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

Whats the normal oil pressure for a 235, hot at idle?

I assume using the standard dash gauge as the indicator? This is a good question which I have also wondered. I'll be driving about today and will make note. Does 15# sound right? I know right at startup when cold mine climbs to the top of the ladder at 30 but once it become hot it drops quite a lot.

It depends on the year. The 54 runs at about 30psi.

How abouts a 55-62 motor? Got my 235 started yesterday! *does dance* I've got 35 PSI at idle hot at 750 rpm, rising to 42 psi at 1500 RPM. Man this motor sounds great! I even pulled the distributor to check gear/pump wear, so far it looks good. Engine revvs freely and runs cool. Can't wait to show off the 4bbl/fenton setup at the next local cruise night. Haven't driven her yet, but dammit boy!

Question- How much metal is permissable in 1st oil change? I dropped the oil after the first 30 min, and there was some gold and silver glitter in the oil. But when I run my fingers thru it, nothing sticks to my fingers. I also dipped a piece of typing paper in the oil, and held it to the light. Didn't see much junk. I'm going to let the oil sit in the drain pan and see what settles out.

thanx

chip

My rebuilt 235 runs 30# when first started then drops to 15 after warm. I have 1953 gauges hooked to a 1954 engine.

I don't think you want to see any metal. Check it with a magnet, is it metal?
My oil pressure drops to zero when I come off the freeway. A new cam and cam bearings are in my future.

Chiphead: 40 lbs hot is normal for a new 235 and so is some minor metal in the oil for a few oil changes.

My 261 runs about 32 lbs at idle and about 40 at 1500, but I have the gauge hooked up to the outlet side of the oil filter housing. (full flow)
It sounds like you are just about right.

The 57 235 in my 37 pegs the original gauge when cold and goes down to 15 when hot at idle with 30 weight oil,the motor has about 2500 miles on it.

Chip, yes, you will have a small amount of metal dust at the first change unless you chamfered all the edges on the rod, cam & main bearings before assembly. As for oil pressure, my 54 235 has 15-20 psi hot idle at 450 rpm, about 38 psi at speed. In experimenting, my friend & I have found huge differences in pressure and flow with new oil pumps. The quality control is horrible. We even went so far as to shim the relief valves. With the same amount of shims, my pump maxed out at 45 psi, my friend's pump pegged his guage at 80 psi.

Ah yes, back to the oil pump from hades. You'd think melling would be better about their relief springs. What is the relief spring supposed to lift at?

I haven't driven my car yet, but I've got another question: As the engine breaks in over the first couple hundred miles, is it normal for the oil pressure to rise or drop a bit? Like if the oil pressure falls off about 5 psi should I be worried?

thanks

chip

My 54 powerglide engine in my 48 chevy 1-ton pegs the stock guage whn cold and then settles around 15 to 20 when hot.
I would be concerned if it drops below 10 with a new rebuild.

hello chiphead. that is great news about your engine. it sounds like your oil pressure is right on. i think the releif on the oil pump is supposed to open around 40 pounds. your hot pressure sounds real good. all this might change after a drive around the block, as things loosen up a little the hot pressure might drop a little, but i would be optimistic that all is fine. good luck .

I've seen data somewhere that seemed to indicate you only need about 5 lbs of oil pressure at idle & hot to keep the bearings separated from the crank. Drive it and enjoy. We may only go this way but once.

The 235 was before my time - not even sure if they're OHV, so I don't know how similar to the 250/292's they are, but your info is interesting. I usually T in a cheap-o mechanical gauge, and my I-6's show what I have thought was frighteningly low oil pressure. with 10W40 cold start it goes up to 40psi, stays 40 on the hyway, but drops to about 15 at hot idle. The OEM electric disagrees and says 60 and 30 respectively. I always just thought I had crappy gauges. Even published spec's dont seem to agree - My '84 GMC manual says should be 60 at idle (really - a typo?) but the old story I've heard is 10psi per 1000revs and seems to reflect observation. After all these years I still don't know what I should really be getting at the sender. Guess I'll average out all your recordings and stop obsessing over that needle - but 292's are getting so rare here.

we have got a rebuilt 235 and it is running about 70psi when cold is this too high

Whoah... What was your main and rod journal clearances? What weight oil, what oil pump?

Excessively high oil pressure could mean too-tight bearings, or sticking oil pump relief valve, or blocked oil passage in block. What is the pressure when hot? Are the valves getting oil? Is the motor overheating at all for no good reason? Any metal in drained oil?

I once had 60-70 psi in a fresh '54 full pressure shim-style 235. The mains were shimmed too tight, it ran for 300 miles then went BOOM. Started overheating and making noises. Oil pressure went from great to in the basement. Bearing material came out with drained oil in ribbons. Check for metal in oil.

chip, the master of 235 disaster.

Edit- BTW, the '60 235 discussed in above thread is still running. It has 45 PSI when cold, 28 psi at idle hot, 35 going down road.

My newly rebuilt '61 261 has a hot-idle oil pressure of greater than 30 psig (off scale of the '48's old gauge).

I changed the oil after breaking in the cam. (I was bored and wanted to crawl around under it.) I used a new, clean bucket and let any metal settle out. I didn't see any metal in the oil but it showed one tiny speck of metal on the oil filter. I'll be doing a 125 mile oil change tomorrow.

I realized this week that I now have 10,000 miles on my 235. Oil pressure is 15-20 hot idle, 35-40 at speed. I wrecked my 69 2 weeks ago and am waiting on foot surgery due to other issues. So the 52 is now my daily driver, I'm happy that I got my 4.10 gear swap done just before the doc took me out of service.

The cool part is that I get to park inside the fence at work, since i'm on crutches. I get lots of strange looks from upper management in their SUVs and Lexus' when I pull into the lot in my rusty 52 farm truck.