I just installed some new rally gauges and sending units from CI replacing the idiot lights and trying to keep a stock look. The gauges seem to work fine. Now that I can see the H2O temp and oil pressure:

I'm concerned that I may have a weak oil pump. When I start the car cold the oil pressure sits at about 60 psi. But once it's warm and driving the oil pressure drops real low, especially at idol and never goes above 20-25psi when driving. Is this a sign of a bad oil pump?

The water temp sits a bit on the high side at about 250 degrees. The car has never over heated and I have a resivoir that works great. I installed a new sending unit that the instructions spec'd. Could I just be getting a false reading or are these gauges just not that accurate?
Anyone have these gauges with same syptoms?

BRIAN

Hi Brian
I have the 230 OHC 6 and put in gages to replace the idiot lights and have an oil pressure scare to because when I start my car the pressure is at 35 psi. But once it warms up that drops to 10 -15 psi. I'm wondering about my gages also. My temp gage says from 170 -210 depending on how hot the day is. Maybe we can get some answers from our fellow bird admirers. Anyone have any answers for us? I really want to make sure that my cam is getting oil!!!

I think for the OHC you need a guage at the top end to check the pressure at the cam. There are two threaded and plugged holes, one at each end of the head, which can be used for this. I would like to have this on my OHC, too.

Hi Miles
I know what you're talking about and was thinking of hooking up another pump there to make sure that I'm getting enough oil up to the cam.Seeings how that was the biggest problem with those engines. What do you think?

Too much pressure could be bad too. I don't have any idea how pumping through those passages would work vs. the standard flow through the hourglass. But, too much pressure from the hourglass means uneven oil distribution at the cam (sprays into the middle). Wait for Q to jump in here, because he must have a pretty good idea how that works.

Good idea! Now comes the hard part--waiting.
Mental note: must go out and buy more patience.
Miles, do you know where I can get some?

pressure should be at 30 to 32 at idol 10 to 15 is not good. what kind of oil do you use? only 30wt is required. I use a high volume pump instead of pressure, do to the fact that pressure will blow out gaskets when you rev up. a hot motor will drop your pressure maby a few pounds lower but not more than 5lbs. your pump could be weak but if you have high milage then bearings should be considered also.

Hi Mark
I'm using 10w30 oil and my bearings are good or at least I can't hear any noise.

I just thought of a incident that happend to me. I rebuilt a motor used a new pressure gauge and it was very low i thought it was the motor. turns out that the gauge was the problem you cold have a a bad gauge. 250 is too hot. you should be at 180 to 195 is optimum.

30 is what you really need not 10-30 i think thats your problem.

Thanks for the advice. To bad we didn't have this discussion last weekend cause I just did an oil change too. I was actually thinking of going higher to a 40 or 50. I am also thinking of getting my ign.distributor rebuilt cause I am having timing problems. Could that maybe be giving me problems with my oil pressure? Any thoughts on that?

The distributor shaft drives the oil pump. I hope it's seated all the way...

I'm not sure but if bad timing and poor oil pressure are any kind of sign then it's time for a rebuild. Would you agree?

Well it's time to go. Wife has a bonfire going in the backyard and a few friends sitting around it. I don't want to be anti social there either. I'll check in tomorrow. Good night.

The motor I have was rebuilt about 2k miles ago when I bught the car and I don't have a build sheet. If my oil pump is bad can the pump be changed with the engine in the car? Who makes a good oil pump?
I'm going to put a temporary temp gauge to verify my engine temp.

Brian

You can change an oil pump with the engine in the car, but i wouldn't recommend it. You have to lift the motor off it's mounts to remove the oil pan. If you are that far along, you might as well remove the motor and make it easy on yourself so you can do a good job sealing the oil pan.

I agree. there's a lot of crap to deal with when keeping the engine in the bay. you will have clearences to deal with like the windage tray. the pan won't come out with it in place and the frame is too close. how can a new rebuilt motor do that so early. do you have the proof of it being rebuilt with the list of the replaced parts?trw has a good pump. just make sure its primed with oil before you install it.

I may have to try a different gauge to verify the pump pressure. As far as knowing if the engine was rebuilt, I have to go off the guys word, he was very forth coming with info on the car and did not appear shady the least bit. The motor is really solid with lots of power, doesn't burn oil or show any signs of wear. I hope it's as simple as the gauge.

If I do have to replace the pump it wont be a total loss since I'm planning to do a 200r4 tranny upgrade.

Brian,

You need to verify both temp gauges you mentioned. Take it to a real shop and verify the temps.

1 - The oil pressure going from 60 at idle to 25 while driving warm may not be an issue at all. All depends upon where you are getting the reading from and how the gauge interprets the info.

2 - If your water temp block was hanging at 250 degrees then you would have several other issues and probably wouldn't get too far down the road. Restarting an FGF at 250 plus is almost impossible, so we all would think you'd mention that problem as well. A block that hot would make the starter scream for mercy. Most likely the temp sensor or the guage is reading 20-30 degrees high.

Thanks for the info, I giving it to my mechanic for a couple days to let him play with.

Brian

For Al and Miles (and other OHC owners):

The OHC oiling circuit is unique. Those two threaded and plugged holes in the head are for the lash adjuster oil gallery. The pressure in that passage MUST be held to 10 - 15 PSI, no matter what you are getting at the oil pump. Piping oil into this passage will be destructive to the engine unless you have an in-line 10 - 15 PSI regulator.

The "hour glass" that Miles refered to is the oil pressure regulator tube in the cylinder head. It is in-line with the oil flow between the oil pump and the camshaft. The camshaft has holes in each lobe that are actually metering holes. The cam is designed to "spray" each of the followers. The oil flow through the camshaft is used to determine the pressure in the lash adjuster gallery as the oil flows through the pressure regulator tube.

The oil pressure regulator is VERY sensitive to the pressure coming from the pump. Too much pump pressure is a very bad thing; too little isn't nearly as detrimental unless it drops below 10 PSI.

The factory specs on the OHC oil pump pressure is 31.0 +/- 5.0 PSI.

There is no additional port in the head nor the camshaft housing that allows you to pump more oil to the top end. Internally, it looks as if the engineers at Pontiac were going to take main bearing oil pressure from the mail gallery and run it to the camshaft housing around the second-to-last head bolt on the passenger side. This is one of the places we've been investigating as a possible location for additional oil flow to the camshaft WITHOUT having an external pipe or manifold.

To keep the top end happy, make sure the cam is thoroughly cleaned out. We clean out the main oil passage with a shotgun brush and lacquer thinner. Each lobe metering hole is a .040" (1.0 mm) diameter hole with a slightly larger pilot hole (the dimension escapes me at the moment). These should be cleaned out by hand with a 1.0 mm drill held in a pin vise and turned by hand. Making these holes biggers will cause too much oil to collect on top of the head. If you have weak valve seals this will result in excessive oil consumption.

Excessive clearance between the cam journals and the cam housing (caused by wear) will have similar results. Jerry Woodland had a run of 4-Bbl. cams made with slightly over-sized journals that reduced the problem. Others may still have these cams around. We've developed a couple plating processes to do the same thing; one for the cam and one for the housing. (We also have similar approaches to the oil pump housing and gears, but that's another thread.)

I'm sorry to hi-jack a thread which was obviously for a V-8 oil pump. For that application, the Melling 54-D is your best bet. If you insist on a high pressure oil pump that will simply wear out the distributor gear, go for the 54F.

Believe it or not, the hole in the block that lines up with the oil pump is usually in the wrong place, and should be enlarged and chamfered when you do a rebuild.