On Fri, 06 Apr 2007 03:37:58 +0000, Kevin Bottorff rearranged some
electrons to form:
> "keng2" <keng2@[EMAIL PROTECTED]
> wrote in
> news:4615be91$0$1373$4c368faf@[EMAIL PROTECTED]
>
>>
>> "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
>>
>>
>>
>
> Bingo, most low pressure hot problems I have found are the cam brg.
> eng brgs usually will be low most all the time just get worse hot, but
> cam brg problems will usually have normal pressure gradually falling as
> the eng temp rises. If you think the rest of the eng is ok I have put a
> high volume pump in them and got by a long time. KB
Agreed... especially since you didn't say that you replaced the cam
bearings during your overhaul. If the main bearings were properly
installed (and the clearances were correct) they should not have worn out
in 10,000 miles. How many miles were on the engine *before* the
overhaul?
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
T/S 53
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