[thirtypointer]

I am looking for advice to make what I have work better. I know there are other options for transmissions, etc. I have a iron headed stout 455 paired currently with a Muncie M20. Currently there is a Ram Powergrip clutch in it. The rear has 3.55 gears. I race it a bit nothing seriously, 1/4s and "street" drags at local tracks. I am on my third clutch and last week a rebuilt Muncie M20 broke (cluster gear not racing when it happened). That transmission maybe had 5k on it. The stock flywheel was resurfaced for the two clutch installations I did. Yesterday during some track time, the new clutch (25 miles on it tops) slipped some during two races in 1st gear. It seemed to stop slipping after a break and a couple more runs. Is there any thing rear gear you would suggest that may take pressure off the tranny and clutch?

[XLR8STEVE]

I burnt up a couple clutches also. They were supposedly rated at 600lbft. Changed to the Mcleod RXT rated at 1200.
TKO 600 trans with 2.87 first gear 4.10 rear and 29 inch tall tires launches pretty good. When I had a 3.73 rear it was bogging a little.

I found this forum with all manual shift guys. Lots of info on suspension, clutches, etc.

http://umtrnorth.com/community/suspension-tech/paged/3/

This year i am trying out a clutch tamer. Its an underdash clutch slipper. Supposed to be easier on parts and help you to be able to let er rip at 5000 rpm.

[Skip Fix]

Swap the Nash 5 speed in! A 455 , even a 428 and a stock Muncie or ST-10 are hard to coexist. You can use a centrifugal assist Long style clutch that hits softer then grabs, an aluminum flywheel also to cushion the hit.

There is a company that makes stouter Muncies with some heavier duty pieces.

[unruhjonny]

My only thought is this;
Are you confident that the clutch isn't hanging up?
I have heard of similar issues when the presure plate tension isn't right.

Do you have the 10.4" or 11" clutch?

For all the naysayers against a centerforce dual friction, I found it to be a great clutch, with not too much more pedal pressure than the SR clutch it replaced.

[JLMounce]

One thing that sticks out to me is that you were apparently racing on a clutch with about 25 miles on it?

Are you following the clutch manufacturer's recommend break-in procedure? If not, this could be part of the issue related to going through clutches.

In regards to the transmission, with the m20's 2.56 first and your 3.55 rear, depending on your tire size, your starting line multiplication is either below or just right at the recommended 9-11:1 ratio. Add a car that likely weighs 4200 lbs race weight, and it's also not a huge surprise you're going through clutches.

I'm with XLFR8STEVE on this one. I'd be looking at a TKO600 or new TKX with the 2.87 1st and at least a 3.73 in the back. The trans should live better and you should keep clutches in it for longer.

[thirtypointer]

Originally Posted by unruhjonny

My only thought is this;
Are you confident that the clutch isn't hanging up?
I have heard of similar issues when the presure plate tension isn't right.

Do you have the 10.4" or 11" clutch?

For all the naysayers against a centerforce dual friction, I found it to be a great clutch, with not too much more pedal pressure than the SR clutch it replaced.

It is a 10.4 clutch. Not sure on the hanging up idea. I checked the free play when the clutch was installed.


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[Tom Vaught]

Probably 95% of your clutch issues was caused by not glass beading the clutch disc surface after you installed it initially when you had the transmission failure.

New clutch discs (I have posted this many times) have a resin that bonds the clutch material together during manufacture.
You install the clutch, drive it a bit, and the resin gets hot and excess resin gets on the clutch surfaces between the flywheel and the pressure plate. Then you have clutch slippage under high load starts. So you remove the clutch parts and install a new disc with fresh resin, just like the last time. Same issue again doen the road.

The correct way to do it is to remove the clutch disc and pressure plate, lightly sand the flywheel and the pressure plate to remove the resin on their surfaces, and then GLASS BEAD THE CLUTCH DISC ON BOTH SIDES. Reinstall the disc and the excess resin has already boiled off and the clutch disc, pressure plate, and flywheel works great for 1,000s of miles after that with no issues or slippage.

Lots of people replace parts like pressure plates and clutch discs vs actually fixing the problem: The excess resin smeared on the disc surface causing slippage.

Tom V.

[HWYSTR455]

Ok, so there's 'free play' adjustment, and 'air gap' adjustment, both need to be correct.

First make sure you have the right fork angle. The pad the pushrod goes into, when at rest, should be roughly a 90 degree angle to the drivetrain centerline. If it's not, you eight have the wrong throw out bearing, or the wrong fork ball.

Once that's right, check air gap. If there's not enough air gap, the clutch may not disengage all the way. With the pedal fully depressed, you stick a feeler gauge in between the disc and the flywheel and measure the gap. It should be at least what the manufacturer recommends for the clutch. A common value of .050 is sometimes used, and works with many clutches.

Free play is the clearance for the linkage, which is needed since most pressure plates' fingers 'grow' as RPM increases. If there's not enough free play, the clutch will not disengage all the way and can slip. A common value of @ .150 for a single disc, and .200 for a double disc is sometime used, and works in many cases. Lightly apply a little pressure by hand to the fork while under the car, to just take up the slack in the linkage. Then adjust the pushrod until you have about .150 gap between the rod and the fork.

If it's adjusted right, and it still slips, it could be the disc and/or flywheel is contaminated, and the surfaces are 'fouled'. Always treat a disc/flywheel like you do brakes, both surfaces must be kept clean during assembly, and you can use brake cleaner to ensure so.

If you have it all installed & adjusted right, and it still slips, in most cases the setup is being overpowered, and you need to upgrade.

As for the trans, and making it live, that's all controlled by the amount of power you're making and driving technique. Period. If you're destroying transmissions, either lower the power, or upgrade the trans. (there's no free lunches)

455s can make 450-500+ ftlbs of tq, munchies and ST10s won't live long behind them, and even 'beefed' ones are only adding a little time.

As an example, the last iron head 455 I had, a PROPERLY built M21 would last 15-20k miles before it either failed or started acting up bad. Super cases help, but the weak links are still main shafts and bearing supports.

.