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Old 07-26-2006, 08:04 AM
2000jack's Avatar
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Bend a Flex Plate?

I bought a 350 SBC and the starter I had was too weak for that motor so I had a Proform High Torque Starter installed. The problem came when it was time to adjust it. It seems that the flex plate wobbles so much that every fourth or fifth time the flex plate was too far away from the engaging gear of the starter. When we moved the starter closer the engaging gear seemed to hit flex plate and grind instead of engaging properly. I was hoping that some one had encounter this before and instead of replacing the flex plate which is a lot of labor they had just took a large pry-bar and bent the flex plate to straighten it out.

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Old 07-26-2006, 08:46 AM
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the flex plate is part of the balance of the rotating Assembly,if it's bent that bad replace it.just think what that bent flywheel is going to feel like at say 5000 rpm's.you can cause some bad harmonics and harmonics destroy bearings.
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Old 07-26-2006, 08:50 AM
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Id replace the flexplate, because of what Nitro said, and I have had bent flywheels turn out that they were cracked bad.
The last thing Id want, is a cracked flywheel spinning as fast as they do and have it break apart.



Brad
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Old 07-26-2006, 09:10 AM
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Do you have the 153 or 168 tooth flexplate?
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Old 07-26-2006, 09:33 AM
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Quote:
Originally Posted by 454C10
Do you have the 153 or 168 tooth flexplate?
pretty sure it is the 168 tooth
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Old 07-26-2006, 11:45 AM
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The reason why I'm asking is that lately I have noticed that a 153 tooth flexplate don't fit the early style cranks very well. There is a recess in the flexplate where it bolts to the end of the crank and the recess area is not large enough to cover the end of the crank. The end of the crank is not round due to a protrusion. So, what happens is the flexplate doesn't sit flat on the end of the crank, making it look bent. I figured this out when I build an engine stand that allows me to run the engine and break in cams. Kind of hard to see this under a car.

The cure is to use two 0.030" thick spacers which are sold by summit for about 6.00 each.

FYI, the 168 tooth flywheel uses the starter that mounts with a diagonal bolt pattern and the 153 tooth flexplate uses the starter with a straight across bolt pattern.
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Old 07-26-2006, 03:52 PM
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Because I balance rotating assemblies, I have the opportunity to observe how true flexplates (and harmonic balancers) run when assembled on the crankshaft. It's quite interesting to see that the worst offenders are usually aftermarket SFI-approved pieces. The ones with least lateral and/or vertical run out are your typical parts store stock replacement types.

Most of the time, if they are .250" or less out, I will "tweak" is back to shape. Anything more than that I tell the customer to send it back.

And yes, some cranks will interfere with the proper mounting of the flexplate. This is usually a poorly-designed or finished flexplate.

tom
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Old 07-26-2006, 04:36 PM
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flex plate

i used a 168 tooth flexplate on my 350 chevy with a starter for a 427, worked great.
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