JimS

My friend, a very experienced hotrodder who has built several very high hp engines beginning in about 1960 has recently built a Merlin 540 and has a oil pressure problem he can't figure out. He's asked me to ask some forums for help.

Merlin 540, Crane solid roller and Crane valve train. Brodix heads. High volume oil pump. He built the short block himself so I know it was done accurately and with extreme attention to detail. That's just who this guy is.

The engine was first fired about 8 weeks ago and held about 50 pds oil pressure. It was started in the shop a few times for timing etc and it was first driven about 2 weeks ago. Ran fine for about 5 miles with about 50 lbs oil pressure but when he slowed down to turn a corner the pressure dropped enough that the red light flickered. He raised rpms to about 2k and the pressure went back up. He can't figure out what caused the drop or what to do about it.

Crane says not to restrict flow in order to raise pressure.

He plans to tear down much of the car over the winter and wants to find out what is wrong with the oil system and wants to get some ideas from you folks as to what he could look for within the engine that might give a clue as to why the pressure drops.

Any ideas what might cause the drop in pressure? Any ideas as to what he might look for as a clue to why it dropped? Any ideas how to fix it?

Thanks, JIm

Carbed4thGen

iTrader: (2)

Was there enought oil in the system? It sounds almost like when he turned the corner (since that's the only timeit did it) that it starved the pump maybe?

JimS

Plenty of oil. Any ideas anyone?

simca1955

I had a small block once that the oil pump bolt back out just enough to cause oil presure drop at idle, just a thought

Firechikn

iTrader: (15)

I would also check cam bearings. I had an engine with the same problem. At idle after the engine was hot the oil pressure droped to 15 - 20 # but while at driving speed the pressure was 50#. I replaced the oil pump in attempt the repair the problem, but no change. I drove the motor for 3 years and no problems, even with solid roller cam. After I tore it down I found 2 cam bearing were scared pretty bad, likely from installation. I replaced the bearings and rebuilt the engine and the problem was solved.

slow trap

iTrader: (22)

i'd say cam bearings also.

JimS

Good input. Anyone else? I'm relaying this information to my friend. We both appreciate you attention. Jim

JimS

ttt bump

BADMOFO

I'd say the pick-up came off of the oil pump....or the gauge or sending unit may be bad.

1bad71

what pan is he running on the motor? does it have a baffle? does the oil pressure stay the same after it's warm and only drop when he turns or stops the car? did he weld the pick-up to the pump?

i had a motor that pushed the pickup up when i launched from the oil and when i stopped all the oil went forward in the pan, starving the pump and dropping oil pressure! only on stops and around corners.

just a possibility?

NEokcTERROR

iTrader: (10)

Oil pressure relief valve in pump sticking partially open, or pickup tube. However when the pickup tube is out of the pump on a big block the oil pressure will drop at higher RPM also as the oil level in the pan drops below the high oil intake hole in the pump as it is not on the bottom of the pump like a small block. Also I don't know if the Merlin blocks have the same cam bore diameters as a stock BBC. A DART block has different bore diameters and require the use of DART specific cam bearings made by Enginetech to DART's specifications. I have seen the wrong cam bearings used in a DART block, and they walked out of the bore over to the lobe and dropped the oil pressure.