The Stovebolt Site Forums The Shop Area Engine Shop '46 235 oil pressure

Hi all--

I'm still learning my way around our newly acquired '46 2 Ton. One of the things needing addressed is the oil pressure gauge -- stuck at zero. I pulled the gauge and sure enough it's stuck but I decided to hook up a temporary gauge while the original is rebuilt and lo and behold I'm only getting 5 PSI or so at cold idle, basically zero warm.

Engine runs great, no noise that I'd call rod knock although it does have a ticking lifter. I chalked the lifter up to needing adjustment but now I'm nervous.

Obviously there's something wrong -- if the 235 is like other engines it's probably rod bearings. Is this engine babbited? How low is too low on oil pressure for these chevys? There's no oil filter but I doubt that would justify the low pressure. On one hand the engine performs great; I would never have suspected low oil pressure if it weren't for hooking up this temporary gauge. On the other hand if it's just a matter of dropping the pan and the bearing caps it would be foolish to risk major engine damage to save a few hours in the shop.

Thanks,

Pete P.
Harborcreek,Penna.

235 truck engines were low pressure through 1953.

0 psi is, of course, low (you can go no lower). Put 20-50 oil in your vehicle and see if it helps. Do not high-rev your engine as a pre-caution. You might get some pressure out of dropping the pan and checking to see if there are rod-bearing shims to be removed. I will not tell what I was told to do with the rods in your situation, when I worked in a shop in the early 70s.

What is the pressure at higher RPMs? It should be at least 7 lbs at 2000 RPM. The reading at idle is not all that important.

Rod bearing clearance has no effect on oil pressure on a splash engine but should be checked while in there.
You will most likely need to pull shims on the mains to improve the pressure.
The oil pump relief valve is set at 14 psi so that should be max when warm, about 7 psi at idle if all is set up correct.

Oops, I jumped to the rods too quickly. Thanks for the correction, as usual, Dave.

all this is assuming gage is correct.

In the literature that I have, I have not seen a minimum oil pressure specified for idle. I have seen the figure 7 lbs at 2000 RPM specified as a minimum. It stated that at that point, the cause should be investigated and corrected.

I'd drop the pan and have a look. You might find a significant amount of sludge in the pan. As mentioned you should check the main bearings adjust as needed. I would also check the rod bearings and adjust shims if needed. Be careful not to bend the stuff in the pan. You need the adjustment tools to set up the nozzles and dipper trays.

When you installed this temporary guage do you know that the guage is accurate? Don't rule out a pinched guage tube or crud in any fitting or block.

If you drop the pan be sure to check out the oil pump before going further into the engine.

Tom Langdon has a good article about these oil pumps.

http://stoveboltengineco.com/2010/09/prepairing-the-235261-oil-pump/

I have a '46 4400 truck with the old 235 in it. At idle the oil pressure gauge shows 10 psi when hot. It has been running since 1946 and so far no issues. I do set the rocker arm clearances once a year and tune it up then.
Normbc9