"Shorter" 80 master and booster install in 40

[bikersmurf]

New 40 boosters aren't available anymore. So I found a booster from a diesel 80 series to replace my tired one. Little did I know how tired my 25 year old 40 master had got.


Length of 80 master.



Length of 80 master/booster from firewall.



Brakelines needed to moved a bit so they don't get pinched. It does clear the ebrake cable (despite the way it looks in this picture).




Booster clears the Clutch Master... Only by 1/8".
It'll need to be loosened off to remove the clutch master cylinder (but I've rebuilt it twice now while it was still in the truck).






I first installed the 80 booster with the 40 Master cylinder. It required some adjustment, but it was a direct bolt on. The booster needs an external inline check valve, the input to be shortened, and to be rotated 180 degrees (upside down).

Next I installed the 80 master. Wow! Do the brakes ever work. I can bring the truck to a screeching halt (on dry pavement) by pressing the brake pedal with one finger.

I next realized this could be the solution for carb interference with the master cylinder on 2F conversions on earily 40s which have an added vacuum booster. Be aware that 80s came with four wheel disc brakes... So you may need to add residual valves to make them work right with drums... Or just convert to 4 discs and say goodbye to adjusting brakes.

 

[grant5127]

The master cyl is ok, but a 60 series booster works much better.. even more so if a 1/2" spacer is added between the booster and firewall... a spacer also removes the worry of the rod connection being too long to the pedal...

 

[bikersmurf]

Why/how does a 60 booster work better?

The 80 booster has tons of power! It makes it effortless to stop the truck, and 80 series are much newer... & easier to find used parts for. 60s around here seem to need new boosters.

A 1/2" spacer would be perfect... But I've not made/found one. The studs are plenty long to work with one. I found I was able to make the rod the same length as a 40 one by removing the nut and screwing the yoke till it bottomed out on the shoulder of the rod.




Here is a photo showing the potential clearance issue. (shamelessly stolen from the web)

 

[Biscuit]

Nice write up. I may go this route after finding my booster is the current source of my vacuum leak. Improving the brakes is on the upgrade list.

 

[bikersmurf]

I've read on mud that others have also used: mini truck, 4runner, and 60 series boosters. They all seem to work. Some need an inline check valve... I used an "ATE" one that was OEM on an earlier Volkswagen van.

The brakes are almost over boosted... If there can be such a thing. I feel confident that they'll be able to stop the 40 with a 4000 lb trailer behind it again (with or without trailer brakes).

 

[bikersmurf]

Nice write up. I may go this route after finding my booster is the current source of my vacuum leak. Improving the brakes is on the upgrade list.

Let's see some pics of your install... Of any non stock booster for that matter. Trying to grow the wealth of knowledge, and keep more 40s safe and on the road/trail.

 

[cruiserjunktion]

I used a mini truck booster/60 master on an adapter from jto, when adding 60 series front brakes.

 

[bikersmurf]

Cool, thanks for sharing.
How much space is there between your booster and carb? Which carb?

I've seen some 2F carbs interfere with the booster. My 2 barrel 1.5F carb would've cleared.

 

[cruiserjunktion]

It sits next to the weber/ stock air cleaner, w/o any clearance issues.

Sorry I don't have any pictures with the air cleaner off.

 

[bikersmurf]

No worries
The 60 master looks very similar to the 80 one. It looks like a 40 one wouldn't clear the air cleaner housing.

 

[Trollhole]

I use 4runner boosters for everything I replace in the shop when the customer wants the most economical.