Hoping some of you guys can shed some light on a problem I've got with the engine in my Sprint and just can't seem to resolve
It's a 1.7 8 valve unit with hydraulic valve lifters.
Basically the engine idles like a bag of spanners and I've got a strange popping noise coming out of the barrel on number 3 cylinder which is most noticeable at idle. However I only discovered tonight that if I pull off number 3 plug lead while the engine's idling, the popping noise goes away completely
First I thought it was a carb issue so I completely rebuilt both with new needles, floats, seals, gaskets and main jets. Float heights set properly and the ignition timing is spot on. Tried messing about with the idle mixture settings but that didn't make any difference either. All jets are correct spec for this engine
On the go the engine pulls really strongly and there's no issues with exhaust smoke. I've compression tested it several times and I'm getting even readings of around 190 lbs in every cylinder. The plugs aren't sooted up and look as they should do in a healthy engine but at idle the engine feels like it's running on 2 cylinders
Now on the basis that this popping noise disappears when you remove the plug lead I'm now thinking that I might have a sticking hydraulic valve lifter and it's firing with the inlet valve still partly open ? Question is, would I get such a strong compression reading with a sticking valve lifter ?
Unfortunately the cylinder head's got to come off on this engine to get access to the hydraulic lifters which is a bit of a pain but if I thought that it would sort the problem I'd be happy to do it. Just need to convince myself that it's the right way to go
Still think the carbs will need setting up properly to get it idling perfectly but no point taking it to get set up till I resolve the other issue.
Grateful for any constructive input