BB - Replace high pressure oil pump?

[Joe L.]

Re: BB - Replace high pressure oil pump?

All,

Thanks for the advice. I was hesitant to pull the pan and pump because my time to work on the car is very limited. But I have decided that it is better to do the job right the first time. I have ordered the GM 3969870 pump from my friendly local Chevy dealer.

My next question is, what do you guys recommend using for the oil pan gasket?

Thanks in advance,
Joe

Joe-----


It depends what your priorities are. If it's exactly correct configuration, then you need to use a "4 piece" gasket set, as-original, with steel-reinforced, cork rail gaskets and rubber end seals.

If you want the best sealing, then use a 1 piece, neoprene type gasket of Fel-Pro #OS-30061T or equivalent.

[Tim S.]

Re: BB - Replace high pressure oil pump?

Joe,
Ain't that the truth! It seemed like Joe Raine had some inclination to have the car judged, hence, 4 piece. After using a couple of the new 1 piece Fel Pro's, I wonder why I would screw aroung with anything else!

Tim

[Joe R.]

Re: BB - Replace high pressure oil pump?

Joe and Tim,

Thanks for the tip, I've got the Fel-Pro one piece gasket on order. I may get the car judged someday, but it's far from being a Top Flight car. For right now I'd like to drive it and enjoy it, oil leak free.

Joe

[Jim L.]

Re: BB - Replace high pressure oil pump?

As an interesting side note, it's my understanding that 9000+ rev unrestricted NASCAR engines only run about 30-40 psi oil pressure (and 5W-20 oil for the race, 0W for qualifying).

Duke

Duke, do you have any idea what range of bearing clearances they run in those engines and what oil temperature they maintain?

Jim

[Clem Z.]

Re: BB - Replace high pressure oil pump?

Duke, do you have any idea what range of bearing clearances they run in those engines and what oil temperature they maintain?

Jim

the oil temps runs from 200 to 240 degrees and that is why they all use synthetic oil. same with water temp since the engine is a heat pump and the hotter you keep the combustion chamber the more HP they make. these engines also run small crank pin diameter,1.800 to cut down on friction

[Duke W.]

Re: BB - Replace high pressure oil pump?

Duke, do you have any idea what range of bearing clearances they run in those engines and what oil temperature they maintain?

Jim

As far as bearing clearances are concerned, typical machine design books recommend .001" per inch of journal diameter, but road engines are generally tighter. I recommend .001" minimum for mains and .0015", +/- .00025 for rod bearings, both of which can be managed by using one-half of a .001" underside or oversize bearing as required. When I rebuilt my 327/340 I got these clearances with standard bearings. The crankshaft just received a Magnaflux, straightness check, and polish. All the journals were right in the middle of the OE tolerance range.

A racing engine would likely be closer to the .001"/inch guideline or even a bit looser, so I expect they run clearances in the .002-.003" range.

What Clem said on oil temperature, and I don't think they pull tape off the grille until coolant temp gets to 230F. Higher internal temperatures generally make more power due to less heat transfer to the cooling system.

I believe they run straight water with an additive such as Water Wetter, and 21 psi pressure caps. I'm not sure what the boiling point of this setup is, but it's probably at least 250F - whatever the temperature is for water to have a vapor pressure of 21 psi.

Duke

[Jim L.]

Re: BB - Replace high pressure oil pump?

A racing engine would likely be closer to the .001"/inch guideline or even a bit looser, so I expect they run clearances in the .002-.003" range.

I'm aware of oldde tyme racer practice of running very loose bearings and 50 wt oil. Given the low viscosity oil used in NASCAR, I would have expected tighter bearing clearances..... maybe less than .002, but that's just a guess.

Higher internal temperatures generally make more power due to less heat transfer to the cooling system.

I've heard this often. Yet, I've got two data points which, if accurate, point the other direction.

First data point is a test I read years and years ago that compared engine power output at three different temperatures (160, 180, and 195, I think, but don't quote me). The highest power output was observed at an engine temperature of 160.

Second data point is more recent. The 261 6 banger Russ Uzes just had freshened up for his '53 made the most power at a coolant temperature of 105F.

Don't shoot the messenger; I'm just reporting what I've read/heard.

I believe they run straight water with an additive such as Water Wetter, and 21 psi pressure caps.

I believe this to be true, possibly by rule and possibly for beter heat transfer. In my vintage racer, I'm required by racing rule to run straight water (altho soluable oil and water wetter is permitted). The reason for this is so I won't make the track slick if I blow coolant, as I would if I ran an antifreeze/water mix. I'm sure similar thinking is present at NASCAR events.

Thanks, Duke,

Jim

[Clem Z.]

Re: BB - Replace high pressure oil pump?

I'm aware of oldde tyme racer practice of running very loose bearings and 50 wt oil. Given the low viscosity oil used in NASCAR, I would have expected tighter bearing clearances..... maybe less than .002, but that's just a guess.

I've heard this often. Yet, I've got two data points which, if accurate, point the other direction.

First data point is a test I read years and years ago that compared engine power output at three different temperatures (160, 180, and 195, I think, but don't quote me). The highest power output was observed at an engine temperature of 160.

Second data point is more recent. The 261 6 banger Russ Uzes just had freshened up for his '53 made the most power at a coolant temperature of 105F.

Don't shoot the messenger; I'm just reporting what I've read/heard.

I believe this to be true, possibly by rule and possibly for beter heat transfer. In my vintage racer, I'm required by racing rule to run straight water (altho soluable oil and water wetter is permitted). The reason for this is so I won't make the track slick if I blow coolant, as I would if I ran an antifreeze/water mix. I'm sure similar thinking is present at NASCAR events.

