Balance question

[Royce]

How much Mallory does it take to balance a stock 428 crank in a 390 block?  Is it cost effective to do so?

[jayb]

I assume you mean with a 390 flywheel, no counterweight like on the 428 flywheel?  It certainly can be done, but I don't know what the cost would be these days...

[Royce]

Yes  internally zero balanced...I had one done back in the 80s but I think the price of Mallory has gone up...Plus with different pistons and rods who knows how much adjustment would need to be made using the 428 flywheel

[mbrunson427]

Royce, depending on the pistons and rods you use, I'm thinking you may actually end up pulling weight out of the crank. I took a look at pictures of the 428 crank we balanced for the Mustang's 428 engine and it had one single small piece of mallory (maybe 1/4") in the front of the crank.

I'm not sure how most balance shops charge. I think they charge a normal balance rate + the cost of the pieces of mallory? I wouldn't expect it to be more than $300?

[mbrunson427]

By the way, we used a McLeod zero balance flywheel.

[475fetoploader]

Last month the crank I had balanced the mallory was (2) 7/8 slugs and (2) 1/2 slugs.  Scat crank with light pistons.  This quantity of mallory was $175.  The balance job itself not including parts was a flat $600.  This was the entire rotating assembly, including the clutch, which actually needed alot of work.  This was probably not the cheapest in town.

[Royce]

Thanks guys.  Just what I needed. Stock spec Eagle rods and Mahle forged piston.

[Jim Comet]

My RPM steel 3.98 crank, Molnar rods and Mahle piston rotating assembly required no mallory to internal balance. Jim

[mike7570]

I have a 3.99 stroke 391 steel crank for sale 2.20 journal FE specs. It was going to cost me too much to balance with factory weight piston rod assembly.
Shop told me it was a fairly easy balance job if I had light rods & pistons.  (it's in the classifieds)

[fekbmax]

What types of rotating assembly weight or Bob weight are you guys generally seeing with 6.700 steel rods and modern pistons?  Just curious of a general ball park.

[My427stang]

2230 on my last one, Ross piston, Eagle H beam, 1/16 ring pack.   Not the lightest setup by any means, Molnars and a custom light piston would drop it if someone wanted lighter

[winr1]

418 I am building has a factory 428 crank

The rods are 70 grams lighter than the factory 428 ones

.040 over 390 pistons, shaved tops are 77 grams lighter than a factory 4V 390 piston

Maybe I wont need mallory... or much

Have an auto flywheel, steel flywheel and a 13 pound aluminum fly wheel... all 0 balance

New harmonic balancer

Do yalls balancer guys mount the flywheels and balancer when balancing ??


Ricky.

[StarlinerRon]

Can you really cut .10" off piston tops and still be solid enough to run?

Ron.

[My427stang]

418 I am building has a factory 428 crank

The rods are 70 grams lighter than the factory 428 ones

.040 over 390 pistons, shaved tops are 77 grams lighter than a factory 4V 390 piston

Maybe I wont need mallory... or much

Have an auto flywheel, steel flywheel and a 13 pound aluminum fly wheel... all 0 balance

New harmonic balancer

Do yalls balancer guys mount the flywheels and balancer when balancing ??


Ricky.

I do crank with timing gear and 2 keys, then add balancer, then add flywheel.    I can't say I think the timing gear and the two (or 3) keys matter that close to centerline, but it gives me an excuse to fit everything at the same time

You can easily just do crank and trust the bolt ons later, if not spinning it really high,  I have only had one need work on the bolt ons, and those were original Ford flywheel and balancer

[Joe-JDC]

Can you really cut .10" off piston tops and still be solid enough to run?

Ron.

As long as you still have at least .180-200" left, then Yes you can cut the top of the piston safely.  I ran a TRW 427 piston cut down for a 3.98 crankshaft in my 452 FE for years without issue.  Joe-JDC