They did a compression test which showed all cylinders within tolerence, but a leakdown test showed the right hand rear cylinder (under the carb that broke) was approx. 20% down.
There is very light smoke on initial start up and if the engine is revved hard, but they advised it has been improving.
Therefore I will try to run her gently for a while in the hope that we have got away without scoring the liner and that the oil seal beds back in completely, which I am told is a real possibility.
I will then have another leakdown test to see if we have any improvements, assuming nothing goes wrong in the mean time.
Trev,,, I knew a leakdown would tell you what the engine was doing. Compression tests are not really very good, but now you know.
I hope the rings will reseal in that cylinder, but after a gas washdown in that cylinder, you may have scored the surface of the ring as the builtup grunge was washed off the sidewalls of the piston and the ring grooves.
But, I think you are doing it right, drive it as you said, and see if the cylinder will seal again. As a final thought, if you find that the cylinder does not seal and an engine rebuild is necessary, before doing that. get the engine hot and run it hard one time as see if the rings will get a grip on the cylinder walls again. At that stage, it can't hurt much. Best Regards, Bob
Many thanks Bob, I think both youand Steve have been right on the money throughout our exchanges and your helpful advice has potentialy saved me a lot of money by not panicking straight away and agreeing to a full rebuild yet.
Trev, My old brain forgot to ask about the leakdown test. The test, if done correctly, WILL show what part of the cylinder is leaking. You can hear the air blowing out the leaking area,,,, Piston rings will blow air into the crankcase and you can hear that at the Crankcase vent, If an intake valve is leaking, you can hear it blow back into the intake or carbs, and same for the exhaust valves,, they will blow air into the exhaust system. At your quoted 20% leakdown, you will hear a fair amount of air moving very easily. Might want to answer this question as another part of your "adventure"
Best,,, Bob
Hello Bob,
I have only just read your last message! The results did not give me that info. unfortunately. I have run the car out a few times and she is smoking only only first start-up and if I rev her hard I get a slight amount. She runs great upto about 50-60 mph, but over that she gets a little rough and seems to misfire.
I have noticed some backfiring when revved but have not had time to do anything yet.
I was advised the spark plug caps are pretty tired and that this could create a misfire - but i don't know if this is true?
Smoking on first startup might be intake valve guides. (guides scored from gas washdown from carbs and or bad valve stem seals..) Misfire trick when you have time. run the car into the backfire condition, shut it down quickly, pull the plugs and see if you have fouled or carbon on the plugs. note which cylinder. Also, old school trick on misfires is to see which exhaust header cylinder tube is cool when the car is running. Old spark plug wires and connectors become brittle or corrode with age and can be high resistance that will cause your problem.Another thought is a good vacuum gauge to check the valve guides. a fast fluxuation of the vacuum gauge needle would be consistant with loose (and leaking air and oil) valve guides. just some more thoughts, keep us posted. regards, Bob
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
Linear Mode
