Chevy 235 L6 Oil Pressure Problem

I have a 1958 Chevy 235 Six Cylinder engine in an old pickup truck. The engine has hydraulic lifters. I was out driving around today. After about 20 miles I stopped and got gas. When I restarted the engine the lifters where very noising. I looked at the oil gauge and zero pressure. I was about a 1.5 miles from home so I decided to run it home. After about a half mile the oil pressure came back up and the lifters settled down. Got home and turned it off. Let it sit for an hour. Restarted and everything seems normal. I am thinking the pressure relief valve on the oil pump stuck open. Anything else I should check? Normal oil pressure is 25 psi which I believe is normal for this engine.

Probably about the only thing that would affect oil pressure on an intermittent basis. I'd keep a close eye on it, maybe flush the crankcase just to be sure. Those have pressure lube to the rods, don't need a lot of pressure, but still watch it.

Couple things to check, sludge build up under the valve cover not letting the oil drain back down. But strange it did it after being shut off...

Other possibility, those came with a fiberboard cam gear. As they fail pieces flake off and get in the oil, get in everything, oil pump, oil screen, relief valve. Might drain the oil, catch it in a clean container, see what's in there. If the gear is failing, it will eventually strip and quit turning the cam. Best to drop the pan and clean everything out if that happens.

I don't know your truck from any other one on the road, so I gotta ask: Has it been well maintained? I've have seen rare cases where there is so much sludge in an engine that the oil will hang up in the valve train area and it won't drain down to the pump. So the pump will eventually run out of oil, suck air and all the oil is right under the valve cover. After it sits awhile, it all drains back to the pan.
But I'm SURE your truck has been well-maintained and that couldn't happen in this case, correct?

(quoted from post at 19:58:05 06/12/15) I don't know your truck from any other one on the road, so I gotta ask: Has it been well maintained? I've have seen rare cases where there is so much sludge in an engine that the oil will hang up in the valve train area and it won't drain down to the pump. So the pump will eventually run out of oil, suck air and all the oil is right under the valve cover. After it sits awhile, it all drains back to the pan.
But I'm SURE your truck has been well-maintained and that couldn't happen in this case, correct?

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ey, the thing is[b:341a087149] 57 [/b:341a087149]years old,..it's bound to develop an itty bitty problem by now :wink:

Might be a toss up on the fiber gear. Truck engines had aluminum gears installed in them.

I had it happen to one ov mine with that engine. It was the hex shaft from the distributor to the oil pump. It had worn the hex in the pump and on the shaft to the point that a little piece of crud caused it to start slipping. I was not going to drive 50 miles with a load and no pressure, so I folded 3 strips of tin can (real steel can) and pounded the shaft back in the hole. It was working when I sold it. Jim

That hex shaft was also a problem on Ford 6 cyl. engines. I carried a replacement shaft right in the vehicle.

I have done some more reading on the 235 hydraulic lifters. A common issue is that air gets sucked up by the oil pump and gets into the lifters. I do have a problem with a lifter making noise. The noise comes a goes. The engine has sat most of the last 25 years so I figured a lifter was sticking and just starting to drive it would get things freed up. I am now thinking that the issue is air and maybe something is wrong with the oil pickup tube. The oil pump in this engine is not submerged in the oil but uses a suction tube. I read that the connection between the tube and the pump can draw in air. I am wondering if the pump got air bound and lost its prime. I am just getting this truck back on the road after a five year frame off restoration. It almost has to be something with the oil pump. I guess if this is my biggest issue to get fixed than it is not too bad. The engine is not original to the truck. The truck is actually a 1947 International KB1. I bought the truck without an engine and it was easier and cheaper to swap the drive train over to Chevy than find and rebuild an International Engine. Plus I love both Chevy and International so now I have a Bow Tie Binder.

Another reason not to buy a chevy

If I am not mistaken, that engine would have dippers on the rods, which are NOT pressure lubricated. I believe that only the mains, rocker shaft, and lifters get oil pressure.

Not hijacking your thread, but on your 235 OHV I6, back when I was a teen, a lot of badmouthing was going around the Ford circuits about Chevys and their Babbit bearings....Mains and rods.

Well, in my quest for information associated with my current off time hobby, I got the Wikipedia on the subject of these engines including the Jimmy 270 which was popular with a split exhaust manifold and dual glass pack mufflers and pipes.

Anyway I know that rod and main bearings are copper with a layer of "Babbit" but the distinction between what we do with the metal today, and Ford and others apparently did back then, was to put it in a removable shim.....the insert, whereas GM cast it into the engine block and cap for mains or rod bearing surface for connecting rods. This required a shim, copper as I recall, to be inserted between the crank and rod if wear wore the gap out of acceptable tolerance.....had heard of people using shoe tongue leather for the purpose.

Anyhew I learned something. Another thing I learned was that the I6 was an inherently balanced and smoothest engine design without special tweaking to neutralize the natural occurring harmonics. Said it was one reason for it's popularity. If you have time and are curious, lot of great info online at that site.

The original post states that the engine is a 1958 model year.

There were quite a few changes in the engine from when it first came out with Babbitt mains and splash oil system. The original engine wasn't much more than a bored out 216. By 1955 they had changed to full pressure oil system with bearing inserts for both mains and rods.

Thanks, my circle of young adults, er ah teens was before that change came into effect. My first road worthy vehicle was a 1947
"chebby" P/U. Worked all summer saving my money and blew a chunk of it on that worn out sucker....I think I paid $75 for it and it was
well used. But it was a Chebby and it was "mine".....yeah! Big laugh! When I got it home, first thing I did was to change the oil and
when I cranked it up, with single grade 30 wt oil, you'd have thought I was spraying mosquitoes. Dealer must have had 90wt and
sawdust in the thing to get it sold.

The last 235 chevy sixes with dipper rods were built in 1953 or 54. After that the rods were pressure lubed.

(quoted from post at 05:30:03 06/13/15) Another reason not to buy a chevy

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ou are right.
A GMC is a far better option :wink:

(quoted from post at 19:07:18 06/13/15) The last 235 chevy sixes with dipper rods were built in 1953 or 54. After that the rods were pressure lubed.

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In '53 cars with the Powerglide transmission as well as the truck engines were full-pressure as I recall.