455 oil pressure

Hello everyone,

About 3 months ago I put a "freshened" 1975 455 in my '73 LeMans. Since it ran when pulled and had good compression (between 165 and 180 psi on each cylinder), I tore it down to the shortblock but no further. I did not change rings or bearings. I put a new oil pump & hardened shaft in (Summit generic brand I believe) and new timing chain & gears (along with a new Comp XE 274 cam & lifters) and of course new gaskets. I am using straight 40 weight Valvoline race oil with ZDDP. Primed it w/a drill and got lots of oil coming up thru the pushrods. First time I fired it, it made like like 60 psi at cold idle, no problem at all. It runs fine so I haven't been paying much attention to the oil pressure gauge, but I happened to glance at it today and it was low, like close to 0 at low speeds and only up to 20 or so at 2200 rpm. This is at 190 degrees. I am waiting for the car to cool down now so I can recheck it cold. The gauge is a cheapie from one of those little 3-guage mini kits you see all the time. I took it out & bled the air out of it, but same result. I am running the oil line from the hole in back of the distributor. I still have the idiot light sensor hooked upo at the filter housing (who knows if it works?) The motor still runs fine & does not make valvetrain noise. I guess my next move is to check the validity of the gauge, maybe pull a a valve cover again... I'd sure hate to have to take this @#$%& motor back out again if I can avoid it. Any ideas? Thanks a whole bunch, Dave  

I would test or try another gauge first and then go from there.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks Pontiacman, that's where I was planning to start. Unfortunately we're having some friends over for dinner at the moment or I'd be out there working on it right now! I just sneaked away to check the thread... gotta go back & be a good host...  

Just found my receipt from Summit for the oil pump... part number is SES-8-60-08-015. It is listed as a "high pressure oil pump". Anyone have any history with these units? Thanks.  

Well in the meantime... I let it sit for about 6 hours & went for a drive. When cold and idling in neutral, the gauge reads about 15 psi. It responds when you blip it, but not as much as i think it should. Once it is warm, it is giving a little less than 10 lbs per 1000 rpm. I get about 20 lbs at 2300 rpm. Hot idling in drive, just about zero. But I don't have a lot of valvetrain noise (like, if you pop the hood & listen for it, you can hear a little). If it was really almost zero at idle, would the lifters lose their oil?

I took the driver's side filler cap off while it was idling. Didn't get oil splashing outta there, but I don't know if it should be or not. I shone a flashlight in the hole, but you can't get a good enough view of the rocker arm to see if oil is coming up through.

Too late to work on it now, gotta put the kids to bed etc.    Tomorrow I'll try another gauge, maybe pull a valve cover... if anyone has any ideas between now and then, I'm all ears. Thanks!  

One last question before I turn in for the night... is there a supposed to be a gasket between the oil pump and the block? I can't remember if I put one in, but I think I certainly would have if A) I had to remove an old gasket when I changed the pump or B) I got a new gasket with the new pump. This was my first time changing an oil pump on a Pontiac and it was 3 months ago, so I don't recall. My shop manual mentions a gasket but I thought I'd check with you the forum. Thanks again for your time.  

Yes there is suppose to be a gasket between the oil pump and the block and the bolts torqued to 30FTlbs.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks a lot. I know I torqued it right but I can't remember if I installed a gasket. I looked in the Summit catalog and it says the pump I bought doesn't come with a gasket, but I may have gotten one with my fel pro gasket set... I think I'll look through the leftovers & see if there's one there. But what I don't get is how it had great oil pressure 2 1/2 months ago and not now. I've put maybe 100 miles on it.

Well today's mission is to switch gauges & see what happens.... keep your fingers crossed!  

