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Author
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Topic: compression test question
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turbo50
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Member # 6700
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posted
 
 
Will taking a compression reading with the intake manifold off (stock 91 5.0) cause any false readings?
I have honestly never done a compression test without an intake on an engine.
This is cranking compression.
I was getting 140-145 in all cylinders but 5,6,7.
Found blown head gasket and want to slam it back together with a new gasket.
The block and head decks look good and check out good with a straight edge BUT just in case I want to do a compression test after I put the head back on, before I button the rest of the engine back up (install intake, headers etc).
Any input will be appreciated.
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Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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whitelx50
New Member
Member # 6512
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posted
having the intake manifold off will not cause false readings because the intake and exaust valve will be closed.
Posts: 8 | From: Roseville | Registered: Feb 2006
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turbo50
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Member # 6700
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posted
Thanks.
I only ask because in the manual it states to have the butterfly open if carbed and the throttle plate open if EFI. So I was thinking that maybe no intake at all would/will cause some weird readings but it makes entire sense that it wouldnt.
Thanks, again.
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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86BackInBlack
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Member # 5372
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posted
quote:
Originally posted by whitelx50:
having the intake manifold off will not cause false readings because the intake and exaust valve will be closed.
but you have to turn the engine over to do a compression test right ![[Confused]](confused.gif)
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http://i.imgur.com/go1nj.gif
Posts: 1438 | From: san jose | Registered: Feb 2005
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AJBlackGT
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Member # 3936
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posted
quote:
Originally posted by 66backinblack:
quote:
Originally posted by whitelx50:
having the intake manifold off will not cause false readings because the intake and exaust valve will be closed.
but you have to turn the engine over to do a compression test right
Whats that got to do with having the intake on/off
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90 Notch
Posts: 1896 | From: Sacramento | Registered: Dec 2003
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AJBlackGT
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Member # 3936
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posted
quote:
Originally posted by 66backinblack:
becuase if you turn the engine over the valves are gonna open
haha yeah no shit. The compression tester gauge holds the highest reading.
You might be thinking of a leakdown test. In which case you have to make sure the valves are closed.
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90 Notch
Posts: 1896 | From: Sacramento | Registered: Dec 2003
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86BackInBlack
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Member # 5372
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posted
no i was just responding to the other post where the guy said the valves were gonna always be closed. ive done many a compression test on the stang
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http://i.imgur.com/go1nj.gif
Posts: 1438 | From: san jose | Registered: Feb 2005
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lxlaw
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Member # 7547
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posted
quote:
Originally posted by court:
Will taking a compression reading with the intake manifold off (stock 91 5.0) cause any false readings?
I have honestly never done a compression test without an intake on an engine.
This is cranking compression.
I was getting 140-145 in all cylinders but 5,6,7.
Found blown head gasket and want to slam it back together with a new gasket.
The block and head decks look good and check out good with a straight edge BUT just in case I want to do a compression test after I put the head back on, before I button the rest of the engine back up (install intake, headers etc).
Any input will be appreciated.
no it will be fine
Posts: 49 | From: Odem, TX | Registered: Apr 2007
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