Oil pressure gauge

[Randy R.]

My 67 L79 was rebuilt using a high pressure oil pump. Could I install an 80# gauge with a 60# face? I would rather not open the engine.

Thank you,

Randy

[Bob R.]

Re: Oil pressure gauge

I had a similar situation for several years and just left the 60# gauge in place. It was always pegged when the engine was running, eventually I had the correct spring installed in the pump and all is fine. No damage was done to the gauge that I am aware of. It isn't that difficult to change out the spring a couple hours of work to remove the oil pan and then the pump you could schedule it for your next oil change. I think it is easier than remove the gauge cluster and putting that back in. I hate working under the dash I'm getting too old to fit under there.

[Mark E.]

Re: Oil pressure gauge

I agree. Dropping the oil pan on these cars is easier and less risky than tearing into the dash. It's also an opportunity to renew the RMS, as needed.

[Duke W.]

Re: Oil pressure gauge

Your oil pump might also be a high volume type. "Engine builders" do this stupid thing all the time. As others have said it's probably easier to drop the pan and install a proper standard volume oil pump with a correct 40-45 psi spring, which I believe are still available from GM, and most of the aftermarket springs will result in too high pressure, which your engine doesn't need. There have been dozens of "high oil pressure" threads over the years.

I believe Joe Lucia has listed the GM part number for the spring, which should be an easy search.

Duke

[Donald H.]

Re: Oil pressure gauge

I had the same issue with my 66 L79. When I bought the car some previous owner had installed an 80# gauge and high pressure pump. I pulled the cluster during restoration and put in a 60# gauge and installed a Melling 10553 pump. This pump had the wrong spring from the factory so I purchased the Melling green spring, which if I recall is rated 49# and my idle sits at 45 on the 60# gauge just like it should.

[Duke W.]

Re: Oil pressure gauge

45 psi idle oil pressure is way too high. The GM spec is 40-45 psi at 2000 engine RPM with the oil at full operating temperature.

GM has no spec for idle oil pressure, and it's highly dependent on idle speed. The higher the idle speed the higher the pressure, so SHP engines that usually idle in the range of 750-900 in neutral will show higher pressure than a base cam engine that idles at 500 in neutral. Typical range is 15-30 psi depending on idle speed, oil temperature, and oil viscosity range.

A "high volume" pump will show higher idle oil pressure than a standard volume, even with the same relief spring.

The lowest pressure relief spring offered by Melling is 49 psi, which is still too high, so it's probably best to bite the bullet and pay the price for the OE GM spring, but why replace the oil pump in the first place.

Most so-called "engine builders" replace the oil pump, apriori. However, the fact is that most oil pumps are entirely serviceable for the life of a rebuilt engine. They are easy to disassemble, inspect, and "blueprint" to as new or better specs, especially gear end play. If the oil pump has never ingested a lot of debris from something disintegrating in the engine, there's about a 90 percent chance that it's perfectly reuseable.

Duke

[Guest]

Re: Oil pressure gauge

Why fool around with the stock gauge for the car just drop the Pan replace the spring only on pump

[Randy R.]

Re: Oil pressure gauge

I have the original oil pump and pickup. They have been in cold storage and have some surface rust. Where can I get the pump blueprinted?

Thank you for the responses.

Randy

[Timothy B.]

Re: Oil pressure gauge

Randy,

Do it yourself, it's a simple gear driven pump and when you take it apart if the gears are not damaged by pits it's completely serviceable.

Google for information but all you are really doing is a good cleaning and check/establish a tighter end play for the gear to pump body This end play will keep oil from bypassing inside the pump body.

In the cap, remove the retaining pin to clean and make sure the bypass piston moves freely in it's slot then reassemble with the same stock spring. Broach the cap surface so it's tight against the pump body when tightened. I would purchase a new pickup and make sure it is set to the correct angle (depth in pan) before you drive the interference fit tight. After you twist it tight at the correct angle take it to a machine shop because they have the correct tool to drive it home without damaging the flange then let them put a small tac weld. Be careful you don't make it to low because it will drum on the pan bottom when the engine is run.

[Bob W.]

Re: Oil pressure gauge

Randy The GM part # are std 3814903- high press 3848911. Hope this helps.

[Duke W.]

Re: Oil pressure gauge

I have the original oil pump and pickup. They have been in cold storage and have some surface rust. Where can I get the pump blueprinted?

Thank you for the responses.

Randy

It's in the book "How to Hotrod SB Chevies". I don't know if it's still in print, but there are probably used copies on ebay, etc. Dress the cover on a flat surface with some 240-400 mineral spirits wetted paper to remove any high spots/wear. Measure gear end play, then dress the housing as above and one gear if necessary to shoot for 2-3 thou end play. That will make the pump prime faster.

It's difficult to weld steel to cast iron, so the usual process is to braze the pickup to the pump, say in three places. As long as the pickup has never been disturbed since is was installed by GM it's very unlikely to come loose, but the brazing is a cheap insurance policy.

Duke

[Randy R.]

Re: Oil pressure gauge

I took the original oil pump apart and determined that a new pump is required. What should I buy?

Thanks again,

Randy

[Bob R.]

Re: Oil pressure gauge

I think your only option is a Melling pump. You should be able to get one at any NAPA store but they still have the wrong spring so that will have to be changed.

[Duke W.]

Re: Oil pressure gauge

I took the original oil pump apart and determined that a new pump is required. What should I buy?

Thanks again,

Randy

Why do you think it needs to be replaced?

Duke

[Randy R.]

Re: Oil pressure gauge

The gears are pitted.

Randy