72 Big Block Auto to 4 Speed

[My72BB]

I posted this question in the drivetrain section above and didnt get to far so I am trying here...Need some help please.

I did a search for this and all I could really find was 6 cyl to V8 Small Block Swaps. I am compiling parts for the swap...here is what I have.

V8 Manual Crossmember
Pedals
Straight push rod from pedal to Bell Crank
Ball pivot on block
Long and short bell cranks with straight ends
Bell crank pivot w/slight bend in middle
High Hump 4 speed cover

Need:

Shift Boot with Ring (angled in front)
Clarification on Clutch Linkage

Here's my questions...

1. I have 6 cyl + Small block Linkage setups. It looks like there is a straight rod from pedal to bellcrank for 6 cyl and some V8 motors??? It also looks like there is a bent rod for other V8 applications? Which one is required for the big block?

2. What pivot ball do I need on the block...There is just the screw in ball (which I have) and the ball mounted to a plate that bolts to to bolt holes in block? Any idea on which one would be required...

3. Will the factory Big Block motormount perches stay in same location?

4. It looks like the exhaust might be a little tricky due to Tranny Crossmember on right side (Stock Manifolds)?

If anybody has done this or has some information that would be really great.

Thanks, Alan

[Classic Heartbeat]

I have done this swap, but it was a long time ago. I do know that you will need a Big Block, bell housing crossmember and clutch belcrank frame bracket. It is different than the one for the small block. WES

[My72BB]

Thanks...I guess we are the only two to ever do this...???

[russellmarling]

I have done it. 6 cylinder and small block bell cranks will not bolt on, however, they make a good basis to fabricate from. Original big block bell cranks and linkages are all but nonexistent. I looked for one for months, and finally decided to make one out of a small block one. You will need to section it in the middle and drill for a new zerk fitting or work around the original one, you can't just lop off an end because of the area that is machined for the ball on each end. You need to use the small block style linkage that goes from the pedal to the bell crank. You will have to make a new arm for the top side of the bell crank to meet up with the linkage that goes to the pedal. You will also have to make a plate that will mount the ball to the block. I mounted mine in the two bolt holes above the oil filter, being sure that the bell crank would be level before mounting the ball. You can use the factory bracket on the frame without any modification. A high hump is not necessary if you have the engine mounted in the V8 position with the correct mounts, and you are using a Muncie 4spd or something similar. This setup looks and operates like factory.

New bell crank and bracket


Small block bell crank for comparison


You can kinda see the small block linkage that goes to the pedal in this one- it provides plenty of clearance.
If you have any questions I will be glad to help. -Russ

[Tom Vogel]

These are some pics of my factory (NOS) z-bar. The first two show how it sets between the frame and the engine. (Sorry about the auto steering column [yes I know its the wrong one, the 4 spd column is still in the box]) I know this is in the way, but I needed to be able to steer the carcass and these were the only pictures I took at this point.
The third picture shows the linkage coming through the proper hole in the firewall. Its not hooked up to the clutch linkage yet, as you can see, but this is how it should sit.
Hope these help. Tom

[fast_dev]

i have done this twice with no special parts and very little fabrication. the first time i did it i didn't have the correct ball for the big block so i modified one from a small block by grinding off the weld on the back and relocating the ball in the plate, second time i had the correct ball. i used the rod from the pedal from a 6 cylinder truck, only had to take a little off the back to miss the hooker super comp headers. i did have to trim a little off the engine side of the bellcrank to make that work and i think i had to bend the bracket that hooks to the rod from the clutch pedal (its been a while, lol) the engine is on big block mounts with the original bell housing mount moved forward (holes are in the frame already). i used a muncie 4 speed from a car. search my posts there is more info on the swap. Devin.

[notchbackgta]

Originally Posted by russellmarling

I know this is old, but I'm hoping that you're still around. I am attempting to do what you did here by sectioning your bellcrank. I attempted to cut it with my band saw, but it appears to be hardened. The blade on the saw just scratched it, barely and my file didnt want to do anything at all.

How did you cut yours?

James

[russellmarling]

If I recall, I just cut it with a small cutoff wheel on my air grinder, then tig welded it together. I'll be glad to help if you want any measurements or pictures or anything.

[Green Machine]

I assume you are using a truck 4 speed since you mentioned a high hump cover. Just double check the bearing retainer hole size on the bell and the tranny, most cars were 4 11/16, starting in 68, the trucks went to 5 1/8, just make sure they match.

[My72BB]

Thanks to everybody...Now the work begins!

I am using a 72 4 truck 4 speed from a 3/4 ton GMC so high hump for sure...Sounds like a little modification time...

T400 is great tranny but I like the idea of rowing the gears...Kinda wish GM had the same thing in mind back in 72...Seems like original parts are going to be tuff due to lack of quantity when new.

Thanks again, Alan

['72_GMC]

Looking at the photos Tom posted, it looks like the bolt hole forward and low below the z-Bar on the block lines up with an Oil port plug, can somebody tell me how the original was secured there? From those photos of Tom's, it almost looks like that hole was just set over the oil port plug allowing that plug to be a "pin in a hole" Seems like it would be good to have a bolt there? Is that part simply set over the plug????

[notchbackgta]

I din't think about using the cutoff wheel. I'll try that, thanks!