Technical Early gm dual master cylinder questions

Hey all, quick question regarding the early gm truck dual clutch and brake master cylinder. As I’m sure you guys who have used them before know, the clutch and brake bore are swapped on the ansen pedals so the clutch is the brakes and the brakes are the clutch. Causes a very stiff clutch pedal and very easy brake pedal. Is there a solution to this? Like sleeving the clutch bore down? Or is there a different version of the master I should use. Thanks in advance

 

Looks like the AC Delco below is what you need and not the Raybestos for larger trucks.

 

The bore for the clutch is too big - both bores are the same size.....the solution is either to 1) get the international version of this master that has a smaller bore (same bolt pattern and appearance) 2) have this one sleeved down on the clutch side 3) get a slave cylinder with a larger bore to match the existing master or 4) some combination of the above

 

I've had my local machine shop sleeve several of the clutch side of the above MC. I've done both 3/4 and 7/8th depending on the slave I am using. The brake side seems to work fine as is as. The brakes used with this MC have always been Bohling Bros Lincoln's. For the re sleeve I use a Willwood rebuild kit.

 

1/2 ton version is 1 1/8.
I’m using that to push a 1 inch bore slave cyl.
Works great

 

I used one of those back in '62. My left leg used to quiver as I was stopped at an intersection. Completely f'd up my knee and some years later I had arthroscopic surgery to rebuild the knee cartilage. I was young and foolish and thought that was the way it was supposed to be.
Warren

 

Many years driving tractors , kicking the old Harley’s to life made me wonder if it caused my knee issues . Getting old is a scary thing , wondering what did I do to cause this pain today .

 

A 1/2 ton pickup slave cylinder has always worked good for us.

 

I'm using that on my car with the Bolling brothers Lincoln brakes and Buick drums on rear. Works great. Also using the stock gm clutch slave cylinder. The clutch is no harder to push than my stock Corvette.

 

The issue I’m having is no so much with the clutch but the brake. The pedal is extremely squishy and barely stops the car. All wheels are adjusted properly and I’m still having trouble. I’m thinking I need a larger bore on the brake side. And the clutch side could use a smaller bore as well but I can live with how stiff it currently is

 

If pedal is squishy but no air trapped anywhere and you are still not able to brake properly, its time to check the brakes. If you use a larger bore MC, the squish effect might be gone but the brakes will work even less.

 

As you are probably aware, in the original truck application Chevy had a Z bar arrangement under the dash that switched the positions and had some mechanical advantage. The Ansen setup has been used for a long time and typically has no issues related to pedal effort. That said, there are numerous variations of the original being made today. The issue has been the clutch side when not using the original truck slave and using an aftermarket slave or HTO and you need to sleeve the clutch side to match. The brake side usually works with most drum / drum brake setups. What brakes are you using?

 

Is there some basic math or some general rules of thumb here that would simplify matching up calipers, wheel cylinders and clutch slave cylinders with appropriate brake and clutch master cylinders? There seems to be more than a little mixing and matching, experimenting and guessing going on with some of these brake and clutch upgrades.

It just seems possible to me that there might be a better method for ***embling a brake or clutch conversion package without as much guess work, expense, disappointment and ac***ulating piles of brake parts that won't work properly for a one off combination. Maybe there's just too many other variables to really simplify the process.

 

https://www.joesracing.com/master-cylinder-math/