Harmonic Problems

pvtysux

Registered User
I wonder if a broken harmonic balancer would prevent the car from starting. It is a 1990 super coupe with 140000 miles I was trying to replace the crank sensor and found it was destroyed. Any ideas on how it got broke. Also do you know of a replacement or if any one has on to sell please reply asap. you can e-mail me @ mroseberry@cox.net for any info about prices on the harmonic balancer. Thanks Mark also i will be looking at selling the in a year so peeps keep your eyes out.
 
Yes that's why it won't start. You got normal mileage out of it and it broke because Ford didn't make them to last. You need to go to the dealer and get a new damper and pulley assembly along with a new 3.8 Mustang bolt and washer to fasten it to the crank (you don't know it yet but your bolt is broken, don't believe me, go look for it). A used one won't last very long in most instances, no way for a year, they are more of a one crank only item. Expect to pay Ford $200-$350 for the kit. Now that I've answered your questions hopefully this prerecorded message will answer your new ones.

Here is an overview of the damper situation, problems and their causes and recommended repair methods. This was learned from experience and sharing information with others. I keep it on my hard drive for a ready response to a common problem. The subject of dampener balancing is one that is still debated by long standing members of the SC community and the views expressed by me are from my experience only. It is my opinion that if the original balance can no longer be verified, as is the case with a broken dampener the new assembly installed should be neutral. This article was last updated 3-16-03.

For a good reason to get upset at Ford (as if you don't have enough already) take a closer look at the dampener snout. It is made of aluminum with a steel inner and outer sleeve. Thin steel sleeves. The factory pulley is heavy steel casting with a machined belt surface; this makes it impossible to be balanced without adding weights. Some have more balancing weight than others welded on the pulley. This could be a washer or similar pieces of steel that gets it close but not neutrally balanced. Then to achieve a final neutral balance of the assembly Ford used two methods on SC’s over the years. The first technique used small steel pins inserted into the backside of the dampener hub that has a circle of evenly spaced predrilled holes for balancing weights. As far as I know this was used from ’89 through ’92. Then in ’93 SC dampeners were balanced by drilling to removing material. This limp wristed design can barely handle the stock HP and weight levels; many break of old age. I made the mistake of overdriving the blower with a stock exhaust system and blower top; this increased power and drive loads. That's what broke my OEM unit. I then installed another damper with it’s own pulley out of a junkyard and because of confusing instructions in the Haynes manual I relocated the balance pins to match my old dampener assembly on it. This caused that assembly to be out of balance while still overdriving a blower with stock top and exhaust; I think that one lasted about 4000 miles. After that one broke I bought a complete assembly (pulley and damper) from Ford for less than $200, it comes balanced, and I didn't mess with it. That was my first SC, when I got around to increasing horsepower on my current (2nd) SC I used Auto Specialties under drive pulleys to reduce the damper weight and drive loads. I also did the exhaust and installed a raised top at the same time. These were steps made to increase damper longevity; the increase in performance was secondary at this point.

In efforts to get this figured out and avoid any more breakdowns I took the dampener assembly and both pulleys to a machine shop and had them checked in every configuration. With the stock pulley and pin arrangement, it was neutrally balanced. Then the dampener itself without the pulley but with the balancing pins still in place was out of balance. Then the dampener alone without pins went back to neutral, establishing that the damper itself is neutral. And then the dampener without pins but with the ASP crank pulley that ASP had said would be neutral and it was. ASP’s pulleys are machined perfectly round with precision tolerances from billet aluminum; therefore are neutral by design and need no after installation rebalancing done. So I installed it like that, ASP pulley without any pins, doing the other tricks to improve durability (top and exhaust and others listed below) and it's been working with lots of HP and hard driving ever since. The engines new smoothness over the swap pin arrangement was immediately evident. If this one ever splits I'll get one of the BHJ steel hub dampeners and that should be the end off it. Since I have acquired another SC, this one is a ’95. At 125K its dampener elastomer failed and the ring walked backwards until it started rubbing the cover then crank-sensor. I purchased another assembly from Ford along with another ASP under-drive pulley set. Because of the long-standing debate over the pins and their true purpose I once again had the machine shop check the initial balance of the stock assembly. This being a ’95 it didn’t have pins but had some holes drilled into the ring from the backside. Once again the assembly was neutral from Ford and needed to be rebalanced to remain neutral after the ASP pulley was installed.

Which type of crank pulley do you have, stock or ASP under-drive? If you do have under-drive pulleys already and you didn't remove all the balance pins from the factory dampener then that’s probably why it failed. They are fragile and without proper care will break anyways. The factory dampeners are neutral; the pins are used for the unbalanced and heavy pulley. With an ASP pulley all pins should be removed to balance it out. If you use a stock pulley and dampener from two different engines you will need to have the assembly dynamically balanced for the new combination. You would be better off using an Auto Specialties pulley set, not only will it lessen the load on the next dampener greatly, it can be installed on a dampener without re-balancing.

