The Stovebolt Site Forums The Shop Area Driveline 41 truck master cylinder conversion

I am wanting to upgrade to a dual master cylinder for my 1941 ak truck. Anybody's have thoughts on using the corvette (1967-1977) style master cylinder. I have original front brakes but I have swapped the rear end to Chevy S10. Thanks

Hi 41fan.

I have that master cylinder on my '47 Art Deco truck and it works fine. This is not a straight forward swap. Let me know which model AK you have and I can help you make it happen.

Steve

Steve, I am working on my 41 1/2 ton pickup. I plan on running new lines to the front and back. Question of sizes of new lines (1/4 or 3/16) and building mounts for the master cylinder.

Need to compare volume of new MC to old, if larger bore, less powerful brakes, smaller bore, more powerful.

Ed

My suggestion is to first determine what you will be using your truck for - and be sure of that.

For example, I have a Vette front suspension on my 57 1/2 ton with the dual piston calipers and matching master cylinder. It's just fine since I basically use it as a car - meaning I don't haul anything of weight with it. And I wouldn't.

I am still building my 41 3/4 ton (5 yrs. now - I'm slow) and I am building it for weight. Consequently, I installed a brake system equal to a 3/4 or 1 ton truck. Take care in designing your brake system - nothing more important. Bore of master cylinder, brake lines, wheel cylinders all need to match. If the bore of your master cylinder is not large enough for your wheel cylinders, you will not be supplying enough fluid to activate the brakes properly - even if you have adjusted properly. So you end up hitting the brake pedal twice- - - - not what you want!

Thanks, it definitely won't see any heavy loads. I have a 235 engine in it with a s10 T5 transmission. The original mc was 1 inch as is the one I am looking at

If you kept the original bellhousing from the truck, you have the same setup I have so here is what I did. As you have probably found, no one sells a dual master or disc brake setup for the AK series trucks. I purchased the disc brake kit and dual master cylinder kit from Performance Online for a 1947 Advanced Design truck and used them on mine. The front axle is the same on both so the disc brake pieces went on following the instructions that came with the kit. I also upgraded to the roller bearing style wheel bearings at the same time. Using the original 16" wheels from the truck I needed the wheel spacer and had to grind about 1/16" off the high spot on the calipers for clearance.

On to the master cylinder which was a bit trickier. The dual circuit master is quite a bit wider than the original as is the T5 trans and the two are now competing for the same space if your using the original pedal set from your truck. I have read on this forum of others making brackets to move the master straight back to where there is clearance and extending the pushrod from the original pedals back to the new location. I recall one forum member using a Ford master which was smaller than the corvette style but don't know which one he used. I discovered all that after my alternative setup was well under way. My solution was to use the pedal set and brake linkage from a 1 1/2 ton AK series truck. On those trucks the pedals mount only to the bell housing and the master is mounted to the frame. A pushrod from the brake pedal travels rearward to a pivot assembly which reverses direction and pushes forward to the master cylinder. The Advanced Design trucks use a frame mounted master so everything I needed was in that kit. I had to disassemble the unit to reverse the direction of the master to match the linkage setup but that was simple. Drill a few holes and adjust some pushrods and your done. The hardest part was moving everything around to find the optimal position for the pivot and such. Those large deep throat vise grip clamps came in very handy for that task.