Clutch Issues and Parts

I only have a little over 8000 miles on this car and have had clutch problems on and off for almost half that time. Chatter for one thing, but replacing a leaky slave cylinder fixed that. For a while.

Over the last few years, I’ve been suspicious it was slipping. During some testing last Fall, it finally showed it’s evil ways. No doubt about it and probably due to the new found power from my new larger, freer flowing air filters!!!

Back when I began building the car, the kit manufacturer gave recommendations for clutch parts. It turns out the recommended pressure-plate I installed only has an 1800 lb clamping force. My engine ought to have somewhere shy of 450 ft-lbs of torque, which calculates to a 2000 lb pressure plate for an 11 inch clutch... in fact they recommend 20% extra to allow for gradual degradation, so it should be a 2400 lbs pressure plate.

On the subject of clamping force being 1960’s thinking, my only reference was Tom Monroe’s book on clutches, originally published in 1977 and slightly re-written in 1991, so no doubt Tom learned a lot in the 1960s. Add to that the fact that the clamping force is the only spec that McLeod publishes other than dimensions… that I can find.

Also, I don't really like the Long style 3 finger pressure plate as if any of the fingers exhibits a bit of weakness or wear over time, the throw-out bearing will tilt and orbit. This makes clutch fork and possibly clutch pedal vibration likely. A diaphragm plate should reduce this effect. The diaphragm P-P is also easier to depress than the Long style, so that will help make up for increasing the clamping force and hopefully everything will operate close to how it did before.

I thought a little extra clutch grip might be nice too, so I looked at dual friction discs. McLeod sells one however theirs has the metallic facing against the flywheel and the organic side against the pressure plate. I really would rather replace the pressure-plate at a later date than the flywheel).

However RAM sells a similar product, but with the ceramic side facing the P-P. I’ve given up on McLeod. The fact that they don’t offer the clutch disc I would like and to top it off,, they never answer my e-mails asking about their parts, I decided to go with RAM.

Also, as the Diaphragm P-P has a lower profile than the Long style, changing over might put my clutch fork out of position. It really ought to stick out of the bell-housing at 90 degrees, or perhaps a bit forward. I have ordered a spacer kit for the clutch fork fulcrum in case I need it.

By the way, RAM and McLeod both sell kits for what I’m doing, but they list them for a Tremec conversion. Little did I know that as far as the clutch is concerned my Richmond Gear 5-speed is the same as the Tremec.

My throw-out bearing was shot. It turned easily enough, but had side-to-side movement that whether it should be there or not (for self-aligning), it was tough to move and when it did, there was a clunk. No doubt the reason for the clutch fork vibration. Why did it fail? It turns out it was in constant motion when the engine was running. The three fingers of the P-P flop around loose until the clutch is depressed. You can’t tell the throw-out bearing hits them when adjusting the free-play. Once the engine is running, centrifugal force sends them out quite a bit and they contact the throw-out bearing, rotating it.

The chatter appears to be due to the clutch slipping and resin boiled out of the facings and deposited itself on the flywheel and P-P.

Bell-Housing Alignment

While everything was apart, I decided to check the bell-housing alignment. The instructions that came with the Lakewood bell-housing stated to make sure the alignment was within spec, but at the time I thought that a cover-your-arse statement. As I didn’t have a dial indicator back then, I just skipped the step.

So time to do it. First I checked the flywheel face run-out and was less than 1 thou., approximately 0.0007

I then checked the bell housing face parallel to the flywheel. It measured 2 thou. at the top, 0 at the bottom and 1 thou each side, so that's good.
Finally, and the moment I’d been waiting for, I checked the concentricity…. And “oh No!“, I got a TIR (total indicator reading) of 0.002" Left to right and 0.037" TIR up and down, with the bell-housing needing to move up 1/2 of that for correction.

So what’s OK? Ford seems to require a TIR of 0.015 and a book by Tom Munroe says 0.010. Other sources say 0.005, but I have to admit that during my research on bell-housing alignment, it seems there's a lot of confusion between TIR, offset and runout. The term "runout" seems to be used to describe both TIR and Offset, depending on who you listen to.

