Acceptable engine compression? 86" 2.0l

Mmmm, still chasing a persistent miss. It seems to be in cylinder #1 as it does not change when the lead is removed from this spark plug when idling. Removing all others increases the miss. The miss stays with a new spark plug installed. The spark seems as strong as the others when arcing to the motor. It has near new copper leads. I reset the leads into the dizzy cap last night with no real improvement. The compression on cylinder #1 is still 110 as tested previously.

The motor is a siamese bore 2.0l. I am wondering if I have a leak at the head gasket between cylinders 1 & 2? I don't know why it would affect cylinder #1 more though unless the firing order has something to do with it?

I would like to take it for a blast down the road to clean it out but it is not registered yet. It seems glugged up from slow running all of the time....

When you turn over the engine with the crank handle, does the compression feel and sound the same on all four cylinders ?
.W.

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Originally Posted by B.S.F.

When you turn over the engine with the crank handle, does the compression feel and sound the same on all four cylinders ?
.W.

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Hi B.S.F.,
Ha I surprise myself sometimes. I managed to walk out to the shed and locate the crank handle straight away in the spares pile of bits....
No there is no perceptible change in compression between the four compression strokes when turning with the crank handle.

Thanks for your feedback though. It is much appreciated.
Cheers,
Chris

You mentioned valve clearances are ok .Maybe check valve lift particularly inlet valve.possible cam lobe wear? Bent pushrod etc .

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Originally Posted by theelms66

You mentioned valve clearances are ok .Maybe check valve lift particularly inlet valve.possible cam lobe wear? Bent pushrod etc .

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Re a bent pushrod, wouldn't that be taken up with adjustment to the tappet clearances?

Apart from inspecting the cam lobes, how can you measure valve lift?

Dial indicator on top of valve or rocker arm . Amount not so critical i guess as long as it is the same as 2 3 and 4

If there is even compression, it is difficult to see what could cause a miss in one cylinder at idle other than the suggested cam wear or, possibly more likely, an ignition issue*. Have a close look at the distributor cap and, if using the original spark plug covers, try swapping the one on the suspect cylinder to another cylinder. Another possible issue is wear on the distributor spindle allowing the shaft to wobble, possibly worn so it affects mainly one cylinder.

*Another possibility - a very slight leak on the manifold gasket affecting mainly that cylinder. Put some light oil on the joint between the manifold and the head while idling - it should stop the miss and/or show up in the exhaust.

Have you removed the radiator cap and checked for air bubbles at idle? (after the thermostat opened ,if there is still one fitted). Being a Siamese engine it could still have a sheet metal head gasket fitted, but I don't see how that would make a difference unless it's damaged, but the same could happen with a later gasket. The leak doesn't necessarily have to be from cylinder to cylinder.
.W.

Well I do feel like a bit of a doofus. I realised that the thing I had not changed back to check is the new dizzy cap I had installed a year ago. Transfer the plug connectors back on to the old leads and cap and it fires up beautifully.

A mystery solved. At least I know a bit more about the engine condition. An engine rebuild is on the radar soon but will see how it behaves in the short term...

A great result. I know exactly how you feel. The only time I had a problem with my engine was after I installed a brand new rotor arm that after half an hour developed a short to the shaft. Of course that was the last thing I checked, I never expected a brand new part to fail..W.