| [GMCnet] Subject: GMC engine suggestions needed [message #141911] |
Wed, 31 August 2011 20:58  |
rallymaster
Messages: 662
Registered: February 2004
Location: North Plains, ORYGUN
Karma:
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Senior Member |
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Subject: GMC engine suggestions needed
Everybody:
As far as I know, the attached rebuild data sheet is the last major work
done on the engine.
January 1989 at 141,200 miles. 1978 Oldsmobile 403 cid.
The only thing most of the rebuild info means to me is it was rebuilt a
long time ago to RV specs, and sounds expensive to fix.
If I remember correctly, the other 7 cylinders had about 140-145 #
compression.
The current rebuild has about 135 thousand miles on it.
ignoring option 1, the cheapest solution, who has suggestions, and why?
If I have to have the engine rebuilt, I'd prefer to have a solution that
doesn't rely on oil change places using only the oil I tell them to use.
That probably means a roller tappet system - $$$.
Of course, some of the engine people say that large amounts of ZDDP only
matter during the break-in period. Some say, until it's well broken in,
others say, FOREVER!
Feel free to disqualify yourself for any reason...
thanks,
Ron
Pics available if anybody wants to see them.
Ron, Today the intake manifold came off. As you can see in the pictures
the following is what we found:
1 bent push rod.
1 broken push rod.
1 bent rocker arm pivot. (hard to see)
2 disassembled lifters. (not shown)
1 oddly worn cam shaft lobes for #7.
Possible cause of the bent push rod and rocker arm pivot – valve seized
in the valve guide.
Possible cause of the broken push rod – when the rocker arm pivot bent
the push rod was hitting the hole in the head while it continued to spin
scoring the push rod until it broke.
Possible cause of the 2 disassembled lifters – without the push rods to
keep the lifter loaded it lost the keeper and plunger inside the lifter.
Possible cause of the worn cam shaft lobes – unloaded lifters bouncing on
cam shaft lobes.
Possible solutions:
Cheapest – replace pushrods, rocker arm pivot and lifters with used
parts. No guarantee. May not fix what caused the problem in the first
place. Cam may eat the lifters.
Mid cost – rebuild heads, install new cam, lifters, push rods and rocker
assembly.
Most cost – rebuild engine.
Do you know the history on this engine? Someone has been in it because
the inside has been painted. If the engine has a lot of miles on it,
rebuilding the heads only can turn the engine into a big oil pump. The
compression on the other cylinders did look OK so the mid cost option is
a possibility.
EngineExcerpt from engine rebuild data
Automotive Test Equipment
24990 S. Kirchner Rd.
Oregon City, Oregon 97045
503—632—7080
Jan, 1989 141,000 miles
Rebuilt (Automotive Test Equipment OR City141200Jan-89
Engine (with above)Gas & Vent LinesBrunetto141200Jan-89
Engine (with above)Mondello Camshaft & lifters141200Jan-89
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Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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