Got back from my regular visit to the Slowest Machinist/Engine Builder in the world today. Seems that my rotating assembly is finally back from the balancing shop. But, like always, there was some strangeness.

I was told that, because of my preference for 6-inch rods in this new 406, that it wasn't able to be properly balanced using a "correct" 400-style offset-weighted flexplate. What we're going to have to do is use the "correct" 400-style offset-weighted damper on the front and an uncounterweighted, 350-style flexplate.

The rotating assembly, if it matters, consists of a 3.75" Eagle forged crank; Eagle ESP 6" rods, and forged SRP flat top pistons (P/N 138100.)

Am I worrying about nothing? :confused:


[Modified by Jack Sweet, 11:48 AM 10/20/2001]


[Modified by Jack Sweet, 2:06 PM 10/20/2001]

 

Was your crank designed to be internally balanced? I purchased a Scat 3.75 crank designed for use with 6" rods and it has extra material in the counterweights so it can be internally balanced.

I'm surprised they couldn't use Mallory heavy metal for a internal balance.

 

Jack, I think that something is amiss. Where you bought the crank rods and pistons didn't they offer to ship it pre balanced so all you have to do is slap it together? I am very pro internal balancing. Less mass to get spinning. I used the small SFI fluid damper in front and a SFI 168 tooth flex plate with a mini starter.

I posted a motor pic in C-3 of how i drilled the PVC in the rear passenger side of the Dart cast aluminum valve covers and a breather in the drivers side front cover.

 

Yep, I just checked out a site that sells Eagle Cranks. My part number--440037505700--was designed for 5.7" rods. (That's what the "5700" part of the number means.) And it is designed to be internally balanced.

I ought to be OK using 6" rods with this crank because the pistons match. (I did THAT math myself instead of relying on the "expert."

I had a chat with the guy actually doing the balancing and the mix-and-match 400-style balancer with a 350-style flexplate is the result of using the 6" rods on a crank internally balanced for 5.7" rods. Greater rotating mass, yadda, yadda. This kind of setup is--very surprisingly--going to be OK.


[Modified by Jack Sweet, 1:15 PM 10/21/2001]

 

I don't think so Jack. I disagree with your machinist.

If you have an internally balanced crank, you should have a neutrally balanced flexplate and harmonic balancer. Mix and match is bullcrap. That's not right at all. It shouldn't throw it off going from a 5.7 inch rod to a 6 inch rod. The only thing to check is the need for a small base-circle cam and clearancing. Mallory metal will more than adequately fine tune your balance.

And if it's an externally balanced 400 crank (as most are, unless custom ordered), then you MUST use the weighted 400 balancer AND the weighted 400 flexplate.

Your slow-as-snails machinist is highly suspect. Do yourself a favor and go get a second opinion at another engine builder or machine shop.
I would promptly pay him what you owe him and take everything back.

 

I think slow is the norm for the industry. I have yet to hear of one that could do engine work on a normal schedule without something going wrong. My engine has been at one for about 2 1/2 months, but seems like 4. All they are doing is a bore and hone, sleeving 2 cylinders and assembling a set of heads.