I spent about an hour fiddling… we’ve all had that part that wont fit then suddenly it does. Even coming straight down the assembly is simply too long by about 3/4". I also tried coming in ‘nose down’ but the firewall gets in the way.
I wondered same. The pedals did not appear to be in the way, but to be sure I actually removed the pedals half way thru the fiddling.
I think that is a fact vs. a possibility. My adapter plate pushed it 1/4" forward, so I think the non-ABS housing holds it about 1/2" back of where the un-modified ABS housing would (1/4+1/2=3/4 which is the amount of interference I have…) I looked at milling off the face of the ABS housing, but there is not enough material there. Looking at the drawings, it looks like the face of the non-ABS housing sits slighty above and behind where the face of the ABS housing does.
In fact, I did not think I had a diameter problem until I did the measurements sans-booster last night. Measuring from the center line of things gives me a good picture of what’s happening.
8" might fit. Diameter-wise, there are a couple of spots that measure exactly 4" from center line. Since length is also a concern, I am also looking for the ‘thinnest’ option. This 8" looks to be it, and the 45d bevel on the front below the master cylinder might just give me the clearance I need. I am sure the 7" will fit, but I may order both. The 8", being dual diaphragm, would alleviate my concern about giving up too much boost with the smaller diameter.
Best I can tell it is. It’s a Cardone 53-5950, which Rock Auto says crosses to CAC1227. It looks visually the same as the one in Greg’s car.
Yeah… if I can find one. I’ve been looking around as a fall-back plan and they are harder to come by than I expected. There are a couple of parts cars on eBay, I may email and see what they want.
True- but I have solved the brake pedal problem. I am going to keep my existing A/T pedal and cut down as necessary. I am not sure how well the pre- and post- ABS pedals interchange… they are different part numbers.
I ordered a 7" dual diaphragm and and 8" dual diaphragm. I did a bunch more measuring and because of the way the nose of the booster tapers as it approaches the MC mount the 8" just might fit. Fingers crossed as an 8" dual is similar boost to a 9" single. The 7" dual will represent a significant (~28%) decrease in brake pressure (at same pedal pressure) and thus will result an a harder pedal vs. the 9" (which I assume is a single based on the shape…).
If I have to go 7" I will look at 7/8" bore MC in order to get the pressure back up, and deal with the additional pedal travel, which according to my math would be about 1/2" at the pedal.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
63
There is a switch on the housing that disables the cruise control when you hit the brakes. I think there may be a contact area on the pedal itself to hit that button. And that’d have to be dealt with when a clutch pedal is added, as I think it’s right where the clutch master cylinder goes. But that may be the difference in pedal part numbers.
Having driven an E Type with no brake booster, and having to bypass the booster on my Alfa a couple of times, I love the progressive feel of unassisted brakes. It’s hard on the left foot but well worth it.
Bob, I’ve got a pre-ABS pedal box I’m thinking bout selling. It is just the aluminum box that bolts to the firewall. There are no pedals or clutch master cylinder with it. I bought it several years ago if you are interested in it PM me and I’ll send you pic and the part number so you can confirm it is pre-abs.
I don’t disagree… my experience has been similar. However, I have also “un-powered” a couple of other cars and hated it. Over time I figured out that the pedal ratio matters… if the car was never designed for non-power brakes, the pedal ratio can be too low and the pedal way too stiff… I’d be curious if anyone has removed the booster from an XJS. I wonder what those who race them do…?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
67
I’ve had issues with the Girling brake booster on a couple of British sports cars. This thing isn’t like the vacuum booster on the XJ-S and most American cars where it fits between pedal and master cylinder. Rather, this is a stand-alone vacuum booster that fits in the line somewhere. Typically it applies boost to the front brakes only, the rears are unassisted. And when they act up or start leaking, the easiest solution is to pitch them over the hedge and couple the brake lines together without them. The brakes work better than they ever have. I’m convinced the only reason the %^&* things exist is so they can list “power brakes” as a feature on the car, because stupid Americans wouldn’t buy a car without power brakes.
