After having spent all weekend whipping the engine out of my rst and then rebuliding and putting the new block in it ran really rough. so we ran a comp test on it and all cylinders were around 9 bar except number 3 wich was not even one.

We think this could be one of two things.

1. Head gasket, which was brand new at rebuild stage and was seated properly.

2. Piston rings, this is the most likely problem i think as there is only a low comp on one bore.

Anyone got any ideas or second opinions?

Cheers

 

To have no compression at all the piston to bore sealing would have to be very poor and even with a damaged headgasket i would expect some compression. Have you had the rockers off? If you have make sure the rectangular washer has been put back under the pivot arm, if its not then the valve will not be seating!