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james5275
10-14-2003, 11:36 AM
Hello everyone,
I have a good topic today. I know that our SC's are known for breaking the stock balancers. But is the bolt that secures the HB related to that problem? I have about 2300 miles on my 89 rebuilt engine. At about 1000 miles the bolt sheared and the HB broke. At 2300 miles, I heard a rattling sound (like a loose washer) so I checked the bolt. I turned it by hand and once again the bolt sheared off. I looked at the HB and it looks fine (no cracks.) Both balancers and bolts are (or were) bought used. The engine runs very smooth so I dont think its vibration. I purchased a new bolt from the dealer but it would be nice to know what caused the first 2 bolts to break. Anyone??? JJ

Jim Cook
10-14-2003, 11:46 AM
Do a search and you'll find plenty of history showing that re-using an OEM balancer is a common mode failure point for the bolt. Bottom line: buy a new one or get a BHJ damper which is all steel and can be reused

MercXr7-5speed
10-14-2003, 12:01 PM
I have had more than several balancer problems. Never re-use a bolt, it WILL break. Reusing a balancer is very very iffy. I put two used ones on my 89 and they both broke. One broke within 8 months the other within 1 1/2 months. Both of them broke the used bolt inbetween. On the 90 I put a used one with new bolt and washer because of limited funds. I have on order a brand new one from ford. This balancer has lasted 7 months but I am surprised I got that much. I also put a brand new one from ford in my 89 and it had lasted well over a 1 1/2 before I put the car to rest. Basically do what Jim Cook said. Good Luck.

Joe

james5275
10-14-2003, 12:11 PM
I did a search and found a thread by 'notsofine89'. I didnt think it would be a problem using those used parts. [email protected]! I always learn the hard way! Thanks for thr help fellas. BHJ is on order.....JJ

LJGriggs
10-14-2003, 01:36 PM
A little locktite on the bolt threads (and 100ft/lbs of torque) will help to prevent breakage. I have broken the balancer without breaking the bolt and broken the bolt without breaking the balancer...Hard to say which one causes the other...sort of the chicken and the egg thing. One thing for sure, a broken bolt will result in a broken balancer eventually and all of them break except the BHJ (knock on wood).

victor malvar
07-22-2004, 06:19 AM
Hi, When Rich Thompson, brought the "BOLT" issue up it only concerned the BHJ, We just sent a stock Harmonic Balancer to BHJ, so they could look at this Mustang bolt verses a bigger bolt and stronger as well. When BHJ wants to address the bolt issue, I did not think there was much credence to this but now that BHJ is looking into it, who knows there may be something there?
I do have a few of the new bolts if anyone decides to change their bolt out. I have not changed mine but have some for who ever may want one. $2.00 for the new bolt and $1.00 to ship it to you. If you happen to purchase anything and want one? I will just give one to who ever wants one. I have about 3 but can get more. The jury is still out on this issue.
Victor and Diane
Spinningwheels-sc
www.spinningwheels-sc.com

Mike8675309
07-22-2004, 07:58 AM
The main issue is that the bolt is not intended to be the primary retension method for the harmonic balancer. It's role is secondary with the interference fit of the balancer hub on the crankshaft being the primary retension method.

If the bolt is breaking regularly, then the primary retension method has failed. This would mean the harmonic balancer is no longer exibiting a interference fit on the crankshaft and the bolt is having to play a role of primary retension, which it was not designed to do.

The stock bolt is a known weak part. The later Mustang bolt is stronger, and the new bolts from Rich or Victor are stronger yet. But if their strength is necessary, you should take a hard look at replacing the balancer to start with.

james5275
07-22-2004, 09:37 AM
The main issue is that the bolt is not intended to be the primary retension method for the harmonic balancer. It's role is secondary with the interference fit of the balancer hub on the crankshaft being the primary retension method.

If the bolt is breaking regularly, then the primary retension method has failed. This would mean the harmonic balancer is no longer exibiting a interference fit on the crankshaft and the bolt is having to play a role of primary retension, which it was not designed to do.

