valves....
looking at valves im sure i will need to do a valve job if i put in 2.02 intake in stock seat and does any one by chance know the part number for stock ls6 valves intake exhaust ? thanx
time to pull the heads and change the valves.... looking at valves im sure i will need to do a valve job if i put in 2.02 intake in stock seat and does any one by chance know the part number for stock ls6 valves intake exhaust ? thanx
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Staging Lane
Joined: Dec 2005
Posts: 61
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From: reno
Still have not pulled off my heads but was doing some research and found that the ls6 valves are 0.023622" longer. Cause of the ls6 cam base circle... I’m wondering if my thinner head gasket and base circle on ms3 cam 7.400 pushrods is holding my valves open slightly… any one think this is possible or had any problem with this before ??? my calculations make my pushrods .030622 to long
Last edited by LSXRX7; Aug 5, 2008 at 03:11 PM.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
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From: BFE
Still have not pulled off my heads but was doing some research and found that the ls6 valves are 0.023622" longer. Cause of the ls6 cam base circle... I’m wondering if my thinner head gasket and base circle on ms3 cam 7.400 pushrods is holding my valves open slightly… any one think this is possible or had any problem with this before ??? my calculations make my pushrods .030622 to long
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From: Orange Park/ Jacksonville, FL
Still have not pulled off my heads but was doing some research and found that the ls6 valves are 0.023622" longer. Cause of the ls6 cam base circle... I’m wondering if my thinner head gasket and base circle on ms3 cam 7.400 pushrods is holding my valves open slightly… any one think this is possible or had any problem with this before ??? my calculations make my pushrods .030622 to long
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From: Was New Orleans, but swam to Baton Rouge
