I have a 360 assembly that I will be getting balanced. Stock crank, scat I beam rods, SRP pistons. The motor will be a street/strip with mostly strip, but will not see about 6500. Is it worth the extra money to have the assembly made internal vs external balanced?

Last time I had this done it cost a little over 500 bucks. Probably not worth it. The other stock crank 360 apps I've messed with, just used the b&m plate, and external balancer with the neutral converter.

You have a serious machine. yes, & get a 318 (neutral) dampener. plus on the other end this will let you get/use a good aftermarket neutral converter & swap em later if ever needed.

Being a cast crank and the other things that
would need to be changed.. damper and conv and
the balancing cost... I dont think I would..
but if your buying a balancer and you can knock
the weight off of the conv it would be up to you..
on all my forged and billet cranks I always go internal
but I also turn way more rpm than you

Just to clarify the external still got sent out for balance job. Which was around 200 bucks.

SRP pistons (at least flat-tops)and Scat I-beam rods are lighter than stock. You may not need as much Mallory metal, if any, as you may think using a neutral damper/balancer and flexplate!

I dont think this combination of rods/pistons will require any mallory metal.

BTW, using King rod bearings will knock quite a few grams off.

i agree i built this combo years ago almost exactly the same and was easier to internal balance.........

Agreed, those Scat rods are about 100 grams each lighter than the 645s, and the pistons should be around 100 grams lighter as well.

Shouldn't be too hard to do a test run with the new bobweights and see if it needs some extra weight added. If it does, then you can go to the external stock balance, but there'll be a lot of metal drilled out of the crank and if that's the case I'd suggest cutting down the counterweight OD.

Or if it's just a slug I'd think seriously about internal balancing.

Choices..........
R.

It takes about 2 minutes longer to spin it without the external weights on it and determine if it can be internally balanced without heavy metal.

I wouldn't bother putting heavy metal into a cast crank. At that point, it's time to put that money towards a forged crank. S/F....Ken M