The stock bolt is a known weak part. The later Mustang bolt is stronger, and the new bolts from Rich or Victor are stronger yet. But if their strength is necessary, you should take a hard look at replacing the balancer to start with.
Good info. thanks everyone. JJ

BT Motorsports
07-22-2004, 12:15 PM
Mike has hit the nail on the head. A stronger bolt is not the solution to this problem.

Paul

Mike Puckett
07-22-2004, 08:51 PM
My drag racer's HB is an anomaly. It has been on and off 3 times now, always with a new bolt, and the last time was when my cam was installed before last year's drag season. I've been taking it drag racing week after week for 2 years now and no breakage, no problem. I inspect it every so often and carry an extra balancer and bolt around with me just in case, though. I don't worry about it any more. I think that the reason I've had no problem is that I've got the small aluminum pulley with the underdrive set and it doesn't stress the HB like that humongus steel pulley does.

victor malvar
07-23-2004, 01:38 AM
The main issue is that the bolt is not intended to be the primary retension method for the harmonic balancer. It's role is secondary with the interference fit of the balancer hub on the crankshaft being the primary retension method.

If the bolt is breaking regularly, then the primary retension method has failed. This would mean the harmonic balancer is no longer exibiting a interference fit on the crankshaft and the bolt is having to play a role of primary retension, which it was not designed to do.

The stock bolt is a known weak part. The later Mustang bolt is stronger, and the new bolts from Rich or Victor are stronger yet. But if their strength is necessary, you should take a hard look at replacing the balancer to start with.
Hi, I agree with you, and I also beleive that you could probably intall a HB without the bolt and it would probably stay in place temp. anyway. The bolt was just a friendly offer. I use the BHJ and have not had any problems with the current bolt. I'm not trying to make this an issue. I plan to be selling this balancer the BHJ soon. I have already applied and sent them my credit refrences about 7 to 10 day's ago...No re-ply yet. I sell all types of SC XR7 Parts, and the BHJ is one of the parts that we plan to carry in our store very soon. There cant just be one person allowed to sell this balancer. We are just as entitled as anyone else after all this is the land of the free and the brave. I thank you for your respond and appreciate your words of wisdom. We are a fast growing company and have sold many many BHJ HB that we bought from SCP alot of them came from Spinningwheels-sc.We have alot of demand for the BHJ. PLease re-read our post and you will see that I'm just offering this bolt IF any one was to want one?. Have a real pleasant day, and also it was nice communicating with you. :cool: :) All the Best to you!
Victor and Diane
www.spinningwheels-sc.com

BT Motorsports
07-23-2004, 06:32 PM
The stock bolt is a known weak part. The later Mustang bolt is stronger, and the new bolts from Rich or Victor are stronger yet. But if their strength is necessary, you should take a hard look at replacing the balancer to start with.
Mike, I have to disagree, the SC bolt and mustang bolt are both grade 10.9.
The bolt that Rich lists is also a grade 10.9, just longer in length.
As an FYI for all: I have spoke in depth with Brian (engineer at BHJ) as well as a few other knowledgable sources and have concluded that a stronger bolt material is not the way to go. It pretty much comes down to, do you want the bolt to break or the snout off the crank when getting into a stronger material bolt. I did finally manage to source a company to make a higher grade bolt, however, at their recomendation and that of BHJ and others, I decided against offering it. Taking into consideration that the company which would have undertaken the role of making the custom bolt suggested against it at the loss of the sale, I feel it is the best decision on my part and do not suggest anyone else persue a stronger fastener.


There cant just be one person allowed to sell this balancer. We are just as entitled as anyone else after all this is the land of the free and the brave.
Victor, what are those statements supposed to mean? BHJ has a network of dealers across the country that offer this balancer in addition to Bill and I exclusively carrying it for the SC.

Paul

93SuperCoupeBoy
07-23-2004, 11:11 PM
I've read this thread, and just putting my 2 cents in...

isn't the whole point of using the "new" bolt to provide the extra travel needed to compensate for thicker material. It isn't that the bolt is any stronger, it is simply making up for lost material. 4 threads aren't going to hold a balancer on when you're hot rodding your SC around town! The bolt isn't "bad", it's just too short. Do we need a senario to provide the information needed for some people to comprehend this?

