Small Block Oil Pump/Pressure help needed

[Dave S.]

Re: Small Block Oil Pump/Pressure help needed

For your benefit and the Performance Verification nit-pickers, please let me refer you to page 6 of the July 1965 Chevrolet Service News:

"High Engine Oil Pressure!
Corvette 327 CU. In. - 365-375 HP.

The above 327 cu. in. high performance Corvette
engine oil pressures in the area of 80-95 psi (at
2,000 RPM) can be expected and are perfectly
normal. However, damage may occur to this en-
gine if the 283 cu. in. engine oil pump is used
which delivers oil pressure of 65 psi at 2,000 RPM."

Thanks Loren and Gary.
Loren - Very interesting. Maybe I have a normal situation. I did try straight 10W oil to see if the oil pressure was lower but that produced no change in oil pressure. Before this excercise I was getting pressures of 70 psi to pegged (80psi) at 2000 rpm when hot. Maybe that is normal. I'll report back after I change the spring in the GM pump. I'll find a copy of the July 1965 Service Bulletion.
Gary - I appreciate the offer but will go the GM route for now.

[Patrick H.]

Re: Small Block Oil Pump/Pressure help needed

Gary - I appreciate the offer but will go the GM route for now.

Melling supplies the springs to GM.

[Dave S.]

Re: Small Block Oil Pump/Pressure help needed

Melling supplies the springs to GM.

Not surprising.
Not sure which Melling spring matches up to which GM spring. The Chevy parts guy tells me the 911 (high pressure) springs are discontinued but there are still some in stock so Melling may be the only option in the future.

[Duke W.]

Re: Small Block Oil Pump/Pressure help needed

Dave,
The standard oil pressure spring, for hydraulic lifters, is Melling 55049, they come in a package of 5 springs. I you need a "green" low pressure spring, let me know, I'll mail one to you. The yellow, 55048, what I call a medium pressure spring, most solid lifter engines use these. That is what all Melling pumps are shipped with today. Melling also offers a high-pressure spring, 55070, which is pink. All the oil pump spring rates can be found on the Melling web site:

http://www.melling.com/Portals/0/Spring%20Packs%20Updated%20PDF%20100710.pdf?ver=2010-10-07-082542-910

Gary B

Prior to the use of a 55-60 psi spring in late '63 mechanical lifter engines, all SBs, both mechanical and hydraulic lifter used the same 40-45 psi spring. (All measured hot at 2000 revs.)

Ya gotta wonder about some of those TSBs... reminds me of owner's manuals dire warnings about "serious engine damage" or some such verbiage if you overfill the oil, but says nothing about letting it get too low.

Back in the fifties Corvette racers ran a quart or two over to prevent oil starvation under high dynamic loading, and GM finally recommended this for the first time on the '01 Z06.

I did the same thing with the Cosworth Vega when I ran it in track events and never had a loss of oil pressure, but I knew of several that suffered bearing damage when the owners jazzed them around with the oil level low.

Duke

[Joe L.]

Re: Small Block Oil Pump/Pressure help needed

Not surprising.
Not sure which Melling spring matches up to which GM spring. The Chevy parts guy tells me the 911 (high pressure) springs are discontinued but there are still some in stock so Melling may be the only option in the future.

Dave------


Assuming that Melling supplies the oil pump relief springs to GM, that does not mean the springs they use in Melling-branded pumps or otherwise supply separately are the same. This is the kind of assumption that folks often make but it's often not valid. It's very possible that Melling makes the GM springs to a GM specification and makes Melling-branded springs to their own, different specification. Many automotive parts manufacturers have OEM divisions that manufacture parts for the OEM manufacturers and aftermarket divisions that manufacture parts for sale into the aftermarket under their own or other brand names. Sometimes, the OEM and aftermarket parts are not even manufactured in the same factories.

[Patrick H.]

Re: Small Block Oil Pump/Pressure help needed

It's been 20 years, but someone at Melling told me that the pumps installed (then) on small blocks are the same ones we buy OTC from them, and that they were supplying GM with the pumps and parts. So, according to Melling they were the same units.

[Joe L.]

Re: Small Block Oil Pump/Pressure help needed

It's been 20 years, but someone at Melling told me that the pumps installed (then) on small blocks are the same ones we buy OTC from them, and that they were supplying GM with the pumps and parts. So, according to Melling they were the same units.

Patrick---------


Yes, GM did cease the internal manufacture of small block oil pumps quite some time ago and I also believe that Melling has supplied them to GMSPO and for SERVICE engines since then. However, I believe the pump they supply is the Melling 10553 and not the far more common M-55.

As far as the pressure relief springs go, I'm not so sure. I'd like to see the GM springs side-by-side with the Melling equivalents. I've got many NOS examples of all the GM springs. Maybe some day I'll obtain the Melling springs and compare them.

[Patrick C.]

Re: Small Block Oil Pump/Pressure help needed

Here are the presures my L84 shows at idle and 2000 rpm. 15w40 oil, recent stock rebuild on a low mileage engine with original oil pump.

[Dave S.]

Re: Small Block Oil Pump/Pressure help needed

Thanks Patrick,
Looks like you have 40 psi at hot idle and 75psi at 2000 rpm. That seems about right to me. I'll have my GM high pressure spring (911) This week and we'll see what happens. Hopefully that will provide proper results.

[Richard M.]

Re: Small Block Oil Pump/Pressure help needed

Thanks Patrick,
Looks like you have 40 psi at hot idle and 75psi at 2000 rpm. That seems about right to me. I'll have my GM high pressure spring (911) This week and we'll see what happens. Hopefully that will provide proper results.

Dave, I think it's reading around 60psi at 2000 rpm.

Rich