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Brake booster interference with Clifford dual Weber setup

4K views 23 replies 9 participants last post by  gwistrup 
#1 ·
I have a 1983 CJ7 with a 4.2 six cylinder engine that I have done some modifications to and I am seeking some help with the finishing touches to complete the job. The modifications include: Clifford dual Weber intake and carb setup, Clifford 6 into 2 header, Iskendarian 270 camshaft, .060" milled off the cylinder head. The rest of the engine is freshly rebuilt but stock. I put the body back on the frame last week and I found that the brake booster will not clear the rear carburetor. The booster has a bracket that spaces it out from the fire wall about 3". I have read through some previous threads that the bracket is used to help the booster clear the hood when it is closed and it also has a linkage to multiply the effort from the brake pedal. What is the solution to this problem? Is there another brake booster that I can use and eliminate the spacer bracket? Thank you in advance for your help, Gil
 
#2 ·
The bracket aligns the thrust on the booster from the pedal, dead straight.

I had a CJ with the booster attached direct to the firewall, it worked but the brakes were better after I put the bracket in because I was not putting stress on the nose of the booster. It would lock up its brakes so it was not like it was compromised on brake ability.

What diameter booster do you have? would it help to put a smaller diameter but longer booster on?

There are remote boosters if you are really stuck. they are a bit more pricey as they are a custom option.

If you want to make your life more difficult, look at hydroboost. A lot more stopping power at the pedal

Pictures please!!!
 
#4 ·
gwistrup

I have attached some pictures (sorry that the one one the bottom needs to be rotated 90 degrees) and I will do my best to describe the situation. I have a 9" booster on the Jeep. The rear carb is 6" from the fire wall and the fuel inlet (this part sticks out the most) is 8" from the fire wall. If you eye down both carbs to the center of the hole in the fire wall for the brake booster, the fuel inlet is about 2 1/2" from the center of the booster hole. Therefore, if you had a 5" diameter booster, it would just clear the rear carb. If you were to install the master cylinder without the booster, it will clear the fuel inlet by about 3/4". If you remove the bracket behind the booster, the booster and master cylinder will fit. Am I correct to assume that if I were to install a 9" brake booster without the bracket assembly, the hood will not close? There are a zillion aftermarket boosters out there. There has to be one that will work. I don't think that the smaller diameter booster that you showed in your reply would clear the rear carb unless you took the bracket off. I have a Porsche 944 that I put a 5.3 LS engine in it and I used hydro boost to clear the passenger valve cover. I would prefer to use a vacuum booster if I can. Thank you. Gil
 

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#7 ·
Looks difficult but as far as I recall my brake booster, when bolted direct to the firewall, was not conflicting with the hood. it is a RHD but the brake mounting hole locations are mirrored.

It came that way, the first change i made was to remove the Toyota master cylinder and put on the correct master.

I ran it like that for some years but the rod from the pedal cracked the snout as it was not pushing directly into the booster, on a slight angle. It ran like that for a long time. I like everything more or less stock, as I trust AMC put it in for a reason, so I fitted the right bracket. The snout I cheated and glued it back up as it was not integral to the operation.

As it stands now it has the correct master cylinder and booster assembly, combination valve and hard lines and flexible hoses and is correctly set up so it is flawless in braking. the greatest improvement came from getting the clearance between booster and master cylinder correct.

Would I try the booster bolted direct? I guess I would look pretty hard at the rod coming from the pedal and whether it would catch the outside of the snout. If it did, could I grind it back a bit to get clearance.
 
#8 ·
I called Larry at Clifford first before inquiring on this forum. He mentioned a smaller booster such as one off of a 1950's Corvette but I was surprised that he couldn't really give me a specific list of parts to adapt the brakes to fit. I found a universal dual diaphragm booster that is smaller in diameter that I think I can bolt directly to the firewall. I am going to call the vendor to get the details to make sure it will work. On the bright side, I got the engine running the other day and it sounds really healthy. The carbs seemed spot on. It ran clean, good throttle response, Idled well, no vacuum at the port on the side of the carbs. I didn't even have to turn any of the mixture screws. Once I can get it to stop, I can take it for the true test. It was pretty lame in stock form.
 
#9 ·
Take a look at my set up...smaller, double diaphragm booster, same funky pivot brackets, and a Weber 38

BUT

I mounted my Weber 180 degrees from the way you did. No clearance problems at all.

