the ZF 5 that bolts behind the 300 are they all internal slave cylinder or do they make an external slave cylinder model for a two wheel drive?

 

All small block ZF5's had the internal slave, as did the lighter M5OD.

 

If installed in older trucks with a lever action clutch, what size (diameter) clutch master cylinder would be correct? Thanks, ...jack

 

I'm not sure on the exact size of the master, but I do remember that it was cheaper and would've been more convenient if I would've gotten the master, slave, line kit, especially since it comes pre-bled. I went with the 87-91 master because it has a hole in the pushrod kinda like a heim joint, so it made fabbing the 77 f250 pedal to the master easier. Anyway, getting the !faster, slave, line kit will eliminate the guess work on which master it the right one.

 

Do you have any pics of how you fabed it in your 77 f250

 

Sorry, I just saw this today. Here's a few quick pics, but they should give you an idea of how I did my zf, whether I did it right or wrong.

Here's the trans tunnel. It was probably the hardest part of the job. It took cutting roughly a few inches off the front 1/3rd of the tunnel, then patched in more material on the cover to fill the gap. I also welded in the top of an 88 f250's cover to add a few more inches of height. The ZF is much bigger than a np435. There's a few tabs on the zf that I had to trim up to help skinny up the zf so I didn't have to do more modifying of the trans tunnel.


Swapping to a hydraulic clutch was the next hardest part. The black plate is 1/4", and not nearly enough support for the firewall. It flexes when the clutch is pushed, so I'll be adding a support form the firewall to the dash, plus tieing into the brake booster support.


I don't remember what size to use for the hole, but I do remember not to insert the pushrod into the master cylinder until you fabricate a bracket to the clutch pedal. I used a peice of 3/8" steel bent up to clear the brake pedal and get proper alignment to the master, then welded on the right end of the 88 f250's pedal assembly to the 3/8" steel. I bolted it together first, but even with a 1/2" bolt torqued down, it wasn't enough to keep it from moving, so I welded it up.


The clutch hose runs right behind the oil filter, and doesn't touch anything master to slave. I still want to fab up a couple of supports just to keep it from waving in the wind.


The trans cross member had to be slid 2"-3" back, and only an inch of the crossmember sits on the old frame mounts. I know a really good fabricator, who happens to be my step-dad-inlaw, and he made some new mounts that work in conjucntion with the old mounts. I chose to bolt them in place instead of risking messing up the frame by welding them in. I'm sure it'd be fine, but I've never welded on a frame, and didn't want to screwing it up. My truck is a 250 2x4, and the stock crossmember works fine. It will make a little more noise than a zf specific crossmember because the zf crossmember comes with a vibration damper. It sounds like you 4x4 guys will need to fab up a x-member, or get one from a donor truck.


Here's a lousy pic of the crossmember. I did have to get 2.5" taken off the drive shaft.


I did almost all of the work myself, but a few helpers along the way proved really handy. Here's one of mine!

 

What kind or rpm, power, and mpg difference do you get now

 

Its hard to say because the valvetrain and carb were shot when I bought the truck. I do know that it was pushing it going 60 mph with the 4 speed and 4.11's, while getting 8-11mpg. It still has the 4.11's, but it'll do 70 with the zf. When I get the street demon dialed in, I'll post mpg's.

 

The 625 street demon?
Man I was just about to buy one...but then I ended up trading my 450 economaster for a 600 Holley!