Hi Listers,
I thought you all would be entertained by the outcome of my engine noise
quest. For those of you who don't remember... The loud banging noise was
produced by hard acceleration. I had lower than I liked oil pressure and
suspected all kinds of things and chased all of them all summer. Well it
turned out to be the engine mounts. While pulling the engine it was obvious
that the rear and right front mounts had failed completely... the rear from
oil damage... the front from poor quality or rubber aging. The two metal
parts of the front mount would bang on the frame has the engine lifted from
the torque.
I was glad to find the cause but thought I had wasted all that effort... if
I could find no problems in the engine.
Well I found my smoking gun for low oil pressure.... big time!!! The
connecting rod bigend bearings on all cylinders are a mess and worse so on 3
& 4. Right through the gray bearing metal to the steel shell... with
grooves and pits. It's a good thing I pulled the engine... as these were
set up for failure somewhere in the very near future. There are noticeable
wear traces on the crank as well... I hope they can be reground without
falling out of spec.
This engine was obviously rebuilt before but has a weird set of other
characteristics.
The main bearings are fairly normal and show only... some minor wear. The
pistons slid right down and out with just the pressure of my thumb from
above.... no detectable ridge. There are also 2 different kinds of
pistons.. both AE but different part numbers and markings... they look
identical from outside... only when you turn them upside down can you see
the different color and casting marks. The pistons are almost new looking
with no pits on the crown and the wrist pins are perfectly clean with no
play. All the pistons had thick deposits of carbon on their centers and #1
looked a little burned black while the others were bright aluminum.
The camshaft front bearing looks almost new... but the camshaft lobes appear
to have some sort of surface discoloration. The cam followers are in mixed
shape.... some are pitted slightly , some show signs of not turning any
more, and others are perfect.
Haven't looked closely at the head yet. But the rockers are worn with
indentations on the valve side. I will check the shaft for wear but the
rockers will have to be replaced.
I think this engine was rebuilt not to many miles ago but many years ago.
>From the owner history I have that would be at least 15+ years ago maybe
20+. It is not unlikely that the engine has less than 10,000 on it but has
sat for long periods without use. The areas of the crankshaft bearing
surface where the bearing doesn't ride have a brown... almost rust colored
look.
What would explain this strange set of conditions and the badly worn con-rod
bearings. Any thoughts. Should I not replace the pistons and liners if
they pass inspection by the machine shop.
Any advice and/or opinions from you folks that have done this before would
be highly valued.
Brian Sanborn
62 TR4 CT16260L - Groton, MA
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