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 Post subject: flex plate
 Post Posted: Fri May 12, 2006 6:02 pm 
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May be a dumb question but how much balance weight should there be on an internal balanced BBC flex plate,

I'd have thought very little ???

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 Post Posted: Fri May 12, 2006 6:13 pm 
 
i would have thought none ... being interaly ballanced and all...


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 Post Posted: Fri May 12, 2006 6:28 pm 
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that was my line of thinking also.

the flexplate has a bit of steel welded one side about 7 inches long by over an inch wide and about 1/4 inch thick...

(it was manufactured like it as it is the same powdercoat as the rest of it)

any other opinions as I'm about ready to reassemble it ??

I'll check back in the morning it's late here

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 Post Posted: Fri May 12, 2006 6:38 pm 
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Yup, that's what they look like all right! Big hunk of metal welded next to the ring gear. Should be a dowel in the end of the crank so it will only go on in one position.

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 Post subject: Re: flex plate
 Post Posted: Fri May 12, 2006 9:48 pm 
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Sam wrote:
May be a dumb question but how much balance weight should there be on an internal balanced BBC flex plate,

I'd have thought very little ???


Sure sounds like an externally balanced assembly to me. Were there any heavy metal slugs in the crankshaft counter weights ?


Last edited by DCarr on Sun May 14, 2006 12:33 pm, edited 1 time in total.

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 Post Posted: Fri May 12, 2006 11:05 pm 
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Yep Sam I think you got the wrong flexplate. I have no weights at all on my BBC flexplate. If you are running an internal balanced setup you have to get the one for the 427 as it was internally balanced. The 454 was externally balanced. Same goes for the harmonic balancer.

George


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 Post Posted: Sat May 13, 2006 2:41 am 
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Yes Mel, that dowel, I dont want it coming out again.

seems to be a split decision.

I dont have any dowels in the crank, a previous post had said that the bolts are offset so you cant get it on wrong.

I just wondered as it has internal marked on the crank and there is no heavy metal on it.

Judging by some of the other things I have found (and talking to someone who knows the car) I would not be surprised if a wrong flexplate has been fitted. It does not shake or vibrate badly (well not that you would notice with open exhausts etc)

I'm leaning toward it being a wrong one, based on the fact that it does have a big chunk of weight on the plate and the fact that I have had 2 bellhousing dowels fall (make that 3) out.

I'll try and put a picture up, to post this message has meant a 200 mile round trip for me... I gotta get my new workshop here... plans are approved in principle. proper application goes in next week.

laters guys

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 Post Posted: Sat May 13, 2006 7:47 am 
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Sam I wouldn't bet my life on this but I've never seen a Chevy with offset bolt holes in the crank? EVERY one I've ever seen has a dowel hole for positioning the flywheel to the crank with the bolt holes equally spaced, not offset! Years ago, before the external balance thingie came about with the 454BBC I put a couple of 396 BBCs in 55-57 chevys using the 283SBC flywheel which was internal balance!

Check the crank to see if there is a hole for a dowel. There also should be a hole in the flywheel to match that one in the crank, if it's there. If there is a hole in the crank and no dowel, then the flywheel could have been off by one bolt hole, not had that much vibration but still be significantly our of balance. Oh, one other thing. Those block dowel pins you have are "home made" aren't they? How much press fit do they have in the block? Locktite 609 should be on them if they're a little sloppy. They should be a "drive in" fit around .0015 to .002 press fit.

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 Post Posted: Sun May 14, 2006 3:06 pm 
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Ken,

If I made the dowels anymore of a tight fit they would split the block going in... there tight... all of them have been tight....

I'm picking up a new flex plate either tomorrow or tuesday night... internal balance, I'm taking the old one with me to compare..

It's the first time the flex plat has been off, I've not even looked until when I was going to refit it.... just struck me as to why it had a lot of weight on it and its only a spinning disc of metal

I'll fit a new one and be sure its right.. as to the dowels they have been pinned in place now...

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 Post Posted: Sun May 14, 2006 4:48 pm 
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I have put a 454 flywheel on a 427 internal balance before, sounds bad feels bad. youd swear you forgot to tighten a rod end. The only time I felt anything worse was when I was a kid and tried to balance a flat head myself with a postal scale lol. It says shut me off right NOW! like mel says. Could it be possible your engine wasn't internaly balanced with an un weighted flex plate?

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 Post Posted: Mon May 15, 2006 4:36 pm 
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Well rightly or wrongly I have now got a brand new TCI internal balance flexplate which I hope to fit at the weekend.

I'll try it and see how it runs when I start it.

If it jumps across the workshop floor I'll change it back.


Personally I think that the guy I boight the car off fitted a new one after he had the trans rebuilt.. and when they asked him what engine it was he just told them it was a 454 ( the block is) it would make some sense of the front pump and dowels saga..

I'll let you know how it goes..

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 Post Posted: Mon May 22, 2006 12:07 pm 
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Well the new internally balanced flex plate was duely fettled (drilled holes out for convertor bolts, removed burr's (lots of them), ground away at motor plate to allow clearance for cam oil gallery plugs that protuded beyond the back of the block, drilled and pinned the dowels and fitted the trans.

Long story short and possibly several more posts and it started and ran fine and according to a couple of people its a lot smoother now....

Same as a lot of the stuff on this car is after I've looked at it and put right the mess ups...

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 Post Posted: Mon May 29, 2006 3:11 pm 
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Sam,
I may have missed it but did you verify that the harmonic balancer does not have a counter weight on it??
My old 468 was externally balanced and didn't require any heavy metal.

Doug


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 Post Posted: Mon May 29, 2006 3:37 pm 
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yep Doug,

the balancer had no counterweight on it, it checks out as an internally balanced damper.

I think I got it right when I said that he must have asked for a 545 flexplate and renewed it when he had the trans rebuilt. What he should have told them was that it had an internally balanced crank and damper on it.. that would answer the problems I had with the trans and block dowels...

nice to see you here doug..

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 Post Posted: Mon May 29, 2006 3:38 pm 
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Good point Doug! I never thought of that one! O:)

How bout it Sam?

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