The best thing to do would be to replace the dampener with one of the new aftermarket ones that Steve Webb (blackbirdsc) sourced out from BHJ and using the ASP pulleys. If you don't have the money for it then you should at least get another Ford dampener and pulley assembly. They come with the pulley installed and balanced. Hopefully they're still available. And how much do these assemblies run nowadays? Mine was under $200 but that was several years ago, it could be that the BHJ unit is competitive now. Just be aware that more power and airflow along with bottlenecks anywhere in the system could cause it to break again. If you find one from the salvage yard then try to get it with the pulley still attached. This way you don't have to spend the time and bucks rebalancing it. If you go with another dampener and your old pulley then it needs to be balanced as a unit. Also be aware that the Ford dampener’s shaft sleeve wears out or takes a setting to the crank over time and should be considered as disposable. Using a salvage part is risky and should be done as a last resort. With any damper the proper tools have to be used during removal and installation to prevent shaft sleeve warping or stretching, it you use a hammer of any kind on this part you won’t do it the next time.

As far as getting the old bolt out it’s best to use a reverse cutting drill bit along with a reversing drill. Usually the drill bit will only get in so far before the bolt shaft starts twisting out of the crank snout. If you use a right angle drill adapter you won’t have to remove the radiator. They cost about $15 at Home Depot. As long as you didn't use lock-tite on it, it should come right out. If you did, and I did once, just heat it up first. Ford doesn’t use lock-tite here. As for a replacement bolt, get a new one from Ford for the late model Mustang 3.8 along with its washer. They redesigned it and the washer for more strength. This is why they discontinued the SC bolt, it would be nice if they cross referenced it to the old part number but they didn’t and cause many a panic attack among SC owners. Use the maximum recommended torque on install. In fact find out if they raised this torque specification for the Mustangs new bigger hardware, and if so, use the larger torque. Our cranks are stronger than the normal 3.8’s and it can take it without any problems.

Ford part numbers for the Mustang bolt and washer are:
Crank bolt F58Z-6A340-A
Crank bolt washer E2DZ-6378-A

Another thing for the wise to do is replace the woodruff key with a new one. These things develop some slack with use and once a dampener has broken loose on one it is useless. Without a tight fit the next dampener will fail soon. I hate Pep boys but they had these things in bulk, try Ford first.

My crank sensors never got hit by the broken dampener but it's always a possibility so do look carefully. In fact as troublesome as the crank sensor is now would be a good time to replace it. If you do just make sure the vanes on the back of the dampener slide into the sensor groove on install otherwise a sensor misalignment could crush the sensor and or bend the vane on the back of the dampener.

In theory the weak hub could develop a fatigue fracture failure due to erratic crank momentum. If you have an ignition misfire you should know it, but what about a clogged or stuck injector? They could cause abnormally high crank harmonics that would accelerate wear. Maybe a good injector flush would be cheap insurance. In this same line of thinking a bad A/C compressor could stress the dampener in this way and I’ve heard of two occasions when clutch chatter immediately preceded a balancer failure. Does yours run smoothly?

A large throttle body increases HP not only from more CFM but also by reducing blower vacuum drag on the rotors; thereby it reduces pulley loads also.

Sorry for the long lesson but I the more you know the better your chances of figuring it out. I had to learn all this stuff the hard way on my own so I like to share when I can as others have here with me.

Vernon
 
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George I know I need to update this badly so if you add any part#s, phone #s, etc. I promise to add them this time.

Vernon
 
Hey, buddy, you've had your chance! LOL

I just wanted to point out that Steve Webb (blackbirdsc) was the guy responsible for getting BHJ to make the things in the first place! Dr. Fred did organize one of the early group buys on the items.

I believe now that both Super Coupe Performance and Blue Tongue sell the BHJ dampers for less than the group purchase price used to be. At SCP they are $350 for 89-93 and $375 for 94-95. In both cases you'll need the crank sensor trigger ring from you old damper. The BHJ unit does *NOT* include the pulley.

Part numbers for the newer 'Stang crank bolt and washer (fits all years of SCs):

Crank bolt F58Z-6A340-A
Crank bolt washer E2DZ-6378-A

The issue with the pins is still one of the great unsolved mysteries of the SC kingdom. All of the stuff I have read says that the pins are there for final engine balancing and not for balancing the the pulley to the damper. I know Duffy Floyd got this same info from a retired Ford engineer. I have read it in the Ford shop manuals. It says to put the pins from your old damper/pulley set onto your new damper/pulley set before installation. I have also never seen a new pulley/damper set with pins. (Although, I haven't seen that many!)

I know you had your set checked at a shop, but don't know if that is a big enough sample to support your theory that they balance the pieces together.

Last great SCCoA pin discussion:

http://sccoa.com/forums/showthread.php?s=&threadid=16442

Damper pics and more pin discussion:

http://sccoa.com/forums/showthread.php?s=&threadid=7250
 
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