Oil Pump - too much pressure?

Reply Subscribe

Thread Tools

Search this Thread

Mar 30, 2002 | 01:14 PM

kaiserbud

Thread Starter

Melting Slicks

Joined: Feb 2001

Posts: 2,608

Likes: 3

From: TEXAS - you mean there are other states?

Oil Pump - too much pressure?

I took my car to the shop to replace the oil pan. Its a 427/435 and the pan was pretty beat up. Anyway - while inside the motor, the shop identified that the pump was partially plugged. (See pic - gives credibility to being careful when applying sealant). Although the pressure would go way up when in race mode (60++), the idle pressure was low (5-15).

I previously had pump # 390 6629 88 GM 22 (can anyone identify?) :confused: and was happy with it. It gave fair pressure at normal operating and volume/pressure went up appropriately with high RPM's.

For years, I have always been a supporter of high volume over high pressure. The shop said they would put in an equal pump and installed M77HV (can anyone identify this one?) :confused: At idle it has 70 psi ! :eek: I am sure the volume is there, but isn't this overkill at idle? Granted, the hot Houston summers will thin the oil and pressure will drop. Any thoughts?

Thanks, kaiserbud

[Modified by kaiserbud, 11:23 AM 3/30/2002]

Mar 30, 2002 | 01:23 PM

Scott78

Drifting

Joined: Mar 2001

Posts: 1,514

Likes: 1

Re: Oil Pump - too much pressure? (kaiserbud)

The 77HV is a Melling High Volume pump for big block that'll come with 2 springs and a 3/4 inch pick-up tube inlet. A colored High pressure spring and a "regular" pressure spring. I'm not sure what the PSI difference is between the two spring are. I like Melling pumps I've used several never a problem. I have the 55HV (smallblock) with high pressure spring in, with Mobil Synthetic 5W-30 I have 80 PSI cold and 40 PSI hot at idle and 60 PSI hot at cruise. Hope that helps.
Scott

[Modified by Scott78, 11:23 AM 3/30/2002]

Mar 30, 2002 | 01:26 PM

zwede

Race Director

Joined: Sep 1999

Posts: 11,361

Likes: 383

From: Plano TX

Re: Oil Pump - too much pressure? (kaiserbud)

I don't like HV pumps on big blocks. As you can see, idle pressure is way up there. I had the same pump and buried the needle over 1500 rpm, even when hot. I feel the high pressure promotes leaks and increases stress on the distributor gear.

I switched to the regular melling pump (same PN, but no HV at the end). I used the corvette spring that it came with. I now have 35 PSI hot idle and 60 at high rpm.

Mar 30, 2002 | 03:11 PM

kaiserbud

Thread Starter

Melting Slicks

Joined: Feb 2001

Posts: 2,608

Likes: 3

From: TEXAS - you mean there are other states?

Re: Oil Pump - too much pressure? (zwede)

Markus - Scott

Appreciate the info. I still would like to figure the old part number info. I have to agree with Markus regarding high pressure - I think the HV (High Volume) is very appropriate for a big block - moreso in the heat of Houston. I may pull it out again and look. I wasn't happy with the work this shop did in many aspects. Future posts will discuss other issues.

Can anybody adivise the old ol piump specs?

Thanks Markus and Scott

Reply Subscribe