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  #1 (permalink)  
Old 07-07-2010, 06:48 PM
chevykid90's Avatar
454, what turns your crank?
 

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Wrong Flexplate??

my question is, will a SCAT flexplate that was made for 1991 and newer one piece rear main work for an older 2 piece block?

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Old 07-07-2010, 07:11 PM
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Quote:
Originally Posted by chevykid90
my question is, will a SCAT flexplate that was made for 1991 and newer one piece rear main work for an older 2 piece block?
I am pretty sure the flexplate for the one piece has a different bolt pattern then the flexplate for the two piece. So i have been told it will work but I dont see how with the different bolt patterns. I was told there are somethings you will have to change, Like different bolts smaller ones for it to work and clear things,JMO Someone might know something i don't so wait and see if someone else chimes in on this in a bit. and the one piece should have externally balanced flywheel/flexplate also. Is it 153 or 168 tooth flywheel it makes a differance when it comes to the starter and the starter pattern. I am not 100% on this working or not, But i had a buddy go thru the same deal a while back so maybe someone else will fill in the blanks i might have left. Just trying to help.


Cole

Last edited by eloc431962; 07-08-2010 at 02:34 PM. Reason: had to re-phrase
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Old 07-07-2010, 07:32 PM
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454, what turns your crank?
 

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well when i was eyeballing it it looked like it would bolt up. but i will know for sure tonight when i get it off the stand to find out... i hope its good news or once again my project will be stalled.
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Old 07-07-2010, 07:38 PM
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I hope it works for you also. I think the difference is only slight which makes all the differance, But you will know when you place it on the engine. Good luck. keep us posted.


Cole

Last edited by eloc431962; 07-08-2010 at 02:35 PM.
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Old 07-07-2010, 07:55 PM
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Also i was going to tell you if the flexplate you have is from 91 one piece then it should have the weight on it, and is a externally balanced flywheel/flexplate.
So you would also have to remove the weight for it to work even if it would work on the older two piece seal engine. JMO


Cole

Last edited by eloc431962; 07-08-2010 at 02:37 PM. Reason: added text
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Old 07-07-2010, 08:20 PM
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When chevy changed from 2 piece to 1 piece seal in 1986 the crank flange was changed so it won`t bolt on, the bolt pattern doesn`t match. Also when the change was made the counter weight that used to be on the 2 piece seal was redesigned completely round for the 1 piece seal, so the weight had to be added to the flexplate to keep it in balance. Chevy changed the flange intentionally so they wouldn`t interchange as they knew if a older flex plate was bolted to a newer block it would knock it out of balance and destroy the bearings.
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Old 07-08-2010, 04:45 PM
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454, what turns your crank?
 

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well this flex plate i have bolted right on to my crank, and the counter weight is more rectangular with pointed ends. so i guess when i start it up i will find out weather or not its in balance..
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Old 07-08-2010, 05:22 PM
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The ONLY SBC engines to use a weighted flexplate is the 400, '86-up one piece rear main seal engines and 3.75" strokers.

If you have a 2-piece RMS engine and it is not a 400, you have the WRONG flexplate if it is weighted.

For the record, just what engine are you working on, anyway??

Last edited by cobalt327; 07-08-2010 at 06:51 PM. Reason: GMCBoogie reminded me of the strokers.
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Old 07-08-2010, 05:25 PM
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Quote:
Originally Posted by chevykid90
my question is, will a SCAT flexplate that was made for 1991 and newer one piece rear main work for an older 2 piece block?
No.
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Old 07-08-2010, 06:36 PM
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Whoa! Hold on there chevykid. Do not bolt it on and go.

A flexplate for a one piece seal sbc crank will not fit a 2 pc seal crank.

If your flexplate has a weight and it fits your 2pc seal crank hopefully you have a 400sb or an externally balanced 3.75 stroke crankshaft.

otherwise you are going to have problems.
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Old 07-08-2010, 07:02 PM
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Is he talking about a SBC? If it's a big block 454/502. Yes the flywheel will bolt on. No... It is not correct. Motor will shake..
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Old 07-09-2010, 09:24 AM
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454, what turns your crank?
 

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its a 454, i havnt put it in the car yet and not going to until i know i have the correct parts. but it did bolt up to my crank, so my question still stands on what are the differences in the flex plates. if it bolts up why wouldnt it work? dont get me wrong, if i have the wrong one i will buy the right one, just for future knowledge i would like the answer
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Old 07-09-2010, 03:45 PM
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Didn't know it was a BBC , Anyway it will bolt on then but it's not going to work. Wrong for the engine you have you need one for the 2-piece RMS. It will vibrate do not use it. Or you will be tearing it back apart to put the correct one in it.JMO


Cole
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Old 07-09-2010, 04:00 PM
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Both the one piece seal flexplate and balancer will bolt to 2-pc rear block. The one piece stuff has heavier balance weights and if used on a two piece motor will shake .

The proper two piece flexplate has a long narrow weight that somewhat resembles a sbc 400..
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Old 07-09-2010, 08:31 PM
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454, what turns your crank?
 

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ok, thank for everyones help with this. i didnt know so thats why asked. but i went out today and bought the correct flex plate and the project can now keep on a rollin.
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