Melling Oil Pump Spring Pressure

[Joe L.]

Re: Melling Oil Pump Spring Pressure

SBC use 5/8"dia pickup tube and BBC uses 3/4" dia pickup tube.

clem------


You're almost correct. However, there were some PRODUCTION small block applications that used a 3/4" tube. Does anyone know what they are?

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

clem------


You're almost correct. However, there were some PRODUCTION small block applications that used a 3/4" tube. Does anyone know what they are?

my guess the first ZR-1 and LS series.

[Stuart F.]

Re: Melling Oil Pump Spring Pressure

With this thread in the back of my mind, I went for a ride with my 63 L-76 this morning. At around 2500 to 3000 rpm I'm seeing about 65 psi on my gauge: full warm, w/Rotella T 15w-40. As far as I know, mine has the original oil pump w/ about 44k on the clock. The pan was dropped to remove dents, fix the drain fitting, and change the timing chain and sprockets back in the early 90's. The Vette shop that did the work stole some parts from me so I would not put it passed them to have changed the pump. Why? I don't know. They didn't charge me for a new one.

I was recovering from open heart at the time and my son was managing my Vette then.

Stu Fox

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

With this thread in the back of my mind, I went for a ride with my 63 L-76 this morning. At around 2500 to 3000 rpm I'm seeing about 65 psi on my gauge: full warm, w/Rotella T 15w-40. As far as I know, mine has the original oil pump w/ about 44k on the clock.......

Stu Fox

Thank you Stu, Those pressures seem consistant with the 55 - 60 lbs number in the archives for late 63 solid lifter engines.

tc

[Duke W.]

Re: Melling Oil Pump Spring Pressure

I believe the change to the 55-60 psi spring on mechanical lifter engines was quite late in 1963 production. So, Stu, what's your sequence number?

Also, the change to the higher pressure was accompanied by an 80 psi gage, but I'm not sure how they co-ordinated the new instrument cluster to the new SHP/FI engine part numbers that had the higher relief pressure spring.

Duke

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

I seem to remember Stu's VIN in the 19,xxx range. Mine is 20,3xx with the 80lb oil gauge.

tc

[Joe L.]

Re: Melling Oil Pump Spring Pressure

my guess the first ZR-1 and LS series.

clem-----


Well, the LT5 (ZR1) and LS series engines are fully metric engines, so I expect their oil pick-up screen tube size is some metric size. However, it's possible that they were/are close to 3/4" equivalent. I don't know what the tube sizes were/are for these engines.

The ones I was thinking about, though, are 1st design 1993 LT1, 2nd design 1994 LT1, and all 95-96 LT1 and LT4. These applications use a 3/4" oil pick-up screen tube size.

And, no, I didn't make a mistake on the 1993 and 1994 applications. 1st design 1993 used 3/4" tube. 2nd design 1993 used 5/8" tube. 1st design 1994 used 5/8" tube. 2nd design 1994 went back to 3/4" tube. Then, all 1995-96 LT1 and LT4 used 3/4" tube.

[Stuart F.]

Re: Melling Oil Pump Spring Pressure

Tracy has my sequence number right, and I do have the 80 lb gauge. I picked up a spare gauge from a junk yard near Seattle back in the mid 70's thinking I had a cracked bourdon tube as mine kept leaking a drop every now and then on the E-Brake handle. I finally cured that about a year ago so never changed the gauge. I do believe I'm seeing a tad higher pressure at hot idle now with the Rotella T. Also, at cold start up, it nearly pegs the gauge.

Stu Fox

[Domenic T.]

Re: Melling Oil Pump Spring Pressure

I am with Duke on this, especially if you have your engine rebuilt by someone else.

The casting thickness has nothing to do with the quality of the gears and tolerances.

I have NEVER seen a broken case yet and had to look at a number of STOCK pumps to find one that didn't look new inside or measure out bad.

They actually use this type (positive displacement pump ) in factories that pump every thing from abrasives to water.

I hate to say this here but every apprentice that builds engines and has to turn the page in the book to do so buys an oil pump rather than open up his own SIMPLE pump (4 screws) and look inside. Oh yes I forgot, there is a pin that holds the spring in.

The stock pump is so powerfull it needs a by-pass to RELIEVE the pressure or it will take the babbit of the bearings.

The people that manufacture pumps will paint a doom & gloom picture of what could happen if the pump went bad. They want to sell pumps.

Well the worst oil pump I took out in the 50 or so years was pumping oil. You have to really wear one out to stop the by-pass from working. All you will see is low pressure at idle.

