BB - Replace high pressure oil pump?

[Clem Z.]

Re: BB - Replace high pressure oil pump?

one thing to check is the pump output passage alignment with the recess in the rear main cap. sometimes you have to do a little relieving on the cap recess to make sure the pump out put is not restricted.

[Joe L.]

Re: BB - Replace high pressure oil pump?

The idea here is simple: a high volume pump works harder, requires more torque and thus robs more power from the engine. Using arguments such as "I don't think", and "I think, for all practical purposes" does not change this simple fact. If you don't believe it, then I have a perpetual motion machine that I'd like to sell you.

If your pump, in whatever flavor you choose to install, is well blueprinted, with streamlined and enlarged passages, then you will absolutely minimize the effects of a high capacity pump. Don't forget that if you do the same treatment to a standard volume pump, that the relative differences in power robbing will re-align to their original values.

In this exploded view:

http://moroso.com/catalog/categorydisplay.asp?catcode=14444

please note the anti cavitation slots, which are a modification added to very high end pumps. These can be added to any pump, and go a long way in minimizing chatter and resultant spark scatter.

The bottom line is that if you don't need a high volume pump, then don't install one.

Joe-----


The terms "I think" and "I don't think" are alternates for "it's my opinion" and "it's not my opinion". So, if those terms are more "digestible" to you, just substitute them. Certainly, I have a right to my opinion.

It remains my opinion that the difference in power requirement between a big block standard volume pump and high volume pump is not worth worrying about for a street engine.

It remains a fact that GM validated the use of a high volume pump for all Mark VI big block engines. That represented a lot of engines built. It is true that the Mark VI oiling system is somewhat different than the Mark IV. Nevertheless, it remains my opinion that the high volume oil pump can be used just as effectively and safely for Mark IV engines.

Personally, if I were building another big block, I would be using a GM #3969870 pump (and I have 5 NOS GM #3904826 pumps in the collection [none for sale]).

Also, I have consistently and "forever" recommended against the use of a high volume pump in a small block for ANY street application. However, I have recommended and continue to recommend the use of a high volume pump (specifically, the GM #3969870) for big blocks. Now, is this to say that I do not recommend the use of a standard volume pump for big blocks? Absolutely not! A standard volume pump is just fine for any street application if one chooses to use that. I choose to use (and recommend) the GM #3969870, though.

[Joe R.]

Re: BB - Replace high pressure oil pump?

the reason the ZL-1 aluminum block engine used a high volume pump is because the clearance in a aluminum block open up as it heats up so you have more internal oil leaks. this happens around the lifters and where the distributor fits thru the lifter gallery because aluminum expands more than steel. you need 1 quart over if you run the engine to the red line because it is slow to return the oil to the pan

Clem,

That is very interesting! It sounds like GM spec'd the ZL1 pump as a service replacement for all BB Chevys because it will work for the aluminum and cast iron blocks. But it still seems like it's less than ideal for the cast iron blocks. I'm not interested in throwing away HP unless I have to.

Am I correct in gathering that the standard vs. high volume pump does not make much of a difference as far as oil returning to the pan at high RPM?

Joe

[Joe R.]

Re: BB - Replace high pressure oil pump?

How many HP do you lose running a high volume pump vs. standard volume?

Duke recommended Sealed Power earlier in this thread. Is this a good pump?

https://www.napaonline.com/Catalog/C...219107021&An=0

So far I haven't gotten much feedback on the two questions above.

Is it safe to say we're talking 5 to 10 HP difference between the factory L72 and ZL1 pumps?

I should have mentioned how I came up with the link to Sealed Power pump. In another thread, Joe Lucia provided this info:

"If you mean the ORIGINAL part number, it was GM #3876868. However, that part was discontinued and replaced in December, 1966 by GM #3904826. That, in turn, was discontinued in July, 1981 and replaced by GM #475908. Finally, in September, 1992 the 475908 was discontinued without supercession."

Using NAPAonline's interchange, I tried 3876868 - got nada. Then I tried 3904826 (which I also found out is the L71 pump). 3904826 crossed to the Sealed Power pump shown in the link. I guess no one has used that one? Are any of the GM #'s listed by Joe still available from Chevy?

Joe

[Clem Z.]

Re: BB - Replace high pressure oil pump?

Clem,

That is very interesting! It sounds like GM spec'd the ZL1 pump as a service replacement for all BB Chevys because it will work for the aluminum and cast iron blocks. But it still seems like it's less than ideal for the cast iron blocks. I'm not interested in throwing away HP unless I have to.

Am I correct in gathering that the standard vs. high volume pump does not make much of a difference as far as oil returning to the pan at high RPM?

Joe

the return is strictly by gravity nothing to do with the pump. blueprinting your engine to specs and doing A PERFORMANCE VALVE JOB WILL GAIN A LOT MORE HP THEN YOU WILL LOOSE WITH A 3969870 oil pump.. this pump is still listed in the GM performance parts catalog of 2010

[Joe L.]

Re: BB - Replace high pressure oil pump?

Clem,

That is very interesting! It sounds like GM spec'd the ZL1 pump as a service replacement for all BB Chevys because it will work for the aluminum and cast iron blocks. But it still seems like it's less than ideal for the cast iron blocks. I'm not interested in throwing away HP unless I have to.

Am I correct in gathering that the standard vs. high volume pump does not make much of a difference as far as oil returning to the pan at high RPM?

Joe

Joe------



The GM #3969870 ZL-1 oil pump was never cataloged by GM as a SERVICE replacement for all big blocks. As far as GM cataloging is concerned, it was (and remains) only cataloged for the 1969 ZL-1 application and was only used in PRODUCTION for that application. However, that does not mean that it can only be used for that application.

