Allcoupedup

I'm building a parts needed list for the winter and will be pulling the engine for a cam and intake change and some cosmetic work. I leak from the front - can't tell if it's the timing chain cover or the oil pan so I'm taking the pan off.

WHile I'm in there should I go ahead and change the oil pump? My readings are about 20 at hot idle and 30 at cruising rpms.

I have no history on this engine and it's a passenger car 327 - supposedly a 250 or 275 HP 10.5:1 setup.
Thanks,
Brian

GaryC

Brian.

It would be cheap insurance to replace the oil pump since you will already have the engine apart.

Your readings are a little low but, you should not blame this directly on the oil pump (i.e., there are other components that can cause low oil pressure). So, you may need to investigate why the readings are low. (Note: There are not really bad, they’re just not great.) If the engine can be started now, you may want to do some testing (like check the compression of the cylinders) before you tear it down. This can help you with determing if changing the cam and intake is OK to do and if you need to do anything else. I am saying this because you stated that you do not have any history on the engine. It is better to have a good idea of what you have before you start adding new components.

If you do invest in a new oil pump, don’t listen to the hype about high pressure pumps. You absolutely do not need one. You can replace your pump with a stock unit. The high pressure pumps are a waste of money for street engines.

Good Luck,

GaryC

MikeM

You have four bolts or screws that hold your pump cover on. Take the cover off and see if it has grooves in it that you can catch your fingernail in. If it does, replace it. If it has something less than this, you can dress the cover plate down with sandpaper and a piece of glass and put it back together.

This would also be a good time to pull the rod and main caps and do a bearing inspection, both visual and plastiguage check for clearance. If you have loose bearings, this could be where your oil pressure is going.

If you change the pump, braze or mig weld the pickup to the pump housing
so it doesn't fall off.

Mike

Allcoupedup

Gary,
My compression test gave the following results
175, 170, 176, 174, 152, 170, 170, 165

I added oil to the cylinder with the 152 reading and it came up to 170 which I believe suggests a weak combustion ring.

I do not want to tear the engine down as a rebuild is not in the budget and I'm trying to avoid project creep (set a goal - get in, get out - be done. If the engine runs well (smooth and quiet) and there is no smoke or oil consumption is there any reason to be concerned?

Thanks,
brian


[Modified by Allcoupedup, 2:12 PM 8/13/2003]

ghostrider20

When you did the compression test did you have batt. charger hooked up? If not may want to try again.

I don't think an oil pump will put you over budget, get a new one. IF you have the motor out, why not just have a machine shop freshen it up. Shop around, you may find it reasonable enough not to pass up.

Mark

Allcoupedup

Mark,
No charger but It was I did this test twice over a 6 month period and went in reverse order the 2nd time. Same results.

When you say "freshen up" what do you mean? I'm trying to get around pulling the heads and the crank.

I'm a rebuild rookie so go easy on me!
Brian

GaryC

Brian,

You make a good point about having a goal and sticking to it. Otherwise, we may be talking you into doing a port-and-polish to the heads. I mean come on, they will be off the engine anyways, right?

:lol:

Mike made a good point about if you do replace the pump, make sure that you weld the pickup tube. The pressed on pickup tube could fall off.

I would not worry too much about the compression. The spec is +/- 10% between readings. You are not that far off.

As we may have stated before, changing the pump is cheap insurance but, it may not bring your pressure back up.

I would say, just do the mods that you stated, change the pump if you have the money and then just drive it!

Good luck.

GaryC

Paul L

Those readings are low in my experience. I would change the pump.



And while you are there, change the rear main seal.




[Modified by paul67, 4:10 PM 8/14/2003]

ghostrider20

Quote
"When you say "freshen up" what do you mean? I'm trying to get around pulling the heads and the crank."

I mean bring the whole motor in for a basic rebuild. Just a basic tear down and rebuild. No fancy blue printing or head work. Just a rebuild kit. I would imagine you could get the whole project done for under a grand.

Mark

MikeM

Might be a good idea to confirm your oil pressure with another known good guage before you spend any money. I agree with Paul that your pressure is low but if your main and rods are in good shape with the right clearances, I wouldn't worry a whole lot about it.

JohnZ

An oil pump in decent shape (no scoring on the cover or major wear on the gear teeth) generally has nothing to do with oil pressure; oil pressure is a function of restriction to flow, which is bearing clearances, rod side clearances, etc. Verify pressure readings with a known-accurate gauge and go from there. :thumbs:

tuxedo

Just to get a known number on oil pressure. What do you guys see as " good" oil pressure and "excellent " oil pressure on your guage?

Brutal64

My oil pressure runs 20-30 psi at idle, 80 psi on initial startup and 60 psi when warmed up. Those are all good numbers.

Allcoupedup

I checked my notes and I wrote "between 30 and 40 psi". I used three gauges - the stock which read 15, a crappy sun-pro gauge with narrow has marks (hence the 30-40 range), and then a nice dial gauge. I don't remember what the dial gauge read as I was dripping oil because the fitting was a little loose I was going to "write it down later" --- you know how that goes.

The crappy gauge and the nice gauge were attached after the engine was warm. I have not taken a reading at start-up.


I appreciate all the advice and I'm going to need a LOT more once I get going.

:thumbs:
brian

JohnZ

20 psi at hot idle and 30 psi at cruise (around 3000 rpm) is fine; I wouldn't worry about it. My 327/300 runs about 30 psi at hot idle and 45-50 psi at cruise, but it's all fresh inside with .002" on the rods and mains and .014" side clearance and a stock oil pump. The "idiot light" on passenger cars doesn't come on until 3-5 psi. :thumbs:

ghostrider20

My 365shp motor:

Cold idle - 80+ psi.
Hot Idle - 60 psi.

Hot Cruise - 70 psi @3500 RPM and by 5000 RPM peaked at 80 psi.

Oil weight can vary oil pressure readings. If you are running 10-30 they will be a bit lower then 15-40.

Mark

Nicky71

Brian,

I get 30-35 PSI at hot idle and about 50 PSI at cruise with 10W-30 Valvoline.

Your readings do not sound too low, but I doubt changing the pump will increase the pressure appreciably.

If you need any help or need to borrow any tools, let me know. I'd be happy to stop by and drink all your beer :D

Later,

tangel

From hottrodding books to old racers, I had always heard 10 pounds of oil pressure for every 1000 rpm is a good rule of thumb, except it shouldn't go below 10-15 psi at idle. It can't hurt to change the oil pump, especially if the engine has a lot of miles on it.

Matt Gruber

if you are flat broke shim the pressure relief spring with 1 or 2 washers.
Otherwise spend the $12 for a new Melling M55.