Oil pressure

[fishman1]

I was at the dyno on friday and started the motor up for first time 60 psi oil pressure........u did some pulls on the motor and the oil pressure dropped slowly by 8 to 10 psi......as the motor warmed up more had same rsults.........my clearnaces are fine on the crank and the rods. At first thought maybe to much oil so we drained some and with same results, so we added some and same results..........ok for the rest of the story........pulled off the oil filter and cut it open and found foam in the oil......we ran quite a few pulls on the motor and did 4 filter changes on the motor...foam was present in all filters.......we changed the oil twice and the oil had some foam in it............the pump has to be cavitying, have you ever seen a oil pump have a crack in it........i pulled the pan off tonight and measured the clearnace between the pan and the pump it was fine............so next i will pull the pump out and check the screen and pull off the pump and look at it.........is there anything else for ideas to check you guys can think of..........also i don't have a gasket between the pump and the block, do u recommend one or not............i don't think i am running out of oil it is 7 quarts oil pan not sure of the oil pump brand suppose to be high output..............thanks for any input

[OneBadGMC]

not sure of the oil pump brand suppose to be high output

Oh my...

How about you throw it away and buy a good pump before you have to buy another crank and set of rods, and maybe a block, pushrods, rockers, the list goes on!

[fishman1]

not sure of the oil pump brand suppose to be high output

Oh my...

How about you throw it away and buy a good pump before you have to buy another crank and set of rods, and maybe a block, pushrods, rockers, the list goes on!

I already ordered a new pump i was checking if anybody had any other ideas on the problem

[sp2816]

I would make sure that the pick-up tube doesn't have a crack in it and that it is sealing good inside the pump. I weld the pick-up into the pump, but have seen the tube have a crack before. Also, no gasket between the pump and the main cap, but do make sure that the cap has a good sealing surface and doesn't have divots or cracks causing leaks. I use an ARP oil pump stud and nut, but make sure that it doesn't thread down too far into the main bearing.

You might also want to make sure that the oil is draining back down into the pan OK. Because that is a way to go through the 7 quarts, if it is staying at the top and not draining quickly out of the heads and past the lifter screens.

I don't think that you ever mentioned what weight of oil that you are running.

Bill M

[fishman1]

I would make sure that the pick-up tube doesn't have a crack in it and that it is sealing good inside the pump. I weld the pick-up into the pump, but have seen the tube have a crack before. Also, no gasket between the pump and the main cap, but do make sure that the cap has a good sealing surface and doesn't have divots or cracks causing leaks. I use an ARP oil pump stud and nut, but make sure that it doesn't thread down too far into the main bearing.

You might also want to make sure that the oil is draining back down into the pan OK. Because that is a way to go through the 7 quarts, if it is staying at the top and not draining quickly out of the heads and past the lifter screens.

I don't think that you ever mentioned what weight of oil that you are running.

Bill M

I am running 20-50 oil and the block is a dart little m shouldn't be a problem with oil coming back fast enough

[bjuice]

are you saying the oil pressure will start showing a drop in pressure as you are turning up the rpm's or when you are off the throttle and rpm's are backing down. ?
after motor was warm what was your final full throttle oil pressure?

last question, what type of oil pump is in motor now ?

[fishman1]

are you saying the oil pressure will start showing a drop in pressure as you are turning up the rpm's or when you are off the throttle and rpm's are backing down. ?
after motor was warm what was your final full throttle oil pressure?

last question, what type of oil pump is in motor now ?

Bjuice

the oil pressure starts to drop very slowly as the rpms go up....starts at 60 psi oil pressure and dropped to 52 psi, warmed up the motor further after more dyno pulls and oil pressure started at 50 psi and dropped to around 40 psi.

