Clutch Replacement

[Bob Cowan]

A short while ago, I developed a significant engine vibration. It turned out to be a broken clutch hat. More info here: Engine Vibration.



I replaced that clutch with a Weber clutch I had on the shelf. Now I have the same vibration again. After checking everything else, I think it might be the clutch. I used my See Snake for inspection, but couldn't see anything. So I have to take the clutch apart for inspection. Since it's apart, I bought a new clutch for installation.

Based on a number of recommendations, I narrowed it down to a Ram HD or a Spec 2+. They cost about the same. I could get the Ram from Summit in a couple of days. The Spec would take 2-3 weeks. I ordered the Ram.

The Centerforce clutch disc has an excellent feel, and really did not wear very much. It was the clutch hat I was concerned about. The centerforce was made by Valao, and appears to be a stock replacement hat, with weights attached. I want something stronger (see above picture). I was told by a number of people that the Centerforce hat was "junk, and the Ram HD hat was the bees knees. Just by looking, I'm not impressed.

Just by looking at the two parts, I would say they are both the same parts! I bought another stock replacement Valeo clutch hat. The only differance is that this one is stamped "Ram" instead of "Valeo".


Even the tool/ stamping marks are identical

[Bob Cowan]

I like Ford bearings. They have an exc ellent reputation, and I'v never used anything else. Same with the clutch cables. The Ram kit comes with a bearing, and it's Labeled "Made in China". I don't know where the Ford bearing is made.









The Ram bearing spins more easily. I'm not sure if that's good or bad. The Ram bearing is also slightly heavier, by 3/4 oz. I'll use the Ford bearing.

[Bob Cowan]

The clutch discs are very differant. And I suppose this is the "Magic" with the Ram HD.







I didn't weigh the discs. Interesting that the Ram disc has pucks on both sides, and the Centerforce doesn't. The Ram has more springs, and they are covered with some kind of plastic sleeve. Ram states it provides smoother action under heavy use.

We'll see how this goes. I'll get in it, break it in over a few hundred miles, then go racing. If I don't like it I'll try a Spec 2+ this winter.

[Erik W. Treves]

Bob, FYI , mine chattered a lot.

[Cobra 302]

I went with a McLeod twin disk unit with and AL flywheel, 13 pounds lighter than the stock setup.
So far so good. I'm around 575HP at the motor.
I have been testing it all summer.

I have no chatter. A little grabby on take offs but like it.


John

[DOHCCobra]

I wouldn't chance the throw out bearing, I toasted a spec clutch in my mustang with the bearing that came with the clutch. Then put a ford one with the new clutch and it was much better.

[DAVE LITHWAY]

Bob, I bought the Valeo from Forte's for non-racing, street use behind a 340 HP - 302 crate engine. Only about 2500 miles on it, but no problems. Relatively light accuation pressure, no slipping or chatter. Ford throw-out bearing. I like it.

Dave

[Bob Cowan]

I'd love to have a twin disc - but I can't afford $1,000 for a clutch.

I demand a lot from a clutch. My engine makes a lot of power. At the race track I use every bit of power I can make. The clutch has to hold up to that kind of heat and abuse lap after lap with a smooth linear engagement at every shift up or down. OTOH, I also cruise the highway and byways of the Rocky Mountains. I need a smooth clutch with no surprises. And I don't want a Popeye leg, either.

The disc isn't really the issue. You can look at the used Centerforce disc and see it's not worn out or scorched. I think this disc has another year or two on it.

It's the hat that broke. I'v used three differant clutch set ups with this car. I'v only had one failure, and that was the broken hat. Maybe that was a fluke, and will never happen again. I'v never seen or heard of that happening to anyone else.

What bothers me though, is that of all three clutch set ups I'v used, they all have the same hat! I hear from pro builders, racers, and trusted suppliers that the Centerforce is "junk", and the Ram or Spec is a much better/stronger product. Am I the only one that compares them side by side?

And, Erik, your comment worries me a little. I researched clutches for hours, here and in a lot of other places. You're the first one to say the Ram HD chattered a lot. I'm not calling you a lier at all - I totally believe you. Considering all the other "accurate" information I received, I am now suspect about all the good reports I heard about this clutch.