Now if you are going to run your vette around the track all day at 5K+ then look into a better pump and oil pan, and bearing clearances.

GM did put HP/HV pumps in some of their HP engines BUT remember that it had to be PRODUCTION to race in STOCK events. Why the large gas tank fill on our vettes? To fill the tank faster at the track. NO not at the pump.

Some pumps that fail we all hear about are usually not pump failures but PUMP DRIVE failures like the 5/16 hex Ford shaft drive or just run out of oil.

I took the pan off a 64 impalla at the Chevy dealer and the W/O read "replace oil pump Pressure intermittent". There was about 4 qts of jello looking oil and 1 QT of oil that the pick-up sat in. The dip stick read full.

Cleaned the old jello oil out, looked at the gears and re-installed. Pan gaskets only. The pump was operational for the condition of the engine.

look inside one once , SIMPLE. I have a shelf full of oil pumps given to me by guys that were afraid to look inside and purchased new ones.

DOM

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

....
The casting thickness has nothing to do with the quality of the gears and tolerances.

I have NEVER seen a broken case yet and had to look at a number of STOCK pumps to find one that didn't look new inside or measure out bad.

...
DOM

DOM..

You might want to check out the pics from Clem in post number 6 of this thread..

https://www.forums.ncrs.org/showthre...+pump&uid=6787

I think you've missed my point.. I do not know the origin of the pump I have. It is NOT a GM pump, It does however have the narrow casting that is prone to breakage.

If you like, I'll sent this old pump to you and you can "inspect the gears" all you want. I do not want to reinstall the old pump in my engine if there is even a slight chance it will fail under any condition.

tc

[Domenic T.]

Re: Melling Oil Pump Spring Pressure

DOM..

You might want to check out the pics from Clem in post number 6 of this thread..

https://www.forums.ncrs.org/showthre...+pump&uid=6787

I think you've missed my point.. I do not know the origin of the pump I have. It is NOT a GM pump, It does however have the narrow casting that is prone to breakage.

If you like, I'll sent this old pump to you and you can "inspect the gears" all you want. I do not want to reinstall the old pump in my engine if there is even a slight chance it will fail under any condition.

tc

Don't need to inspect your gears, but the case failure in the pic looks like it was the aftermath of what failed before it.

DOM

[Wayne M.]

Re: Melling Oil Pump Spring Pressure

.....The correct stock-equivalent pump for a 396 would be a Melling M-77. The Melling M-77HV can be used, but it's unnecessary. For a big block, using a high volume pump will usually cause no problems, though.

Joe -- I realize the focus of this thread is on pressure and not volume, but is there a chance that a previous owner of my '65 motor, with stock '65-6 grooved rear cam journal and grooved rear cam bearing (see below), but no distributor was included, would have opted for the high volume pump to compensate for a lower BB distributor housing that might not have been stock [ie. partially grooved] ? I've heard that there's a possibility of a "massive internal oil leak", according to 'How to Hotrod BB Chevs'.

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Don't need to inspect your gears, but the case failure in the pic looks like it was the aftermath of what failed before it.

DOM

Really?... I'd figure that if something was swinging around on the rotating assembly and whacked the oil pump hard enough to break it, there would also be damage to the oil pan. That doesn't appear to be the case.

I guess we will never know, but I'm still not betting my engine on it..

tc

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

Really?... I'd figure that if something was swinging around on the rotating assembly and whacked the oil pump hard enough to break it, there would also be damage to the oil pan. That doesn't appear to be the case.

I guess we will never know, but I'm still not betting my engine on it..

tc

most all of these pump breakage problems were pumps used in rough service like boats,dirt track racers and wheel standing drag racers. if you are concerned about this several aftermarket suppliers that sell a strap that attaches the pump body to the windage tray stud

[Joe L.]

Re: Melling Oil Pump Spring Pressure

Joe -- I realize the focus of this thread is on pressure and not volume, but is there a chance that a previous owner of my '65 motor, with stock '65-6 grooved rear cam journal and grooved rear cam bearing (see below), but no distributor was included, would have opted for the high volume pump to compensate for a lower BB distributor housing that might not have been stock [ie. partially grooved] ? I've heard that there's a possibility of a "massive internal oil leak", according to 'How to Hotrod BB Chevs'.

Wayne-----


I don't think that failure to use the "partial groove" distributor in a 1965-66 big block would have caused any oil pressure problem, at all. I would much more expect that if someone used a high volume pump they did so for the same reason that most other folks do---they think that "high volume" must be better.