Crank balancing

[jphii]

Anyone know who would be my best bet to get an OMC crank balanced?

[Freddie Webb]

Hope you do better than balancing my phone does with service here!

[Forkin' Crazy]

Bruce Leonard Marine would be your best bet! :thumbsup:

[Lockjaw]

bruce leonard marine would be your best bet! :thumbsup:

lol!!!

[Lockjaw]

I'd check with Paul Nichols, they might have a recommendation if they can't do it.

[RichS]

Check with Racer.

[Chaz]

You have one of the best engine guys in the country just west of you in Graham NC . Brett Nesbit performance engines ... he's a car guy .. but bobweight is bobweight and they have the latest Hines balancer.

[Instigator]

When I was still in Columbus I called a national level shop in town and asked them. The guy on the phone was very sharp but wanted to know "internally or externally" balanced. Told him I wasn't sure but guessed externally meaning the flywheel was what balanced it. He told me he wouldn't tell me anything w/o seeing it and I never got around to going to see him.

[Chaz]

Instigator ,
When Chevrolet made the 350 into a 400 as well as the 396-427 into a 454 they took the easy way out and added a bit of counterweight to both the harmonic dampner and the flywheel. It makes a mess to start swapping parts without knowing what you have. Sounds like the machinist you spoke with was unfamiliar with your OMC , yet a sharp cookie for making sure you were going to bring all the pieces to the puzzle with you ... :thumbsup:

Charlie ...

PS .. the Mrs. and I took the blue Superboat up to that pirate joint ;) you hang out at a few weeks ago for lunch .. I was lookin for ya .. kinda thought I would buy ya a drink for all them good stories you told us about the "romp" last time I was there .. :D

[Instigator]

Instigator ,
When Chevrolet made the 350 into a 400 as well as the 396-427 into a 454 they took the easy way out and added a bit of counterweight to both the harmonic dampner and the flywheel. It makes a mess to start swapping parts without knowing what you have. Sounds like the machinist you spoke with was unfamiliar with your OMC , yet a sharp cookie for making sure you were going to bring all the pieces to the puzzle with you ... :thumbsup:

Charlie ...

PS .. the Mrs. and I took the blue Superboat up to that pirate joint ;) you hang out at a few weeks ago for lunch .. I was lookin for ya .. kinda thought I would buy ya a drink for all them good stories you told us about the "romp" last time I was there .. :D
I remember the car motors that were balanced like that and it made sense to me when he told me that. This was a huge shop that did work nation wide and was very good but I never did get him a crank.

As far as the tiki bars....., we should have the Sonic out this weekend. And you can buy ;)

[jphii]

Thanks guys. I have a shop here in town that I but a lot of parts from and I found out yesterday that he balances cranks. He started asking the same questions Gary's guy did, but luckily I had the crank with me. His minimum spec is balancing to within 1/4% on a pretty nice CWT machine.

[Instigator]

Thanks guys. I have a shop here in town that I but a lot of parts from and I found out yesterday that he balances cranks. He started asking the same questions Gary's guy did, but luckily I had the crank with me. His minimum spec is balancing to within 1/4% on a pretty nice CWT machine.
Are you going to have him do one Joe?? Be interested to hear/see what he says/does. Heard they aren't close from the factory but don't know that statement to be accurate.

[Forkin' Crazy]

Heard they aren't close from the factory but don't know that statement to be accurate.

That depends on what rods you use, doesn't it?

[Instigator]

That depends on what rods you use, doesn't it?
Good point considering they used the same cranks w/the little and big rod's even though there's a 100 grams difference. PER ROD!

[jphii]

Yea Gary, I'm having one done. I have a brand new lightened crank that weighs about 34 pounds. And that is without anything taken off the counterweights. I think he can get another pound or 2 out of it. Should be interesting....

What I hear is they are within about 5% from the factory. It's considered internally balanced from what I got out of the conversation with him. The external vs internal means does it have a harmonic balancer. The flywheel has nothing to do with the balance (had one with me, that's what he said). The flywheel is already lightened & balanced (3 1/2# if I use the MSD). Then you have to consider under vs over balancing if you are going to use different rod/piston assembly weights.

[Instigator]

Yea Gary, I'm having one done. I have a brand new lightened crank that weighs about 34 pounds. And that is without anything taken off the counterweights. I think he can get another pound or 2 out of it. Should be interesting....

What I hear is they are within about 5% from the factory. It's considered internally balanced from what I got out of the conversation with him. The external vs internal means does it have a harmonic balancer. The flywheel has nothing to do with the balance (had one with me, that's what he said). The flywheel is already lightened & balanced (3 1/2# if I use the MSD). Then you have to consider under vs over balancing if you are going to use different rod/piston assembly weights.
Remember too that the 8's do have a balancer.