No actually there where only 3 sets left.
I needed one set for myself and my friend is restoring xjs after engine fire so he will need one as well. And third I was planning to keep “just in case”
Progress. The 8” Summit dual-diaphragm booster fits like it belongs there. It is 1” smaller in diameter and 1/2” shorter that the jag booster. Result is about 1/2” clearance right where I needed it.
The bolt pattern on the Summit booster is 1/8 smaller (3.375 vs 3.5) that the jag unit. Which means I need to re-engineer the adapter plate a bit as we are too close to the Teves pattern on two corners. Not a big problem, will relocate the two offending holes in the pedal housing, there is plenty of room to do so.
There appears to be plenty of room for a variety of master cylinders, I am researching my 7/8 inch bore options, as I want to pick up a little extra brake pressure vs the 15/16 stock unit. And save some money.
The new booster has a threaded actuator rod which will make setting the brake pedal height easy. I ordered an adjustable clevis kit from Summit, unfortunately it looks to be more suited to a 60s Buick them to a jag. It’s the silver unit on top. So I tore down an extra teves unit that I have, wanting to get access to the original clevis. It will fit perfectly on the pedal of course. Couldn’t figure out how it was held on to the actuator rod, seems like it should be threaded, couldn’t figure it out. So I tore it all down, drilled it, and it’s threaded. Now we know. I will drill and tap it to match the threaded actuator rod on the summit master cylinder, back it up with a quality nut. and we should be good.
UPDATE: Extracting the Teves clevis was a waste of time. It’s not deep enough to reach the threads. The ugly unit I got from Summit has a different cross pin size, and the jaws are 3/16 narrower than the Jag brake pedal, thinking I will make one from scratch.
Mount the booster so that the master cylinder studs are horizontal and any GM master will fit the pattern; don’t know if you would have clearance issues with the integral reservoir though. They are available in 7/8, 15/16, 1”, and 1 1/16”. Mostly cast iron.
Good call. But the integral reservoir won’t clear. There are a couple of 7/8 wilwood options that have remote reservoirs that would work. But at the moment I am looking at this. https://www.summitracing.com/parts/clp-430/
Update: I will get to building the adapter plate V2 hopefully this weekend.
It will have the smaller bolt pattern so that it mates with the Summit booster, and I may
tilt it forward slightly to give more MC clearance. Honestly, a slight tilt could be achieved with a couple of washers between the booster and the plate.
I will also have to add two new mounting holes to replace two of the four Teves mounting locations that I had previously used; the new smaller booster bolt pattern is getting too close to the Teves mounting bolts.
I will make it out of one piece instead of two, since I know about the “hump” now
I spoke to CLP, there is not a remote reservoir option for the universal 7/8 MC that I have been looking at. I ordered it anyway, it might fit and it’s only $68. Would be nice to have the integral reservoir.
I spoke to Wilwood. Their tech spoke my language, we talked about pedal ratios, vac boosters, bore sizes and so on. He did not recommend going to a 7/8 bore, he thought if anything the dual-diaphragm 8" would provide more boost than the stock 9", so he recommended keeping the 15/16 bore. He said that 4-4.5:1 pedal ratio was typical for vac booster, (as did Robert @RGK20m3) so my 3.83:1 is not out of line. (I was worried that the Teves setup had a purposely high pedal ratio due to the assistance provided by the pump…) Wilwood does not make a 15/16 bore remote reservoir MC unit that is made to go on a vac booster, they all have a pushrod coming out the back as they are for manual brakes. So, no additional MC options there unless I got to 1" bore, which the tech did not recommend.
I found a Jag booster (Centric) that PartsGeek says includes the elbows, so I ordered one of those as well. The minor issue there will be that the mounting holes on the Jag MC are slightly closer together than the studs on the Summit booster. I will likely have to oval them out a bit, which is not a big deal.
That could be an option. I don’t know much about it or how available it is. I am looking for simple, inexpensive and easy sourcing of parts. I have heard that others have gone from teves III to IV.
