360 internal or external balance?

-
6

66dartman

Well-Known Member
Joined
Apr 25, 2005
Messages
1,164
Reaction score
11
Location
Littleton, CO
I know when the engine is internally balanced it makes it easier to change converters, etc, however, are there any other advantages to internal versus external balancing? I have called a couple of balancers in Chevyland where I live and they have told me it is cost prohibitive to internal balance a 360 cast crank and that I should keep it external balance. If I have it externally balanced, will they have to have the torque converter to balance the assembly? I have a sfi balancer from Mancini that is for external balance and a B&M flexplate for a 904. Anyone's experience on this would help, it seems the machine shops around here only work on small black chevies.
 
I don't know about it being "cost prohibitive". But it will definitely be more.
But yes, if the assembly is to remain externally balanced, they will need the balancer and a counterweighted flexplate for a 360.

This way you can either use a neutral converter with the B&M plate or use a neutral balanced flexplate with a 360 weighted converter.

I would guess that if the flexplate is neutral, they will need the converter too.
I've just never asked about or seen a crank with a converter on it on a balance machine!

You didn't say if you have an original style 360 or a Magnum 360. For reference, the external balance weights, front and back, are different.
 
The 360 comes as a cast crank externally balanced from 71-92.Can the exernally balanced crank be internally balanced,YES,but it comes down to being cost effective and replacing the dammpener and the flex plate and the mallory metal,big bucks.If you have the B&M offset balanced flex plate for the 360,you do not need the convertor and can remove the weights on the convertor.This allows you to run any convertor.You should be looking for a nother shop that does more than just GM,s,as they are not thinking much out of the box of how to balance motors as GM has cast and forged cranks.With the SFI dampener and the B&M flex plate you have the right parts to balance the motor and do not need the convertor.The flex plate with its cut out section is compensating for the convertor to run a regular convertor and your dampener is a SFI approved and is perfect as long as its a 360 unit.Mrmopartech
 
Thank you guys. It is frustrating to get work done in my area since the attitude I run into is if it's not a chevy than good luck. It has been this way with just about everything on the car. I may even send the parts to Hughes Engine to get the balancing done and eat the freight.
 
You might want to check around in Colorado. I believe there use to be a guy named Dennis Maurer, or perhaps somebody else that raced and may have had a Mopar machine shop. There is also an ex NHRA tech guy named Barry Conner who raced Stock with a Challenger and now has a stroker in it. If you can find him, he might be able to give some advice on nearby Mopar machine shops. But I don't think barry is a member of this forum.
 
just for conversation- Locomotion- you can balance the crank with the balncer on it- Its a royal pain in the butt but I've done a few- its actually the only way to balance an external crank without weights on the flexplate (mopars).- By the way why the he!! did Mopar do that to us in the first place (ring gear on converter too)- was it a joke on Chevy guys that tried to work on mopars or what?! :drinkers:
 
mrspeeddemon,

I think you made the same mistake I did before edititing it - Saying "balancer" instead of converter? I figured it was possible, just never looked into it.

As for the external balance thing, I think I read somewhere that cast iron is lighter than steel. So the extra weight had to be added! But that might take some research to confirm with crank and piston weights over the years.
 
your right I did mean converter- I guess thats what happen when you stay up too late. thanks for catching it! :drinkers:
 
As far as advantages, there are a couple. The biggest is that the weight used to "balance" the reciprocating weight is contained within the main caps. This means less stress, and less flex in any crankshaft. Dont believe it, look at any Honda 4cyl crank..each throw has a counterweight. The longer the crank, the worse the effect. the softer the material (ie cast cranks) the worse the effect. it can lead to bearing wear, and cracks in the cranks. That being said, the factory used it, as did everyone else, for many years with success. It comes down to how good do you want your assembly to be. I want much better than factory, because the factory work is meant for low rpm, and average life, while being the most cost effective for the maker. I internally balance all the engines I do. The last "heavy" rotating assembly cost me $80 more for mallory over a std competition balance job. Competition in this case means less than 1gram out. Most factory stuff is +/- 25grams or more, and many other balanced assemblies I've worked with were over 10grams after being "balanced". It doesnt seem like much, until you take the effect of rpm into it. stress increases as a square of the rpm. so 25g at 100 rpm isnt bad..25g at 6500 is very bad, and you prob wont feel it, but it's really stressing the crank.
 
