compression failure?

[novaexplod]

my car is only firing on 3 cylinders and rattling like fook when idling, i thort it mite just be a fooked spark plug or lead but ive checked them all n they seem alrite, ive bin told it could be compression failure at the cylinder head, is this true? cheers

[nova_rally]

Sounds like a broken rocker.

[novaexplod]

is that difficult to replace? cost?

[johnny27]

its possible but difficult to replace ONE rocker with the cam carrier with cam still on the engine. Rocker should'nt be more than a couple of quid. Just remember to put the collets back on they've probaly fallen off to. Happened to me when i was replacing cam and head on my nova, its alot of messing trying to get the rocker back on, have'nt much room with the cam but it can be done.

[oggy]

hi mate my engine did that and it failed its MOT for it due to emissions
all it woz the inlet manifold gasket seal had gone and then it ran sweet as a nut after that, just cheak the seal for any cracks at all

[Philsutton]

could be a few things, melted piston? Had a 20xe that did that, the rattling was bits of the piston rattling round in the cylinder.

[johnny27]

Check the brass rods in the distrubtor cap first to see if they're intact. Have you tried the sparkplugs out and laid against an earth to make sure they're firing? It should be a nice blue spark, anything else like red then the cyclinder would fire very poorly or not at all. I suppose if the compression was very badly gone, you could just hold your finger on the sparkplug hole to feel the pressure it would either be alot or very little as the cyclinder should fire a fair bit with low compression, and you said its not firing at all, try comparing it with the other 3 cycinders. Or just get someone you know with a compression tester.