Conversion to decent brake booster

Ok here I go again, I want to convert my barking system on my 1964 MKII 3.8 to a decent booster rather than the vacuum tank system.
Has anyone out there done this and if so what part were needed and do you have a diagram on the setup.



The tank is only there so you have power brakes after you turn the engine off , think it’s around 10 presses on the pedal !
Not sure why you want power brakes with no engine running , but there you go !

I took my tank off , and have a one way valve in line to the manifold !!

Tell me more, in words of one syllable (or fewer if possible) - remember who you’re talking too. This sounds very interesting…

My barking system is a small but annoying Labradoodle. I threw away the booster and fitted a bark collar. So far no improvement in performance.
Seriously. The tank is there to give you a period of brake boost if the engine conks out. Seems reasonable to me.
The standard aftermarket replacement booster/slave combo (from SNG & others) is crazy hard to fit. I tried and gave up. Linn Rose documents a beautiful conversion on his Valvechatter site, but beaucoup bucks. The stock brakes are decent. Modern calipers would be way easier to install and adjust. That’s where I’d put the effort. good luck, David

Not sure my question has been understood.
I don’t really care why the tank is there it is going to vanish.
I just need help if anyone has done a conversion to a more modern system and if so what booster was used, obviously it will not be mounted directly on the brake pedal but will probably be located somewhere in one of the front wings (maybe where the tank was), I have already upgraded the front pads and rotors with a very nice Willwood kit from XKS Unlimited, I will probably leave the rear brakes alone for the moment.
Any help would be gratefully received.



Just wanted to say I went to the Valvechatter site and WOW that site is great I shall be using it a lot and its got me thinking maybe I should just restore my booster etc.

HHHHMMMMMMMM what to do ?


Hi, I have seen a picture where the owner has installed a double braking system. He has the master cylinder and brake booster from I guess a S3 XJ6. It is mounted sideways where the battery used to be. I assume it has a lever type of action.

got a mk2 with a series 3 booster + system, works well…

I would forget to take the Asahi bottle out and shut the bonnet, if I rested it in there. Paul

That’s a good looking conversion.

I wouldn’t leave an unfinished beer anywhere :slight_smile:

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And that’s fair enough.

Hi Gary,
why a more modern system? There are Lockheed boosters available for low prices with various boost ratios that work fine and all without that vacuum tank. Have done that for our Mk2 and am very happy with.

Best regards

Years ago I fitted a VH44 booster to my 3.8 ‘S’ in from memory the same place as the original.
Having said that I have just looked on line and they now say it is not suitable for 4 wheel disc brakes, can’t say I had any trouble stopping the car. Maybe the small calipers helped?

Hi all, I have fitted the cheap one from SNG Barrett and it was easy to fit and works very well.
Just completed a 1000 km round trip and no problems.

Can you in detail explain the metal box behind the engine with hose entering from both cam covers.

Can’t make out the header company name, are they Jaguar specific and did you see increased performance.


Hi @sixfan - Don’t want to hijack this thread but I’m really interested in your crankcase ventilation system. Is the box behind the engine a custom oil catch can system - or a clean air inlet filter or both maybe? I just converted a Series 1 XJ6 to Mk 10 Triple HD8’s and same as you I have 3 separate air cleaners. This precludes the use of the original Mk 10 breather system so I’ve been trying to decide what to do about it.

Are you pulling a vacuum through a PCV valve? If so from where? Like I said, didn’t want to hijack the thread so you can message me directly if you want to. I’d love the details on that thing - Beautiful work!

72 XJ6 (x2)
74 XJ6
85 XJ6
84 XJS
60 Mk2

G’day, sorry for the late reply, was off the grid for a bit.

Yeah, the system you see is a crank-case breather system with oil catch-can, there is a black hose (you cna’t see) that runs under the car and has a small filter on the end, to stop oil vapour from coming into the car… It isn’t working 100%, it would probably work better with stainless steel wool stuffing in the box and the drain-plug really should be plumbed back into the sump…apparently. It does have modded cams but pulls more than enough vacuum for the booster, a single non-return valve works just fine. That said, I didn’t do most of the work to this car, someone did a lot of good work, then someone else owned it for a while and did quite a few bodgies on it… It’s mostly all sorted now…only major job left is to replace the front main seal…ugh…not looking forward to that one…
The ventilation system can be seen on page 108 of speedpro series “how to power tune XK 3.4 3.8 & 4.2 engines”

Hi Peter,

I knew that that it looked familiar - I look at that book alot. That box it’s in is really a nice touch.

So where are you pulling the vacuum from? The brake booster line through a PCV valve?