Thanks moper, great info. I agree about the stress on an external engine being further outside the caps. I will try to find another balance shop around here that will work with me or as I said I will send the stuff to someone who cares to work on mopars.
 
Locomotion said:
You might want to check around in Colorado. I believe there use to be a guy named Dennis Maurer, or perhaps somebody else that raced and may have had a Mopar machine shop. There is also an ex NHRA tech guy named Barry Conner who raced Stock with a Challenger and now has a stroker in it. If you can find him, he might be able to give some advice on nearby Mopar machine shops. But I don't think barry is a member of this forum.
Click to expand...
Dennis Maurer is now in Tempe, Az. Maurers Auto and Machine. Specilizes in the small block Mopar, and can sure make them run!
 
My Sons 360 that runs 6.54 (10.20-10.30’s) is externally balanced. We went with an aftermarket externally (balanced) balancer and an externally balanced flex plate so we could use every convertor we have. Cheaper, easier.
 
pittsburghracer said:
My Sons 360 that runs 6.54 (10.20-10.30’s) is externally balanced. We went with an aftermarket externally (balanced) balancer and an externally balanced flex plate so we could use every convertor we have. Cheaper, easier.
Click to expand...
So are ALL factory 360s cast crank and externally balanced? Ive always been a big block guy, so just learning about the 340/ 360 motors.
 
Garys72Duster said:
So are ALL factory 360s cast crank and externally balanced? Ive always been a big block guy, so just learning about the 340/ 360 motors.
Click to expand...

I won’t go out on a limb with that question because mother Mopar has done some pretty strange things especially in the early 1970’s. Every cast 360 crank that I have or have ever seen are externally balanced
 
Part of what you’re going to pay to have a stock 360 crank internally balanced with heavy metal will depend on the economy and cost of doing business in the area the shop is located in.
Also, the 360 is the most out of balance of any of the externally balanced Mopar engines, so it will require the most heavy metal to do the job.

Around here, it would definitely be what I considered not cost effective to do to a stock 360 crank.

If you were going to turn enough rpm where it was really a concern, you should probably be looking at an aftermarket steel crank.
 
PRH said:
Part of what you’re going to pay to have a stock 360 crank internally balanced with heavy metal will depend on the economy and cost of doing business in the area the shop is located in.
Also, the 360 is the most out of balance of any of the externally balanced Mopar engines, so it will require the most heavy metal to do the job.

Around here, it would definitely be what I considered not cost effective to do to a stock 360 crank.

If you were going to turn enough rpm where it was really a concern, you should probably be looking at an aftermarket steel crank.
Click to expand...


Exactly. A 50.00 cast crank is only worth X amount. Although they are a great crank why waste good money when not needed. I think my Son shifts his at 6700-6800 rpm
 
When i had my 360 built over 12yrs ago i had it internally balanced because i was planning on swapping in a 4 -speed but never happened, that thing still runs very smooth and revs pretty fast totally worth it not having that big stupid looking counter weight on the front of the engine too.
Oh and it does have a 4-speed behind it now but in my dads valiant.
 
pittsburghracer said:
I look at it this way. Some guys weren’t even driving or racing 13 years ago so it’s new news to some that may need it. Who knows it may save someone a few bucks. Lol
Click to expand...

I was originally going to say that I had the 360 I built in 2005 internally balanced, 2 slugs of metal ( if foggy memory serve's me right ) and and the job cost me $275.00 (that much I remember ), bob weight was/is 1837 grams ( found the job ticket ). I know that this was 14 years ago, prices change, how ever I still beleave that it makes sense to balance internally, makes things like flywheels easy, converters become easy; yes I know about B&M flex plate, got one hanging on the wall collecting dust; I beleave it is better to keep weight as close to the center line of the crank, less inertial forces; is it a huge difference.........probably not.........just my opinion
 
You must log in or register to reply here.
-

Back
Top