[jphii]

One thing I'm glad we don't have to deal with!

[Markus]

Joe,

Are you going to have it lightened or balanced?

The only type of engine where you balance the crank is a cross-plane V8...

[Chaz]

As far as the tiki bars....., we should have the Sonic out this weekend. And you can buy ;)

The Mrs. and I are in Savanna Ga. this weekend ... but I looking forward to being back out in the water next weekend on the Keys run .... hope to see you there ... :thumbsup:


Are you going to have it lightened or balanced?

The only type of engine where you balance the crank is a cross-plane V8...

A little while back I needlessly went round and round with a guy on here on a balancing thread who never mentioned the word balancing without also adding the word lightning at the same time. While it would be foolish to lighten a crank and not follow up with a good balance job, the two processes are not tied together. He mentioned he had breakage problems with cranks that had been lightned, and I have no doubt that someone had either gotten greedy with how much weight they removed or failed to leave a proper radius or surface finish on the area's that were machined as being the reason for breakage.
I can only think of a handfull of guys I would trust when it comes to shedding weight off of a crank, so thats not really a job for just anyone.
Crank balancing on the other hand is a process that any engine can benefit from , except for maybe a flat opposed pancake such as a VW, Porsche or Subaru which are self canceling in their primary harmonics. Everything else has a bit of tolerance stacking and a target RPM range where they are designed to run at. Most shops today shoot for a 48-52 % over balance . And while your at it spinning up the flywheel , propeller and to a lesser extent, the drive and prop shafts will show you some imperfection's in manufacturing. It all depends on how much time and effort you want to spend on the little gains .

[perfmarine1]

There is no power gain from balancing a crank. Only insurance of better longevity.If anybody balances your outboard crank without knowing the combine weight of the ,piston,wristpin,wristpin brg,wristpin clips,rod,and rod bolts,for each cyl and flywheel you are getting ripped off. they must know the reciprocating weight of each assemly,hopely the same,to add to the bob weight before spinning. I would contact Monty Racing,they did the last one for me,or racer he would know where to go if not in shop.

[Markus]

Crank balancing on the other hand is a process that any engine can benefit from , except for maybe a flat opposed pancake such as a VW, Porsche or Subaru which are self canceling in their primary harmonics. Everything else has a bit of tolerance stacking and a target RPM range where they are designed to run at.

Chaz, engines other than cross plane V8s are not balanced with crank counter weights. They are either inherently balanced, like I6 and V12 engines (in addition to the boxer engines you mentioned), or are balanced with balancing shafts, which you will find on I4 and I5 engines.

[jphii]

Chaz, engines other than cross plane V8s are not balanced with crank counter weights. They are either inherently balanced, like I6 and V12 engines (in addition to the boxer engines you mentioned), or are balanced with balancing shafts, which you will find on I4 and I5 engines.

No....

[Chaz]

There is no power gain from balancing a crank. Only insurance of better longevity.If anybody balances your outboard crank without knowing the combine weight of the ,piston,wristpin,wristpin brg,wristpin clips,rod,and rod bolts,for each cyl and flywheel you are getting ripped off. they must know the reciprocating weight of each assemly,hopely the same,to add to the bob weight before spinning.

There's an ol NASCAR crew chief who got into building "stocker" 5 hp Briggs motors for go carts. He once said .. they wont let me do anything to build power , so I do everything I can to not lose any ... ;)

Your correct about what it takes to balance a crank .. cept for the weight on the big end of the rod is considered "rotating" and is deducted from the equation.


Chaz, engines other than cross plane V8s are not balanced with crank counter weights. They are either inherently balanced, like I6 and V12 engines (in addition to the boxer engines you mentioned), or are balanced with balancing shafts, which you will find on I4 and I5 engines.

As you can see , even a crank with near perfect 120* crank pins like this 3.0L Mercury has a counter weight at each end to deal with"rocking coupling" harmonics. The longer the crank becomes from one end to the other .. the worse this problem becomes.
as far as balance shafts go .. think about them like this . The guy who designed the motor to be as compact as possible .. threw out the fact that it was going to need to cancel out the effects of piston inertia on the bottom end .. so he later went back and linked another out of balance shaft to the first one in a out of the way place to cancel out the problem he created ... :eek: And Ohhh what a mess when those link plate chains let go ... :cool:

[Instigator]

they wont let me do anything to build power , so I do everything I can to not lose any ... ;)
Great quote. Sounds like one of my hero's,.... Smokey Yunick ;)