keng2 wrote:
> "Roger M" <rnddmauck@[EMAIL PROTECTED]
> wrote in message
> news:46145298.35CF5876@[EMAIL PROTECTED]
> >
> >
> > dcnisbet@[EMAIL PROTECTED]
wrote:
> >
> >> 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.
> >
> >
> >
> > You lose oil pressure because the bottom end has a bunch of wear.
Likely
> > the source of your vibration also. When driving on the highway the oil
> > gets hot and thins out causing the oil pressure loss. In town driving
> > should net the same result but may require a lot of in town driving.
Your
> > vibration is probably coming from a bunch of mismatched parts wobbling
> > around in a bunch of loose bearings caused by poor assembly
techniques. IE
> > poor quality parts (crank kit), no balancing, dirty assembly
environment,
> > etc.
> >
> > I would stop driving it, remove the engine, disassemble it, measure
> > everything, replace parts as necessary then carefully and cleanly
> > reassemble it. I would also spring for a professional balancing job,
> > professional crankshaft servicing and anything else that was
absolutely
> > needed to make it last. You got ten years so you did ok time wise but
> > mileage wise you didn't get much for your rebuild money.
> >
> >
> > Roger
> I had a low oil pressure problem with my 390 which turned out to be worn
> camshaft bearings!!
>
> KenG
Great, glad you found the problem. How bad did it vibrate?
Roger
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