[Big Willyz]

Hey guys. Just wanted to run this by the gurus here in Camaro land. I have an internally balanced 406. The machine shop that balanced the internals lost the balance sheet they were supposed to give me upon pickup of parts (yeah, I know). The balanced kit included a flexplate. To make a long story short- I am now going with a M-21 4 speed vs the slushbox I was gonna use. Since I need a flywheel for a manual, and I have an internally balanced engine- the standard 350 manual flywheel for an internally balanced engine would be fine, right? Just spent a lot of time and money on this build, and dont want to screw it up. Thanks for the reassuring words ahead of time!

[john68]

Sorry, if you don't know, its your call, how well do you trust them, your call??

[CNC BLOCKS N/E]

Originally Posted by Big Willyz

Hey guys. Just wanted to run this by the gurus here in Camaro land. I have an internally balanced 406. The machine shop that balanced the internals lost the balance sheet they were supposed to give me upon pickup of parts (yeah, I know). The balanced kit included a flexplate. To make a long story short- I am now going with a M-21 4 speed vs the slushbox I was gonna use. Since I need a flywheel for a manual, and I have an internally balanced engine- the standard 350 manual flywheel for an internally balanced engine would be fine, right? Just spent a lot of time and money on this build, and dont want to screw it up. Thanks for the reassuring words ahead of time!

If its interanlly balanced you should be fine and look at your flex plate if thats has no big weight on it you know its neutral.

[Big Willyz]

John- The shop in question is really good- The older gentleman that does the balancing work is getting up there though. He was sincere enough and rather embarassed when he couldnt find it.

I will take a look at the flexplate Carl. Hopefully its neutral. If not, I guess I can just get a stock balancer and flywheel for externally balanced SBC. Whats your take on that?

[Nashville Beth]

Originally Posted by Big Willyz

John- The shop in question is really good- The older gentleman that does the balancing work is getting up there though. He was sincere enough and rather embarassed when he couldnt find it.

I will take a look at the flexplate Carl. Hopefully its neutral. If not, I guess I can just get a stock balancer and flywheel for externally balanced SBC. Whats your take on that?

If there is ANY doubt that it is internally balanced, I would be back there talking to that nice man.

Your engine will be wrecked if you use the wrong flywheel and balancer.

If they aren't sure, make them do it again.

[srode]

You can tell very quickly looking at the flex plate and harmonic balance wheel if it's internal or externally balanced - theres a big weight on the flex plate and a big notch in the harmonic balancer if it's externally balanced. If it's internally balanced you are good to go with a standard flywheel. If its externally balanced then get an externally balanced flywheel for a 400 and you should be good to go.

[bcm66]

Tell the guy that did the machine work your problem.

He should be able to tell you what flywheel to use. That way if it flies apart, you have someone to go back and talk to.

[keithl1967]

If you are going manual, make sure that 400 block is tapped for the Z-bar stud...many of them were not...

[Nashville Beth]

The problem is it's a 400 externally balanced from the factory and the shop told him it's internally balanced- and now they aren't sure if it really was internally balanced.

There should be heavy metal in the crank throws if it's internally balanced. (correct?)
Looking at the flywheel and balancer won't tell you how it's balanced.

[77wolf10.85]

listen to Carl
look at what you have first, then go from there.

Bethanne, heavy metal is not the norm. If he has heavy metal, he'd know it from a light wallet.
Yes looking at the flexplate and balancer will tell him what he has.

[BillK]

Willy,
Anyone that does balancing should be able to take your automatic flywheel (flexplate), spin it on the balancing machine, record the out of balance if there is any, then take your manual trans flywheel and match it to the flexplate. With a modern digital balancer like my Stewart Warner Pro Bal, it is about a 15 minute job. Probably takes longer to set the machine up than anything.

This way you will be certain that the manual flywheel is balanced or unbalanced identically to the automatic flywheel and you will not have any issues.

[Big Willyz]

Thanks for all the info. I didnt even think to look to see if the block was tapped for the Z-Bar. The block doesnt have the tapped hole to mount a Z-bar stud. Thanks Keith for bringing that one up. I looked at the flexplate, and it is has a weight welded to it. So obviously it is externally balanced. Question though- why balance the rotating assembly to +/- 1 gram if you arent gonna go neutral with the balancer or flexplate/flywheel?

Just seems like a waste of time to hang additional rotating weight on each end after paying for balancing.

[68rs406]

Originally Posted by Big Willyz

I looked at the flexplate, and it is has a weight welded to it. So obviously it is externally balanced. Question though- why balance the rotating assembly to +/- 1 gram if you arent gonna go neutral with the balancer or flexplate/flywheel?

Just seems like a waste of time to hang additional rotating weight on each end after paying for balancing.

It's externally balanced then I would bet, provided they used the correct flexplate on it of course. Check the balancer out, on the back side it should have a large notch which would further reinforce it's externally balanced.

It's not a waste of time to balance an externally balanced motor, internal or external they all require balancing external is just a different way to do it. It has become less common and it's not the preferred way but there are ton's of 400's and 454's that are still running external balancing as GM did it originally with no issues.
Just verify what you have as much as possible (money says it's external balanced though and don't sweat it, you'll be fine.

[srode]

Originally Posted by Big Willyz

Thanks for all the info. I didnt even think to look to see if the block was tapped for the Z-Bar. The block doesnt have the tapped hole to mount a Z-bar stud. Thanks Keith for bringing that one up.

I had to drill and tap mine as well - was surprised to find it was missing after someone on here reminded me to check - looked just before installing it in the car - glad I didn't get it in and find it after the fact. The block material drills pretty easy thankfully.