Yep, good luck.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Well, looks like it ain't the gauge. Tried the same gauge it in my other car ('73 Grand Am, also a 455 but this one has a real recent professional rebuild) and it responded exactly as the existing gauge did. On the G/A motor, whichever gauge I use, the pressure is at 60 at cold idle, and stays pretty high even as it warms up. It doesn't respond much when you rev it, just stays high all the time. In the LeMans, it reads near zero at idle, but I can get it to swing around when I rev it. I can zing it up beyond 60 lbs, but there's a lag, and you gotta rev it & it's like it's gotta build up to that. Overall the pressure when hot seems to be about 8 lbs per 1000 rpm. I hear people say you can live with 10 lbs per 1000 rpm, but what if you are idling a lot, driving in town, have 2:73s and don't get above 2500 rpm much? I don't think i want to risk it. Well, it least its not ticking or making funny noises, so i don't think I've done any damage yet. Haven't pulled the valve cover yet (@#$%&$ interruptions) but that's next on the list.

Another thing... my G/A has the oil line plumbed to the filter housing, whereas the LeMans has its line going to the hole behind the distributor. Think I'll try moving it over to the other hole & see what it reads there.

But if it indeed has low pressure... why did it have at good pressure 2 months/100 miles ago? I did break in a cam, but I used the moly lube on the cam, and oil w/ZDDP AND some more ZDDP additive in addition (Redline break in oil) and held it at 2200-2500 rpm for 25 minutes etc. I even changed the oil & filter a little while ago (after I'd put maybe 80 miles on the break-in oil) and there was very little metallic glitter in the old oil from the break-in, I was kinda surprised actually. I feel if there's a problem, it must have something to do with the break in, and the fact that I hadn't changed the bearings. But the thing runs great, & doesn't seem to burn oil (well, not enough that you can see blue smoke anyway, I haven't run it long enough to see if it consumes it). I'm thinking before I do any damage I have to yank it and at least change the bearings & the pump. I could try 50 weight oil I guess but that seems like kind of a band-aid. How much pressure can I hope to pick up going from 40 weight to 50 weight? The oil that's in there has like 40 miles on it.

If I end up tearing into it, is there a certain kind of oil pump I should or should NOT use? I don't know if I want to buy another one of the same thing I got (Summit brand), just in case the problem is the pump itself.

Thanks everyone for your eyeballs & opinions!  

I donot go by that general saying 10lbs per 1000Rpms That is just not true.

Yes I always plug the oil pressure line to the filter housing.
Going from 40WT to 50WT donot exspect much difference.
I always use melling oil pumps and never had a problem.
It could be that the engine has loose bearing clearances or the pump.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks again. I plumbed the oil line back there because I read somewhere that it was a better reading, and I also wanted to keep my idiot light/sensor, which was plugged into the filter housing. But it turns out that idiot light doesn't seem to be working anyway. I don't get the "oil" light coming on, whether it is plugged in or not, with the key in any position. When I get home from work I'm going to send 12 volts to the wire & see what happens. And yank a valve cover. But I guess a change of bearings is in my future... shoulda done it the first time I guess. This is the problem with having 2 project cars -- you've got half as much money to spend for each one.  

putting 12 volts to the wire for the idiot light won't do anything because it is already 12 volts. The sensor completes the ground circuit when there is no pressure. If you want to check the light, ground the wire with the key on and check if the light comes on.
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

Yeah, I vaguely remember that was the case, sort of like a doorbell circuit, the switch interrupts the circuit rather than closing it... thanks a lot Steve!  

Hi There!
   This is Adonis from Italy!
 Im new in this site!
 looks like it ain't the gauge. Tried the same gauge it in my other car ('73 Grand Am, also a 455 but this one has a real recent professional rebuild) and it responded exactly as the existing gauge did. On the G/A motor, whichever gauge I use, the pressure is at 60 at cold idle, and stays pretty high even as it warms up. It doesn't respond much when you rev it, just stays high all the time. In the LeMans, it reads near zero at idle, but I can get it to swing around when I rev it. I can zing it up beyond 60 lbs, but there's a lag, and you gotta rev it & it's like it's gotta build up to that. Overall the pressure when hot seems to be about 8 lbs per 1000 rpm.

Thanks!...

 See you soon Guys!...