1979 Chevrolet C70 Conversion to OEM Air Conditioning

[C10 - C90 Bill]

If your Detroit did not leak oil, there is something wrong with it !! Lol.

Hopefully it is something minor as mentioned.

Keep those old Detroit's going.

[Airdirect]

In my experience, the 53 series are much less prone to leak oil. The only oil leak I see is a few drops from the blower drain. This only happens when it sits overnight. I have left it idle overnight during cold weather and do not have any drips under it.

[C10 - C90 Bill]

Originally Posted by Airdirect

In my experience, the 53 series are much less prone to leak oil. The only oil leak I see is a few drops from the blower drain. This only happens when it sits overnight. I have left it idle overnight during cold weather and do not have any drips under it.

I'm not sure if the 4-53 or the 4-53T would be different, and I hate to say this, but I learned years ago not to let a 53 Series idle for a long period of time. I know of an oil company that would start their 6-53's early in the morning and they ended up having to rebuild what I believe was the top end on all their trucks. I don't even like my 2-53 to idle long at all, once it has hit operating temperature. I believe it has to do with the effects of low Oil Pressure. How does your Oil Pressure look at a long idle?

[Airdirect]

My oil pressure when hot at a stop light will drop to 5 psi. However during a long idle it will come back to 10 to 12 psi. My uncle was a supervisor in a DD overhaul facility, and he told me that 1.5 psi per 100 RPM was all that was necessary. I have spent the night many times on the road (bench seat) and in cold weather I let it idle all night. However I now have either a broken top ring or a head gasket problem, I have not opened it up yet to see. Will post what I find. I am leaning toward a head gasket. I stopped to have the oil and fuel filters changed at a major truck facility. After installing both primary and secondary fuel filters they could not get it to start. They ran it on ether (two tall cans worth) trying to get it to bleed. I sat in the customer lounge listening to it hammer on ether (they do not let customers into the shop) and was about to die. I got the mechanic's attention and was able to advise him that is was very easy to bleed, he must have a air leak on one or both of the fuel filters. Sure enough the primary filter can was not seated in the groove. Once it was seated the truck started. I have been wondering if that event could have started a head gasket failure.

[Airdirect]

I removed the cylinder head today. It appears that cylinder 2 has started pumping oil, most likely I will replace all pistons and liners, not sure what kits I will go back with. Here are pictures of what I found.

[Airdirect]

More pictures.

[Airdirect]

I have pulled the pistons and liners. The number two piston has a broken top compression ring. I was very fortunate that the broken pieces of the ring exited through the ports into the air box. Was able to recover the missing ring parts. No damage to the head, piston top or valves. The main and connecting rod bearings look almost new.