chip: I guess there's more to the story, than just
shim's. Troubled waters....
Yes, excessive end thrust is a telltale sign of
problems. Possible troubles and/or causes:
1. Incorrect main bearing fit, during the power
stroke's of each cylinder near a (loose main) the torsional vibrations will lift/push the crank
fore and aft. (most likely. You know how to
correct this. Check those bores. My money says,
there all spazzed from where they should be in diameter, to give the main bearings the proper
fit. The crank is probably jumping and moving
all over the place. Each bearing is not carrying
the same load. Every power stroke that strike's
the crank, causes it to jump around. A few (12000)
thousand miles is nothing.
2. Bent connecting rods, likewise they will move
the crank fore/aft in there power stroke. The
rod (thrust) is in a oscillation, instead of a
rotary motion. (likely, but check. Take all rods
to machine shop, they can check for distortion,
out of round, twisted, and bore parallelism.
3. Out of round Main bearing bore(s) This will
more or less give the same effect as #1.
(need to shim correctly, and check) This is
most likely the trouble. The mains are not on
the same centerline because of incorrect shimming!
4. Crankcase distortion/warpage. This effects
all the mains and can cause the crank to walk in
either direction. (very likely, because you said that engine was overheated, and later siezed.
Will have to shim all main bore's to standard size of insert, then check for alignment. If off,
get undersize bearings and align-bore. Take block
to machine shop, they will have (should) correct
mandrel to place in mains to check. You can check
with a quality straightedge and feeler gage)
Block should be very carefully checked out for
cracks around main web's. (magnaflux)
5. Balanced crank, and assembly. This is a must,
to insure main bearing life. Most guys have the
crank and flywheels balanced. Take all rotating
parts to mach shop. This includes, crank, rods
with attached pistons, flywheel, p.plate, damper.
Same(even)piston and rod weights, and rotational
stability go a long way toward increasing engine
life. Will run better, and idle smoothly. This
was probably not the cause of your engine sieze,
as you have bearing and other probable troubles,
but it never hurts to cover all the bases.
6. Crankshaft straightness. Your crank may have
been bent/warped. But since reground, I would think that the shop would have noticed if it was
bent. This is easy to check- rest front and rear
main journals in V-blocks. Lay a piece of paper in
the V blocks so as not to scratch.
You can set this up on the deck surface if need be. Rotate, and check for any runout on/at #2 and #3 journals, snout, thrust face, and flywheel flange and face. All readings should be dead on.
Use your indicator!!!!!!!!
Always check work that a shop does! Those guy's
are human and screw up too!!! You never know until
you check. The shop should have magnafluxed the
crank before they reground, or did they? The crank
forging hardness should be around 200 Brinell.
The shop can/has a ball tester to verify.
I don't know your situation, as to what's been done so far to your block? Piston's? Overbore? Cam? Or, what kind of additional performance parts you want to put onboard?
Since you have to take all this down to the shop
anyway, why not just have them assemble the short block? It would be way less hassle, and they will
have to check rods and block anyway. Just a
thought.... This would work for you, because the
shop would have to guarantee their work, and you
would have a receipt for work performed. Cover
your butt.
Another thought! Why don't you pick up pte359's
235 just for buttcovering material? I don't know
if he's selling it complete?, or what?, from his post.
Most of us bolter's have a spare engine or two,
for our ride.
Don't sweat it!!! Spring break is a long way off!
Good Luck, and repost!
Think Chevy!
:rolleyes: :p
