390 vs 427/8 Clutch

This should be easy. I have a '67 Big Block Mustang and need a fresh clutch. OK, I'm an idiot. *Nothing* about Ford FE series engines is ever simple and direct. A few assumptions and you are down a path of great resistance.

So I go to my usual parts store and pickup a pressure plate and disk for a "390 BB Mustang" .. after all, that's what must be in my 67 GT500, since there was no production 428 Mustang in 1967, and they're both bigblocks, gotta be right.... now my memory is getting fuzzy, this was 12 or so years ago....

Being the careful, anal type, before I install the PP and clutch disk onto the motor, I double check that the disk actually slips over the tranny snout... whoops, it's too small. Wrong disk.... OK, I get the right disk and proceed to install PP and disk and the bellhousing (note to future self: If one part is wrong, maybe the other also is). Anyway, I get it all installed. Here's where it gets ugly.....

Being the self reliant type, I attempt to install the tranny and it doesn't seem to want to slide right in. I enlist the help of my local Mustang expert and together we successfully get the tranny bolted up with some difficulty. With my buddy watching, I step on the clutch pedal hooking everything up. Man, that clutch is stiff.... actually, too stiff... so stiff that I bend the equalizer arm!

OK, something is seriously wrong. Out comes the tranny, out comes the clutch. Now it's a scramble to retreive my original PP and clutch disk in order to compare parts.

Look carefully at the picture above. The clutch on the right is what I was trying to install. The one on the left is my original after being rebuilt. Can you see the difference? Realize that these are both Big Block FE clutches.

Number 1

Compare the fingers:

The 427 pressure plate on the left has shorter fingers with a step in their construction. The 390 PP on the right has longer fingers with a pronounced upward angle. When I installed the tranny with the wrong PP, the front bearing retainer of the tranny barely fit, and when I tried to release the clutch the fingers hit the bearing retainer and I bent the equalizer. 390 Top Loaders DO NOT have a big snout .... they have the same size snout as a smallblock toploader ... shorter, but small.

I also was told that the 427 PP I had was a so-called blow proof version. Rare....

Number 2

Compare the springs in the disk

Notice the size of the springs in the 427 disc on the left compared to the regular size springs on the right. The disc on the right is a stock 428 style. (The first disc I had was a 390 and had the smaller splines for a 390 top loader)
More rare parts.

Moral of the story:
© 2007 Walt Boeninger - all rights reserved