I know that these old engines are notorious for being able to run with low oil pressure but my question is how low is too low. I’ve finally had a chance to put a few miles on my ‘52 Chevy with a 235 installed. It pegs the needle on the 30 lb. gauge when I first start it but falls to 15 lbs. when it warms up (180 degrees) and running at 35-40 MPH. At idle it drops to almost 0. There is no valve clatter from the hydraulic lifters and no other unusual noises.
I’m running 10w-30 Valvoline.
This seem unusually low to me. This engine was rebuilt in 2013 and then sat for 5 years before I got it.
How much oil does it burn? Try 10w40.
I haven’t driven it enough miles to tell if it is using oil. I don’t believe that it is burning oil because it doesn’t smoke and was rebuilt by a PO in a reputable shop. It came with the paperwork to prove it.
possible inaccurate gauge. Id put 15w40 or 20w50 in it. See what gauge does then. Could try a different gauge also. Was the engine broken in or ever ran prior to you getting it?
Heck, I’d try 20W50 oil - it is readily available and costs $20 (Walmart).
I don’t know if it was properly broken in because I didn’t buy it from the owner who had it rebuilt. That was two owners ago. The story I got was it was running when the guy parked it then it sat for five years until it was sold 9/18. I bought it in 2/19 and it wasn’t running supposedly because of an electrical issue. It had many other issues including electrical!
What kind of gauge are you running and where is the line tapped into? I am with the others, try another gauge just to double check. Also, any chance you have an oil filter mounted? If so, what kind?
Stupid question! If it’s a 1952 235, isn’t that still running babbit bar rings? If so, isn’t 15 psi about normal? My 216 normally sits between 10-15 psi.
Please educate me here as I don’t know much about the 235. Didn’t they change to full pressure around 1955.2?
That is a bit strange because those numbers are about perfect for the low pressure version.
The 1935 engines were babbitted bearings - and, the low pressure oil system, both as you describe.
The original poster/post says at the end of the first post: “ At idle it drops to almost 0.”
That is not good for the engine’s bearings.
I’m not arguing that it isn’t good. At idle my pressures drop as well once warm. Depending on the gauge range, it might look lower than it is (if not the stock gauge). I’m guessing mine sits at 7ish psi when idling.
Title says 59 235. Lets clear this up. Is the motor a 59 or 52 235?
I’m using the dash oil pressure gauge.
It is a full pressure 235 from a ‘59 passenger car.
It does have a by-pass oil filter mounted on the manifold.
It’s tapped on the drivers side of the engine, tee’d with the oil filter connection.
The rubber hoses clamped to the fittings.. Are the actual oil pressure hoses or something else that may be heating up, and flexing enough to cause pressure loss?? They really shouldn't be clamped. They should have fittings to attach them properly. Even if that aint your problem, it might become a very big one...
Thanks for giving me the heads up on those oil lines. I don’t know what they are, more than likely gas line. I’ll have to study that bypass filter system. Maybe the restriction isn’t doing its job. I’ve never had it apart to see.
What do the proper fittings look like?
I dont have a pic handy of what the lines look like. You can google em. Hose/lines will have fittings crimped or permanently attached.. I actually had longer hoses made at a hydraulic shop to relocate my filter to the inner fender. See pic. You can see 1 of the hoses routed near the carb.
Found a better pic of what I had made. alitta different from "factory" but you get the idea.
You never know whats been done to these motors in the past so I might try getting the oil lines sorted out first (some new correct versions) and see if that does not improve the matter. The GM oil filters had a restriction in the filter housing, depending on the application, but some GM did not and its possible you have one that does not. Also, not all of the after market filters had a restriction. So, you may in fact be drawing too much oil from the galley and killing your pressure. Try pinching off the rubber hose at the T connection. Its a bypass filter so you will not starve the motor at all because the output of the filter just dumps directly into the pan. If anything, you will be increasing the pressure and volume to the motor. If the pressure goes up, you know you are headed in the right direction.
If that turns out to be the case, and new correct lines don't help the problem, run without the filter.
Well, I might have found the reason for low oil pressure. I disassembled the by-pass oil filter, supply and drain hoses, and could not find any restrictor installed. In the meantime I going to just install a couple of 1/8” pipe plugs and eliminate thee filter and see if the problem goes away.
Where is the restrictor installed. In the filter housing, supply/return hoses?
I think it does not matter; however, put it in the inflow port (which is usually the port on the top side of the canister)..
Can't be the hose unless they expand indefinitely like giant balloons.
Your funny! I meant the fittings! LOL
Did the pressure go up without the filter and hose?
Are you using an original-type canister filter, or some type of modern spin-on filter adapter? Original Fram or AC filter housings have the restrictor orfice built into the center standpipe and no further flow control is required. Some sort of Mickey Mouse spin-on setup will dump practically all the oil back into the pan and destroy the bearings due to lack of lube unless you install a restrictor orfice. I use a Holley carburetor main jet since I've got about a hundred of them left over from my round track racing days.
