Roush 402 R Oil pump question!
 

Hello!

I just bought a bdr cobra with a roush 402R engine in it. I just need to know what are the problems for a low oil pressure? The engine runs on new 10w40 Motoroil and the gauge shows 30 psi at start. After a while, when the oil gets warmed up it drops to about 22 psi. I heard it could be a bad ground cable of the gauges. I have to look at the oil pump if I can see a problem! Where should I start to look at first. The engine runs normal, but i stopped the engine when the pressure droped. Do you guys know, what kind of oil pump this engine needs, just in case if I need a new one. Would be happy to get some informations about this motor!
Thanks from germany!
Marc

What's wrong with 22 psi hot at idle?

Does the oil pressure go up with rpm? If so, I wouldn't try to fix a problem that doesn't exist.

I am pretty sure 10w30 is the recommend oil for that series motor.

Exactly.

Dropping from from 30 psi cold to 22 psi hot is perfect.

Many other engines have larger pressure changes.

What pressure does the engine have at 3000 rpm hot?

The first thing I would do is connect a mechanical gauge to the engine and verify the gauge in the car is reading correctly. If they are within 5 psi of each other at idle and revved up, note if the gauge in the car is a little high or a little low.

Even assuming your gauge is correct, 20 psi at idle wouldn't bother me, as long as the pressure goes up to 50 or more at high rpm. 15 psi at idle might not actually be a problem but that is getting low. I have had old worn out engines idle clear down to 5 psi and still run another 50K miles, with no problems. If your pump is the standard volume pump, 20ish is normal. If it is a high volume pump, I would expect more, but not be overly concerned.

Do not go to 10-30 if the pressure is already low with 10-40.

If you have low oil pressure odds are that it is something other than the oil pump. Oil pumps rarely go bad unless they are starved for oil. I would be making sure any external oil filter plumbing or oil cooler was done correctly.

Usually low oil pressure is caused by loose bearing clearances. When I was a puppy, the racing crowd purposely set bearing clearances loose an ran heavy oil. Now the trend is to set bearings tight and run thin oil. I think the latter is better, but the fact is both strategies work. If my oil pressure dropped below 15 at an idle, I would put in heavier oil and run it, as long as there were no other signs of problems.

The motor has 13000 miles on it! Roush says 25-30 psi on idle! On the data sheet of the motor it shows something between 55-60psi from 3000-6000rpm.
I talked to other people with 402r roush engines and they have also the pressure from 55-60 psi. I can‘t believe that the oil pump has a problem, because of the low miles. I will test it with a manual pressure tester!
Thanks for help.

Roush recommends straight 30W oil. Your pressures might be normal with the heavier oil.

Is this via a conversation? Their literature and my tag says 10W30 427 R Crate Engine

I have a 427 and the link is for same but I do have an original catalog with the 402R and they recommend the same.

Roush recommends 10w30.

Try 20w50 non synthetic and see where your pressure goes.
My Roush 427sr ran 45-50 lbs at startup and then settled around 42 lbs when cruising warm. Hot idle was around 35lbs at an idle speed of 900 rpm. This was with 10w30 royal purple synthetic oil. And then the engine destroyed itself.

Do you know what the cause of the failure was?

In these days of multigrade oils, why would one run a single viscosity oil?

Depending on how the engine is clearanced is a high determining factor in oil viscosity selection.

30W cold is thicker than the majority of current multigrades.

And then when hot is thinner than most.

Oil flow with a thin oil is more important than low flow with a thick oil.

Valve guides worn, cylinders scored, piston cracked, bearings shot. excessive oil consumption. No single cause. At 13,000 miles it looked like it had 100,000 hard miles when we tore it apart. Needed a complete rebuild.

What rods in this engine?
Do the rods have a timed spit hole, I doubt it.
Is rocker geometry correct with minimum contact patch width on the valve stems?

For those interested really to read facts and not myths about oils I strongly suggest to look here: https://540ratblog.wordpress.com/

Also, will answer the question regarding what oil/viscosity and weight to use and why