My car is a Cutlass with a 350 engine that was rebuilt about 17k miles ago. The engine received several performance upgrades during the rebuild including a Melling Hi volume oil pump. The engine has performed great and the OP ran around 35- 60 psi after the rebuild. Within the last 2k miles the pressure started running high according to the gauge. It is the factory gauge so I am not sure of the actual OP. I though it was a gauge or sending unit issue. Wrong! Last weekend I got on it hard and heard a pop and smoke started coming out from under the car. It blew the oil filter gasket. Any ideas on what could be causing the high OP. I really, really, really do not want to pull the pan. Thanks in advance for your help.
Steve

 

Sounds like a stuck relief valve in the pump (pan removal) but could it possibly have anything to do with bypass valve in block? I don’t think so but smarter people are likely to come along soon with answers.

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About the only thing that it could be is the relief valve in the pump. The relief valve in the filter mount only lets oil bypass the filter if it gets clogged. It will not cause high oil pressure.

 

I agree with both of the above. Sorry but you’ll probably need to drop the pan.

 

Just want to add that before you get rid of the old filter cut it open and make sure the filter paper did not come apart and possibly get into the engine. I know of two guys who ruined Chevy engines by blocking the filter bypass and then running a cheap filter. Both times the filter paper came apart and clogged the main oil galley going into the engine

 

DAMN DAMN DAMN. YOU GUYS CONFIRMED MY THOUGHTS EXACTLY.. Sooooo this begs the question…….can I get the oil pan off with the engine in the car? Or will I need to pull it?
thanks for the input.

 

I block the bypass myself, what filters were these? I do it on the Olds too.....

 

Mark,

They were cheap Fram filters from Walmart etc. I don't like blocking bypasses but have done it when I know that the customer is going to use a good filter and warm up the engine before really ragging on it.

I honestly don't think having the bypass causes any type of problems. Other than maybe on initial build start up if the engine is is good condition it really should hardly need an oil filter anyway. If there is something in the oil that is going to cause a problem the engine is probably doomed anyway

 

You’re right, it doesn’t, unless you get a clogged filter.
I’ll bet he has crap in the relief valve. I had a build I did years ago that I shipped to CA and it sat. When he fired it up it had almost 100psi. Changed the pump, he’s still driving it.

 

Either that or rust if the car isnt driven very often. I see that every once in a while in marine engines. They tend to be in wet areas anyway and then they dont use the boat for a year and thats what happens.

 

The car never really sits for too long. Maybe a couple months in the winter. Another observation is that the pressure seemed to get gradually higher over time. I never bypassed the filter bypass but, seeing the comments above about a filter coming apart and clogging an oil passage has me concerned. This problem transcends a couple of oil changes and if the filter came apart it has long ago been discarded. Again this was monitored by the factory electric gauge and not a mechanical gauge. Not sure how I would tell if there is paper in an oil passage unless there is residual paper in the pan. Anyway I agree the next step will be pulling the pan and it will be a while before I can get to it. I will let you know what I find out.

 

I finally found some time to drop the pan (it can be done with the engine still in the car but not an easy task). Pulled the oil pump and the damage is Shown in the pics below. You can see scuffing on the relief valve plunger. Not sure what caused that. Of bigger concern is the damage to the rotors. Something definitely went through there. I guess I should pull a couple of main caps to check the bearings and crank. I really do not want to though. Any thoughts on what caused this and what the next step should be would be appreciated.

 

I think I still have a new Melling high volume and a regular pump if you need either. If interested send me a pm and I will get some pricing. Good luck with your repair.

 

Thanks For the offer Glen. I bought one already. Now I need to get back under the car and fight the. Oil pan. Kind of scared to check the bearings though.

 

I have had several defective melling pumps.

 

This was a Melling High Volume. Going back with standard Sealed Power from NAPA.

 

Good idea. I replaced the defective units with GM pumps.

 

How do the Sealed Power compare to the Melling quality wise? Cutlassefi mentioned there has been issues with Melling as of late, high volume with less than smooth geats. My 22F regular pump had no issues, only aftermarket I have used. Hopefully the Melling High Volume going my 350 build doesn't do this. Is the Sealed Power High Volume Pump, even in stock anywhere currently?

 

honestly. I am
not sure of
the sealed power unit qualitu. Ordered it through NAPA and it
arrivemwithin a
day. After
reaxing
many posts
on here about
yjr
vapie
of
high volumn pumps
I regretted
using
it
in
the first place.