It appears to be an original housing but there are no markings or logo’s on it. I looked thru the center tube and it does not have any restriction. The only restriction that I can see is the 1/8” NPT hose barb fittings. That restricts it down to maybe 3/16”. If I remember correctly, were looking for 1/16”. Please correct me it that is wrong.
Would it be better to add a restrictor so the canister is at full pressure (installed in the outlet) or in the inlet. I would suspect installing it in the inlet would reduce the pressure in the canister.
I haven’t run the engine yet because I didn’t have any 1/8” pipe plugs. I got them now so today I should have some answers.
HRL, its great to see your pecking away on the keys! Hope you op was a sucess!
You're looking in the wrong place. About 2/3 of the way up the standpipe there will be a hole drilled through the side of the pipe. The rubber rings on the top and bottom of the filter cartridge seal against the tube, and the cover bolt plugs the top. The small hole in the side of the standpipe is the ONLY way oil can get to the bottom of the tube and out the drain hose. Even if the hoses get hooked up backwards, the restrictor still works. Smart folks, those engineers- - - - - -they made those things idiot-proof!
One-handed keyboarding sucks!
Well, Jerry, your right again. I was looking in the wrong spot and the standpipe does have a tiny hole in it. I’ll still plug the holes and run without the filter until I get the proper hoses, but I don’t suppose that will change the low oil pressure issue. I have a spare gauge so I’ll hook that up to check the dash gauge.
Where do I go from here?
Hmmm. Well if you dont think that will help the oil pressure problem, then why are you dealing with it? If the problem is with the filter, hoses, or the restrictor then your oil pressure reading should be reading much higher when they parts are bypassed or eliminated..
I believe I've suggested running the oil pump with a 1/2" drill motor to see how much pressure builds up. You need to have a known accurate gauge plumbed directly into the oil gallery port instead of the line to the dash while running this test. These procedures NEVER change, no matter how much wishful thinking gets done, and I get very frustrated explaining them over and over. That's particularly true when my right hand is wrapped up like a mummy clear to my elbow and I'm having to correct dozens of typos caused by keyboarding left-handed only!
I installed the pressure gauge In the fitting where the inlet line to the oil filter was installed and ran the engine for about 30 minutes and once the engine came up to temperature, the oil pressure dropped to about 5 lbs. at idle. The dash gauge and the temporary gauge were the same. This appears to be a little bit higher than before, but still too low. I’ll keep the filter off until I solve this mystery.
I still want to take her out for a run to verify my results. Further troubleshooting is warranted.
Will the oil supply to the rockers effect the pressure?
The most common causes of low oil pressure are worn rod, main, and cam bearings. As oil leaks past a bearing and drips back into the oil pan, there's a bit less pressure left to push oil down the gallery to the next bearing in line. If all the small leaks accumulate sufficiently that the oil pump can't keep up with the demand, pressure drops. Hot oil flows better than cold (it's thinner) so hot engines have less oil pressure. There's two ways to fix it- - - - flow more oil, or install tighter bearings. Unfortunately, nobody makes a high volume oil pump for a stovebolt engine, so new, tighter clearance bearings on a round, proper-sized crankshaft are the only answer to oil pressure problems.
I've figured out a way to run a small block Chevy V8 oil pump on a stovebolt engine for more volume, but I don't have a working prototype built yet.
What is your oil pressure at 2500 RPM once its warmed up?
While 5 PSI at idle seems low, it is 5 more than zero.
"Idiot light" switches turn the warning light on at pressures below 7 PSI. Most people who drive vehicles without a pressure gauge don't realize how low oil pressure can get on a hot engine without doing any damage if the pressure rises quickly above idle. The warning sign to beware of is a "loose bearing" rattle at higher engine speeds and no load. Holding the RPM at a steady 1500-2000 rate and listening for a rapid rattling noise is the best way to diagnose loose rod beatings. Loose main bearings present as a repetitive deep-sounding THUMP noise as the engine accelerates, which moderates once the speed levels off. Main bearing noises are much slower and deeper than rod rattles.
Even with worn bearings I'd think the oil press would still be in the range of, say 10-15 lbs. hot and winding. I'd pull the oil pan (it isn't that hard) and pull the pump assembly for a look. I pulled one apart one time with similar symptoms and found old gasket material clogging the pickup screen, AND as a result of the crud, the oil pressure relief valve was stuck open. After a good cleaning all was normal, i.e., 30+ lbs hot and winding, 15 lbs hot and idling.