Regardless, it would appear that my bell housing out to be aligned so the transmission is moved up approximately 0.018”.

You realize how small that is? And yet they tell you to expect all kinds of horrible problems such as hard shifting, jumping out of gear, premature wear of all clutch components, a wallowed out pilot bearing and a worn out transmission input shaft bearing and seal. With over 8000 miles, there's none of these signs or symptoms, yet it was misaligned. The pilot bearing looked like new! Made me doubt my dial indication readings, so I repeated the test a number of times and got consistent results within 1/2 a thou.

The much touted answer is to fit offset dowel pins. Now the reputation of extreme difficulty removing the bell housing dowel pins from FE engine blocks is well known, yet persistence will work with a number of methods. None of these are easy with the engine in the car with the possible exception of a slide hammer with the proper collet chuck (read expensive here for something that would hardly ever get used).

So I decided to relocate the dowel holes in the bell-housing flange. Of course this begs the question of what will happen if I want to use the bell-housing on another engine block? I suspect not much. My offset was 0.018" vertical and it's doubtful that line-honing/boring would move the crank up more than a few thousandths... maybe 3? So I concluded that it's the Lakewood Bell-housing that is out (it has that reputation), and that my correction should work with other blocks.... not necessarily with the same results, but probably within spec.

First I decided to make a jig to see how that would go. A piece of small aluminum channel with two 1/2" rod pieces bolted to it. I put a small slot in one end so I could adjust the spacing and it fits like a glove. Will keep me from many trips to check the bell-housing to the block as I alter the dowel holes in the bell-housing flange. See pic below (I did a rough cleaning of the bell-housing to get rid of the throw-out bearing grease, and it sort of made a mess.... oops... need to finish that cleaning!)

If you look at Step 1 in the picture below, I used a small chainsaw file to make a notch in the direction I wanted to move the hole. I kept checking until the distance from the apex of the notch and the other side of the original hole was 0.518 (as I needed 0.018 offset). Next I filed out the remaining material... the area in green. It took 1/2 hour per hole due to the constant need to keep checking things. The actual filing didn't take very long as I only had to remove something the size of a finger-nail clipping.

Using a rod and dial indicator to check movement in the hole during filing, I finally fitted the bell-housing and checked the alignment. TIR vertical dropped from 37 to 7.5 thou. and the horizontal did change slightly from 0.002 to 0.003

The next step was filling in the gap on the far side of each hole I filed. MIG seemed to be the answer, but I'd have to start on the flange, back from the hole, weld over to the hole and then down inside. This would preheat the inside edge of the hole without using a torch (I only have propane). MIG wire is generally harder than regular steel to file and a big blob would take a long time to file to shape.

At any rate, I welded up the gaps and then filed them down. This is shown in Step2 where the other side of the holes were welded, and then filed to size (and shape). I used the same "notch" method as per Step 1, but it took a lot longer as the welding took up a lot of room.

My jig for maintain the dowel separation/orientation didn't work as well as I wanted. It fit fine in the original holes, but after welding it wasn't so good. I filed those holes for 0.501 to 0.502 and the rod I made the jig from turned out to be 0.504. A little too tight, but it gave a good indication none-the-less.

The bell-housing was slightly tight to install, but it went on with a slight kick or two. I think making those holes a tighter tolerance for the dowels helped quite a bit.

Finally, the test fitment of the bell-housing. Huge success! (no doubt a little luck in there too)! I now have 2.5 thou TIR in both vertical and horizontal. directions.

I will say I strongly recommend against moving the holes. I lucked out, but it would have been far too easy to screw it up completely. Plus, it took 1/2 hour per hole for the first filing, and then another hour per hole for the welding and secondary filing. A total of 3 hours! My advice is "unless you already know your bell-housing is fine, remove the dowel pins before the engine goes in the car. Even if it turns out you only need to put the straight ones back"!