Frankie the Fink

My 250hp '63 idle oil pressure after car warmed up for 10 minutes. 80# gauge, 700RPM idle... Mobil 1 15W-50W

Engine was rebuilt in 2004 and I don't know what oil pump/spring arrangement was used...

Robert61

If you followed what I wrote I listed a Melling M55HV. That is a high volume pump. Just to note where the springs might come from, they have one spring for high volume and one for high pressure. No changing out anything in a stock pump will not change the volume it's capable of but it will change the pressure and pressure is the OP concern.

Robert61

Like I said earlier people never complain about too much pressure only when it's low. The OPs engine has been together for 29 years, unless there's been a recent change as in engine damage, it's survived this long with just what he has. I just happen to be one that likes a lot of pressure. It may not be necessary but they didn't put 80lb gages in em just for decoration.

Robert61

I have a dyno for these but it's for stock class engines. One of these would be a bit much for it. These blocks came simi finished, they had no seats guides or sleeve. They were special Briggs racing blocks no longer available. Now days everyone use overhead valve motors. i snapped pics of installing the seats just for Mike M.

tbarb

The stock or HV Melling pumps are constant volume, the gear set is taller in the HV pump which simply allows a greater volume of fluid. There is no spring I have ever seen that controls volume.

On a small block pump, the relief spring tension in the pump cap controls when the spool moves to uncover the port that will allow oil to bypass back to the pump main body.

IMO, to much pressure is as bad as low pressure, it over comes the baffles in the valve covers and will leave to much oil in the top of the motor. The 80lb gauge is installed because the SHP engines used a high pressure spring which relieved at approx 55-60lbs.

I am sure you already know all this stuff but I don't want the O/P to think he can change a spring to correct his concern about the gauge reading at idle RPM. Different story at the other end of the RPM scale.

Robert61

But he can change it at idle with a stronger spring or stretching his. I've never seen a case where it wouldn't. The plunger doesn't just start to work at higher rpms. My daughter has a Yukon XL 6.2. It had a low oil pressure warning chime that was driving her nuts. I stretched the spring in it and at cold idle it would have 80lbs which was the max on her gage. She was scared it was going to blow up. I told her don't worry about it after it warmed up it idled at 40 and drove at 60+. That was with the same original pump.

SWCDuke

Oil pumps are of the "constant volume" variety. Delivery volume increases with engine speed, and this also increases back pressure, which is what you see on the gage. Once the pressure relief valve begins to open, excess volume is shorted back into the pump inlet and pressure and flow remain about constant with increasing revs. If there was no pressure relief spring, both volume and pressure would continue to increase with RPM, and eventually the pump will either cavitate or break due to excess stress levels.

With same spring a high volume pump will achieve pressure relief spring opening value at lower engine revs.

It takes more power to drive a high volume pump with the same relief spring as a standard volume pump, but more is being shorted back into the inlet while delivery to the main oil gallery is essentially the same.

Duke

Nowhere Man

Duke what can happen if you have to much oil pressure?

Robert61

I don't do engines anymore except for very close friends. But when I do I prime and make sure they have plenty of oil pressure before they leave. I set the pressure with the spring. I did a BBC a couple of years back. I had the pan off of that thing at least 6 times. I couldn't get above 30lbs. It went so far that I was about to tear back into the motor when I focused on the gage which was nearly new. The gage was bad.

Robert61

Read what I posted about the girls Escort. It blew the filter off.

Frankie the Fink

If a crankcase becomes pressurized and can't dissipate it quickly enough, the car can develop leaks, blow out an oil filter or launch a dipstick out of its tube. Not sure, but if it causes foaming oil - that's certainly not good either...

tubman

I'm not "Duke", but I had a freshly rebuilt L79 with a Mellings M55HV pump with a high pressure spring installed. From the beginning, the engine ran with the 60 lb oil pressure gauge pegged, even at hot idle. It caused all kinds on problems, the worst of which were blue smoke on startup and excessive oil consumption. I put up with it for the first thousand miles or so, hoping that the engine would "break-in". It never did. I installed a standard pump with the standard spring. This brought the pressure back to normal (25 lbs at idle and 47 lbs on the road), but didn't cure the oil consumption (1 quart per fill up). I gave it a couple of years to clear up by itself, but it never did. In addition, higher than designed oil pressure puts extra strain on the pump drive system and generates extra heat into the oil.

Finally I had had enough; I pulled the heads (from an engine with less than 3000 miles) and took them to a machinist I know and trust from my flathead builds. He found the stock type valve seals distorted and pushed out of place. He said this could have been from just a bad installation job, but most likely was caused by the rocker arm covers being overwhelmed with oil and actually filling up and causing undo pressure on the seals. He installed the special new Viton seals that he said will absolutely solve the problem. I have the engine half together and will know for sure when I get it running. The re-assembly has taken longer that it should have, because I have decided to clean up the mess in the engine compartment caused by the oil mist and dirt that this caused. Everything was coated with a fine mist of oil, which of course, attracts dirt.

If you check the Mellings price list, you will find that the M55HV sells for about $20 less than the standard, proper pump. The builder can say, "Look, I upgraded you to a hi-volume pump for no extra charge" and put the $20 in his pocket. I will never again have an engine rebuilt by a guy who says he specializes in "Racing Engines", since I've been burned twice by them.

