I have a390 from a 66 T-Bird in my truck and it can't seem to maintain oil pressure. When you first start it the pressure is almost past the normal range on the factory gauge but when the motor warms up it drops to about a 1/3 up the gauge or less. Is it normal for the pressure to fluxuate that much? It never dropps out of the "normal" range but it just seems wierd to me that it fluxuates that much. The motor has a fresh rebuild and a new HV oil pump. Is this an common FE problem? Every FE engine I've ever had held terrible oil pressure and I don't want this engine to deteriorate to that point.



"Like a Rock"; on the sides of roads everywhere.

 

I wouldn't worry too much about it. Oil pressure will inherently be higher when the motor is cold then it will drop as the oil warms up and thins out.

 

The factory spec for oil pressure on an FE is 40 psi @2000 rpm. So at idle, you might be at 20 psi or less when the engine is warm and still be within specs depending on what weight of oil you run. I used to run straight 30 weight in my 390, and the pressure would go from 65 psi when cold to about 15 when hot and about 35 @2000 rpm. This all sounds a little low if you're used to a shivy or newer Ford engine, but the old FEs just run a little low. No worries.

 

Jeremy, it would be easier to know whether to worry or not if we knew the pounds per square inch. Any chance you can borrow a real gauge and check what the pressure really is? How thick is your oil ? Was the oiling system correctly modified on your engine, specifically was the oil restricted to the rocker arms? Lots of FEs have pressure loss there, and you can fix if you are willing to pull the valve covers and rocker arms. DF

 

I don't really have access to a "real" gauge yet but plans are to buy a set soon. As far as the oil I'm running 10W 30 right now. I have no problem pulling the valve covers and fixing this thing. I aint afraid to get my hands dirty, in fact I look forward to the oppertunity Other than a HV oil pump the oil systenm is completely stock. As far as i know no mods were done to the oil system. I bought this motor off my brother cause he needed cash so I know pretty well what's in here.
Thanks,
Jeremy

"Like a Rock"; on the sides of roads everywhere.

 

I have a 390 a the pressure is a little low.I would like to know more about restricting the the oil port at the rocker arms.I would be interested in doing mine.Could one of yall tell me how and what to do.

 

There are two reasons to do this valve train restrictor mod.
1. a lot of FE's use small front sump oil pans and a HV pump can run it dry and start to suck air (VERY BAD).
2. the mains need more oil than the valves do and many believe the valve get too much.

the mod is designed to restrict the oil flow to the valve train and thus keep more oil to the mains where it's really needed. The mod is very simple...

remove valve covers
remove rocker arm shafts (one or 1/2 turn at a time, from inside to outside to prevent bending)
drop a Holley carb jet or drilled rod into oil passage

The oil passages are 1 per head and are down in 1 rocker arm bolt hole. You'll see a hump near the base of the hole, that's the oil passage. I think the standard size is .1~.09" but cutting it to 1/2 current size would be fine.

Don't forget, the valve train uses 3 different bolts, 1 long reduced shaft for oil hole, 1 med reduced shaft, 2 standard for the ends. The washers on top are extra thick and must be flat to seal oil. torque 1 turn at a time from center outward to about 40~45# so as to not bend the shafts. This is a good time to look at the bottom of the rockers, slide the rockers over and inspect for wear at the bottom of the shaft, the bottom has the holes in it for oil passage. also look for mushroomed tips where it touches the valve.

I like to run the engine without valve covers for a few min to check for proper oil flow out of the tips of each rocker and NOT out the side of the rockers which would indicate a worn shaft which is common (napa sells new shafts for $25).