Thanks, Duke,

Jim

the engine in question is not a good example of the highly efficient race engine. i used water soluble oil in the cooling water in all my race cares because it helped heat transfer and it prevented the water passages from rusting which would hurt the heat trsansfer. you are correct as most all asphalt tracks do not allow anti freeze because of the reason you stated.

[Duke W.]

Re: BB - Replace high pressure oil pump?

Most carbureted road engines have some sort of manifold/carb base heating using exhaust gas or coolant to promote good idle/low speed, low load fuel atomization and prevent carburetor icing. In these cases quick tests before the manifold/carb get hot might show more power.

For an engine with no intentional manifold/carb heating that runs continuously at high load, higher coolant/oil temperatures make more power, and this is stated in the 30+ year old Chevrolet Power manuals.

It's always in the details.

Duke

[Joe C.]

Re: BB - Replace high pressure oil pump?

I'm aware of oldde tyme racer practice of running very loose bearings and 50 wt oil. Given the low viscosity oil used in NASCAR, I would have expected tighter bearing clearances..... maybe less than .002, but that's just a guess.

I've heard this often. Yet, I've got two data points which, if accurate, point the other direction.

First data point is a test I read years and years ago that compared engine power output at three different temperatures (160, 180, and 195, I think, but don't quote me). The highest power output was observed at an engine temperature of 160.

Second data point is more recent. The 261 6 banger Russ Uzes just had freshened up for his '53 made the most power at a coolant temperature of 105F.

Don't shoot the messenger; I'm just reporting what I've read/heard.

I believe this to be true, possibly by rule and possibly for beter heat transfer. In my vintage racer, I'm required by racing rule to run straight water (altho soluable oil and water wetter is permitted). The reason for this is so I won't make the track slick if I blow coolant, as I would if I ran an antifreeze/water mix. I'm sure similar thinking is present at NASCAR events.

Thanks, Duke,

Jim

Jim,

You can't use broad terms, like "coolant temperature".

You must separate combustion chamber temperature from intake manifold temperature.

If the combustion chambers are allowed to retain maximum heat between combustion cycles (adiabatic boundary), and not reject it to the heads and pistons, then the engine will make more power. This is accomplished by coating the chambers and piston crowns with reflective ceramic surfaces.

Intake manifold temperature helps determine charge temp. If the manifold is relatively cool, the intake charge remains denser, thus containing more O2 molecules (or, you can use nitrous). Too cool an intake will lead to the problems with icing and fuel atomization that Duke mentioned. There is a lot of experimentation happening today, with annular venturi boosters. These address that very same phenomenon.........better atomization/emulsion, for better distribution/combustion with lowered temperature intake plenums and/or low vacuum signals due to big overlap camshafts.

Higher oil temperatures ALWAYS make more power. 230-240 is probably optimal.

[Clem Z.]

Re: BB - Replace high pressure oil pump?

at restrictor plate tracks like daytona and talladega when they qualify they turn the oil pressure down to get the last .5 HP from the engine. with a dry sump system the oil pressure can be adjust on the externally mounted oil pump. i have seen them turn it down a little bit too far and screw up the engine

[Joe R.]

Re: BB - Replace high pressure oil pump?

All,

I'm sorry to drag this up again, but I was trying to help Mark Nagy with his oil pump. He also has a 66 L72 (427 / 425).

I bought the ZL1 pump GM #3969870 based on Joe Lucia's recommendation. It is higher volume, standard pressure compared to the original L72 oil pump. So it should fit the Corvette pan fine and give the right pressures. Here are some of Joe C.'s words earlier in the thread: "But it has larger flow passages, and larger lobes on the gears. Because of this, it takes more crankshaft horsepower to drive than a standard volume pump. Additionally, it vibrates and pulsates more than the standard volume pump, and has a greater effect on a distributor's spark scatter rate."

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

Also I seem to remember seeing a recommendation by Clem a while back to run the BBs one quart over full. Does that imply anything as far as the oil pump choice goes?

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

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

Thanks,
Joe

P.S. As you can tell, nothing moves very quickly at my house.

[Clem Z.]

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

[Joe L.]

Re: BB - Replace high pressure oil pump?

All,

I'm sorry to drag this up again, but I was trying to help Mark Nagy with his oil pump. He also has a 66 L72 (427 / 425).

I bought the ZL1 pump GM #3969870 based on Joe Lucia's recommendation. It is higher volume, standard pressure compared to the original L72 oil pump. So it should fit the Corvette pan fine and give the right pressures. Here are some of Joe C.'s words earlier in the thread: "But it has larger flow passages, and larger lobes on the gears. Because of this, it takes more crankshaft horsepower to drive than a standard volume pump. Additionally, it vibrates and pulsates more than the standard volume pump, and has a greater effect on a distributor's spark scatter rate."

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

Also I seem to remember seeing a recommendation by Clem a while back to run the BBs one quart over full. Does that imply anything as far as the oil pump choice goes?

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

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

Thanks,
Joe

P.S. As you can tell, nothing moves very quickly at my house.

Joe----


The big block high volume oil pump might require a little more power to operate but I think the difference is negligible for all practical purposes. As far as the other reputed problems you mentioned, I don't think so. As a matter of fact, big block oil pumps are sometimes used on racing small blocks to help reduce spark scatter. That's because big block oil pumps have more teeth than small block pumps. I recommend the ZL-1 pump for any Corvette big block.

Unlike PRODUCTION small blocks which never used a high volume oil pump, GM did use a high volume oil pump on PRODUCTION big blocks. The first was the ZL-1 (which used the still available 3969870). In addition, all Mark VI big blocks used a high volume oil pump. So, the use of such pumps has been validated for PRODUCTION purposes.

[Joe C.]

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.