oil pressure w/ bypass spring

[priobe]

ok quick question, hopefully this is easy.

By changing the spring pressure to a stronger spring in a oil pump, will it

A) increase pressure
B) decrease pressure
C) nothing at all
D) increase the limit for when the pump will bleed the oil back into the crank case.


Please describe your answer, and remeber that many aftermarket oil pump sellers sell a different spring ( for what?)

[lineslinger]

I shimmed the spring in a Mellings HV oil pump to increase pressure. I also removed the spring in the relief valve from the rear of the block, (passenger side of block as you sit in the drivers compartment) to maintain higher OP throughout the rev range.

[bobcowan]

The relief valve is held closed by spring pressure. When oil pressure exceeds spring pressure, the valve opens.

So, more spring pressure will increase oil pressure.

[Barnsnake]

Increasing the relief valve spring load will increase the Maximum pressure.
If the pump/motor combination only makes 20 psi with cold oil, putting in a 100 psi relief valve won't make any difference.

[Gaz64]

Oil pressure at low speed is oil pump capacity minus the engine "leaks" (oil flow out of bearings etc)

Max pressure is relief valve spring.

I've seen engines with 10 psi at idle and 90 psi at 5000 rpm, and other engines with 30 psi at idle and 45 psi at 2000.

It all depends on the internal clearances of the engine AND the oil pump, then the relief spring pressure.

[RICK LAKE]

Proibe What is the problem and why change the spring??? Oil pressure low? If you want to increase oil pressure, you have to increase the pump volume. The spring only controls max pressure for the motor mostly when motor oil is cold. It stops the oil filter from becoming a rocket from under the car and an EPA mess. The spring is behind a plunger in the pump or block and bleeds off extra pressure.
The other issue is the gear in the distributor that drives the oil pump and the oil pump shaft itself. More pressure, higher volume, more stress on this part of the motor. Another thing to look at is the end play on the camshaft. If too loose on play this will accellerate the wearing out of the gears on the distributor.
If your car is on the street IMO an HVHP oil pump with an 80 psi spring will work fine. For racing an FE motor in auto cross and road racing 100 # spring in the motor. You will also need a larger oil pan, 7-8 quarts of oil in the pan.
Alot is also going to depend on what the clearances are in the motors bottom end. The tighter they are, the higher the pressure. This also depends on what oil you are running. Heavier oil will increase oil pressure 5-10 psi when hot.
Sorry Priobe the question is a good one, but not a simple one to answer, too many varibles. If you are having a problem with the motor, spill the beans. It might be something simple to repair or major and now is the time to save the motor and not explode it all over the road or track. Rick L.

[priobe]

Rick,

There are no issues with my motor , THANK GOD!

I was reading an article and just wanted to see what other have to say.

Here is the article:

http://www.aa1car.com/library/us1097.htm

Enjoy

[RICK LAKE]

Proibe Most of the article is basic true to a certain point. Leak down test is not going to show you if you have bad valve guides unless the valves are off centered on the valve seats. Unless you have the valve cover pulled and have a bad valve you might not see the air leaking though the valve stem seal and know how good or bad the valve guides are. This is where the machinist shines with knowing clearances. Tigher rod and main clearances will raise oil pressure. Cross drilling cranks years ago was used to help extending the life of motors at high rpms. Problem with this is at idle you have almost no oil pressure. They have figured out that on some cranks to relocate the oiling holes for the rods. This help stop the metal to metal contact on the exhaust cycle. Bet you didn't know that the exhaust cycle is the worst of the 4 cycles for stress on the motor. Blue printing a motor takes time and good equipment. Over all the motor should last longer, have better power, less vibration and just run easier. Gald your motor and car are ok. Rick L.

[priobe]

Thanks for the response Rick.

Just wanted to post a question

Take care all