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I was with a friend today having been asked about his engine.
It was producing some smoke only on the overrun, this could indicate oil being sucked in when the butterfly is closed.
The other observations that I made. There was good oil feed to the Exhaust cam and therefor the cam box.
There was no visually discernible wear on the cam lobes then even from my fingernail, so I am happy that there are no cam issues.
We decided that a compression test would be a good place to start to try and eliminate possible issues.
I will precis my 66.3 workshop manual following :-
Rated compression 12kg/cm^2 = 170psi
When Compression measures over 12kg/cm^2 150psi ? (not my typo, it's in the book), the head is probably carboned.
When the compression is below 10.5kg/cm^2, valve, piston ring, gasket, head and or cylinder gasket may be leaking.
The results on the starter motor were 165 Rt 150 Lt (Hot, WOT & no Choke).
We then tried the compression tester with the engine running on the opposite cylinder fully opened the throttle and keeping it open as the revs were building to app 6K cut the ignition. Nearly 180psi.
My question is this. What rpm should we run the compression test at? Is it specified at starter motor speed? Kicking over speed? Or indeed, is the value we obtained valid?
Before venturing into the engine there are other things we can look at. The valves need re gapping the exhaust were running at 0.08mm. Just over 0.003" which is 3 times the prescribed and 50% more that we normally run. I did not check the inlet valves as there really was not time and the light was going but I expect that they will be similarly loose.
I can't see this really reducing the compression although I am always willing to learn more.
I will check the Head nuts torque settings, although I can't hear, or see any sign of leak past the head/cylinder gaskets.
I would welcome learned comments
It was producing some smoke only on the overrun, this could indicate oil being sucked in when the butterfly is closed.
The other observations that I made. There was good oil feed to the Exhaust cam and therefor the cam box.
There was no visually discernible wear on the cam lobes then even from my fingernail, so I am happy that there are no cam issues.
We decided that a compression test would be a good place to start to try and eliminate possible issues.
I will precis my 66.3 workshop manual following :-
Rated compression 12kg/cm^2 = 170psi
When Compression measures over 12kg/cm^2 150psi ? (not my typo, it's in the book), the head is probably carboned.
When the compression is below 10.5kg/cm^2, valve, piston ring, gasket, head and or cylinder gasket may be leaking.
The results on the starter motor were 165 Rt 150 Lt (Hot, WOT & no Choke).
We then tried the compression tester with the engine running on the opposite cylinder fully opened the throttle and keeping it open as the revs were building to app 6K cut the ignition. Nearly 180psi.
My question is this. What rpm should we run the compression test at? Is it specified at starter motor speed? Kicking over speed? Or indeed, is the value we obtained valid?
Before venturing into the engine there are other things we can look at. The valves need re gapping the exhaust were running at 0.08mm. Just over 0.003" which is 3 times the prescribed and 50% more that we normally run. I did not check the inlet valves as there really was not time and the light was going but I expect that they will be similarly loose.
I can't see this really reducing the compression although I am always willing to learn more.
I will check the Head nuts torque settings, although I can't hear, or see any sign of leak past the head/cylinder gaskets.
I would welcome learned comments