[Dave Kovar]

What do you consider a good clutch and pressure plate for a 480 horse 455 motor.

I had a Center Force Dual Friction assembly.

After about 3,000 miles it gave up. I had about 1.5 inches of pedal and now, no pedal and it seems harder. I have this "I don't care if it ever runs again attitude right now, so I haven't tore it apart yet to see what happened. I am sure that will change. Any suggestions on a clutch and plate and what might of happened??
Dave

[Dave Kovar]

What do you consider a good clutch and pressure plate for a 480 horse 455 motor.

I had a Center Force Dual Friction assembly.

After about 3,000 miles it gave up. I had about 1.5 inches of pedal and now, no pedal and it seems harder. I have this "I don't care if it ever runs again attitude right now, so I haven't tore it apart yet to see what happened. I am sure that will change. Any suggestions on a clutch and plate and what might of happened??
Dave

[Blackcat]

Have you checked your linkage. Has it bent?
What kind of car is it in. 68-72 GTO's have
a problem with the linkage twisting in the middle.

[Dave Kovar]

It is in a 70 TA. Linkage looks fine. I took off inspection plate and there is black clutch dust.
I don't want to put another centerforce in if this is what happens to them.
I thought I bought a good clutch when I bought that one. I have a 3:73 rear end and N50 Mickey Thompson Indy Profiles on back. This should not be enough to ruin a clutch.
Someone mentioned a broken spring?

[PONTIAC DUDE]

What size disc are you running as this has alot to do with grabbing ability. If it's the 10.5 try the Hay's 10.85 assembly as I've run it. Also you will get flex in the z bar, and will need to reinforce it. also get the sprung hub assembly,but with the solid center section or maybe the paddle type. All kinds of possibilities. Later dude. http://sites.netscape.net/pontiacdude428/homepage

[Dave Kovar]

Finally took the clutch out. The clutch disc has two cracks in it. The flywheel has some blue and hair lines cracks on the surface. The pressure plate has metal sort of smudged as if it got hot and moved. I think I lost pedal because the disc is very thin about an eight inch of material on each side. There is some oil inside the bell housing. I don't know where it came from. Does a Muncie have a front seal? or just the drain back hole, and is this hole positioned so it is on the top of the transmission?

I had synthetic oil in engine for a while, but it leaked thru my cork gaskets. My roller rockers sounded like they were going to come apart. I went to regular oil and it seems to work alot better.
The clutch itself is dry. Could oil have gotten on the plates. My leaks a litte, about the size of a fifty cent piece after I have run it for awhile. Why would the disc have two cracks in it. I am running N 50 MTs with a 3:73 gear and 455 app 450 horse. This Center Force dual friction clutch was supposed to be good up to 600 horse. The car has never been to the track either. Just some runs on pavement. Tommorrow I am calling Center Force and getting their oppinion.
Any experiences or help will be appreciated.

[Scott Misus]

That Centerforce thing's a bunch of marketing crap; basically a diaphragm cover with a bunch of silly weights. You may also have a leaking rear main seal, like 95% of the street-driven Pontiacs out there.

Call McLeod; their technical staff is top drawer.

My information is a couple of years old, but you may wish to consider this baseline:

Try a Long style pressure plate from McLeod with a base pressure of 2000 lbs. from fully out(may require an adjustable fork pivot, if you run a Lakewood shield). Each turn equals 175 lbs. Order the pressure plate measured "precompressed", since it will lose 200 lbs. after the initial compression. Make sure they measure it AFTER they compress it once. Order the plate with McLeod's optional Gold Billet fingers. Use a Hayes 11" Kevlar disc with a sprung hub and with a marcel. I seem to recall that the old Kevlar facing was an 89-09 material. The new style material was part number 49220 with a 535 suffix. Deal directly with the clutch manufacturers, instead of an intermediary clown like Slummit Racing; You'll be much happier.


------------------
"Hi, Honey!" --

Overheard between Gach and Jillian in the Classical Pontiac chat room; 1998.


[This message has been edited by Scott Misus (edited 06-26-2000).]

[Tom McQueen]

Scott is right. Call McLeod direct. If you can afford it, go for the street twin. Its unlikely you will need another clutch.

[PONTIAC DUDE]

Scott's useful posts=1 Scott's unuseful posts=365.

[Scott Misus]

"unuseful" = "useless", Gach Jr.

------------------
"Hi, Honey!" --

Overheard between Gach and Jillian in the Classical Pontiac chat room; 1998.

[Dave Kovar]

I talked to the people who make Centerforce clutches. The tech said I need an elevan inch clutch behind a 455. And that Pontiac made a flywheel to accept that clutch. Has anyone heard of this. The tech said the 10.5 inch is two small for that much torque.

Any comments on that statement?

[Blackcat]

Dave,
Pontiac had an 11 inch clutch behind 73up 455's and some 400's I could be wrong on the starting date. Nearly all had a small crank hole. Early had the large opening. Your clutch more than likely went up because of oil on the clutch (been there done that). I wasted a new clutch in one day once oil got on it. It will burn up and blue the flywheel. Synthetic oil really does it quicker due to it being a better lube.

[KEV]

Hey Dave! I agree with Blackcat. I too burned up a 10.5. I think a it had a bit to do with me getting some oil on it as well as hitting it hard with my slicks.

I went with an 11" clutch in mine. I have a '66 GTO and when I did this I also installed an aluminum flywheel (has both bolt patterns for 10.5 and 11) Everything worked like a charm. If you look at the centerforce web page they list applications and the size of clutch. If I remember correctly the part number is the same for a few hi-po chevy applications. You may be able to back into your part number that way. If you want to know the part #s I used let me know and I will dig them up for you.

My clutch works great at the moment and I am very happy. Will this solve your problem? I don't know. As we all know the '55s are hard on things. You may want to persue Scott's post and go with a bit more than what you think you might need (so your not doing this project again).

Just my .02

Good Luck,
Kev

------------------
Kevin Swaney
Gold '66 GTO, 389 4 spd with Trips
13.042 @ 106.64 mph

[Scott Misus]

From my best recollection, ALL 3.25" main journal motors received an 11" clutch from the factory. I've taken apart a '69 428 SJ Gran Prix and I owned an oddball '69 Catalina with a 428 and a three on the tree. They BOTH had 11" clutches.

[Old Man Taylor]

I have run both the 11" Center Force Dual Friction clutch, and McLeod's diaphragm clutch (single disc) with success. I will never use another three finger type clutch in my car due to some old bad experiences. My car is not a 455, but it is a nitrous assisted 428 that makes well over 600 HP. With this type of engine I think you should be running an aftermarket flywheel anyway. I just bought a 30 lb steel wheel that I had turned down to 20 lbs to replace the 15 pound aluminum wheel I was using. I loved the aluminum one but I need a little more inertia for rolling starts on the street. E-mail me if you want details or have questions about flywheel applications. PS - I am not in the business, and I do not sell anything.

------------------
Jim

['ol Pinion head]

Confirming what Gach Jr said ???, the '70-76 455 M/T cars, 428's, & 400 Big cars from '67 through 71 or so with HD clutch option, all came with 11" clutch & bigger flywheel. I believe Scott is to be commended...Two useful posts in the same topic, much less on the same Bulletin board, in the same year... Too much for me to take.

[77TA]

I have a RAm 11 inch diaphram behind my 455 and it seems to be a great clutch so far smooth never chatters and locks solid. cost about 125 from summit with bearing and alignment tools may not be the best for a heavy race car but seems fine on the street.