master cyl and prop valve drum vs disk - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Custom 68 · 04-09-2003, 10:48 AM

Hey all I believe I saw some recent reference on this but wanted to clearify. I recently swapped to disk on my 68 front. I had the power drum drum setup. I didnt change the master cylinder or prop valve. I have only driven a few miles and boy it sure stops great. the truck is apart now for a resto.
Do I need to swap these last items out? It all works very well but I didnt know. I thought I saw a coment regarding a check valve on the master cyl that keeps slight pressure on the drums to over come the springs and this is not on the cyl for the disk fronts. Any help.
Thanks
Dave

Stout72 · 04-09-2003, 11:45 AM

There was a post on this just a few days ago. You are correct, there is a check valve in a drum/disc master cylinder that keeps some pressure in the rear system that helps overcome the brake shoe spring tension. Continuing to use the drum/drum master cylinder will cause your disc brake pads to be in constant contact with the rotors, generate heat, and prematurely wear out the pads. You should fit it with the proper master cyl and prop valve.

SWINGSAX68 · 04-09-2003, 12:12 PM

I have a prop valve for drum/disk, I will post a pic so someone can verify if it is the correct one.. If it is the right one and you want it $15, or make an offer.

Custom 68 · 04-09-2003, 03:39 PM

sent you a PM swingsax68
Also thanks for the clarification and help guys.

71402BB · 04-09-2003, 06:53 PM

ok heres a question just for the hell of it. What if you where to do a disk disk setup?

04-09-2003, 10:48 AM	#1
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,937	master cyl and prop valve drum vs disk Hey all I believe I saw some recent reference on this but wanted to clearify. I recently swapped to disk on my 68 front. I had the power drum drum setup. I didnt change the master cylinder or prop valve. I have only driven a few miles and boy it sure stops great. the truck is apart now for a resto. Do I need to swap these last items out? It all works very well but I didnt know. I thought I saw a coment regarding a check valve on the master cyl that keeps slight pressure on the drums to over come the springs and this is not on the cyl for the disk fronts. Any help. Thanks Dave __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

04-09-2003, 11:45 AM	#2
Stout72 Not my good side. Join Date: Mar 2002 Location: Fairfield, California Posts: 222	There was a post on this just a few days ago. You are correct, there is a check valve in a drum/disc master cylinder that keeps some pressure in the rear system that helps overcome the brake shoe spring tension. Continuing to use the drum/drum master cylinder will cause your disc brake pads to be in constant contact with the rotors, generate heat, and prematurely wear out the pads. You should fit it with the proper master cyl and prop valve. __________________ 72 Chevy K20 Custom Camper, 350/350, 4" lift, dual shock suspension front & rear. Daily driver and a work in progress. 00 Suburban LT 90 Camaro RS 79 Yamaha XS1100 Special (Ol' Reliable)

04-09-2003, 12:12 PM	#3
SWINGSAX68 Now the others dig........ Join Date: May 2002 Location: San Antonio, TX Posts: 1,520	I have a prop valve for drum/disk, I will post a pic so someone can verify if it is the correct one.. If it is the right one and you want it $15, or make an offer. __________________ 68 Chevy C10 Stepside Black Primer 78 GMC Longbed White 09 Chevy Silverado Shortbed Granite Blue *LOOKING FOR A 67 4 DOOR IMPALA!!!Just like Sam and Dean Winchester!! 'Cause Mustangs are for p^#$ and you can fit a body in the trunk of a 67 Impala* MEMBER OF THE DRUM BRAKE CLUB Bachelor of Music in Jazz Studies Texas State University-San Marcos, TX Certified Music Educator I hope Mom is up there watching and being my Guardian Angel "I've got a fever.....and the only prescription.....IS MORE COW BELL" -The Legendary: Bruce Dickenson "F#$@ 'em up!!!!!!" -The Legendary: Rogelio Escobar TRUCKY LINKS** http://67-72chevytrucks.com/vboard/s...d.php?t=457750 http://67-72chevytrucks.com/vboard/s...d.php?t=461184 http://67-72chevytrucks.com/vboard/s...d.php?t=472848 http://67-72chevytrucks.com/vboard/s...d.php?t=417541 http://67-72chevytrucks.com/vboard/s...d.php?t=477788

04-09-2003, 03:39 PM	#4
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,937	sent you a PM swingsax68 Also thanks for the clarification and help guys. __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

04-09-2003, 06:53 PM	#5
71402BB now thats a true COON DOG Join Date: Nov 2000 Location: Franconia, NH Posts: 1,977	ok heres a question just for the hell of it. What if you where to do a disk disk setup? __________________ current project 67 402BB stout th350 3.08's with a locker. Plan on tubs 18.5's out back! (thanks Burnsman!) 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's ( was crushed by a tree, bed sold, motor pulled) was my first truck!... oh well... 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE work in progress, soon to have 250-I6 with a 3-speed on the tree 4.11's and posi ( currently sitting in back yard tarped awaiting time, $$$, and lots of love!) 67 1 TON- work truck 396 sm 420 4-speed, flat bed 4.57 gears "big red" (my first landscape truck, very rusty and crusty! but still gets the job done when needed!)



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