Page 1 of 1
compression test P 6..??
Posted: Wed Apr 04, 2012 11:06 am
by RICCO the TRIKE
hi guys ..
doing a compresion test on my P6.......
what readings should I expect..????
TA ...
Re: compression test P 6..??
Posted: Wed Apr 04, 2012 3:01 pm
by DaveEFI
RICCO the TRIKE wrote:hi guys ..
doing a compresion test on my P6.......
what readings should I expect..????
TA ...
The quoted figures are only a guide as there are so many variables. What you do look for is them all being within 10% or so.
compression test P6
Posted: Thu Apr 05, 2012 2:14 pm
by RICCO the TRIKE
ok .....
so would this be ok
psi ....50 50 50 30 50 30 30 50.......
or should they be higher ???
Posted: Thu Apr 05, 2012 2:27 pm
by kiwicar
Not really because three of them are 40% below the others. . .
Without knowing static compression and cam timing figures it is hard to say beyond that, however assuming hat we are not looking at an 8.13:1 compression unit that someone has fitted a 300 degree advertised duration cam to I would say they are all pretty low. I would expect 75 to 130 PSI range, but that is real finger in the air stuff with no motor specs.
Put a squirt of oil dowm each bore and try again noting the new numbers against the figures just posted. If they increase on average more than 50% or any one increases by 100% then I would say with some confidence it needs a rebore and re-ring minimum and really a rebuild would be a good idea.
Actually as it is a P6 would you not be better off just looking for a 3.9 lump to rebuild?
Best regards
Mike
Re: compression test P6
Posted: Thu Apr 05, 2012 2:45 pm
by DaveEFI
RICCO the TRIKE wrote:ok .....
so would this be ok
psi ....50 50 50 30 50 30 30 50.......
or should they be higher ???
It's most unlikely all the compressions will be very low on a running engine. Bores and pistons don't wear out evenly - and valves usually fail individually.
Then there's a question as to how you do the compression test, and how good your tester is, and how fast the engine cranks. If you must have a ball park figure, 130 is it. Slightly higher if an early P6 engine.
Posted: Fri Apr 06, 2012 5:13 pm
by Ian Anderson
When you were doing the compression test did you hold the throttle max open?
If not the engine cannot draw in enough air to make the compression pressure correct!
Ian
Re: compression test P6
Posted: Fri Apr 06, 2012 6:42 pm
by unstable load
DaveEFI wrote: and how fast the engine cranks.
This is important along with the wide open throttle.