73 Challenger, part time project, full time lifestyle!

[ShelbyDogg]

Probably a good time to have your flywheel checked for balance and weighted like your old one. If you have a '72 340, you most likely have a cast crank. Your flywheel will be non-neutrally balanced (unless someone balanced the entire engine for neutral balanced flywheel and balancer) and your American Power flywheel probably is.

Look at you harmonic balancer. Does it say "use on 340 cast crank only"

[ToxicWolf]

Probably a good time to have your flywheel checked for balance and weighted like your old one. If you have a '72 340, you most likely have a cast crank. Your flywheel will be non-neutrally balanced (unless someone balanced the entire engine for neutral balanced flywheel and balancer) and your American Power flywheel probably is.

Look at you harmonic balancer. Does it say "use on 340 cast crank only"

  When I got my new flywheel from American Powertrain I had to make sure I got one that is balanced because I have a 360 block with a cast crank.

[Tonker1]

Probably a good time to have your flywheel checked for balance and weighted like your old one. If you have a '72 340, you most likely have a cast crank. Your flywheel will be non-neutrally balanced (unless someone balanced the entire engine for neutral balanced flywheel and balancer) and your American Power flywheel probably is.

Look at you harmonic balancer. Does it say "use on 340 cast crank only"

When I got my new flywheel from American Powertrain I had to make sure I got one that is balanced because I have a 360 block with a cast crank.

I'll call American Powertrain on Monday and find out if I bought a pre-balanced flywheel or not. Do American Powertrain even sell balanced flywheels?

Thanks for the tip ShelbyDogg and ToxicWolf, I have a note somewhere reminding me to ask about balance, but since you guys are on the ball I might ask a couple of questions:

Where on the harmonic balancer would it say "use on 340 cast crank only".

I no longer have my old flywheel, were the old flywheel balances put in a standard position for the relevant engine size or is at match to the specific engine kind of thing?

Thanks in advance!

[ShelbyDogg]

[Tonker1]

Wow, thanks for the quick reply and awesome picture! I'll take a look at that this afternoon when I'm back home.

[ToxicWolf]

American Powertrain actually billet cut a balanced steel flywheel for me.  It is a thing of beauty. Just talk to Bill if you have any questions. He really knows his stuff.

[Tonker1]

The harmonic balancer is marked like in your image ShelbyDogg, so I do require a balanced flywheel.

American Powertrain actually billet cut a balanced steel flywheel for me.  It is a thing of beauty. Just talk to Bill if you have any questions. He really knows his stuff.

If you had to specially request to have a balanced flywheel cut, chances are the new flywheel I have from the American Powertrain is not balanced. Out of interest what information did you have to provide them with?


I have a couple of questions about balancing the flywheel; if it is relevant the engine identification sequence under the drivers side cylinder head starts with JM, the J being for 1973 assembly.

1. So for balancing, were the masses on the stock flywheel a standard weight and at a standard radius for a '73 340 engine? Basically trying to work out if I can just take the flywheel into a shop and have some masses added or if I need to remove the engine and take that in as well?
2. Working on the simply take the flywheel into the shop idea, the new flywheel being of different mass (compared to the old flywheel) should not make a difference to balance because the flywheel itself is balanced?

Thanks in advance.

[ToxicWolf]

You should be able to tell if it is balanced by looking at it.  This picture is for illustration, it is not mine.  If you see the three indentions in yours like this one has, it is balanced.

Added: I put up the second picture with three white dots on it to mark the indentions I was talking about.

[ShelbyDogg]

American Powertrain should have asked what engine you were putting it behind then sent the correct flywheel. If they know what they are doing, they should have known a 72 340 probably had a cast crank installed.

Call them and see if they can send the correct one. The picture shown above is for a 360 with 3 huge holes.

To modify neutral balanced flywheel, you have to look at the Mopar performance engine manual. It shows where to drill a hole to fix it. You onlu need to do this if you know that your engine was never balanced at a machine shop with your stock balancer.

[ToxicWolf]

ShelbyDogg is absolutely correct. I would be really surprise if American Powertrain sent you the wrong flywheel. Talk to them if you have questions. They have always responded to any questions I had by phone and by email. Just take a look at the flywheel and see if any of the areas in the drawings ShelbyDogg put up are cut out. If they are, you should be fine. But, in any circumstance, the people at American Powertrain will help you fix the problem At least that has always been my experience with them.

[Tonker1]

I've just pulled the transmission and checked the flywheel, would these be the holes be the balancing holes?
The holes are threaded and do not got the hole way through the flywheel and they are significantly smaller then the holes in ToxicWolf's images

ShelbyDogg is absolutely correct. I would be really surprise if American Powertrain sent you the wrong flywheel. Talk to them if you have questions. They have always responded to any questions I had by phone and by email. Just take a look at the flywheel and see if any of the areas in the drawings ShelbyDogg put up are cut out. If they are, you should be fine. But, in any circumstance, the people at American Powertrain will help you fix the problem At least that has always been my experience with them.

