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MG MGB GT V8 Factory Originals Technical - 1977 MGBGTV8 Conversion Brake Servo

During my rebuild and Rover V8 conversion I opted to retain the remote brake servo (ex UK car). I have an Offenhauser inlet manifold with Holley carb. I take it that I need to drill and tap the intake manifold to fit a nipple to provide a connection for the vaccuum hose from the servo?
I know that this is elementary but I need confirmation.
Paul Hunt - you will probably discount the need for the servo but I'm a bit of a gadget man and also a stickler for originality as far as practical.
Thanks
Peter M
Peter Malkin

Peter
A lot of Holley carbs have a fitting on the rear of the carb,down low in the centre-rear of the throttle plate. If yours hasn't got it you might be able to swap your carb for one that has. Drilling the manifold is fine--just below the carb in the centre at the back.
Is your Offy a dual plane or single plane item ?--Just out of interest, If it is dual you will need to be fairly acurate where you drill so that you pick up both sides of the manifold porting.
Willy
WilliamRevit

"Paul Hunt - you will probably discount the need for the servo ..."

Dunno why you say that, I have them on both my cars and would repair them if they develop any problems. What I *have* said is that the remote servo gives very little assistance, and I wouldn't bother to add one to a car that didn't have one to begin with.

FWIW original installations have a non-return valve in the take-off for the servo supply. You need to make sure that any existing port on a carb you are thinking of using is definitely on the manifold side of the butterfly, and not covered by it when the throttle is closed which is the take-off for vacuum advance.
P Hunt

I've got an Offy twin port manifold which has a vacuum port for the servo & a Holley 465 cmf which does not have a vacuum port at the back of the carb. My GT has a Buick manifold circa early 60s.The Rover manifold is a copy of this except for the SU carby mod. This also has a vacuum port for a servo.I don't know what model manifold you're using, but it seems strange that there isn't a dedicated port for the servo.I can send you a pix of a Rover man.if you want . It might give you an idea as to where to drill. Barrie E
B Egerton

Willy
I have an Offy 360 (single plane?) manifold with no servo tapping - nor can I locate one on the carby (450 Holley #RH4548). I believe these carbs were standard Holden fare when they used carburettors - I purchased mine from a chap in SA complete with intake manifold and exhaust manifolds.
Paul
Thanks for your comments but cannot locate a vacuum port on the carb other than the vac advance.
Barrie
Would love to see some photos - malski5@bigpond.com.au.
Many thanks
Peter M
Peter Malkin

Peter
As your manifold is a single plane you can drill anywhere into the main plenum part of the manifold but for best results try and get approx. half way between the top of the manifold and the start of the runners-- You will get a smoother vac. right there in the middle of the plenum probably towards the carb a bit but stay away from the runners.----You would still get vac. at the runners naturally but it is more pulsey and not the best for your booster unless you are using a vac. reserve tank which acts like a shock absorber in the line-----Willy
WilliamRevit

This thread was discussed between 19/12/2009 and 20/12/2009

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