I pulled my own 235 apart a couple of years ago to fix a rear main leak, which turned into a crank bearing job. I found many of the bearings down to the copper and #2 upper rod bearing shell came out in two pieces. There had never been any distinct rod noises or main bearing noises and the oil pressure was acceptable. With new bearings (except cam bearings) the pressure is a little better but not much but it is noticeably quieter. With 20/50 oil it holds about 10 lbs at 700 RPM idle at 250 deg. F oil temp. When sitting idling waiting to pull up the next sage brush plant it holds 30lbs at about 120 deg. F oil temp.
Thank you all for your suggestions. This engine was rebuilt 5 years ago by a supposedly reputable engine rebuilder, and I doubt if there is more that a few hundred miles on it. I find it hard to believe the bearings are worn. So I have been looking elsewhere.
I pulled the valve cover and it appears that the oil feed assembly to the rockers is not for a ‘59 engine but instead from a ‘57 or earlier. From what I see on Chev235guy
, the later versions have the return tube pinched off so all of the oil goes into the rocker assembly. Something seem’s amiss with this setup.
I’m going to pull the rocker assembly and see what else I can find. Maybe all I need to do is pinch off the return line on the feed.
Sun said it best with the slogan they put on all their test equipment- - - - - -"We Test Not Guess!"
Go ahead and waste a bunch of time and effort chasing a problem you won't be able to find with the engine torn down and no oil flowing. Good luck!
The reason the 59 and up connectors are pinched off is because from 59 on, GM had redesigned the oiling system a bit to create a sort of pressurized system. Not only is the connector different, but the rockers are different. For example, earlier rockers had a groove inside the rocker that intersected the dribble hole. On the 59 and up, the rockers are fed pressure and volume right from the oil galley as opposed to the rear cam bearing journal in the earlier motors. Also a larger orifice to the connector tube. the 59 and up connector is pinched off to make sure no volume and oil losses. Now, instead of the grove intersection the dribble hole, the 59 and up rockers and the groove offset from the dribble hole to control oil so that you got a dribble, but not spitting over the rockers and doing no good so you will need to pull the rockers to see if you are using the correct rockers.
That being said, hundreds of thousands of open loop connectors have been pinched off to help a little bit with oil pressure to the rockers. Your problem appears to be that you are getting no oil to the rockers so I would start with installing an aftermarket gauge and use the oil sender port and confirm the operating pressure of the motor. If you have lousy pressure at that port, you have a more serious issue, in my opinion. Bad oil pump, clogged pickup, worn bearings, something. If you have good pressure at that port, then you have to figure out what is keeping it from the head. There is an oil passage in the head that can clogged up. There is also a shade tree work around, tried and true, to feed the rockers, but that will not help you if the pressure in the motor itself is bad so yes, test don't guess.
I've diagnosed low oil pressure problems by adapting an oil pump to a 5-gallon pail with a snap lid and pressurizing the oil galleries with the oil pan removed and a big drain pan under the engine. It's pretty easy to spot where too much oil is flowing, and cam bearings can be the problem in a lot of situations. Back when the first small block V8's started needing rebuilds in the late 1950's, Dad's shop experienced a bunch of "flickering pressure light" complaints after an in the frame ring and rod bearing job was done. They discovered that cam bearings were the cause of low oil pressure with the engine hot and idling, particularly on Powerglide equipped cars. They stopped doing in the frame rebuilds after that and insisted on changing cam bearings if the car owner wanted a warranty.
My low oil pressure issue just got worse. Wanting to find out if the rockers were correct to the engine, I removed the assembly. The entire assembly is pre ‘59. I verified that the oil supply connector overflow wasn’t plugged and the groove in rocker arm aligns with the dribble hole.
I reinstalled the rocker assembly and started the engine to warm it up to perform the oil pressure test as Jerry suggested. One rocker was making noise but this was not unusual as it would quiet down after running for a few minutes and in this case it did. I ran it for about twenty minutes, checked the temp gauge and it was up to 180 degrees. The oil pressure was holding at 5 lbs. at idle. (450 RPM). The engine sounded great, all of the rockers were getting oil and I was thinking to myself that I would not pursue this issue and just keep an eye on it. Shortly after, the engine started making an racket, missing badly and then stalled. Thinking the pump may have failed or other catastrophic failure caused by the low oil pressure, I popped the distributor and drove the oil pump with a battery powered drill (I don’t have a 1/2” electric drill) and looked at the pressure. I could drive it to 30 lbs. at full power and about half power it was about 15 lbs. the oil pressure followed the drill RPM and was not erratic.
I reinstalled the distributor and started it up and the rockers were making making a racket and I found one that had collapsed completely. I can lift the push rod at least an 1/8”.
Could I have caused the collapsed lifter by taking off and reinstalling the rocker assembly? I have installed rocker assemblies before and was extremely careful, tightening the assembly evenly and insuring the push rods were centered and the whole assembly went down evenly. I torqued them to 30 ft/lbs.
