Oil Pump Answers

[Dennis O.]

About a month ago, I started a thead titled "Oil Pump Questions". I got a lot of responses, some much more useful than others. I have since changed out the oil pump in my car ('67 L79 Coupe), and now have some definitive answers to some of the questions I asked. At the risk of repeating myself, my problems were a constantly pegged oil pressure (60 lb.) gauge, excessive oil consumption, oil fouled plugs, and a large puff of blue smoke out of the exhaust at startup.

Here is what I found :

1. The pump in the engine was Melling "M55HV" which is their hi-volume pump.

2 The spring in the pump was their high pressure spring.

3. I replaced the pump with a Melling "10553" standard volume pump.

4. I did not go to my Chevrolet dealer ship for a pump, because a pump from them would probably have been the new design light weight pump (which is also made by Melling, but to GM specs); these have a reputation of breaking in service.

5. The "10553" pump came with a hi-pressure spring installed, and an intermediate spring in a plastic bag.

6. I called Melling and told them I needed a standard pressure "green" spring (part # 55049); it was sent to me no charge and showed up in my mailbox 2 days later.

7. I did not got to my chevrolet dealer for a spring as I did not want to spend the time and money and possibly end up with an incompatible spring.

8. I put a light coasting of grease on the oil pump gears to facilitate priming.

9. After installation, I cranked the car three time for 10 seconds with the coil wire out; half way through the third crank, I had 30 LBS. on the gauge,

10. The car started immediately and ran great and idled at 45 LBS. of oil pressure.

11. It now idles at 45 LBS. cold, 40 LBS. hot, and shows 50 LBS running down the road.

12. After the first couple of starts, the car no longer puffs out a blue cloud of smoke at start-up.

I have solved two of my 4 problems with this change. I am going to install a new set of plugs next week; I probably won't be able to tell if I solved the other two problems until sometime next year; it took several months for a new set of plugs to foul and start misfiring last time.

I beleieve the hi-volume, hi-pressure oil pump was putting more oil into the rocker area than the return drains and valve seals would take.

Stay tuned for the next installment to see if I have actually solved this problem, Everything looks good now from where I sit.

[Joe R.]

Re: Oil Pump Answers

Dennis,

Went back and read the original thread and now I remember why I never read threads on oil pumps and oil pressure. When it comes to oil pressure, well everyone has one!
Don't think you are going to be completely satisfied with this engine rebuild. Sounds like the fellow that built the engine is dead and probably killed by one of his customers.
Race car engine builders usually build an engine with such loose tolerances that problems can develop on the street. An example would be with low tension rings and liberal end gaps for those rings. Along with the low tension rings they usually add about one and one half thousands in the piston clearences. That would translate into burning oil on a street engine.
All the responses you had before were from the hands of experience! And most of those guys have been introduced to your engine builder or his clone!
From where I stand me thinks your oil consumption problem will decrease but never go away until the valve guides are repaired and the engine bored correctly for a street application.
Good luck and please keep us posted! You may keep someone from making the same mistakes!

JR

[Mike G.]

Re: Oil Pump Answers

Dennis:

Nice to see that "normal" oil pressure reading isn't it?

Here's one for you: when I replaced the hi-pressure spring in my Melling, I suddenly had lifter noise. These were Crane-supplied lifters purchased in 2000.

Suspecting that these may have been from the "offshore lifter" era, I replaced them with the GM lifter set 123710044. Now, not only was the valve train quiet --the motor ran MUCH smoother. Seems clear that the old lifters were not delivering the proper lift consistently.

Had I not been bugged by the pegged oil pressure gage needle, I'd still be running around trying to figure out why this fully balanced motor was not smoother running.

Mike

[Domenic T.]

Re: Oil Pump Answers

Dennis,
Joe has a point about loose clearances but I can say from experiance on a different kind of engine that to much oil squirted under your pistons from the rods due to high oil pressure can definetly cause oil burning, some call it (wet sumping).
One of the things a windage trays did on HP engines was help keep the oil from over oiling the pistons.

Again it was not a car engine but the reduction of oil pressure on that engine limmited the oil to the oil control rings and the burning stopped and the engine lived happily ever after.
I have a big block in my chevelle that has loose piston to wall clearance and you can hear the pistons for a very short time untill the pistons grow with heat and gets closer to the walls.
Maybe your problems are solved.
One more thing is that now the oil will be able to drain out of your valve covers before it rises above the guides. Back in the late 50's we had to cut the tops off a set of old valve covers and use them to hot adjust solid lifters because the oil would not drain fast enough and pour over the sides. With a high volume/pressure pump the oil would rise over the guides. Also had to use clips on the rocker cups to keep the oil off the garage walls and in the cut down valve covers.

DOM

[Dennis O.]

Re: Oil Pump Answers

Thanks for the replies guys.

Mike : Yeah it sure is nice to see the oil pressure guage where it should be.

Joe : your points are well taken. However, I don't think I'll have any bearing problems with the oil pressure I'm getting with the standard pump. Numbers like those are typical (or a little better) than a lot of small blocks I've seen. As to oil consumption, it may not end up being perfect,, but I'll bet most if not all of the oil being burned was what was causing the blue smoke at startup. Before it was embarrasing to start the car in public; now there is none.

Dom : I'm glad to see your post, it backs up everything that I have been thinking. I too, remember the cut out valve covers and rocker arm clips.

All in all, the 2 problems I did solve were the most obvious and irratating and made changing the pump out to be well worth the effort. This seems to be a common problem with these "hi-tech race engine builders". I hope I can save the next guy having an engine done from this happening.