Sagging master cylinder - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jfnar · 04-18-2018, 09:43 AM

I'm trying to finish up my disc brake upgrade on my 68 gmc but keep running into challenges. I found yesterday that the booster is very close to the holly 4 bbl carb on the 292. My brand new 10" air cleaner will interfere and I'll have to modify the throttle linkage. I have a plan for those issues. Next I noticed that the booster/master cylinder assembly is sloping down toward the front. I don't know if that causes any problems with the functionality but I would prefer for it to be level. Should I shim the mounting bolts at the firewall to level it up? Any other suggestions? Thanks.

B. W. · 04-18-2018, 11:08 AM

It's mounted correctly. They all run down hill for some reason.

jjzepplin · 04-18-2018, 11:35 AM

Mine is 3/4 ton and is very similar in angle.

jfnar · 04-18-2018, 11:48 AM

Thanks for the input. It looks a little sad but as long as it works I'll leave it alone.

**HIGHWAY BY THE SEA** · 04-18-2018, 01:36 PM

I just had a disc conversion done on my 68, and my new master cylinder is a mile from the firewall now! No clearance issues with the breather because I put a smaller one on there.

panhead59 · 04-19-2018, 05:52 AM

By the way- Those stock brake lines will bend and fit nice if you're REAL careful. I just did mine. Just bend and don't twist. Good luck. Go slow and it'll work!!!!

demian5 · 04-19-2018, 11:05 AM

Only thing I don't like is that if you have any slight issue with the gasket for the cap, your frame rail is swimming in brake fluid.

un4gvn! · 04-19-2018, 11:30 AM

Contact Captfab here on this web sight. He makes a bracket that eliminates the factory bracket that holds the booster to the firewall. My booster was close to the valve cover. By using his bracket, it lifts the booster away from the cover and it's more level. It also moves the booster closer to the firewall. By the look in your picture, it should move the booster back away from the carb.

Bigdav160 · 04-19-2018, 12:13 PM

If you keep it "as-is" there are two additional support bars that you seem to be missing.

cleszkie · 04-19-2018, 05:09 PM

Is that really how the Holly mounts to the manifold? I'm not used to seeing a carb in that sideways orientation. If it where turned 90 degrees it sure would provide more room for the booster. If all else fails, swap in a hydro-boost unit and get rid of the chunky booster.

04-18-2018, 09:43 AM	#1
jfnar Registered User Join Date: Jul 2009 Location: Jonesboro, AR Posts: 410	Sagging master cylinder I'm trying to finish up my disc brake upgrade on my 68 gmc but keep running into challenges. I found yesterday that the booster is very close to the holly 4 bbl carb on the 292. My brand new 10" air cleaner will interfere and I'll have to modify the throttle linkage. I have a plan for those issues. Next I noticed that the booster/master cylinder assembly is sloping down toward the front. I don't know if that causes any problems with the functionality but I would prefer for it to be level. Should I shim the mounting bolts at the firewall to level it up? Any other suggestions? Thanks. Attached Images

04-18-2018, 11:08 AM	#2
B. W. Registered User Join Date: Nov 2014 Location: Bigfork, Montana Posts: 1,137	Re: Sagging master cylinder It's mounted correctly. They all run down hill for some reason.

04-18-2018, 11:35 AM	#3
jjzepplin Registered User Join Date: Feb 2012 Location: Ruskin Florida Posts: 4,567	Re: Sagging master cylinder Mine is 3/4 ton and is very similar in angle. __________________ 70 swb 4x4 406sbc 700r4 203/205 d60/14blt locker yadda yadda http://67-72chevytrucks.com/vboard/s...88#post6935688 Yeller 72 Blazer 2wd conversion project "No Daggum Money" http://67-72chevytrucks.com/vboard/s...d.php?t=550804 LS1-T56 3.73 LSD super budget build Blanco-2014 Sierra SWB https://67-72chevytrucks.com/vboard/...d.php?t=810350

04-18-2018, 11:48 AM	#4
jfnar Registered User Join Date: Jul 2009 Location: Jonesboro, AR Posts: 410	Re: Sagging master cylinder Thanks for the input. It looks a little sad but as long as it works I'll leave it alone.

04-18-2018, 01:36 PM	#5
HIGHWAY BY THE SEA Senior Member Join Date: Nov 2012 Location: BY THE CAROLINA SEA Posts: 922	Re: Sagging master cylinder I just had a disc conversion done on my 68, and my new master cylinder is a mile from the firewall now! No clearance issues with the breather because I put a smaller one on there. __________________ FRANKENTRUCK 1981 Chevrolet C10 Shortbed Stepside GRANDTRUCK 1968 Chevrolet C10 Stepside Longbed http://67-72chevytrucks.com/vboard/s...d.php?t=584617 PROJECT JIGSAW 1967 GMC C3500 GREAT WHITE 1986 Blazer M1009 454 engine w/700R4 transmission gas conversion

04-19-2018, 05:52 AM	#6
panhead59 Registered User Join Date: Feb 2012 Location: Vinton, Va. Posts: 493	Re: Sagging master cylinder By the way- Those stock brake lines will bend and fit nice if you're REAL careful. I just did mine. Just bend and don't twist. Good luck. Go slow and it'll work!!!!

04-19-2018, 11:05 AM	#7
demian5 Registered User Join Date: Aug 2016 Location: Lake Forest, CA Posts: 2,177	Re: Sagging master cylinder Only thing I don't like is that if you have any slight issue with the gasket for the cap, your frame rail is swimming in brake fluid. __________________ "Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC

04-19-2018, 11:30 AM	#8
un4gvn! Registered User Join Date: Mar 2006 Location: Latrobe, Pa. 15650 Posts: 351	Re: Sagging master cylinder Contact Captfab here on this web sight. He makes a bracket that eliminates the factory bracket that holds the booster to the firewall. My booster was close to the valve cover. By using his bracket, it lifts the booster away from the cover and it's more level. It also moves the booster closer to the firewall. By the look in your picture, it should move the booster back away from the carb.

04-19-2018, 12:13 PM	#9
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: Sagging master cylinder If you keep it "as-is" there are two additional support bars that you seem to be missing. __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

04-19-2018, 05:09 PM	#10
cleszkie Registered User Join Date: Feb 2003 Location: Santa Ana, CA Posts: 2,191	Re: Sagging master cylinder Is that really how the Holly mounts to the manifold? I'm not used to seeing a carb in that sideways orientation. If it where turned 90 degrees it sure would provide more room for the booster. If all else fails, swap in a hydro-boost unit and get rid of the chunky booster.



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