The Stovebolt Site Forums The Shop Area The HiPo Shop Power Drum conversion Update/question

Alright folks, so far everything is installed and working alright. Thanks to everyone for the advice on what to get/install with the kit and where. As far as the performance, it's alright and not great. I have ALOT of pedal travel before you feel the brakes taking effect. Then BOOM! they are rock hard.(Already locked'em up going around the block in a test run.) It there something I have missed or did not adjust correctly for this? The pedal travels over 60% and then you start to brake. Would this be a push-rod adjustment issue? Any help would be great! Thanks!

I'm sure Ill be corrected... I believe I read here somewhere that if the shoes are too loose, they have too far to travel and then the self-energizing aspect grabs them and locks up the wheel. Make sure the shoes are adjusted properly and they will energize gradually.

I pretty sure they are adjusted properly because I was just driving it before the conversion and it was stopping fine. The only that has changed it the Duel MC and booster. I do have a residual check valve in both lines. One for the front and one for the rear. Does it matter which outlet on the MC is plumbed to the front/back on a Drum/Drum set up?

I think that depends on the MC and its original use. Another comment I've read here applies to the push-rod from the booster to the MC. IIRC, there are different lengths depending on whether or not thee is a booster. If the rod is too short, the booster may not activate the MC until the pedal is way down. Then it locks up because it is boosted and now you are panicking a little just as the MC is finally getting some push.

I'm really just guessing here, others may have better answers.

Yes, the rod between the MC and booster needs to be adjusted correctly. As to if yours is correct or not, I can't tell from here. There are past posts here that tell you all of that. There is also a ratio of pedal travel to distance the rod to the M/C moves and this might be you problem. This ratio is often overlooked, or the travel is "lived with" as it's a pain to change. Also, one piston in the M/C moves before the other and it goes to the rear. You need to know the details of how your M/C was used when it was OEM. Otherwise, you have to bench test it.

This is the kit I installed:
Duel M/C and Power Booster

So on all duel MC's you need to plumb the outlet closet to the booster to the rear brakes?

Also, if I need to adjust the rods where can I find the info to do that? I'm gonna go ahead and start searching for that. Thanks for the help guys!

Apache, your M/C looks like an early Corvette unit similar to the one I got. Check here.
If so,the port furthest from the booster end is for the front circuit,this ensures the front brakes are activated slightly before the rears.

Uh, Jockbolter50. I think you mixed it up. The rears are suppose to engage first to keep the front end from diving. I think you are correct on the other thing. The circuit nearest the booster is usually the rear, but I've seen it the other way round. The 'vette is a common upgrade for streetrods and I believe the circuit nearest the booster is for the rear.

UPDATE: I found out how to measure and adjust my booster rod. After measuring everything I was already in spec, so that isn't the problem. I also switched the lines running out of the MC so they are for the correct port/front or rear of the vehicle. I have a drum/drum setup so my master cylinder looks like MC11505M in the link that Jock posted.

My last ideas can only go to alot of air is still in the lines, or my residual check valves are installed backwards. They both have a little arrow etched into them. I figured they needed to point in the direction of flow away from the MC, so they are plumbed to point away. Was I correct in my assumption? Of course we all know what assuming does right? haha.

99% of the dual circuit master cylinder I've seen are the other way around, booster end feeds the front brakes, opposite end feeds the rear. Most of these were disk/drum or disk/disk sytems.

It's a good idea to recheck everything for sure. Have you figured your brake pedal ratio yet? If not, just google it and you will find out how, if you need to. The only other thing is, and I don't think this is it. The larger the piston the less hydraulic pressure is built for a given amount of "foot" pessure on the pedal vs. a smaller piston. Drum/drum use to run the smaller piston (7/8"). Call your vendor and ask if necessary.

If that's the case,I stand corrected.

I would imagine the rears activating first on something with a back end as light as an empty pick up would be a bad thing,especially in a panic brake situation in the wet?(comments?)

Brake engagement is first front then back. anti-diving is handled by the geometry of the suspension.

It does sound like a stuck proportioning valve

Mmmm? Do I have my wires crossed? Let me check this out and start another thread as this is off subject and guys need to know this.

Haven't been able to get back to this since Tuesday. School is giving me hell right now. I'm going to go through everything one more time and if that doesn't cut it I will contact the people I bought it from. I will post the result here for future reference.

Apache i got that same kit and the larger resivor, the one further away from the booster, is for the front brakes. the one closest to the booster is for the rear brakes. Make sure you have the lines ran from the MC to the right ports on the proportioning valve. The prop. valve is supposed to activate the rears before the front brakes and if you have this crossed than i imagine it could cause some problems.

I had the same problem on my set up. It's a Mustang m/c & booster with front & trar drums.
I found that on the lower brake pedal arm that goes back to the m/c, the length needs to be extended so that the hole where the rod to the m/c mounts is 1" below the original hole. That improves the leverage & shortens the pedal travel.
If you have a fax, I could send you a copy of the diagram I found.

I think you hit the nail on the head Nvrdone! I have one part left out that bolts to the original hole and extends for another hole an inch lower and forward. I left it out because of how the directions read made me think it was for a older Chevy truck.

The piece will not fit as described but I believe I can modifiy it with no problems. Thanks for the help and info. I will try to take some more pics and reorganize my album so other can see.

Thanks Scott,that was my understanding.
I imagine this is very important,seeing as we're talking brakes here!

Well I am on the road and having to get used to my new POWER brakes! The extension piece made all the difference in the world! One inch made a huge difference. I understand why now after reading about pedal ratio. Thank you all for the great amounts of help and advice. I am going to try and get some pics up and organized soon.