i know that the 335 series engine is externally balanced. i have also heard it is possible to balance these engines internally, like the 429/460. are there advantages over internal vs. external balancing? what exactly must be done to a 400 for it to be considered internally balanced?

 

How interesting, I just finished researching that question and found a few threads with good info. The jest was that it would cost a bunch of money as they would have to add metal to the crank to balance it. It didn't seem like a real good idea cost wise since the benefit is questionable. If I were rich...... I'm wondering the advantages of different types of dampers as well.

 

Hopefully I do not over complicate this question, but maybe if I explain how balancing is done may help.

First step in balancing is to match and obtain a weight on the following items: Rod bearing, ring set, small end of rod, large end of rod, piston, piston pin. We make all the weights with =in +/- 1/2 gram. Then there is a formula where you plug in the numbers and since I am at home I can't tell you exactly. For the purpose of this thread, it does not matter. Once the numbers have been "figured" we then have a bob weight. This is the amount of weight that will simulate the rotating and recipicating weight on the crankshaft. This weight is placed on the crankshaft so it can then be "spun" similar to a tire balancer.

Because of the original crankshaft design, the counter weights are only so heavy. If the weight of the "bob weight" is heavier, then it is added to the outer area's like the flywheel and balancer. By using the material "heavy metal" which is a large percentage of tungsten, you can drill metal out of the crankshaft, and install heavy metal which is about twice as heavy.

Then when you add the extra weight to the crankshaft, the balancer and flywheel can have no weight.

Again sorry if this is complicated.

 

So..Tim..do you see any advantage to balancing a 400 in such a way to do away with external counterweights? I take it that would be by balancing the crank completely as you described. What would you charge for that (assuming it's not a bad idea). Then we would need a non weighted blance/damper and flywheel?

I hope this is in line with your questioning Sparky. I'm curious as well.

 

i was wondering the same thing. i have been reading Tom Monroe's book "How To Rebuild Ford V8 Engines" (351c, 351m, 400 and 429/460). it states that the flywheel from a 335 series is interchangable with a 385 series, but that if they are interchanged the engine will no longer be in balance. if the 400 is internally balanced (like a 460), would you then have to use the 460 flywheel (and harmonic balancer??) to maintain balance of the rotating assembly? also is your 434 stroker internally or externally balanced?

 

To internally balance a engine that was external is not cheap, and to be honest not worth it for a street application. Usually a higher RPM application is needed.

Heavy metal cost about $45 for a 1"x1" piece. Very possible they would require 4-6 pieces. Then you have the extra machine work to install. Usually a job cost about $400-$600.

The aftermarket is doing a good job of engineering cranks with the extra metal in the counter weights. Then it is an easy balance job.

Our stroker crank is internally balanced, the balancer and flexplate is easy to get for internal assemblies.

Obviously we would do it, but I would invest your $$ in other areas.

 

Just as an FYI the 429/460 engines were internally balanced until 1979 when Ford decided that external balancing was a Better Idea. Externally balancing the engines allowed them to lengthen the cylinder walls but I don't know if that's why they decided to do it.

If you scrounge up a flywheel & balancer from a 79 or newer 460 it will be externally balanced.

 

actually Bill the balancer won't be externally balanced on a 79 or later 460, they still used a nuetral balanced balancer but used a hatchet weighted spacer behind it.

 

Cool. Thanks for the info.

 

A friend if mine just had his motor he's doing internally balanced and it cost him 500 buck's.TMI is right it's really expensive.

 

actually my preference on balancing external balanced engines it to go ahead and leave the external balanced flywheel/flexplate, and balancer ont he engine but have the actual balancing done internally IE if you hve to add weight have it done with mallory that way if you have a balancer or flywheel go to pieces you don't have to have the entire thing rebalanced again.

 

wouldn't leaving the weighted counterpieces on an internally balance motor screw up the balance by having the xtra weights that aren't needed.

I learned a lot on this post- thanks. I was wondering if the TMI stroker motor had a balanced crank.

 

If you take your engine to a machine shop and have them balance it they will take the entire rotating assembly, balancer, crank, flexplate/flywheel and balance it as a unit. They will add/subtract weight from the crank as necessary.

 

Usually when ever you add or subtract weight, it is all done on the crankshaft for the reason monsterbaby said. If you are going to internally balance an assembly, then you get a new "neutral" balance balancer and flywheel. It's not considered internally balanced if there is any weight hanging out on the ends.

In some race applications the rear is internally balanced and the front is external, but personnely I think this is dumb.

The our stroker kit is internally balanced, that is because the crankshaft was manufactured with alot of metal on the counter weights, and our pistons are very light.

 

would the 460 flywheel and harmonic balancer be considered "neutral" since it is an internally balanced engine? if so, is it really considered a harmonic balancer if it doesn't change the balance?? or is it just there to add mass and stability to the rotating assembly(neutral balance)? thanks for all the info.