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Discussion Starter #1
Hi, here's a recap.

Stock long block 5.0 from 1994. Was running on the highway and all the sudden, bad vibration appears. Towed car home and balancer bolt broke and balancer too. No visual damage to crankshaft itself. Bought another balancer from ATP and ran since. Few hundred miles later, medium vibration appears so I've replaced again balancer for a Powerbond. Vibrations seems cut in half but still present. Now started some tests.

Transmission removed and engine supported with a frame that used transmission mount on stock crossmember.

With Powerbond balancer (50oz) and Fidanza flywheel (50oz) and no clutch, vibration at approx 1200 and between 2200 to 2800 RPM. I can feel it seated. Bought another stock replacement flywheel (50oz) and issue remains. Verified all spark plugs, wires, no arcing and engine mount seem perfect. With or without engine strap and still present, no change. Found nothing in the oil too. It is possible main bearing have something that cause vibration? When I use force to move up/down the balancer, I can feel a very small bit of moving. Thanks
 

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Did you cut the filter open when you changed oil?

If there is free play on the fwd end of the crank and some bad vibrations then there may be deeper issues.
 

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The next thing to investigate IMO is the rods. Run a compression test and see if one hole is way down on compression. If the rod is bent that will be the hole. I have seen stock 5.0s bend rods but it has usually been from nitrous.
 

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Nose of the crank may be bent.

ks
 

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Discussion Starter #7
The next thing to investigate IMO is the rods. Run a compression test and see if one hole is way down on compression. If the rod is bent that will be the hole. I have seen stock 5.0s bend rods but it has usually been from nitrous.
Might be an idea. Just to understand, how a bent rod would affect the compression test result?
 

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How could we measure or verify this with the engine assembled ?
You would need a dial indicator mounted on the engine some place then rotate the crank by hand to see if there is a wobble. All of this done with the H-balancer removed.

k
 

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Discussion Starter #10
You would need a dial indicator mounted on the engine some place then rotate the crank by hand to see if there is a wobble. All of this done with the H-balancer removed.

k
You're right. If my minds are good, crank is sitting flush with timing cover so when removing oil pan, I will be able to do it.
 

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There is a possibility of a "compression imbalance" but I would really think the crank snout got bent when the first balancer blew.

First off, it seems like you would be able to see that at the balancer when checking timing, but if not, perhaps use 6" stud (with nut) to mount the balancer so that most of the stud extends out past the balancer and you would get a much more visual "read" on whether the snout is straight when the motor is spinning. If it is, the stud would spin perfectly with no wobble, if it off at all I would think it would be really obvious with the stud sticking out. I know it's a crazy idea, I'm just trying to help!
 

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Discussion Starter #14
Havent chance of working that much on it. I removed the engine from the car and did some basic check.

Runout of Crank flange: 0,0041.


Leakdown test (cold engine :)

P-Rear-D
90 --- 92
90 --- 86
91 --- 82
90 --- 80
----F----

Not sure why on driver side, it doesnt seal like passenger one?

Will remove oil pan next to check crank itself.
 

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Havent chance of working that much on it. I removed the engine from the car and did some basic check.

Runout of Crank flange: 0,0041.
This seems like a lot if this is the crankshaft snout where the balancer mounts... I would think it would be .001 or less... Maybe someone else will chime in..

ks
 

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Discussion Starter #17
Did some measurement today. Crankshaft runout on main #1. 0,00085

Some pictures of the bearing are coming. What you think guys?
 

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Thats 8 and a half ten thousandths, correct? .00085. Thats nothing, thats remarkably good. What does the crank snout measure? Bearings are reminiscent of a 25 year old bearing. Little more than 3/4 wipe pattern, crap run through the oil in the last few decades. Nothing shocking. Unless the main bearing clearance is very wide, over .004, main bearings just sit there and go along for the ride.
 

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Yea, measure the snout/shaft that the balancer slides onto at the very end of the crank where the bolt screws into.

ks
 
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