Demi Jehu

Hiya all, my boyfriend has a sierra sapphire cosworth and it has no compression in Cylinders 1, 2, 3, but 4 has 60psi he has had a full head rebuild, brand new inlet valves, also a new headgasket & Also when the cams are removed the compression comes back on all 4 but was weak. As soon they go in its gone again etc please help he doesn't know what else to try!!

gingerturbo

iTrader: (2)

Best thing I would say is speak the engineer who did the head work, sounds to me like the valves ain't seating but spk to the builder

Toe Knee

iTrader: (2)

Does sound like something's up with what was done with the head if it's only just been refitted.

Best bet as said is speak to whoever did the work and get them to confirm they have lapped the valves in properly when they rebuilt it etc.

Once bought a head that had no compression in one cylinder, the guy gave me a refund and turned out there was a problem with a valve guide that had been replaced.

Quick test when a heads off is turn it upside down and pour petrol or thinners into the combustion chamber, should hold the fluid but if not seating properly will leak out, obviously don't help now its fitted though unless/when it's taken off again.