my car is down on power on the dyno and seems to be a base engine fault.cam timing is correct but compression is low(90psi on a zetec).The engine was refreshed with new rings,head skim and valves reground etc but i stupidly put a good quality oil in and its not allowed the rings to bed in.Any suggestions to get it back to where it should be ?
did you glaze bust the bores
[Edited on 29/8/2009 by westf27]
yep..
If the low compression is even across the cylinders it is very unlikely to be the rings.
First question did you do the compression test with the throttle wide open ? as a closed throttle would exactly fit your results.
If not it is Cam timing or valve lifter/clearance problem.
test done with throttle wide open and its 90/100 across all 4 .valve timing is correct and lifters are hydrolic
Its the force of the burn that pushes the rings out, so all you can do is a few seconds at full power, 10 seconds off to let things settle down and
repeat for a few hours at different engine speeds.
When I did this years ago I drove once around the M25.
Are you sure its leaking past the rings, does it have lots of pressure downstairs, if really bad as you indicate I would have thought on the rolling
road the breathers would have been pumping out smoke when running the car up.
Better to check and double check elsewhere IMHO.
The way to be sure is do a cylinder leak down test, Sealley sell two types but it is easy enough to make your own tester, I made one based on
instructions off the web using a few odd parts off a knackered compressor and a MIG nozzle tip. Only part i bought was a threaded adaptor for the
spark plug hole.
One other thing it could be is tappet jacking best to squeeze down hydraulic tappets before refitting and of course it goes without say only to use
5w/30 oil in a Zetec
Note that the majority of DIY leak down tester plans I have seen are not true leak down testers, since there is no mention of a calibrated orifice to measure the leakage via pressure drop.
quote:
Originally posted by MikeRJ
Note that the majority of DIY leak down tester plans I have seen are not true leak down testers, since there is no mention of a calibrated orifice to measure the leakage via pressure drop.
good link
http://en.wikipedia.org/wiki/Leak-down_tester