Early Brake Boosters V8 and 4 Pot

PNP

Member
Are the Lockheed Brake boosters on the early (Series 1) V8s the same as on the 4 Cylinders of same vintage? Have found one off an Early 3500 for my SC restoration Project.
 
Hi,The V8 one is bigger so you will have lighter brakes, however the mounting points are different.

Colin
 
I'm not so sure about that. As long as you're talking about single circuit brakes think the same servo is used for both, the only difference on the V8 brakes being the 3 piston front calipers. Only the NADA 3500S has a unique arrangement with a twin circuit servo.

Yours
Vern
 
I'm not so sure about that. As long as you're talking about single circuit brakes think the same servo is used for both, the only difference on the V8 brakes being the 3 piston front calipers. Only the NADA 3500S has a unique arrangement with a twin circuit servo.

Yours
Vern

Back in the late 1980s, my Rover had a replacement booster fitted. My memory tells me that the vacuum chamber was of a smaller diameter with threaded studs on the chamber face furthest from the slave cylinder. I am also thinking there was something different with the slave cylinder, but I may be wrong there. Anyway, it didn't last long. I took it to different Rover business and was advised that my Rover had been fitted with the wrong booster, one from a 2000. They fitted the correct issue for a 3500 which lasted much longer.

Ron.
 
If i remember correctly, the 4 cyl car use a 7" servo, while the the ones on the V8s are 8".
 
That could be. I checked my microfiche parts catalog and the 3500 does have a different part number for the single circuit booster, vs the 2000.

Yours
Vern
 
So it is a different servo. Though the size of the servo (8" vs 7") isn't really the important part for pedal feel, it's the boost ratio. The 2000 7" servo has a 4.25:1 ratio, which is quite high. All things being equal, my bet would be that Rover chose a 8" servo with a smaller boost ratio. The math says a 8" booster with a 3:1 ratio would match the 7" 4.25 units.

Yours
Vern
 
There are some subtlies in boosters - the slave cylinder bore affects how much pedal travel it takes to open the air valve and get some braking, and probably some other aspects of their operation. I havent seen any data for lockheed units on Rovers, but there is some available for the various models of Australian made PBR boosters. I have a vh44 (possibly a Chinese clone) on my Clubbie that is not quite right - first pedal pressure on the brakes doesnt do much, but as soon as you get past a certain point the boost comes in and it slows nicely - the early response is not linear. After a few miles you get used to it , and it ceases to be an issue. I just dont get to drive it enough.
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Almac, NZ kit. mx5 1.8 +turbo = 215 rwhp. 775 kg.
 

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I recall that there were two different boosters fitted to the single line 3500, one manufactured by Lockheed and the other Girling. There was a difference with the vacuum chambers, the Lockheed had a bayonet type fitting whilst the Girling has a band that is tightened to keep the two sections together. There was also a difference in bore diameter between the Lockheed and Girling slave cylinders. I also recall that the 2000 slave cylinder had a smaller diameter than those fitted to the 3500.

Ron.
 
This is what's fitted to my car (series 1 2000) at the moment. Its a PBR unit but not sure what Pt number ratio or even the bore of the cylinder. I did replace it all a few years ago before I knew much about the cars. I assume someone retrofitted it in the 80s or 90s to keep the car on the road. Seems to brake OK but then again I've not got anything to compare it to. Will investigate a bit further but leaning towards returning everything back to original.
 
found a few specs for this unit on line. It is 9" PBR VH40. 3.27:1 ratio with a 5/8" bore cylinder.
 
above this post there is one titled "2200tc project" if you look at the engine bay pics on page 1 you can see the four cylinder brake booster and its orientation. note its on a bracket, back mounted and upside down. The V8 ones mount to a special recess in the front wing on their front side and are upright. I've probably got a reco version of the correct one for your car.
 
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