Oh crap..... Internally balanced engine with an external balance flex plate?!

[nm9stheham]

I already told you that it was an external flex plate so it has the chunk out and a internal balancer up front. Like I also said, the engine was balanced in 2010, and recently assembled last year. I doubt they would remember.

Ok, I just was double checkin' 'cuz some folks don't know what an external balance plate looks like.....but that obviously does not include you. And you are probably right....2010 would be along time ago. Too bad it is too hard to look at the crank and see if weight was added/removed significantly differently on one set of crank counterweights... then you could know for sure what they did. Edit: Is the engine is out? Any interest in pulling the pan and looking at the counterweights? Some small variations in weights will be normal; any large variation in weights front-to-rear would depend on a few factors like.
- Is the 'bite' out of the flexplate small or large? (Compare the 340 and 360 external balance plates on the B&M site...)
- Was the stoker crank designed for internal or external balance?

I know I would want to be diggign into this so I would know for sure for future work.. but that may be just me.

 

[SRT_DSTRHOLC]

Engine is out. I'll run the part number, I believe the scat cranks were meant to be internal balance for the 4.00 360 cranks

 

[70aarcuda]

my scat forged crank 4 stroke has a couple slugs of mallory metal in it...depends on the the weight of the rods and pistons...this one has scat 4340 I beams and KB pistons.

 

[Rapid Robert]

Well, you did not have it internally balanced if it was an external balance damper up front; the weight changes were necessarily inside but the front half of the engine would still be considered external balance. (The whole term of 'external balance' is a bit misleading anyway; it is just a setup where part of the counterweight is external.)

Oh OK I see your point as he did "balance" it with the external dampener & I assumed that that was (now) an internal balance. to the OP yes it can be balanced with mixing and matching the parts in question & since your shop balanced it it will still be balanced if as you know the same dampener/tc/flexplate is used like he balanced it for. Holler how it turns out

 

[nm9stheham]

my scat forged crank 4 stroke has a couple slugs of mallory metal in it...depends on the the weight of the rods and pistons...this one has scat 4340 I beams and KB pistons.

And the damper and flexplate weighting plays into it. Just curious.... Do you have neutral or external balance parts front and rear? Did it come from SCAT with the Mallory? Their complete 360 kits are listed as internally balanced, but you can get the cranks unbalanced and do it 'in the field'.

 

[moper]

If the engine was balanced INCLUDING the balancer and any flexplate - it is not "internal balance". That's because chances are there was some weight that was in one of those parts that the balance job used to help compensate the internal mass. If that amount was small enough - no big deal to swap parts - like if an internal flexplate was used. But - if the flexplate you gave them was not nuetral, it is not internal balanced.
that all being the caes - if the car vibrated at anything beyond idle then you have a mismatch. BTW - 1400 is NOT and idle - you're already off the carb's idle circuits. Size has nothing to so with shake.