Inliners International Forums General Discussion Engines Oil pressure? 261

Well i got my new cam and lifters in my 56'261
gave it a 20 minute spin at 1500-2000 rpm. and just took the fist drive.
Using straight sae 30.
When i started the engine the oilpressure went straight to 45-50 psi. and 30 psi at idle.
when i returned from a 30 minute drive i noticed that my presurre with a hot engine was max 35 psi and 5-15 at idle. I am not sure if this is a problem. I also blocked of the bypass filter that was in the truck when i bought it, it did not help very much.
any advice?

Thanks,

Dennis

how is the engine temp doing? during breakin it runs hotter which also thins the oil. what does it run for pressure with the engine cold again. tom

Engine temp stayed below the middle bar on the gauge, i think the temp i allright.

Engine has cooled for about a hour now and i started it up, pressure went up to 30 psi at idle now but it will sink again when i go for a drive. I just want to know for sure, i already lost a cam on break in.

Dennis.

Cam damage at break in would involve one or more lobes wearing down and this would show up as progressively rougher running and increasing valve train noise. Low oil pressure as you describe it isn't a direct indication of a cam break in problem.

I understand that but it might cause a cam failure. It's my first engine i rebuild so i just want to make sure not to damage it because the pressure might be to low.
What kind of readings do you guys get on a hot summer day at idle?

What are you using for an oil pump?

Did you have the crankshaft ground, and did you plastigage the bearings while dry?

you may want to try a multi viscocity 15w 40. it is used in diesels here. it will provide better pressure, unless your oil clearances are just too much for the pump to keep up with. tom

I dont think 15 is going to starve your cam at idle but 5 is way too low. The 15-40 is worth a try. Sounds like the engine is still tight and your oil is working harder and getting hotter than you might think. You can also try draining a quart of your 30 and adding quart of lucas oil stabilizer (some times it only takes a half quart) to keep your pressure up while you break it in.

Dear Dennis;

You've done everything right & your oil pressure is 'normal' factory setting. Multi grade will drop it.

"Don't worry be happy".

Many like a higher pressure but not needed unless you plan to 'rev it up' a lot.

Enjoy.

Is it only the later 261s that had full flow filters and would not properly oil the engine if they were blocked off? If so, what year was the changeover?

Baldy's right.

Believe me; you would know if there was no pressure to the rear bearings.

He probably has the one with the moveable pin & It's out (not in).... A filter in that mode would be a "by-pass" one.

59-62 are full flow, at least they are if the pin is "in". If using the stock 261 full flow filter canister on a 59-62, the filter head has a bypass valve in it.

15 psi is the minimum safe pressure at warm idle. What rpm are you at that it is giving you a reading below 15 psi???

Brian;

Your right, but I've seen (west coast) 'by-pass' type (low pressure 216/235) filters on the 261s.

They don't belong there, but they could have been done by some "hobby shopper".

I think that's what he might have had, as his engine is to old for the full flow type.

If the pin were 'in' and the filter removed, no oil would go th the rear bearings.

This is why they ALL are best removed unless there like the one you pictured here (factory) a while back with the solid steel lines..

I think i have a Fram type filter.`There is a Fram C31PL element in the canister.
This filter was on the cracked engine that was in the truck when i bought it, this was a '54 235.
The 56' 261 (from Canada)has two holes on the left side just like the 235 that was in my truck.
i hooked up the filter inlet at the same hole that my gauge is on. the filter outlet is hooked up at the front hole and it comes out inside the block next to the oilpipe from the pump.

my idle might be a bit to slow at 500 rpm i think i will settle for 600 rpm and take a longer drive this weekend. I will keep a close eye on the oilpressure and rpm's

just installed a tach and vacuum gauge to monitor the engine when i am driving.

I have not seen a moveable pin when i rebuild the engine i am not sure if it is supposed to have one.

Thanks,

Dennis.

I got a new oilpump from Patricks so that should be right.
i did have the crankshaft ground and plastigage the bearings wile dry.
i lubed the crank before i tightend the lower brearings.

Dennis.

If you removed the filter, then It's out of the 'picture' now, which was okay

You should have the proper pressure @ 600 RPM.

Remember the guage is least accurate at that level.

I've rebuilt a few 235-261 engines in the last few years.Even with crank clearances as much as .003,my engines have 30 psi at idle ,around 700 rpm, and 40-45 psi at 2000 rpm fully warm after a hiway run with 15-40 oil.Two of these engines are 261's with full flow filters,and a 235 converted to full flow.All have after market filters and plumbing.The last engine 235 I did last year,again with a filter conversion,has lower pressure readings like yours.On this engine,I reused the old oil pump,which I believe is worn.
Anyways,like mentioned above,your engine's oil pressure is adequate for normal driving.If the low pressure bothers you,and you've eliminated the filter as the problem,and the guage is actually accurate ,then it must be the pump or bearing clearances.
Plastigauge is a general guide,but it's not alway as accurate as it depends greatly on user technique.
I hear this low oil pressure situation alot on rebuilt 235-261 engines.I'm thinking again it's bearing clearance.

Yes; pressure is lost if the bearing clearence is to wide and the pressure(s)Tony posted is usually what they run, unless the pump relief valve is altered to raise it.

When you installed the cam were you very carfull NOT to scratch any of the bearings??

This too, will do it (although rare) in engine assembly.

Either way; Being within 'normal' factory specs. (but low) you'll still need to watch it closely. If it goes ANY lower after 'break in', I would find out why etc.

Good luck.

Dennis,
You have no pin because you don't have a 59-62 truck block. This whole full flow filter issue is not relevant to your situation, so don't worry about it.

I just came back from a long drive.
Idle pressure is around 15 psi when hot.
I set the rpm at 600 instead of 500 and thinks are looking good right now.

Thanks for the info guys.

Dennis.

Canadian blocks do not have the pin or full oil filter flow.

I got a 270(GMC) from a truck that had just been overhauled and never put back together. When I finished and started it up after I added a full flow filter as in the tech section, it blew the filter off.

Turns out it has too much oil pressure, over 150PSI at the aft end of the gallery, so my best guess is they didn't line up the holes in the bearings with the holes in the block. I haven't disassembled it yet, I just rebuilt a 302 instead.

Anyone else have a similar experience?

WOW, Ed;

That's almost impossible to happen as the bearing inserts are pinned to match. I guess nothing is "idiot proof" etc.

You may have a jammed or stuck relief valve in the oil pump. I would check that out.

Good luck.

John,

Thanks for the idea, I'll check that.