To anyone contemplating "upgrading" either the capacity or pressure with a change in pumps or internals, I say "DON"T DO IT". Unless you are building a special racing engines with large clearances, these things can cause more problems than they could ever think to solve. Again and again I have to say : "The Chevrolet engineers knew exactly what they were doing when they designed these engines". Anyone trying to second guess them is playing with fire.

To the O/P : take the advice of the guy who said to deal with it only if it becomes an obvious problem, (like clattering lifters).

65tripleblack

Crankcase pressure is not the same as oil pressure. I think you know this, however the manner in which you expressed the situation can lead to confusion.

Excess crankcase pressure leads to oil leaks, dislodging the dipstick tube, and in more severe cases, oil in the air filter housing.

Excess oil pressure leads to excessive parasitic pump losses, spark scatter, and in severe cases where there is insufficient drainback, oil in the air filter housing. Excess pump loading will cause shaft collar breakage and severe gear wear. I would think that an oil filter wouldn't burst at pressures less than about 150 psi. Why don't you do a test at home and report the results. Should be interesting.

Foaming oil can be caused by too high oil level which results by too much oil being entrained in the crankshaft windage. Also by pump cavitation. Or, mercy forbid, by coolant mixed into it, although that is an emulsion and makes a terrific salad dressing.

Critter1

And don't forget the destruction of the distributor main shaft and bushings.

65tripleblack

Which is why in post #40, I was trying to clear up any confusion Robert61 may have caused.

For an incompressible fluid, flow through a constant area cross section is proportional to pressure differential.

None of this acknowledges that installing a less compliant spring will increase pressure at idle. A stiffer spring will only regulate the bypass pressure.

The only ways for the OP to increase oil pressure at idle is to increase idle speed and/or increase oil viscosity and/or decrease oil temp and/or decrease bearing clearances.

65tripleblack

SWCDuke

Good post. I've been saying this for years that road engines and race engines are completely different animals, but these so called "engine builders" keep installing too big cams, high volume oil pumps, often too low compression, and perform unnecessary machining operations.

Excess oil pressure, within reason, won't do any real damage, but have issues as mentioned in the previous posts.

One risk is running the oil pan dry because too much oil is being pumped up into the engine and it has a hard time getting back down, especially at high revs under high dynamic loading conditions, which can starve the engine of oil due to the pickup sucking air.

Most small blocks only have a four quart oil pan. My Cosworth Vega has about the same size pan, but the top end oiling is restricted by a .090 "metering orifice, so SBs probably have a whole lot more oil going "upstairs".

I recall consulting with a Cosworth Vega owner about an engine overhaul. He said his engine guy builds "killer small blocks". I asked if the guy had any experience with Vega aluminum-silicon blocks. The owner didn't know, so I explained how conventional boring and honing has to be followed by an etching process to remove about .0005" of aluminum to leave a very hard silicon wear surface, and then the pistons require a special plating operation, but I didn't know of any correct replacement pistons or any shops that had the equipment to etch the bores properly, so if there is any problem with the bores the conventional field procedure is to iron-sleeve the bores and use a conventional forged piston, which are available from JE.

I never talked to the owner again, but heard later that the engine seized up 100 miles down the road, and the owner sold it for a song to a guy who has many of them. He rebuilt the engine properly with sleeves and new JE forged pistons and got it back in service.

The story I got was that, as expected, there was virtually no bore wear. When reringing a cast iron block engine it is common to do a fine hone, which removes very little material - only a few tenths of a thou, but you can't do that to a Vega block or other later engines that have similar materials technology.

Apparently "Mr. Killer Small Block Engine Builder", who obviously knew nothing about the GM/Reynolds aluminum block technology honed the cylinders then put back the original pistons with new rings. Live and learn.

I run into these situations with Chevy engines, too. Someone might contact me about an engine overhaul, and once I understand their driving environment and objectives I'll make my recommendations. Then a couple of weeks he calls back and tells me what the "engine builder" says, which is usually very different from my recommendations regarding cams, compression, and machining operations. All I can say is it's your car, so you have to make the decision.

Of course, owners are paying these so-called "engine builders" a good sum of money, so they figure they will get what they pay for. I, on the other hand, offer my consulting for no charge, so since they didn't have to pay me for my analysis, the value they may place on it is zero.

Duke

Robert61

We're on the internet so there's no way to know for sure what someone means when they type. But let's just say Duke is referring to me as a 'so called engine builder'
. And for reference sake I spent 21 years building engines full time. Many race engines but I managed the performance street engine side. We are not talking about racing we are talking about low oil pressure. I would consider good street pressure to be 25-30 idling 60 at cruise. High oil pressure will not bend valve seals, it will not cause excess crank case pressure, it shouldn't pump the pan dry and will not under normal driving. A BBC has a much higher volume pump than a sbc if high volume were to suck the pan dry BBC s would be in real trouble. High pressure can cause cam gear failure or the drive to shear. But we are not talking about that kind of pressure. Chevrolet puts high volume pumps in all of their high performance crate engines. And lastly I'm out of this thread as they always seem to turn into this type of back and forth.

tbarb

I can't speak for anyone but IMO no one is referring to you in that manner. I simply do not agree with your statement about correcting low oil pressure by stretching or changing the oil pump relief spring and I would never want the O/P to think that.

My 63 may be on the loose side also because when hot the idle pressure is approx 15lbs., it doesn't bother me a bit.

wmf62

Robert61
there are some people on this forum that are pompous know-it-alls, and I don't consider you to be one of them.

Bill