Balancing a 401 Buick? Need help

I'm going to be swapping out the dynaflow on my '60 401 Buick for a stick. I'm running an almost new Schiefer flywheel and an Offy bellhousing.

Question: As long as I make sure the the flywheel is balanced, is there anything else I should take into consideration? (i.e. do I need to balance the crank as well since I'm going to a standard?) This was good running, low mile motor when it was pulled.

Also, I've also heard that putting in hardended valve seats in a nailhead is difficult due to clearance issues. What has been your experience?

Thanks

 

No idea on the balance, but hardened seats are not needed on nailheads due to the high nickel content of the cast iron.

 

OldSchoolSS is dead on about hardened valve seats. The nailhead blocks / heads are cast from very high nickel content iron and need no hardened seats. There is also a very good possibility of going into the water jacket if you try boring for hardened seats - DON'T DO IT !!!

Also, be aware that nailheads are an externally balanced engine and replacing the flywheel will change the engine balance. Balancing the flywheel by itself will not insure the engine is balanced.

 

Not only high nickel content but fairly low spring pressure as well....

as for the balancing, the best thing to do is to have the rotating assembly balanced as a unit. I've bolted a flywheel on and run it before with no ill affect that I could discern. Not that it's a good idea. But it has been done.

 

Check which engine the 'almost new' flywheel was off of. If it was a 364" and not a 401"-425" then it has a little more balancing weight added to it than you need. )Assuming it was balanced before)
I beleive the 364" runs about 4.75 ounce of balance in the flywheel, where your 401" should be closer to 4.25 ounce.

As far as having the entire rotating assembly rebalanced, sure that would be great but that means tearing down the motor to do so. I would just have the flywheel balanced to stock tolerances.
If you have a stock flexplate off your motor, have them matched. If not you can use the 4.25oz as a safe bet-just make sure it is in the right location on the flywheel (will be same relative location on 364 and 401-425).
The fine balancing on a Nailhead is done with the crank hub/balancer.

 

What I've done in the past (if you have a flywheel you know is balanced to the engine) is bolt the flywheels together with the weights 180 degrees apart and balance the assembly to zero removing from the new flywheel. Follow me? The hard part is getting it centered.
Jeff

 

I have put hard seats in and it's tight. The seats for the application are very thin. Nickle dosn't expand at the same rate as cast, and if it gets to hot the seat will fall out. The thin seat dosn't soak up or transfer heat as well as a thicker seat. If the seats are ok now I'd not put the hard seats in till you need them.

If it's going in a light car and you don't plan on lugging the engine it should work for a long time.

I just had to put hard seats in my '40 Chevy(see avitar) because the seats went away. The engine has about 30,000 miles on it, bone stock 350 (1970 441 heads) with 3.08 gears. The fuel is expensive, and shitty at the same time. Honestly I don't even think the octane is what it was 10 years ago.

 

Balancing the flywheel to match the flexplate from the motor is a good idea. Make sure it goes on the crank in the correct position as it will fit many ways. Good luck, Frank

 

When I built a 401 with an aluminum flywheel, the flywheel took a bunch of added weight to get the assembly into balance. It has to match the crank.
Bob

 

Thanks for the comments. I'm going to do this the right and get the engine balanced. The engine is out of the car now, so there is not better time......

 

Do not confuse a Nailhead and a 350, there is no reason to put hardened seats in a Nailhead, I haven't seen a set of heads for one yet that needed them. It's way to easy to fuck up and ruin the heads. The Nailhead has a high Nickle content, the SBC does not. The Nailhead also does not have the spring pressure of the SBC either.

 

Back in the old days.when we had a balance job come in to shop,we had to balance the rotating assembly as a unit..(Flywheel,crank,Harmonic)as they were a "Dependantly"balanced engine from the factory.Flywheel and front harmonic had weights to balance and match with the crank.The weights on the crank werent enough to balance without the matching flywheel and front Harmonic.