looking for an odd flywheel, late SBC with internal neutral balance
 

My 383 is built and running and I have a vibration. I had called Eagle when I first bought the balanced assembly. I checked before putting it together and somehow got the wrong story. I was told it uses normal small block balance components. Well that is not true.
I opened it up again yesterday and got the part numbers, the tech help at Eagle confirmed today that it is an internal balance design.
But I don't see any good buys on a flywheel that is neutral.
Most one piece rear seal cranks are combination balanced with a front damper and a weighted flywheel.
The LS flywheels are neutral, do they bolt up?
Do the holes in any of the other styles mate up to a Mercruiser coupler?

I sure hope I haven't gone too far into Frankenstein territory here!

Looking for flywheel help. Should I have a factory flywheel machined down to neutral? Or bite the bullet and spend?

You can have a shop mill off the weights on your current flywheel.

Yes, that was a conclusion I came to after posting. I'm glad you said it though. It's good to get some agreement from more experienced folks before doing something new.
Thanks.

There is a small area on the flywheel not much bigger in total are as 4 quarters and about as thick that needs to be milled off. I don't have a picture though, sorry.

The flywheel will still need balancing after machining. Think engine shop can just drill holes without milling the wheel either way.

I'll have to see if my machinist has balancing stuff. He's an industrial prototype & contract machinist as opposed to an auto & engine machinist. I'm getting it milled flat, but it does have a couple of balance holes.
My engine guy is near my old work.
If it's not smooth it's off to the balance shop.

my local machine shop does them forvme all the time..he charges me 50 bucks to zero balance them

Real cheap to have weight taken off, real expensive to have it put on. Also aren't 400's flywheel neutral (if needed)?

Yah, but 400's use the old 2 piece seal bolt circle and tooth count

It's reassembled and hooray, the shake is gone.
The machinist who balanced it must have done so with either a neutral wheel or nothing. So my summer is back on.
I have only run it on a stand and out of water on the trailer. I'll report back any oddities in use.

Hi, I just had to come back and tell you how happy this has made me.

This is the first engine I have built. I blue printed my clearances and used a balanced assembly.

It absolutely rips when asked to and it has good manners at the docks. The toughest thing is resisting pushing the stick ahead for a shot of acceleration.
Seems to be good on fuel too. We went around 25 miles. Though to be honest I didn't run it very hard, there was so much boat chop (July 4th) that I mostly just ran around on a lowish plane at around 2800 to 3000 rpm.
I like how it sounds above 3000 rpm. Really comes on song as it gets past that point. At 4500 it still had some throttle left, but I came up on someone and had to chill.
I went up 2" in pitch to a stainless 21" Michigan Wheel Apollo XHS that I had saved from my last boat. It feels good back there. I'll have to run it to wide open and see how it matches up.
I put some Amsoil Severe Gear 75w110 in the Alpha, but I'll still roll off easy to keep my drive together.

The previous engine is a 350 mag. It would just barely turn a 19" prop to 4550 shoving that 21 degree deadrise 4000 lb lump. Time to plane was not that quick. But it has tbi truck heads, so I guess I should not be surprised, with their reputation for running out of breath early.
Previous owner said he bought the heads the year before. He said he needed them but didn't explain why. The heads have new exhaust with them. I bet the exhaust rotted and killed the previous heads. Too bad he didn't go vortec.
I'm torn between selling the 350 and keeping it in case I ever ditch the Formula and want to keep the 383.