I'll install and break it in exactly according to the directions. If it chatters a lot, it goes out this winter. Maybe I'll keep the new Ram hat and put the Centerforce disc back in.

[Erik W. Treves]

Bob, this was the second HD clutch I bought. IN my other car I never really noticed the chatter. In the Green Lantern I noticed it pretty much from day one. Not sure on the difference. It may have been more of the fact of the change on level of TQ. In 8000 miles I wore through it...It was chattering pretty bad when I pulled it....and the flywheel was all done too....I does hold though...I replaced it with a 3+ spec clutch and that clutch does not chatter at all....and the pedal effort is reduced.... Good luck and absolutely report either way....

[ROADRACER83]

Bob:

It looks like to me that Valeo makes a lot of clutch pressure plate covers for just about everyone. The difference in the hats is in the diaphragm spring to change the clamping force and pedal effort. I think that your original hat was made incorrectly from a bad batch of steel or a bad heat treat. The question is whether they have now gotten their QC better on the later stampings. Also the disks you show for comparison are really apples and oranges. The original disk is an organic lining similar to a production clutch. You can tell by the fibers running through the lining and pucks. Those are great for no chatter and easy linear take up. That's why they use them on production cars for normal steet use.

The Ram lining has metallic pucks and those are more prone to chattering and are not as easy to engage. To engage a metallic lining you need a little different technique. You can't slip them as much so you need to rev it a little more and then engage the clutch more rapidly. Also the center springs in the disk tend to be stiffer and not as forgiving when you engage.

Ron

[niceguy]

After speaking with the tech guy at Fordracingparts.com I installed the ford HD Clutch Kit, he said the difference in clutch kits was ease of pedal pressure and they cost more. here's the number I ordered from Summit FMS-M-7560-A302N. I always had good results with OEM Ford parts. BTW my engine is a 302 turbo dayno at 546 HP at rear wheels with 616 Lb of tork.

[Bob Cowan]

Finally got the clutch out tonight. This is a Weber clutch I bought from Mike forte a loooooong time ago. I used it for a little while, then removed it. It looked to be in good shape, so I hung on to it in case..... well, in case.

Anyway, this is most likely the cause of the vibration.









It did a little bit of damage to the flywheel, but not much, and not on a friction surface. That'll buff out.

I'll drop the flywheel off at the machine shop tomorrow morning. Hopefully, I can work on getting it back together pretty quickly.

[ROADRACER83]

Bob:

That problem is caused by drive straps that are too small for a big inch motor being used in road racing. Under acceleration the drive straps are OK but under de-acceleration the straps are not stiff enough to resist the compression forces and the occasional mis-match of RPM's. HD clutches usually have more or thicker drive straps to prevent that from happening or at least they should. Clutch manufacturers don't get road racing. Back in the day we used to take GM clutches to a local shop and get them to add thicker straps and one more then re-rivet the straps back on. Some GM engineer gave us that tech tip.

Ron

[Bob Cowan]

Yeah, those straps are in tension during acceleration, and compression in deceleration. Road racing with a high compression engine and a medium weight car puts a lot of strain on those straps.

The Weber clutch has 3 straps and a smallish rivet. The centerforce has 4 straps and the same rivet. The Ram also has 4 straps, and bigger rivets.

[Bob Cowan]

Installation was pretty easy. Just like any other clutch.

I put nearly 1,000 street miles on it for break in. Highway, city, and back roads. Most driving was pretty easy and standard stuff. Some of it was a bit "spirited". But no clutch drops or burn outs.

This past week end we went racing at Pikes Peak IR. It's a short track, 1.3 miles and 10 turns. Down shift to third for the infield road course, and upshift to 4th for the oval. About 17 laps per session, 4 sesssions a day, Saturday and Sunday.

The clutch felt good every shift. Solid engagement, no surprises. Hooked up well when I floored it, and no surprises when down shifting. Good solid feel without being harsh or dramatic.

It does chatter a bit when starting in first. I have changed my techinique a little on the street. But it still chatters a bit. It's not terrible, so I guess I can live with it.

Definatly more pedal effort. I broke my left leg a few years ago. Mostly it's OK. But if I abuse it, it lets me know. Today I'm gimping around a bit.

For track use, it's a good clutch. For the street, maybe a little more than is needed.