Oil Pressure-Oil Pump advice

I did a search on the site but could not find much on oil pressure so here is my question: Rebuilt a 67 400 a year ago that is in the Sportwagon GS400 tribute car. When the car starts cold I will get 40# pressure right away, when it warms up going down the road I get 20# but when I stop at a red light and idle it goes to Zero or 1-2# max, Using a new set of Auto Meter manual gauges for water temp, Amp and Oil.

I have asked the engine rebuilder if they put an oil pump rebuild kit in the engine but they honestly do not remember although they normally do. I have researched the kits and Melling makes three kits, one for stock which is gears, plunger, gasket and springs. They also make two more kits for high volume pumps The difference in the two kits is one gives you the gears, plunger, gaskets and springs while the third one includes the metal housing to enlarge the chamber.

After we dropped the engine in the car we did the pressure test with an electric drill and screwdriver bit into the distributor hole and with medium to high rpms on the drill we got 60# but not sure the engine is turning as fast as we did with the drill.

Any body have advice regarding the low pressures and had any luck with re-build kits? I can live with 20# but the Zero at stop lights bothers me.

Thanks in advance for info and advice.

 

1st question...... the way it sounds this motor has been running a year already and now having issue??????

if yes and now an issue I would ge very very very worried.

if it hasn't been running for a year and it's just recently fired from rebuild. there are a few things here......bearing clearance s???? do we know what they are set at.
it only takes a few minutes to drop the filter housing, look at the gears, the pocket, verify proper clearances, install a booster plate and see if any improvements. too much space between the gear and filter housing/booster plate will cause very low pressure.

worse case you can buy high volume pump gears......longer gears with spacer plate, to increase the oil out put that might help, especially if bearing clearances are set very wide....

most ppl dont like these gears because they put extra load on dist drive and cam.....but you have to do what you have too.


the oil isnt very thin?????? not full of water or fuel correct????

a booster plate should be on every motor no matter what. it acts like a new wear surface if the filter housing is worn.......plus it add strength and keeps the pocket shape from expanding with heat.

if the gear pocket looks worn or has too much side clearance between gear and housing.......might just need a new timing cover

 

Thanks for the input. First, I am off a year on finishing the car because we took it to the BCA National meet in Brookfield, Winconsin in early July 2017. The engine had been rebuilt during the spring of 2017 so we are coming up on 2 years since we finished and started it. I have driven the car probably less than a 1000 miles since then, local around town and on the freeway here and there but no trips more than 25-30 miles each way. No strange noises, not overheating, valves quiet, has a mild Crower cam in the engine that gives the stock components a bit a boost but not a lot. Car always starts right up, does not over heat and stays between 180 - 190 degrees unless it is a Texas summer 100 - 105 degree day and it will go to 200-210 if idling in traffic, all this with the A/C not on.

Oil is Pennzoil 10W40 and not thin and we are getting ready to change it and filter this week. Will take a hard look at old filter and consistency of the oil when drained. I like the idea of high volume gears and spacer plate but if folks have had bad luck with straining the distributor drive and cam gears would like to hear about it.

Appreciate all input.

 

Quick intervention:
If you are searching for a topic/ subject here, try using Google to search your topic/subject and add v8buick.com to the subject line. Seems to work better than the website search engine. Jim

 

Larry, great post and thanks for forwarding it to me. I did research the words 'oil pressure' on the site but should have used 'oil pump' From this great explanation I will discuss my options with my mechanic and we will make a decision on what if anything we would do now. Since I am retired I let him do the dirty work and I do the easy stuff.

 

With the oil pressure that low, the very first thing I would look for is a pressure relief valve stuck partially open in the oil filter housing.

Simply take the 1" nut off, remove the spring, and stick a magnet in the hole, you should be able to pull the relief valve right out.

JW

 

I run the longer gears in my scavenger setup, but on a basic build street fue motor I would verify all the other options first then use the longer gears as a last choice option to fix the problem.

has the oil pressure been this way ever since the new rebuild was first fired u and driven??? or is this a recently new issue

 

This has been an issue since the engine was first fired back in the Spring of 2017. Again, no signs of the engine under duress but bad things could be happening that I am not aware of.

 

Will do Jim, Thanks

 

Next oil change, tear the filter apart and check for bearing material too....just to rule that out..

 

You'll have to disassemble the pump and see if it was assembled correctly. That'll tell the story.

If your engine guy can't remember if he rebuilt the pump, arguably one of the most important part of the engine rebuild, I'd be wary of the rest of the job.

 

We are thinking alike, I am going to change the oil this week and mentioned to my mechanic that I wanted to have a look at what is in the filter.

 

Joe, the engine guy is very good, it has been almost 2 years since they did the engine and have done a lot more engines since then so I can understand a fuzzy memory. He did tell me Saturday that they normally would have rebuilt the pump and they do a lot of Buick engines.

I am going to follow Jim's suggestion about a stuck pressure relief valve. If we find that is the case then we fix it and I see what kind of pressures I get with the valve fixed. If I don't find the pressure relief valve a problem then I do plan to order a re-build kit and install it. We will see what we get out of the engine when I do that.

 

Maybe the oil pump rebuild would be on the invoice?

All things considered a poorly assembled pump would be an easy fix and fairly painless.

 

A little advice. I stupidly didn’t tighten all the bolts on the pump housing a second time after installing and running the engine for 10 or so miles. Retorque the pump housing bolts, cause when I did it, my pressure jumped up everywhere

 

Take a look at the filter bypass valve when you have the filter off.
Early valves were a flat disc, and a lot of times they would get cocked sideways... OPEN
Later valves were conical, self centering.
Had this happen to me on a '75 LeSabre waaaay back.

 

I say it has loose clearances and just put 20/50 oil in it and see what you get. It's still really only 20w oil but with viscosity improvers so it supposedly acts like a hot 50W when hot. Back in the day a lot of people ran straight 40 and that is a whole lot thicker than 10W/40.