Mk IV internal balance flywheel question
 

Gents,
I just bought two PRW flywheels (semi light weight) that are spec'd for small or big block Mk IV internal balanced motors.

They look really, really good but my question is this; In comparison to a Gen VI counter-weighted balancer, the thickness from crank flange to clutch flange seems substantially thinner on the new PRW Mk IV int balanced wheels.
The ext balanced Gen VI flywheel is all I have to compare it to so does anyone happen to have an int balanced MK IV flywheel that they could lay on the clutch face and measure to the crank mounting surface. I'm coming up with just under .72 when measuring.

I don't really want to lose any spline engagement when mounting the coupler to new flywheel.

Thanks in advance,
Dave

Dave,
I dont have one here at home, but I remember a measurement closer to .900 if I am correct. I have one at the shop and if nobody gives you an answer this evening you are welcome to call me in the AM and I will measure the one I have there. 301-843-5700

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

If it is a concern, could you just make a spacer to fit between the flywheel and coupler?

I can tell you that gen IV and gen VI flywheels look almost idenical and will bolt up and work, but the balance is off, thicknesses are the same...Rob

Dave,
I measured a few flywheels this morning.

An early MK4 neutral balance one measures .965
An early external balance MK4 measures the same .965
My AERA flywheel manual shows .965

I happened to have a Gen6 454 flywheel here also, it measures about .770" It has been resurfaced once, so that figure might be off as much as .010, but it certainly would have never been .965.

It sounds to me like the ones you have are even thinner than the Gen6 one ??

Hope this helps, if you have any questions feel free to call. 301-843-5700

I have dismally slow internet at the shop so I am rarely online during the day :(

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Thanks for your time Bill!

I've opted to return them and just order a set of the standard 30lb Hayes. I think they will be better suited to my needs anyway.

Dave