Here...senario.... say you have a nail. And this nail has to hold a board down on your roof. Which nail is going to work better...a 2.2" nail that has .2" into the surface holding it down or a 3" nail, which would have 1" of material holding it down. Now..... on a normal day, both nails would work the same, but lets say a 100mph wind gust comes along....which board has the better chance of staying planted on the roof (disregarding any aerodynamic properties each board may have)?

Like I said....just throwing in my $.02, I'd personally rather have more than 4 threads of a bolt holding something spinning 5000rpms onto my crankshaft, but maybe that's just me?

Nick

BT Motorsports
07-23-2004, 11:17 PM
isn't the whole point of using the "new" bolt to provide the extra travel needed to compensate for thicker material.
The new bolt is for people's peace of mind and not actually needed. BHJ has since changed the depth of the bore to utilize the stock length bolt in response to everyone's concerns as a customer service issue, not a design problem. The anology of the nail is not appropriate to this situation because the press fit of the balancer is what holds it on the crank, not the bolt.

Paul

93SuperCoupeBoy
07-23-2004, 11:21 PM
The new bolt is for people's peace of mind and not actually needed. BHJ has since changed the depth of the bore to utilize the stock length bolt in response to everyone's concerns as a customer service issue, not a design problem. The anology of the nail is not appropriate to this situation because the press fit of the balancer is what holds it on the crank, not the bolt.

Paul

That's like saying that my wheels should stay on because they fit. NO!!! The nuts hold them on. How can the "fit" of something hold it from working it's way off without something there to prevent it from going further, especally under heavy load?

BT Motorsports
07-23-2004, 11:28 PM
That's like saying that my wheels should stay on because they fit against the spindles. NO!!! The nuts hold them on. How can the "fit" of something hold it from working it's way off without something there to prevent it from going further, especally under heavy load?
No it isn't the same. The balancer is an interference fit and that is what keeps it located on the snout. This has already been discussed, debated etc. and Steve Webb said it best: http://www.sccoa.com/forums/showpost.php?p=298315&postcount=34 If you have other questions, feel free to ask.

Paul

93SuperCoupeBoy
07-23-2004, 11:40 PM
No it isn't the same. The balancer is an interference fit and that is what keeps it located on the snout. This has already been discussed, debated etc. and Steve Webb said it best: http://www.sccoa.com/forums/showpost.php?p=298315&postcount=34 If you have other questions, feel free to ask.

Paul

I'm sure some cars are capable of things working like they're "supposed" to. But you have to remember that we're dealing with SCs here ;).

Since I have to keep finding points to argue with and stuff, could the tension of having the blower belt along with the accessory belt be causing strain on the balancer?

Just wondering, since I have to think all the time!

Nick

BT Motorsports
07-24-2004, 12:40 AM
Since I have to keep finding points to argue with and stuff, could the tension of having the blower belt along with the accessory belt be causing strain on the balancer?
Before I answer that, I have to ask why you feel you need to argue this issue?
There is absolutely a strain on the balancer from the tension of the blower belt and accessory belt and that strain is multiplied as the engine turns faster. The failure of the stock balancer though, is due to either the inner hub (which is aluminum) losing its interference fit (possibly from heat cycling over the years) but primarily from the elastomer between the inner and outer hub breaking down. The outer hub then begins to spin on a different axis than the inner hub and creates harmonics instead of dampening them. The result is a broken balancer and/or broken bolt and/or even worse a broken crankshaft.

Paul

93SuperCoupeBoy
07-24-2004, 12:50 AM
I don't mean to argue as in argue...really I just like to get as much information as I can. Don't mean to actually ARGUE my way to the answers though.

Anyways, I'll give up until I develop another theory in my head ;)

Nick

BT Motorsports
07-24-2004, 01:10 AM
That's cool with me, nothing wrong with a little discuss and debate.

Paul