I'm VERY careful about "straying" from GM cataloging when deciding to use parts from one application in another application. However, this is one of those rather rare cases in which I consider "straying" to be worthwhile.

[Domenic T.]

Re: BB - Replace high pressure oil pump?

Gosh,
We would put a 1/16 " washer behind the spring of a good pump and be done with it.

It gave about 10 PSI for about a penny.

By the way I have done research on HYDRAULIC LIFTER leak down.

The leak down is necessary if you are going to get the valve to close and cool the seat.

I measured the bleed down time of hydraulic lifters on a stand that puts 50 lbs of pressure on the lifter. The lifter is filled with the exact amount of diesel fuel and the bleed off is timed.

If the bleed off is to fast you loose a cam lobe, and if it is to slow you burn a valve.

If you have to much oil pressure it can fill the lifter faster than it can bleed the oil out that makes the valve adjustment.

To much bleed off makes the lifter skip on the lobe and causes it to wear.

All the accepted bleed off times were determined for the valve spring pressure, (stock).

I did this test on aircraft engine lifters because over 80% of engine overhaul is because of cam shaft failure, the cam is not removable unless the engine completly disassembled.

I determened the bleed down time using hydraulic lifters removed from the good cam lobes of many engines that made their overhaul time.

So be careful when you get crazy with oil pressure you can burn exhaust valves and in extreme cases blow the babbit off your bearings.

DOM

[Joe L.]

Re: BB - Replace high pressure oil pump?

Gosh,
We would put a 1/16 " washer behind the spring of a good pump and be done with it.

It gave about 10 PSI for about a penny.

By the way I have done research on HYDRAULIC LIFTER leak down.

The leak down is necessary if you are going to get the valve to close and cool the seat.

I measured the bleed down time of hydraulic lifters on a stand that puts 50 lbs of pressure on the lifter. The lifter is filled with the exact amount of diesel fuel and the bleed off is timed.

If the bleed off is to fast you loose a cam lobe, and if it is to slow you burn a valve.

If you have to much oil pressure it can fill the lifter faster than it can bleed the oil out that makes the valve adjustment.

To much bleed off makes the lifter skip on the lobe and causes it to wear.

All the accepted bleed off times were determined for the valve spring pressure, (stock).

I did this test on aircraft engine lifters because over 80% of engine overhaul is because of cam shaft failure, the cam is not removable unless the engine completly disassembled.

I determened the bleed down time using hydraulic lifters removed from the good cam lobes of many engines that made their overhaul time.

So be careful when you get crazy with oil pressure you can burn exhaust valves and in extreme cases blow the babbit off your bearings.

DOM

DOM------


No PRODUCTION GM hydraulic lifter engine, big block or small block, ever used a high pressure oil pump.

[Michael H.]

Re: BB - Replace high pressure oil pump?

Joe------



The GM #3969870 ZL-1 oil pump was never cataloged by GM as a SERVICE replacement for all big blocks. As far as GM cataloging is concerned, it was (and remains) only cataloged for the 1969 ZL-1 application and was only used in PRODUCTION for that application. However, that does not mean that it can only be used for that application.

.

One of the reasons why GM used a high volume pump for ZL1 was tha fact that many of these engines would also be fitted with remote oil coolers for road racing. The cooler required the extra volume.

The high volume pump is not necessary for other applications but, as you mentioned, it certainly doesn't hurt to use it in non racing applications.

[Clem Z.]

Re: BB - Replace high pressure oil pump?

the good thing about it is that it has the correct pickup screen welded to the pump for the BB corvette oil pan

[Joe L.]

Re: BB - Replace high pressure oil pump?

the good thing about it is it has the correct pickup screen welded to the pump for the BB corvette oil pan

clem------


YUP! That, by itself, eliminates a lot of hassle when installing a new oil pump. And, the Corvette pan is the only stock oil pan I know of for which a pump is available with an attached and properly positioned pick-up.

[Domenic T.]

Re: BB - Replace high pressure oil pump?

Joe,
I agree, but many builders (home and shop) put them in.

A little more pressure is good but to much and you get problems.

Thats all I am trying to say.

DOM

[Clem Z.]

Re: BB - Replace high pressure oil pump?

Joe,
I agree, but many builders (home and shop) put them in.

A little more pressure is good but to much and you get problems.

Thats all I am trying to say.

DOM

a little extra oil pressure will not hurt anything except maybe in NCRS judging.

[Joe R.]

Re: BB - Replace high pressure oil pump?

Joe,

I talked with my machinist again. He said that he put a 60 psi spring in the oil pump. He also mentioned that the stock spring gives 52 psi.

Joe

I looked up the AMA specs today. Here it is:

"Gear-type oil pump with fixed intake develops normal 50 - 75 p.s.i. oil pressure at 2000 engine rpm."

So, I'm guessing that I'll be fine pressure-wise with the 60 psi spring that is in it. Now my only question is whether or not it is a high volume pump. I may have the part number somewhere...

Joe

[Joe L.]

Re: BB - Replace high pressure oil pump?

I looked up the AMA specs today. Here it is:

"Gear-type oil pump with fixed intake develops normal 50 - 75 p.s.i. oil pressure at 2000 engine rpm."

So, I'm guessing that I'll be fine pressure-wise with the 60 psi spring that is in it. Now my only question is whether or not it is a high volume pump. I may have the part number somewhere...

Joe

Joe------


Standard volume pump has gears that are 1.15" in length; high volume has gears that are 1.30".