409 flex plate ????

[ketters55]

Do you have to use a special flex plate for the 409 truck motor? It was a manual trans in the truck and i'm converting it to a 700R4 trans for my 1934 ford. Will any early chevy flex plate work? and is there any special balanceing that has to be done to the flex plate?
Any info you have would be great.

Thanks
Ketters55

 

[threeimpalas]

Any 168-tooth flex plate for an internally balanced Chevy engine (basically, any except the 400 or 454) will work.

 

[models916]

Shims

Summit sells shims if it does not sit flat.

 

[Tman]

we also used flywheel shims on a 409 we just dropped in a 62, bought them locally.

 

[W Head]

Flex plate

Since I installed a Turbo 350 trans and new 168 tooth flex plate (internally balanced), in my 59 El Camino, I have a small vibration and the flex plate appears to have a wobble while engine is running. So, please explain the shims and how they are used. May fix my problem!!! :?

Thanks

W Head

59 El Camino 348, 3-2s
59 Impala 409, 3-4s

 

[gearhead409]

flex plate

the 409 crankshaft flywheel flange does not have a relief cut on the counter weight area. some flexplates will interfere in this area. i don't really like using a spacer as you will loose some of the locating area at the converter to crank fit although it will work. the better way would be to find a 168 tooth flexplate that will clear the counter weight.

 

[Tman]

That was our problem. I run the front end of a rodshop, we have a great parts house to deal with. I COULDNT find a flexplate that would clear!!!!!!

The customer had the engine already assembled which didnt help at all either. In a perfect world, I would machine the end of the crank before balancing the engine. Thats in a perfect world, our local 409 guru just grinds a smiddge off while the crank is in the engine and never has had issues.

 

[lgclover]

The flex plate you buy from Show Cars comes with a shim welded on. It is not a true 409 part.

 

[boxerdog]

It doesn't take much grinding on the crank flange to get it to sit flat. A neat little bevel is all it takes...except if it's all together and balanced. Then the shims start to look good, as long as you still leave converter clearance.

 

[petepedlar]

I used 2 of the .025 shims from Show-Cars when I put mine together and everything works well.

Dave

 

[Licensed to kill]

It doesn't take much grinding on the crank flange to get it to sit flat. A neat little bevel is all it takes...except if it's all together and balanced. Then the shims start to look good, as long as you still leave converter clearance.

I assume that "except if it's all together and balanced" means that you're concerned that if it's balanced and you grind the crank a bit, it will throw off the balance. If that's the concern, wouldn't adding a shim to one side also throw off the balance?.....or do you spot a shim of equal weight across from that one but on the converter side just as a counter weight? Will the small amount that would be ground away really affect the balance being located so close to the centre of rotation?.

 

[skipxt4]

That was my thought, also. Take it off, or put it on, what's the difference? Will it really, affect the balance?:

 

[petepedlar]

I don't see how this would change the bottom end balance ???

Dave

 

[Don Jacks]

IF it would make any difference,you'd never see any negitive effect,unless youre turning maybe 10-12,000 rpm

 

[boxerdog]

The shim, being round, has no effect on the balance. It just moves the flange counterweight away from the flexplate enough to avoid contact.

Grinding a bevel on the flange counterweight does have an effect on the balance, because it is not symmetrical. It is there to help balance the crank from the factory. Whether or not enough material is removed to be noticeable, I wouldn't say. I just know I wouldn't do it after I paid $$$ to balance a crank!

 

[Skip FIx]

So that an issue on the Eagle cranks?

I guess I'll have to go try mine tonight!

 

[boxerdog]

I think it is only an issue on factory 409 cranks because of the way they shaped the flange.

 

[Licensed to kill]

I don't see how this would change the bottom end balance ???

Dave

Thanks Dave. That clears things up for me. Based on the conversation, I was not envisioning a round shim but rather, a shim on one side to align the plate. It all makes sense now.

 

[petepedlar]

All the shims do is move the flexplate away from the flange and allows it to sit flat & seat properly.......... You need .050 or two of the Show Car shims.

Dave