406 vets needed

[bigkountry]

After selling my 434 rotating assembly to a racer friend of mine, I have decided to build a stout 406 instead of buying another kit.

I will be using a scat 9000 crank and they come in two flavors, external and internal balance.

What do you 406 vets run? Is it worth going through the balancing process to run a 350 plate and damper? Or will a reputible plate and damper with the 400 counterweights hold up?

Thoughts, ideas?

Thanks

[Captainfab]

I've not used any crank other than a stock one yet, but this is how I understand the useage of the two cranks. If you don't plan on turning much above 5000 rpms then an external balanced crank is OK to use. If you plan on turning above that, then you should consider the internally balanced crank.

[Alex Hayley]

I used an internally balanced crank (Scat 9000) in mine. I have not heard the "internal if above 5000 rpm", but I could not imagine building my 406 and not turning it higher than 5000 rpm.

[chris mc bride]

IMO if its true performance engine it should be balanced. Plus if you get it balanced using regular small block flywheel and balancer you can replace a bad one easier. I've never run a track bound engine that wasn't balanced. Also never heard the 5000 rpm rule of thumb. I've never had a engine that did see more than 5000 most anytime I drove it and never had problem.I never had a street engine balanced and spin them 7000 plus regulary.

[bigkountry]

The entire rotating assembly will be balanced, but the internal balanced scat 9000 does not require the big counterweight balancer and flexplate.

I wanted to know if anyone is using the external balance set up for bracket racing on occasion...this will be a street truck most of the time but I want it to perform at it's max. I want to build it right while I have it tore down.

Thanks for the replies so far.

[Marv D]

I ran a 383 (same stroke, slightly lighter piston) in my truck with a ductile iron crank and external balancing. Motor was street driven and raced considerably for 5+ years or so. Shifted at 6200 (because of a hydraulic roller cam or it would have been higher)

It beats up the bearings at higher rpm's more quickly than internal balancing does is what I've found. I have to agree, if it's a serious track toy then do it right the first time and build with forged crank, internally balanced, neutral damper and flexplate. But I've built a number of upper end street motors that were externally balanced and survived the occasional trip to the track just fine with even 6500rpm shifts. Nothing I would prefer to make a habit of, but it will survive. IMO

[bigsnookmaster]

Yeah, what Marv said!

[jrcaprai]

I had a 383 that was externally balanced and raced it for a few years with no Problems..
I now have a 408 that is Internally Balanced, and plan to do the same... racing that is

Prices are about the same ?????? so you might as well Internally Balance...

You still want to balance the assy, weather it is external or internal, you just do the balancing with the Neutral Balanced 350 Damper and Flex Plate, or with the External Bal 400 Type Damper and Flex plate...

[C20-67_N_MO]

You guys bring up a good point abou the internal vs. external balanced cranks, balancers and flexplates. And would have to agree that it seems like the internal crankshaft seems to be the way to go. Especially if you are turning 6500+ rpms more often than normal use.

Will be looking into a Scat 9000 model in a forged casting.

"Performance only cost what you can affoard!"