Where do I go from here, aside replacing the collapsed lifter
Early stovebolt hydraulic lifters are notorious for making noise and/or collapsing, and the only things worse are "new" ones made overseas. I'd recommend removing the lifters one at a time (important) and give each one a disassembly and cleaning. There's a tech tip on the forum somewhere on how to modify the lifters and the pushrods to assure there's enough oil flow to keep them from collapsing. Since 235 hydraulic lifter engines do not flow oil up the pushrods to the cylinder head (they're solid) it's necessary to create a calibrated leak at the bottom of the pushrod to assure enough oil flow to prevent an air lock from forming in the lifter body.
DO NOT MIX UP LIFTERS AND CAMSHAFT LOBES!
Each lifter establishes its own running fit to a cam lobe, and swapping holes with used lifters is a surefire way to guarantee a worn out camshaft in a very short time. What weight oil are you running? I'd avoid using anything thinner than 15W-40.
May I ask where you are tapping in to check the pressure and whose pressure gauge are you using?
I tapped into the tee fitting where the oil pressure gauge and the oil supply to the bypass filter located on the drivers side. I removed the oil filter barbed fitting and installed the gauge. Both the dash and temp gauge I installed read the same. I’m using an old pressure gauge that I have.
5 pounds at idle is not really what you want so here is what i might consider just as a little low hanging fruit. Get a new mechanical oil pressure gauge. Jegs sells one for like 20 dollars and your local parts joint may have one locally. Just to double check. The other thing is, and I am just spit balling here, any chance you have recently messed with the timing? And by that I mean have you recently loosened the clamp screw on the octane selector/distributor hold down? The reason I ask is that it is possible to run a 235/261 under conditions where the tang on the distributor pump does not fully insert into the receiving slot of the oil pump. This is a long shot but maybe you have just enough contact to move he oil pump enough to get some movement. So, maybe loosen the screw enough to press down on the distributor and see if it will go further down into the pump. Not likely but you never know. When the motor is idling, is oil dribbling out of the rockers, and all of the rockers? or is it spitting and making a mess? Or no oil at all? What is the casting number for the head, 913 or 848? If its 848, what is the casting date?
I am still in the process of making the truck road worthy so the distributor has been in and out several times chasing a rough idle. That issue was resolved. I am confident that the distributor is seated. The low oil pressure has been since I first started the engine, so it‘s not a new issue.
The head is an 848 and the date code is A31.
The rocker arms seem like they are being adequately oiled, with oil dribbling from all rockers, and it is not spewing all over the place.
I do agree that a new oil pressure gauge is warranted.
A new (not rebuilt) Melling M-45 oil pump is only about $100.00 on Ebay and there are literally dozens of them available there. In 60+ years of building engines I've only seen two actual oil pump failures, but they do get a little tired, especially if the pump has ingested some debris and gotten scored inside.
While you've got the oil pan off to swap the pump, put a set of rod bearings in it and fix the real problem.
Don't forget the Plastigage, mic the crank and hunt up a set of tapered bearing shims. Do remember to disassemble the oil pump pickup to check for debris; also check the pressure relief valve. The valve lifter racket could be caused by air getting sucked into the inlet side of the pump. This happens from damaged pickups or loose connections where the pickup goes into the pump. Mind you, it can't be so tight that it won't swivel but it can't be so loose that it sucks air. They can fall off altogether when the locating cotter-pin was forgotten or for some reason falls out. Then no oil pressure at all with the oil level below the pump. Mix of air and oil with the pump partially submerged. I've never seen this happen but I suppose it's possible.
Update: I took out all the hydraulic lifters, one at a time. Cleaned, reassembled, filled with oil, then reinstalled. At the same time, I cut slight grooves into the bottom of each pushrod to alleviate any trapped air as suggested by HRL. I followed Chev235guy
They all looked like new and I found only one that collapsed. I reassembled everything and I’m waiting for a pushrod cover gasket before I continue. I want to run the engine to see if that solved the missing problem before I go into the crankcase.
I ordered a new crankcase gasket along with Plastigauges in the appropriate sizes.
Isn't that lifter plunger upside down in your photo? The spring should be at the bottom, the inner plunger should assemble on top of the spring with the check ball pointing down, and the pushrod seat goes on top, followed by the snap ring that holds it all together.
Yes the plunger is upside down in the picture. I took the picture to show, that they look like new. They were assembled as you stated and I reassembled them the same. I did add oil and purged out the air prior to reinstallation.
The grooved pushrod ball should fix the air lock problem. Whenever the engine stops, some of the valves will be open, and those lifters will bleed down due to the constant pressure of the valve spring. If the lifter is functioning properly, it will refill within a very few turns of the camshaft, as long as the oil pressure is sufficient. Noisy hydraulic lifters are usually the very first symptom of low oil pressure.