Originally Posted by 460Fairmont
The plug on the left looks like it was cross threaded when it was installed and whoever did it just did it up anyway, that would have chewed the thread in the head aswell.
I put all the plugs in originally, and it was definately not cross threaded.
Originally Posted by johnbays
I am not sure whether you mean 20,000km oe 20km but either way you have a problem with no.3 cylinder. How was it idling and running?
Sorry, I meant 20,000 kays. Only in the past two weeks has it begin to miss on the odd ocasion at idle, and then maybe 3 or 4 misses during a 80km run down the freeway. When it wasn't missing it was running perfectly, was making pretty good power infact. Timing has been set at around 5-10'BTDC.
Did you check idle speed drop on disconnecting each cyl and compare them?
The idle normally sits right on 800rpm. When missing it would jump between 600 and 700. I didn't record or write them down as such, but noted a difference as I disconnected each plug, certainly less than 600 for all the cylinders but number 3. As expected cylinder 3 didn't result in as much RPM drop compared to the other cylinders (as it was missing anyway) and was around 600. Hope that makes sense.
Have you done a compression check?
Not as yet, will do that later today.
How is the water in the radiator? Cyl head Gasket OK?
This was my initial worry. I've blown two headgasgets in my other engine and drove it for around 10,000 kays with it the 2nd time. It was so bad that if I let it sit for long enough, enough water/coolant would enter the cylinder and cause hydraulic lock and wouldn't turn over unless I first took the offending cylinders plug out. Yet after all that the plugs were still perfect, infact they are the plugs I've put back in this engine for the time being and its running perfect right now.
This engine has moly chrome rings and an o-ringed block, so I would hope
its almost impossible to blow a headgasget under normal operation like it has been used.
Checked resistance on spark plug leads? Are they all within spec?
Yeah, I measured the resistance of both the old leads and the new ones I put on (about a week ago, a week after it started missing). Interestingly the new leads (Champion Red leads) had around double the resitance compared to the ones that have been on there for the 20,000 kays (Bosch Super Sports), but both sets were consistant.