Why don't you throw some edel heads on that beast DF? I bet you could run on 93 octane then. Worst case would require a little octane boost or a bigger cam.

 

Is there any difference in balancing between the 390 and 410? I know the 390 is internally balanced, where the 410 is externally balanced, but what else?. Will I need a different harmonic balancer, fly wheel, etc?

 

The flywheel is the only difference, the 410 uses the same as the 428 and can be found used or do what I did and buy a new billet steel one from McLeod.

The McLeod one handles the 12" CF DF clutch too.

Always a good idea to have the engine balanced too.

 

I did some research on this matter.This is what i came up with390 410 and 428 all have a deck height of 10.17. Crank throw on a 410 and 428 is 1.99 where a 390 is 1.89. Rod length is 6.488 on 390 410 and428. compression height on a 410 and 428 is 1.687.Compression height on a 67 through 68 390 is 1.687.The way you determine deck clearance is add compression height to connecting rod length to crank throw and subtract from deck height.This will give deck clearance.Any way if you run a 390 piston with a compression height of 1.687 a 410 or 428 crank and rods top it off with a set of 428 cobra heads with a cam with about a .506 lift on exhaust and intake.Top it off with a aluminium intake and holley carb. You will have a bad *** motor that will eat a 429 for breakfast.Just make sure you use this formula with what everv piston you run to make sure you have deck clearance.I got this information out of a book called how to rebuild a big block ford by steve christ.It has all the information you will need.If you decide to run a cam with with a .506 lift and use 390 heads be sure and set valve spring height to 428 cobra jet specks or youll end up with coil spring bind up,Also adjustable rockers would be a good idea.Hope this helps Wes Tanner

 

Also you will have to have fly wheel off of 410 or 428 or you will have balance problems thanks Wes Tanner