The last flywheel I had drilled cost me well over a hundred bucks and took me 2 months to get it back from the machine shop. That is why I tried this balance plate. It was inexpensive, took only a few days to ship and it works.

Thanks for the clarification, Cuda. I'm not totally devoid of mechanical abilities but this was a bit baffling. Okay, I'll cancel that adaptor plate order which went in last night. Just as well have the flywheel drilled. I agree, no trig needed. Centering the flywheel for exact measurement of the radius and angle of the middle of three holes might be a challenge on the workbench but I imagine the machine shop will have laser guided equipment to set it up. Better than tearing down the engine.

Thanks both of you guys. As an amateur I couldn't translate the imbalance stats but I think I'll agree that if they mean the 360 is the most imbalanced of the applicable V-8s, then out of the box it probably will be what's needed for that engine. Why make it heavier than the heaviest requirement of the bunch? The plate must be made to work as is on something without modification.

I just got back from the machine shop. Very nice guy and, typical for his profession, enjoyed brainstorming this problem (machinists who don't like thinking outside the box usually don't last long in that business). He can handle the drilling project okay but the downside is if 360 doesn't work out, it would be difficult going back to a 318 because finding another one of those small 122 tooth flywheels to fit the bell housing might be dicey. So I'm not cancelling the adaptor plate order (forty bucks with shipping is no big deal even if it doesn't work out). He referred me to a Mopar high performance specialist in town before we dig into this further. He also showed me his balancing machine. Very nice and very new. Downside is to use it would require me completely tearing down the engine as he not only needs the crank but also a connecting rod which would mean pulling the head, which means pulling the marine manifold, probably new rings for at least one cylinder, etc., etc. I just as well rebuild the engine (though I'm sure it's almost like new). Problem there is the marine engines used different parts than same vehicle engines (e.g. 160 tooth flywheel in 360 is marine specific). For one thing, as I understand it the oil ports in bearings are larger. Might be tough finding the right parts to do a rebuild.

The arrow on top of 360 engine says rotation is to right as I'm looking at it from front. Is that the same as vehicle rotation? Starter is on the "driver's side" (right side as I look at the engine from the front). Okay, I looked on line ... starter is on same side as truck bell housing so must be same rotation.

Probably the best thing you did was talk to your machinist

Yes same rotation as std pass/truck rotation & good to be edumacated that no trig is needed

The machinist advised me to check with a local Mopar high performance expert and I made it down to his store today. Nice fella now wheelchair bound (I didn't ask). He said "There's about five different ways to skin that cat and they all work about as well." He's drilled the flywheels before and that works just fine. Also said it's no trouble going back to 318 with the same flywheel ... just counter-drill it the same on opposite side of flywheel to zero balance it again. Duh! He has used the counterbalance plates with GM products very effectively. Also he's welded weights to flex plates for automatics and that's worked well too (but not an option for me). Also he suggested I could take both flywheels in and the machine shop could counterbalance 318 to match 360 that way. He says no crankshaft or connecting rod needed. He added that Chrysler never was very fussy about being precise with balancing those 360 engines and they seemed to still work hard and hold up well. He felt the adaptor plate will probably work just fine given the flexibility of those engines. As long as I'm not running it six grand all the time it should do just fine. I am quite sure that boat has NEVER seen five grand and I've owned it since 1984. My late wife and I had our first date on it fishing salmon sixth of August 1987. Now you know why I'm keen on keeping it running.