Hopefully somebody here knows where to look or possibly know of a
newgroup like this that deals with Ford engines. I've got a 74 Ford
F-100 with a 360 converted to 390 apx 10 years or 40,00 miles ago. I
did an in vehicle overhaul, having the heads rebuilt at a machine
shop. I replaced rings, rod bearings and did not balance the rods. I
replaced the 360 crankshaft with a re-ground 390 crank kit with
bearings. It still has decent compression with pump regular knocking
at acceleration. Usually a 50/50 gasoline blend eliminates the
knocking.
After apx 10,000 miles on the overhaul the engine started vibrating
about 30-35 mph or 18-2000 RPM. I get the vibration whether it is in
neutral or in gear. Having the older style rebuilt 3-finger pressure
plate and way to many miles on the clutch I suspect and out of balance
pressure plate might be where the vibration is coming from but don't
know for certain. The vibration is getting progressively worse. I
replaced the vibration damper apx 5 years ago and the vibration did
not improve. The conventional ignition was changed over years ago
prior to the vibration problem and I recently had it scoped and there
were no problems. Advancing and retarding the timing beyond the books
does not help with the vibration.
Any suggestions on where to look next?? I'm trying to avoid the
clutch. Being a 4X4 with a minor nuisance oil leak in transfer case to
deal with, changing the clutch is not an option until it wears out.
Dealing with the greasy transfer case and extremely heavy cast iron
drive train is no picnic and apx 5-700 $'s worth of labor if I don't
do it myself.
The biggest problem is oil pressure. Normal in town driving the
pressure is fine even at idle. After a short trip on the freeway or
high RPM's, the pressure drops the zero when it returns to idle or low
RPM's. After returning to idle after driving just a few miles on the
freeway I have to pick the RPM's up or I will get a lifter ticking
from oil starvation if I sit at a stoplight for a few minutes. I can
drive around town all day and the oil pressure will remain normal even
at idle speed. If I take the truck on a long haul like an out of town
hunting trip I have to add a can of STP or Motor Honey to maintain
decent oil pressure. I've pressure tested the oil pump via the oil
sender outlet both hot and cold and it is doing it's job.
I don't know if the vibration and oil pressure problem are related but
both problems are getting progressively worse. I've talked with a few
mechanics and naturally they try to sell an overhaul or short block.
None has been able to say where the problem is. At a shop that uses
wet back labor speaking through a translator one mechanic that
exclusively rebuilds engines all day said main bearings most likely
fix the oil pressure problem but he had no idea on where the vibration
was coming from. His suggestion was to use 50 weight oil until the
engine goes and live with the vibration.
Any suggestions on where to look for the problem or a newsgroup where
I might look for answers are appreciated. With all the big-block Ford
engines I've owned since the 60's the easy fix to engine problems was
finding a wrecked Mercury, T-Bird, LTD or station wagon and using the
engine until it wore out. Good used 390's used to be a dime a dozen
but now finding a low milage wreck with an engine that is an easy in
and out to fit a 1974 drive train is near impossible to find.
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