The oil pump brand i am not sure as it was fairly new and i just used it off my last motor which only had 130 passes on it and i didn;t build that motor......i have a melling hv55 pump coming..........do you weld your pickup tube in or just press it in..curious how everybody does it

thanks

[bjuice]

my 400ci did the exact thing 5 or so years ago..it was a melling pump also...i replaced it with a moroso and never had any more problems but i have seen mellings run with no problems ( anything can malfunction)..i guess this is the reason for oil gauges...lol :D
with the moroso i purchased the pick up tube had a bracket welded off the pick up tube to the pump housing and had a 1/4 bolt that held the pick up tube in the pump...there is pic of this pump i 'm speaking of in JEGS book ..page 56


i did assume you were speaking of the pressure dropping as the rpm's increased but had to ask anyhow

[cncmotorsports]

You need the melling 10550 oil pump, they are around $50.00
We see them hold the best oil pressure on the dyno.
This pump will hold your pressure right around 60-65 psi from 3000-8000 rpm depending on your exact bearing clearances.

[fishman1]

everybody out in alberta where i live use the melling hv55 pump and they work good for most people, that is why i ordered the melling pump....the pump that is in it has no name as whose pump it is and the numbers on it mean nopthing unless you know whose pump it is

[sg1586]

are you saying the oil pressure will start showing a drop in pressure as you are turning up the rpm's or when you are off the throttle and rpm's are backing down. ?
after motor was warm what was your final full throttle oil pressure?

last question, what type of oil pump is in motor now ?

Bjuice

the oil pressure starts to drop very slowly as the rpms go up....starts at 60 psi oil pressure and dropped to 52 psi, warmed up the motor further after more dyno pulls and oil pressure started at 50 psi and dropped to around 40 psi.

The oil pump brand i am not sure as it was fairly new and i just used it off my last motor which only had 130 passes on it and i didn;t build that motor......i have a melling hv55 pump coming..........do you weld your pickup tube in or just press it in..curious how everybody does it

thanks



Just to let you know that that pump is now made over seas and the gears are junk :shock:

[cncmotorsports]

They do work good, but my opinion is the melling 10550 is a race pump, I feel they are a much better oil pump to use for the money.

[fishman1]

I know the pickup bolts on and is wedged in the pump but do you guys go further and weld the pickup to the pump.........thanks for the replies

[cncmotorsports]

Yes, we weld them on. The last thing you want is the pick up tube to fall off.

[engineaction]

Little M block. Do you have internal restrictors in the block? Small restrictors and cheaper oil pump will create the pump to cavitate, open the internal pressure relief valve and bypass the oil back to the pan. If you had a clear oil pan you would more than likely see foam pouring out of your relief valve outlet on the pump. I don't believe 10550 pump is an anti-cavitation pump, I do not reccommend it on a block with main priority oiling blocks such as the Little M. You need a Melling 10552C which uses a 3/4" pick up tube, and has anti-cavitation properties.

Improper base circle cams and lifters will also cause this to happen. Sometimes the oil band around the lifter can hang belowthe lifter bore and bleed oil off rapidly and also make it cavitate.
you can easily check this by making sure you are getting adequate oil to the top end of the engine.

[fishman1]

No oil restrictors in the block and getting good oil flow on top of the block.....the pump i have is only a 5/8 inlet and only writing on it has the number 5282 on it....i phoned moroso as it is there pan and he told me with that pan and my high rpm's i should be usuing a 3/4 inlet pump.....as far as anti cavation pumps nobody has one around here and it would take 3 weeks to get.....i want to be racing before then

[Tod74]

Competition Products still advertises in their catalog that the melling pumps have billet gears....I thought they went to pm gears?

[Cogburn]

Melling has P/M gears.

Some people are just slow.

CVR has billet gears.

[fishman1]

Some people on this post are recomending 5/8 inlet pump and others are recomending a 3/4 inlet pump......i am trying to understand why moroso told me to use a 3/4 inlet pump with the pan i am usuing and somebody else posted usuing a cavation pump with 3/4 inlet pump for a dart little m block.......will the flow on 5/8 pump and a 3/4 be the same and the only diffrences would be the inlet bigger to keep the pump from loosing suction