Name that part.

Towards the rear of the valve cover on a 258 ci i6, I have a hole. Can someone tell me what fills that hole. Is it a bypass of some sort? It is on the top,about 6 inches from the end of the valve cover on the firewall side. Thank you.

 

Aint that where the breath tube goes?

 

Thats where the pvc valve goes. goes from there to the intake manifold

 

Year? Model?

You need three holes in the valve cover - air in, air out, and oil fill. Filtered air is drawn from the air cleaner, it mixes with the crankcase vapors, and is drawn out through the PCV valve into the manifold, where the air/vapors are burnt with the fuel.

Look at what you've got, and that will tell you what the purpose of the other hole is.

 

On mine, the PCV valve is in that grommet with the hose going to the intake manifold.The front hole gets the breather tube.
Different years have the positions reversed from what I've seen. It's all to the same end. Filtered air in-crankcase fumes out to be burned.

 

Probably the hole in the cover is just for the PCV valve.

If there is a 4th hole in the valve cover, it could be because AMC offered an oil pressure bypass kit for early 199/232/258's with shaft mount rocker arms. There is an oil pressure supply passage in the block that sent oil to the head to lube the rockers and valves if the engine has shaft mount rockers (bridge type stamped steel rockers were fed from hollow pushrods), and this passage had a tendency to clog if regular oil changes were not performed, resulting in inadequate oil pressure to the top, and premature wear of the valvetrain. A kit was offered from AMC that added a couple of fittings and a tubeline that went from the oil filter, entered the top of the valve cover through a drilled hole with a grommet toward the rear of the cover, and entered the top on one of the rocker shaft pedestals to supply oil to the top end.

I had an old book on AMC 6 and V8 performance engines, and there were photos and part numbers of this kit and modification, but I can't find the book or an internet link about it now.

 

The issue and the two repairs that AMC came up with to fix it are referenced here:

http://www.mattsoldcars.com/RestoreAmerican/boltmod.shtml

Quoting from the page:

The problem with the oiling system on these engines lies in the fact that the oil passage leading to the rocker shaft gets reduced to 1/16" where one of the head bolts passes through it. This small passage is actually big enough to get a decent amount of oil to the valve train as long as it is clear. The problem was that not everyone is as diligent about oil changes as we are and the oil available in the 60's was not as stable as it is now. This lead to sludge problems and once that little passage way is plugged up, you get no oil to the valve train. The worst thing about this is that by the time the engine starts making funny noises, the rocker arms, shaft, and valve guides are chewed up.

AMC, most likely annoyed at the results of this problem, issued a TSB (Technical Service Bulletin) on 12/21/1967 detailing how to fix this problem. There were two different fixes authorized by the factory for this. The second fix, which I'm not going to detail, involved running an external oil line to the rocker shaft. This was an extra cost item available under part #8120298. (Note: As of 12/29/1998, one of these is still available. You can find it at http://www.partsvoice.com by searching under Chrysler for part J812029. The other fix was a modification that removed some material from the head bolt that passes through oil the passage.
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Just some AMC 6 cylinder trivia I suppose.

 

Interesting trivia, but that problem/fix only applies to the pre-1971 engines. The 232 used in Jeep trucks and wagons would be affected, but none of the engines used in CJs would.

 

Thanks that helped a lot. I'll fix that problem. I just bought the Jeep. It seems to run a little rough from lack of maintenance.

What problems can be caused by not having the pcv valve on?

Thanks for everyone's help!

 

No PCV means you vent the crankcase vapors to the air. The PCV was the first emissions-related system to be added to cars. Early cars vent the crankcase vapors directly to the air. Make sure there's no big vacuum leak because the PCV hose is not connected to anything.

 

So, it is not especially important that I have a PCV valve, provided the opening to the intake is closed? From that pictures and text the PCV valve is connected to a hose that goes to the intake. Is this correct? So, I need not worry if the intake side is blocked off?

It looks as though the previous owner put a bolt to plug the intake tube connection?

 

Yes, it's connected to manifold vacuum either at the base of the carb or through a manifold fitting.

You can run without it, but your crankcase vapors (oil mist, gasoline from blow-by, any combustion products that get by the rings) will come out ot the top of the engine. Early cars had a special tube that directed the vapors down toward the pavement, and out near the bottom of the oil pan. Having the top of the engine open can't be a good thing, especially in a Jeep where dust and dirt are common. Plus there may be a fire hazard.

I can't say for sure what would happen without it - all modern cars have a PCV valve and it's such a good and benign system, that it does not make sense to delete it... so nobody does. You can run for a while without it, I suppose. If it were mine, I would install a PCV valve as soon as I could.

 

I appreciate that. I will replace it before I drive it. I have almost started from scratch with this Jeep, I have done all the wiring, many body panels, heater vents, some engine work, etc. I'm just getting exhausted, I just need to settle down and do things right. Thanks for the help.