Getting Ready for M50, another booster question!

[isolatos]

I have searched a ton and have confuse myself. I have an E20 booster and need to mod the shaft for my swap. If I cut the E30 shaft and weld it to the E21 booster how much of each do I cut off??What does the total length need to be? And what diameter needs to be where?
Thanks

[justin_l_]

I don't know what an e20 is...

[87e30]

e21 booster.

Basically, you have a clevis that threads on to the booster. The booster is mounted on the firewall and has a shaft which comes through the fire wall and attaches to the brake pedal assembly. The way it does this is the U shaped clevis, which attaches to the pedal assemply and threads onto the booster shaft.

Essentially the e21 booster shaft is too long, and needs to be shortened while retaining the threading for the clevis on the end.

You can:
- cut the shaft then weld the threaded tip back on shorter

- cut the shaft the right length then use a die to add threads onto the end. The problem being that the shaft is too large in diameter, so you can use series of dies and make it smaller and smeller everytime you add threads until it is the right size to fit the clevis. (Not sure what sizes to use, search on e30rob or PM him because this is what he did)

-Lastly, this is what I came up with. I cut the shaft down to the right length by comparing directly with the e30 booster shaft. I used a 7/16th's tap and die. I was able to bring the shaft down to this size, and tap the clevis to enlarge it slightly. (though you want to be careful because the clevis doesn't have very much extra material to enlarge the hole) I ended up with a 7/16th shaft and a 7/16th clevis. Works great for me.

For using the e21 booster these are the only methods I'm aware of. You can always be creative, I talked to a machine shop to figure out the method I ended up using.

[Artful Dodger]

I used the porsche 944 booster. the shaft had to be shortened and re-threaded. once you cut the shaft the outside diameter is too large for the proper die. I chucked the booster in a lathe via clamping the shaft in the chuck. I turned the whole assembly slowly and used a file to narrow the diameter of the shaft to the correct size. then I used the proper die to cut new threads. This worked great and only took about 15 min to complete. this way you do not have to worry about the heat from welding damaging the diaphragm.

[isolatos]

sorry, E21

[isolatos]

Awesome. It sounds like the 7/16th would be the easiest for me. Thanks guys. I am sure I'll have more questions. I am taking pics also. Took the dash out today, I have one thats in a lot better shape. The po was a real pig!!

[5KWattson]

7/16th???? why not just use the correct metric die, i believe it was M10x1.5 and for mine i used a e21 booster cut the shaft and ground it down to approximate size(leaving it a lil large) once i got the die started it thinned off the excess that was left large...its rather simple if you have the right tools...chop saw or grinder with cutting blade, die set(metric) and bench grinder or lathe.

[Spaz]

Just use the 944 booster, right shaft size, just extend the threads down the shaft and shorten the shaft. No messing around and a perfect fit.

-Cam

[Adrian_Visser]

you have first hand experience with this spaz? How is it for clearance against the intake?

I am tryin to decide on which booster to use right now, if the 944 is so easy I'll use that then.

[Spaz]

Yeah 944 booster is on my car right now, no shims either just shaved intake fins.

-Cam

[xwill112x]

why dont you just trim the intake mani like 1/4 of a inch?

[gearheadE30]

I've heard the E32 735i booster is also a good fit with th right shaft, but I have no experience with that one. It would be a bit easier to find than a 944 booster though, I would think.

[Adrian_Visser]

yeah e32 and ix are the same booster afaik

[gearheadE30]

Yeah, they are. Same size as the M34 M5 booster as well, iirc.