New Stroker, Low Oil Pressure

Well, the new stroker is together and fired, sounds wicked as all hell.

Problem: When we first fired it up, the oil pressure was about 20 PSI at idle, and 35 PSI at 2000 RPM.

Did the standard cam break-in of 1,800 RPM for 20 minutes. It held 35 to 40 PSI the whole time, which I don't consider optimal, as my old engine ran 65 PSI at speed. When I let it back down to idle, I was down to 5 -10 PSI.

Pulled the pan tonight, no sign of metal or bearing material, same inside the filter, so I haven't hurt anything yet (I hope). The pump is a Melling High Volume unit, which I've heard has some failures associated with it. Anyone know the nature of those failures?

All pressures were checked with a mechanical guage.

Anyone have any advice on this little problem?

CRASH

When I first fired mine up it did the same thing, and I couldn't figure it out. After I put a few miles on it, jumped up to around 40 at idle and 60 at speed. :dunno:

well that's it then CRASH, guess you need to come wheelin with Billy, Sean and I

Factory specs are 13+ at idle and 35+ at cruise. Mine has always read low.

I have approx 1300 miles on my stroker. It runs around 15-20psi idle and 40-45psi at speed.

I remember it also being very low when I first turned over the motor. Give it time.

I doubt that a new Melling oil pump would cause low oil pressures. I'd understand it if the oil pump was old & worn.
It's more than likely that you have excessive bearing clearances somewhere (either main, rod, or cam bearings). If the mains and rods are OK (most likely since the bearings would have been matched to the crank), the problem's likely to be the cam bearings if you didn't replace them during the build-up.
My stroker's oil pressures were marginal at first (20psi hot idle, 40psi at speed) but now I have almost 1200 miles on it, the oil pressure at hot idle has increased slightly to 25psi while on the highway it remains around 40-45psi.
I've found that the oil pressure can vary quite a bit depending on oil temperature and the grade of oil used. Since it's over 115*F here, I'm using 20W-50. I'll change to 10W-30 at the next oil change, which will be at about 2100 miles on the stroker or when my odometer is showing 285,000km.

Cam bearings were replaced on buildup.

CRASH

2 thoughts -
1 the stock oil pressure guage & sender are not always accurate.
Suggest screwing in a manual guage to check for accurate numbers
2 Low pressure may be caused by oil getting by the pressure releif valve not seating properly - my hi-volume Melling was purchased 4 years ago and provides 60 lbs at startup and 40 lbs when hot with 5W30 syn.

Crash --

Who installed the crank and rods, you or a shop? Were the bearings plasti-gaged? Were the clearances set toward the middle or tight side of the allowable range?

Your pressures are within spec, but I agree -- I would expect and want better in a newly rebuilt engine that's going to work hard.

old_man said:

Factory specs are 13+ at idle and 35+ at cruise. Mine has always read low.

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hinkley


BTW strokers are crossdressing HOs

Eagle said:

Crash --

Who installed the crank and rods, you or a shop? Were the bearings plasti-gaged? Were the clearances set toward the middle or tight side of the allowable range?

Your pressures are within spec, but I agree -- I would expect and want better in a newly rebuilt engine that's going to work hard.

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I installed both, the crank and rods are on the tight side, both sets of bearings were shipped to me with the crank from the crank grinder.

Right now I'm leading to the oil pressure relief valve, just because I can't think of anything else!

Bought a new Melling OEM replacement tonight, I'll drop it in tomorrow and report back.

CRASH

Crash what was the outcome? Curious..

If you have the pan off, I'd plastigauge a few rod and main bearings. I wouldn't take the crank grinder's word for it. Been there, been bit. Melling supposedly dynos their pumps. I haven't seen evidence of it, but numerous people in the industry have told me that. If clearances are ok, make sure pickup and pump mounting are good, no pinholes in pickup, etc.

Dr. Dyno said:

My stroker's oil pressures were marginal at first (20psi hot idle, 40psi at speed) but now I have almost 1200 miles on it, the oil pressure at hot idle has increased slightly to 25psi while on the highway it remains around 40-45psi.
I've found that the oil pressure can vary quite a bit depending on oil temperature and the grade of oil used. Since it's over 115*F here, I'm using 20W-50. I'll change to 10W-30 at the next oil change, which will be at about 2100 miles on the stroker or when my odometer is showing 285,000km.

Click to expand...

I changed my oil to Mobil 1 0W-40 with 3000 miles on the stroker and now I'm at 4100 miles. The oil pressures are still the same (20-25psi hot idle, 40-45psi at speed, 50psi cold) and as long as they stay that way, I'm happy.
I checked the oil level on the dipstick yesterday and it had hardly moved after 1100 miles. The oil also still looked surprisingly clean. By comparison, the 20W-50 dino oil that I had in the pan before the last oil change was as black as the Ace of Spades after only 500 miles.