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External balance Lt1 changing to flexplate - SOLVED pics inside

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Old Jan 19, 2013 | 07:51 AM
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Default External balance Lt1 changing to flexplate - SOLVED pics inside

So I took my t56 out and flywheel off, see the balance pad and drill marks from balancing on my Lt1 flywheel:



I didn't notice which way it was when I took it off!

1) How do I line up my new flexplate on the crank

2) Do I have to take the old and new flexplate to a shop so the new flexplate can be balanced the same as my old flywheel?

Thank you

Last edited by Jason94z; Feb 20, 2013 at 11:11 AM.
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Old Jan 19, 2013 | 10:24 AM
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The crank has a dowel pin that needs to line up with the hole between the bolts in the flexplate. The hole in the flywheel pictured is at about 5 o clock position. The flex plate will also have that one extra hole for the pin..
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Old Jan 19, 2013 | 11:17 AM
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Thank you. I have no dowels so I'll just line up the extra holes.

Do I need to balance my new flex plate exactly the same as my old flywheel?
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Old Jan 19, 2013 | 12:06 PM
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If the engine was balanced with the old one then yes (meaning engine was built and balanced and they altered the flywheel to balance it) If its a factory engine that has not been apart or balanced any more precisely than factory then I wouldnt worry about it.

Put it on and let it rip. Try to locate a dowel if you can, it is supposed to be there. anything newer than 1986 (if i remember correctly) if its a SBC should have one you can rob. 4.3s had them too and im about certain they were all the same.
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Old Jan 19, 2013 | 01:19 PM
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Originally Posted by carlsonauto
If the engine was balanced with the old one then yes (meaning engine was built and balanced and they altered the flywheel to balance it) If its a factory engine that has not been apart or balanced any more precisely than factory then I wouldnt worry about it.

Put it on and let it rip. Try to locate a dowel if you can, it is supposed to be there. anything newer than 1986 (if i remember correctly) if its a SBC should have one you can rob. 4.3s had them too and im about certain they were all the same.
Thank you

Yes it's a built engine it was balanced before with that flywheel on. I'm switching to an auto that's why the change
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Old Feb 2, 2013 | 10:27 PM
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Which flexplate? I want the cheaper one will it last 5500 launches?

http://www.jegs.com/i/Meziere/680/FP...oductId=753983

http://www.jegs.com/i/TCI/890/399173/10002/-1

So should a shop match my old flywheel balance, to the new flexplate to balance it the same? Or is that impossible to do since the flywheel and flexplate or so different in weight and design?
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Old Feb 20, 2013 | 11:15 AM
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Ok so I found a local machine shot that works on lt1's and all kinds of internal/external engines all the time. Does things like this every day.

This is the procedure:

1) They bolt my old T56 flywheel to a crank and balance it on the crank side perfectly.

2) Then, they take off my old flywheel and bolt on my new flexplate. They balance it perfectly taking the weight/adding the weight on the new flexplate.

3) I run 9's. (LOL just joking hehe)

I dropped it off today, it should be done in a week.
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