muncie and hurst shifter downshifting troubles

[Bonnewagon]

Looking good, that flywheel is awesome. I use only the sealed roller bearing. #7109 I think? Never a problem. I lube the fingers of the fork that ride in the slot of the throwout bearing, the pivot pocket of the fork that rides on the stud, the splines on the input shaft that the disc rides, and wherever the linkage connects. But minimal.

 

[mebe007]

This is the one that came with the kit

 

[Bonnewagon]

Looks different. I use this one.

 

[mebe007]

That looks huge

 

[Bonnewagon]

Anyway, I guess anything is better than the oilite bronze bushing type. Every one I've seen had been worn all cockeyed.

 

[mebe007]

You read alot about fragged input shafts from rollers though

 

[pontiacgp]

I had a roller disintegrate on mine and no damage to the shaft..and I replaced with another roller last year which seems to be ok. Your flywheel looks great and I like your clutch assembly.. 🙂

I havn't seen one like this but I like it

 

[mebe007]

my understanding gp is the muncie input shaft has a lower rockwell hardness than the bearing itself causing the issue. i would rather run the roller bearing if i knew for sure it wouldn't screw anything up

 

[Bonnewagon]

"That looks huge"- I always thought all GM's had the same size pilot bearing hole drilled in the crank, hence one part # oilite bushing used across the board. IIRC, the #7109 was the original BCA replacement though Timken, National, etc, all use that part#. I have used this type roller bearing in many cars, all with Pontiac engines, for over 30 years without a single failure. I would think the needle type bearing would be just as good if not better as long as the lube was up to the task. You can't see in the pics, but one side of my bearing is open and the other sealed. I like to pack the open side with disc brake grade wheel bearing grease and position the open side towards the crank. That way none can get out to contaminate the clutch, and should the bearing get hot for whatever reason, the grease will melt and flow back to the rollers. This is in theory similar to the oilite bronze bushing GM used. The bronze is softer than the steel input shaft, and if it gets hot, the oil flows where it's needed. Nice theory, but I've seen many broken, burnt, and distorted bushings. To be fair they were probably way overdue for replacement. Once compromised, that allows the input shaft to wobble and the disc to c*ck, upsetting clutch operation.

 

[mebe007]

this is how my pilot bushing goes in

(not my engine: picture from google)


this is the email i received from act about pilot bearings

Dean Williams <[email protected]>

to me
Mark,

I forward your question to our engineering staff, below is their answer-

“The material is an impregnated bronze (Oilite, SAE 841). I have personally used both these and good-quality needle bearings for many years with no issues.

That said, many pilot bearing/bushing failures in the GM V-8 applications have much more to do with bellhousing alignment than materials. Since the mating pattern has been the same for so many generations, parts are easily mixed and matched. What rarely gets checked is the dowel location in the back of the engine block and the dowel holes in the bellhousing. If their position is off by as little as .008”, the pilot bearing sees a lot more load than it should. Extreme misalignments over .020” usually destroy clutch disc hubs before the pilot bearing problems are discovered.

On the GM assembly lines in the past, engine blocks were color-coded for the amount they were off. They were matched with bellhousings that were marked the same color, as they were off the same exact amount in the opposite direction, cancelling the errors and perfectly aligning the input shaft to the crankshaft. When we hot-rodders scavenge parts from various places, it would be rare to get two mated, “zeroed out” pieces.

This was cured in NASCAR in the late 60’s so teams could mix and match parts at the track while avoiding failures. There are several locator kits on the market (Tilton makes one that has been popular for decades) that relocate the dowels to their ideal position with respect to true centerline on both parts. If the critical alignment of these two components is off, there is no pilot bearing that will put up with that stress indefinitely.”


Thank you,


Dean Williams
Customer Support Supervisor
Advanced Clutch Technology


this is the email Paul over at 5speeds sent me
Paul Cangialosi
to me
If your bellhousing is dialed in, you can run the roller. Any side load of the roller will eat it up and take out the transmission input and your crank shaft.