Shimming Relief Spring in Oil Pump Assy.

[salvageV6]

I assume that increases the oil pressure.

At idle or WOT or both?

What's good to start with? A dime? Two dimes?

Got the yellow spring in the car now with booster plate and idle is okay about 10psi. very hot oil on a very hot day, but higher rpms is a bit weak.

TIA

 

[Russ Merritt]

I use a 1/4-20 allen head screw. Threads fit up inside the spring and the head goes inside the end plug. If your motor isn't junk, should see atleast a 10# increase at WOT. This mod will not help idle pressure. 10# is really enough but I'd like to see more too......WOT you should see 60# or so..

 

[GANGSTER]

They all seem to be low at idle but if you have the yellow spring in there and have bad pressure up high then you prob have excessive clearance in the bearings. that is assuming you are using a descent viscosity oil and not some crap that breaks right down.

 

[Blazer406]

They all seem to be low at idle but if you have the yellow spring in there and have bad pressure up high then you prob have excessive clearance in the bearings. that is assuming you are using a descent viscosity oil and not some crap that breaks right down.

I'll second that.....

I tried to do my SBC like that.... it had poor oil pressure at hot idle.... (I am sure it didn't have anything to do with the 75,000 street miles... or the 200+ quarter mile blasts.... ).... but it didn't have good hot oil pressure.... so I shimmed the oil pump pressure relief spring.... used a 1/4x 20 nut I think.... under the roll pin.....

When I first cranked it up...... 20-50 oil in it.... pressure shot up to 60 or 80 cold idle..... let it run for like 20 seconds..... revved it up a little...... pressure pegged the gauge.... and blew the gasket on the oil filter..... but when it was at hot idle.... still didn't have enough oil presure.....

fast foreward until I pulled the engine down to put a crank kit in it....while it was down... I removed my 1/4x20 nut.... so pressure spring was stock......with the new crank and new bearings.... and the same oil pump.... with the spring un-shimmed...... pressure was about 40-50 cold idle.... and 30-40 hot idle.... probably went to 70 or so when it was hot and motor revved.....

Moral of my story..... don't mess with the pressure spring... to try and correct a worn set of rod brgs and main brgs.....

My best advice.... is increase the viscosity of the oil you are running until the pressure is satisfactory.....to buy you enough time until you can freshen the engine up.

ie.... if you are running 10w40 ..... step up to 20w50 ....

Bottom line is that you probably need to make some plans to go through the motor soon....

Just my $0.02

 

[GANGSTER]

Amen!!

 

[salvageV6]

Thanks, just want to try to get a bit more higher rpm pressure.

Got a mix of 10/40 20/50 in it now will be changed out soon for fresh.

Used car so who knows what's in there for parts, tranny was bone stock most likely the motor is as well.

Maybe it has 220K instead of 120K.

Cold pressure is fine at over 60psi. but that don't mean much.

Tapping shouldn't be all that difficult to do for the shimming as a test.

Just thought I may have messed something up with the booster plate install but it was a bit low before that install as well, most likely not the case since it went up a bit after the plate and biggie oil filter install.

It's got to last another year or two before motor work, only put 4K a year on that car anyway.

Not really worried about idle pressure as it never has gone below 10psi. even on the 95 degree days with the A/C on.

Valvoline dino oil in that car.

Gauge is read from the turbo fitting so that may drop it a couple of psi. as well from the normal reading area most folks use.

 

[Blazer406]

Let me add one more point to my post above.

The drop in pressure most people see is caused by the excessive rod bearing and main bearing clearances beacause the pump does not have enough pumping volume to keep up with the flow required to keep the pressure up. What I mean is that when an engine is new, the clearances are tight... and the pump doesn't have to put out much volume... before the pressure rises enough to trigger the pressure relief spring/bypass.... but on a worn engine..... the clearances are greater.... so it requires more flow than the pump can put out... therefore you see the loss in pressure....

IMHO, you could temporarily remedy the situation by doing either of these two things:

1.) Increase the viscosity of the oil until the pressure (hot WOT or idle) ... is sufficient.

2.) Change to a higher volume oil pump (I assume you can get a high volume pump for these cars) to "keep-up" with the increased flow demands......... BUT

If you choose to do #2, you might also want to consider an increased capacity oil pan, because you might be flowing enough volume... that at WOT.... your pan is nearly or IS sucked dry.... therefore causing

Again.... this is IMHO.

Hope this helps.