I'm running a 72 429 in my 79 250. Rebuilt the bottom end before installing, bearing clearances were tight, but in spec. I used an oil pump for a 80's 460 to get the rear sump. I've got good oil pressure cold but when it's hot at idle with the brakes on pressure drops below 10 psi and the warning light comes on. If I bump it back to neutral pressure goes up, or if I raise the rpms pressure goes up. Any ideas?
Thanks

 

Tighter clearances should give you more oil pressure,.

First I'd verfiy with a known, good machanical gauge.

What kind of OP did you use?

 

Does it have a remote oil filter or cooler that you might have switched the lines on?

 

I'm using a melling standard volume oil pump, got it from summit. No external oil cooler or filter. The gauge I'm using is fairly accurate so I'm leaning toward the pump... Going to order a HV pump and see what happens. Only other thing I can think of would be cam bearings but the engine only had about 40k on it when I got it. Rods and mains were barely worn when I changed them.

 

The "bearing clearances were tight" well what were they set to? Did you plasti-gauge them?

 

Your bearings would have to be really loose to affect oil pressure. If its good cold then I would really check that gauge out first, especially if you are using the stock Ford gauge. I wouldn't trust mine for a second. You say the warning light comes on, are you just relying on the warning light or do you have an external gauge? If it is just a warning light I would definitely get a gauge. Possibly the pressure regulator spring in the pump might be weak but since its good cold that is probably not a problem. As far as the melling stock pump is, It is the best on the market and is all you would ever need in most circumstances.

 

If you can, you might check the pickup tube. Sometimes they are loose or once I found a crack around the tube. Pressure might be OK when oil is thick but when it warms up maybe it is too thin to cover the crack or too much air is getting into the system at that point.

Sometimes the relief spring gets old and the pump no longer supplies enough pressure. You might replace the spring if it is a pump where you can get at it, cheap to do.


Good Luck,

Jim Henderson

 

I'm using an external gauge to check the oil pressure (mounted in engine compt), the warning light just caught my eye. Learned a long time ago not to trust the oem gauges for any accuracy.
If I have someone put the truck in gear and hold the brake the pressure drops (to the point of bringing on the light) but as soon as they bump it back into neutral or park, rpms about the same, the pressure goes back up. I'll have to wait for someone to be around to get the actual readings again.
When checking the bearing clearnaces I mic'd the crank for the one reading. Put the bearings in and torqued the caps then calipered the bearings. Can't find the paper I wrote everything down on (done last august, probably 2500 miles ago), but I know they were within the specs. Never had good luck with plastigauge.
When the bearings were going out of my 400 (in the copper big time) I noticed a big drop in pressure that wouldn't climb back up while under rpm's. But with the 429 as soon as it gets rpm's up goes the pressure.

 

what is your in gear rpms? You might be just enough on the low side the pump is not keeping up and may need to be bumped up a couple of rpms. Oil preasure specs are figured at 2000 rpms everywhere I see them printed. if your rpms are below 700 idling in gear that is most likely your problem