With internal balance, weight is added to or removed from the end counterweights of the crank. With external balance, wieght is added to the flywheel (or flexplate) and the harmonic damper. So the weights are a little farther out with external balance.
I think almost everyone would agree that internal balance is better, but how much better? Is it really such a huge difference in terms of performance and longevity, or is it just easier because no one has to mess with making sure the flywheel and damper have the right weights and are installed in the correct orientation?

 

From what I was told, and it made perfect sense to me, when you are flinging weight around the slighets imbalance will become larger and larger the faster it spins, and the farther from the center of the crank this occours, the greater effect that leverage has on this imbalance, and therefore the more out of balance everything gets.

Correct me if Im wrong, but it makes sense to me..

 

My understanding is that once the crank is balanced it doesnt matter whether or not it was done internally or externally. Again alot of it is going to depend on how much you want to spend to have it balanced, if you internally balance it and your crank is way off its going to take alot of mallory to correct it and that stuff isnt cheap where as if you externally balance it it can be done by much simpler means... If your building a high dollar race motor chances are your going with a very good quality rotating assembly which already costs a pretty penny but comes with much tighter standards and usually wont be very far out of balance to begin with so it wont take much to internally balance it but if its a streety motor externally is easier cheaper accomplishes the same thing. I dont think one is better than the other cuz in the end they both balance the crank correctly it just comes down to what you may need to spend to do it.


-john

 

I was told that the external balancing isn't a good Idea for any engine spinning over 5500 because the balancing weight isn't evenly distributed like in a internal. so it causes more vibration and bearing wear than an internal. the counter weights being so far from center probably has something to do with it also.

check 1 .. 2 .. check.........we need an expert opinion here.

 

TTT..

Externally balanced motors that revv high, usually tend to see more front and rear main bearing wear from the motors that I have torn down.

 

That works! I always like internal for replacement purposes and for the fact that it bends the crank less.

Bret

 

Ideally you want the balance weight in the exact position instead of at the ends of the crank. An imbalance in the middle of the crank should be corrected in the middle, not at the ends. Compare this to your wheels.... you add balance weights to the front & rear of the wheel, (wherever it is needed) whereas you could put all the weights on the back & it is still theoretically balanced, just not as good as it could be. Containing any imbalance between the main bearings takes the loads of the ends of the crank as stated above.

Internal balance is not easier, it is harder as the location of weight is not as easy to place on the counterweights, requiring mallory (heavy metal) to achieve balance. This adds expense, but results in a better job.

 

I could be wrong, but my understanding is that even with internal balancing, balance weight is only added to (or removed from) the outermost counterweights. That's a bit closer to the center than external balancing, but far from ideal. It seems like it ought to be possible to add and remove weight from any counterweight... isn't there a machine capable of drilling the counterweights that aren't at the ends?

 

Correct me here but if it's out in the "center" you have to straighten the crank, It's bent. I'm not sure why a internal balance job is quote: " far from ideal". Quite a few superstock motor's get spun too the moon for RPM and everyone I've seen is internal balanced.

 

I feel that alot of the high dollar motors are already starting off with big money components and why not your putting large amounts of money into something that suppose to perform why not have the best you can buy. Since these components are already high quality they have tighter precision constraints and when they arrive to you are already pretty close to being 0 balanced so the amount of mallory you may need is minimal and therefore is cheap to balance correctly. but if you start with a crank like a scat or something equivalant its hit and miss, and more often than not its the latter. by the time your done putting mallory into a crank that cost 200 bucks and is so far off it will look like swiss cheese when you builder is done balancing it and you may have 3-4 times into the cheaper crank 0f just mallory.

so basically you get what you pay for...\


-john

 

Yeah.....

I've seen Scat Casts balanced internally (with mallory and a low bobweight) and externally (looking like swiss cheese).

The Scat Forged cranks I've done work out perfect. Even superlights with a relatively heavy 1800g bobweight.

Nothing beats a Oliver billet that's made to your bobweight, those are pretty cool too.

Bret

 

MMMmmmm oliver billet...

i havnt looked in awile but whats the going price for one of those bret?



-john

 

Over $2K

It's up there with a Bryant or HTC. Then again unless you have a lot of money on the line and a block stronger than the crank (and more revs than the average guy sees) you don't need them.

Bret

 

yeh thats a littlt out of my budget, lol... im gonna stick with my eagle stuff. he he


later,
-john