You are absolutely right about American Powertrain customer service, they upgraded my shipping and then gave me a discount on the shipping. I called them with my drive-shaft specifications 2 weeks ago, the new drive shaft arrived at my front door on 6 days later. 10 000 miles in 6 days.

American Powertrain should have asked what engine you were putting it behind then sent the correct flywheel. If they know what they are doing, they should have known a 72 340 probably had a cast crank installed.

Call them and see if they can send the correct one. The picture shown above is for a 360 with 3 huge holes.

To modify neutral balanced flywheel, you have to look at the Mopar performance engine manual. It shows where to drill a hole to fix it. You onlu need to do this if you know that your engine was never balanced at a machine shop with your stock balancer.

I'll call American Powertrain tomorrow anyway, as I want to talk with their tech support guy about installing the hydraulic clutch.

The old flywheel definitely had a mass added to it, it looked cast into place as opposed to added after manufacture, I just assumed the new flywheel would be of the same form. How's that quote go about making assumptions and an ass of yourself!!

[Tonker1]

I've called around, the guys at American Powertrain could not confirm if I required a balance on a completely stock rotating assembly or not. If I did require a balance it would be 28 ounces bolted to the flywheel in the threaded holes pictured in a previous post. I thought engine balancing was more specific than that, but I guess it is not surprising considering the lower design tolerances in 1970.

The testing method recommended to me was bolt the flywheel on and start the engine and it will be obvious if the engine needs a balance or not.

It will be quite a while before I can test the flywheel, there a few weekends of worked needed to get the engine running again and my exams start in 4 weeks. So for now, spare weekends is not something I have! Once exams finish I'll boost up my hours at both my jobs and earn as much money as possible so I can afford more parts!

Thanks for the advice and reminding to me check on the balancing.

[ShelbyDogg]

See my pic below.



I'm NOT sure if the 28 ounces would give you the 4.22 inch ounces as specified. Only a guy that balances stuff can tell you what that means.
Looking at your flywheel and my diagram does confirm that removing metal from one side is like adding material to the opposite side. Compare the flywheel holes and you can mark yours to draw the hole.

Those guys saying that they can't confirm that you need an offset balance on a stock rotating assembly shows that they don't know Mopars with a 340 cast crank need an offset balanced flywheel!

 

The testing method recommended to me was bolt the flywheel on and start the engine and it will be obvious if the engine needs a balance or not.

Are they F-in kidding? Who is going to pay for your time to pull your flywheel, bellhousing and tranny back off? You might not feel the slight vibration but it would still be there.
Factory balancing in 1970 was good and you never had a problem till owners started swapping parts around.
Did they say that theirs is neutrally balanced now? Even if you don't bolt anything to or plug those holes?
You can always have the hole drilled in yours per the manual, but you have to start with a balanced flywheel.

[Tonker1]

See my pic below.



I'm NOT sure if the 28 ounces would give you the 4.22 inch ounces as specified. Only a guy that balances stuff can tell you what that means.
Looking at your flywheel and my diagram does confirm that removing metal from one side is like adding material to the opposite side. Compare the flywheel holes and you can mark yours to draw the hole.

Those guys saying that they can't confirm that you need an offset balance on a stock rotating assembly shows that they don't know Mopars with a 340 cast crank need an offset balanced flywheel!

 
Are they F-in kidding? Who is going to pay for your time to pull your flywheel, bellhousing and tranny back off? You might not feel the slight vibration but it would still be there.
Factory balancing in 1970 was good and you never had a problem till owners started swapping parts around.
Did they say that theirs is neutrally balanced now? Even if you don't bolt anything to or plug those holes?
You can always have the hole drilled in yours per the manual, but you have to start with a balanced flywheel.

Yes, the flywheel is neutrally balanced.

Is this,  http://chucker54.stores.yahoo.net/mo9thedensps1.html  ,  the Mopar Performance Engine Manual you were talking about? If so I'll buy a copy

Personally I would prefer to add weights rather than drilling, just in case the internals have been changed (which I highly doubt), because adding a little less final then drilling! When I have some free time this week I'll visit my local flywheel shop and see what they stock in terms of counter balances.

In case I change my mind, For the image below, does flywheel only require a single drill hole at the marked location in Figure 13-10.

Thanks for sharing your knowledge and awesome diagrams!

American Powertrain should have asked what engine you were putting it behind then sent the correct flywheel. If they know what they are doing, they should have known a 72 340 probably had a cast crank installed.

Call them and see if they can send the correct one. The picture shown above is for a 360 with 3 huge holes.

To modify neutral balanced flywheel, you have to look at the Mopar performance engine manual. It shows where to drill a hole to fix it. You onlu need to do this if you know that your engine was never balanced at a machine shop with your stock balancer.

[ShelbyDogg]

Not sure if that is the correct book since mine is old old old!  Someone else here that has one can confirm it.  For $10, I might just buy a new one too.

The 340 balance requires the one hole indicated. I had a flywheel drilled and used it but finally found a 340 cast-crank flywheel at the Mopar National's swap meet last year, for $50.