I've had the motor out of my frist Maverick sitting in my garage for 10 years now, it had an oil pressure problem, the pressure gauge would drop to "0" when sitting at a light, but would come back up no problem, so I decided to pull it apart and check it out. The crank to bearing clearance is .002" on all the bearings, and I've been told by a machine shop that a worn crank can cause low oil pressure, but is .002" worn? I pulled the pump apart, no ware in it, the rotors are nice and tight, my Haynes manual says .015" clearance, I'm not even close to that, and the spring seems good. Any Ideas? I might just drop it off at the machine shop I deal with this week and have the crank polished.
When you checked your oil clearance...are you sure the micrometers were correct? I just went through this. Kept banging my head against the wall. Crank showed 2.0889 on the rod journals, crushed bearing in the rod was 2.0949. .005" clearance...too much for my tastes. Found out that the inside mike was off a little and the outside mike was off even more. Recalibrated them and I'm back to .0021", right where it should be. I agree. Cam bearings are usually a cause for low pressure if nothing else is found wrong. Also look at the main webs, I had a 351w that had cracks in them and let pressure squeak through the cracks. Just a few thoughts.
Yea what they said and check you lifter bres. Gauge is acurate? Oil pump always good to check and always good to replace, also check pick up for cracks and correct depth.
.002 is more clearance than I want on a street engine with the Ford name on it. The Ford specs call for .001" to .00125" clearance for the main bearings, and .0015" to .0025" and .004" to .008" Crank end play for the 289 and 302 engines (before roller cam engines). If you want to run .002" main clearance then you have to run heavier oil and a high volume oil pump to keep up with the oil washing out the sides of the bearings. Paul
Put in a new oil pump and should help. .002 is just fine in any Ford engine I have seen. Cam bearings, or leaking oil galley plug are a possability, look at the very back of the pickup screen(under the metal cover). Sometime's the exposed screen is clean, but way back in there, it is plugged with gook and/or engine piece's. Are you using an electric or mechanical gauge? Those electric one's can give eratic pressure readings for many reasons. Put on a new sender unit and see if that is not the problem, polishing the crank is always a good idea, as long as the clearance is maintained at .0025 max. My all out race engines run .003 on the mains and .002 on the rods, use a HV pump and 10W40 Mobil 1 oil @ 7200 rpm. Never had a bearing failure, only broken rod's and crankshafts. Favoring the loose side on clearance's, seems to make any engine run better and cooler on oil temp. A little better gas mileage, sometimes.
Thanks for all the suggestions, as for the oil pressure gauge, it's a mechanical one (Auto Meter). I dropped the motor (short block) off at the machine shop this afternoon, we'll see what he finds.
