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Posted by court (Member # 6700) on :
 
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.
 
Posted by whitelx50 (Member # 6512) on :
 
having the intake manifold off will not cause false readings because the intake and exaust valve will be closed.
 
Posted by court (Member # 6700) on :
 
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.
 
Posted by 66backinblack (Member # 5372) on :
 
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]
 
Posted by AJBlackGT (Member # 3936) on :
 
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 [Confused]
Whats that got to do with having the intake on/off [Confused]
 
Posted by 66backinblack (Member # 5372) on :
 
becuase if you turn the engine over the valves are gonna open
 
Posted by AJBlackGT (Member # 3936) on :
 
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.
 
Posted by 66backinblack (Member # 5372) on :
 
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
 
Posted by lxlaw (Member # 7547) on :
 
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
 




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