 
#11 ·
I assume you're asking me...
Here you go, pics taken moments ago
I would call center of valve cover to carb center about 8-1/2"
Throttle cable comes in from bottom of bracket, bracket mounted to side of carb adapter, Clifford intake





 
#12 ·
As I understand, the big hurdle is finding a way to attach/coordinate the synchronous throttle linkages on the dual Webers with the OP's power brake set up without interference with the booster. The aft carb is positioned on the #5 cylinder intake, which interferes with the booster. Turning it 90* complicates joining the throttle linkage between the two 38's. Would think Larry@Clifford would have run into this before. Cool setup, hope to see it running-

Hoov
 
#15 ·
Thanks for the pictures. Turning the carbs 180 degrees might work and I can see that the throttle hookup is kind of like it was connected from the factory with the cable coming up from underneath. It looks like you would gain about 1.5" clearance with the carbs orientated the other way. The intake and carbs came assembled as shown. I just installed the intake and header as they came out of the box. I read Larry's note about the 8" booster and carb spacers before I purchased the system. An 8" booster is still too large and you would have to cut a hole in the hood to space the rear carb high enough to clear the stock booster. I wonder if the note pertains to a different make vehicle. I will put up some pictures when I get back out to the garage. Thanks again, Gil
 
#17 ·
:drool: That looks like so much fun.

Did you call Clifford?
Did they supply any spacers? That note was just under the 258 / 4.2 section. I don't think it was jeep specific but everything else I think is wider than a Jeep.

Looks like you might have enough room to turn them 180 degrees. Since they are center hung floats, that won't make a difference which wrong way you mount it... :)
It probably won't matter in a Cj but I had a car that had a Weber on it and it was great in a straight line or making a right turn. But pull some G's in a left turn and the fuel would run to one side of the bowl and keep the float valve closed... Finally had to put some baffles in the bowl to make it work.
 
#18 ·
I have talked to Larry several times and he has been helpful with the setup to make it run right but not as helpful to make them fit. He did supply more spacers with the carbs and manifold but they won't do any good. Height is not the problem. Width is the problem. He did say that if there was a stalling problem around turns, you should install an electric fuel pump. I believe that I have found a 7" dual diaphragm brake booster that I can mount directly to the firewall. I am going to measure it again and order one with the brake pedal kit. I would prefer to leave the carbs as they are if I can. That way I won't have to change any of the hoses and other hookups.
 
#19 ·
I figured I would post how I resolved my carburetor interference problem. Thanks to everyone for all of their input. I didn't really want to change the carb orientation and throttle cable if I didn't have to. I moved the brake pedal pin that connects the brake pedal to the booster linkage assembly from the right side of the brake pedal to the left side. Moving the pin allowed me to use the original linkage from Jeep and it gave me over an inch of clearance between the rear carb and the dual diaphragm booster that I used to replace the stock 9" Jeep unit. I drilled some new holes to the left in the firewall to mount the linkage and booster and elongated the hole for the linkage rod to go through. Now the booster is moved to the left but the pedals stay in the original location.
 

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#21 ·
Are you still able to install/use the left grill support rod coming off the firewall?
Seems like the MC would interfere with the rod since you shifted the MC to the left for clearance of the Weber's.
 
#22 ·
Yes I can. I had to move the rod at the firewall from the bottom of the bracket to the top of it to gain enough clearance to remove the top of the master cylinder. There is about 1/4" between the support rod and the master cylinder clip. That is enough room to remove the top.
 
#24 ·
I'm building this Jeep for a client who owned it since high school and it had been sitting for 20 years. He originally wanted to put a small block Chevy in it but I convinced him to modify the 6 cylinder because it is less common. I think the 6 cylinder is "cooler" because everyone puts Chevy V8s in them. Clifford Performance has been around forever and I figured they would be a good source for information and parts. I followed Larry's advice on everything I did to modify the engine. He said the combination I used should double the HP and torque. I used an Isky 270 cam, milled .060" off the head and installed the Clifford dual Weber intake and header kit. Part of the reason for the dual Weber carburetor setup is for the visual appearance. It looks cool and it sounds really neat because I made an exhaust system including the 6 into 2 header that goes into an X pipe and then into a Flowmaster dual inlet/single outlet muffler. The tubing before the muffler is 2 1/4" and the tailpipe is 2 1/2". The Jeep isn't registered yet so I have only driven it up and down my street a few times. It seems significantly stronger that it was in stock form but it needs a thorough road test to really see how it performs. The owner is really pleased with how it looks under the hood and how the engine sounds so I have checked off 2 out of 3 boxes of his requirements. If what Larry at Clifford told me is true, it should be equivalent to a stock small block Chevy. I guess that is why they advertise "6=8".
 
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