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MG MGA - Brake servo
|Any ideas on fitting a brace servo inside the engine bay of a pushrods engined car? For the vacuum, I am assuming I could tap into one of the holes used to secure the firing order plate on the inlet manifold?|
I do have one installation with the servo behind the O/S/F wing splash panel but am trying to avoid having to take bumper and wing off.
|Several ideas. Star here, and keep turning pages:|
Not sure what size vacuum hole you need? Pity you did not mention this at the Meet on Sunday where I could have shown you my vacuum off-take for calibration and a vacuum gauge.
I bought a pair of ready drilled and tapped black carb spacer washers that fit by the heat shield.
This is the spacer.
I bought the pair from:
Advanced Performance Technology
595 Iowa Avenue, Suite C
Riverside, CA 92507
They are on the web: http://www.aptfast.com/showitem.aspx?id=102819&name=H4%2FHS4%2FHIF4%2FHIF38%20Spacer%20With%20Vacuum%20Fitting&
I think they have improved the design since I bought a pair, judging by the picture. However, mine seal ok.
|For a brake servo vac feed you need a much larger bore than the carb adapters shown by Steve.|
I don't know where you would find the space to fit a servo inside the engine bay.
|I have a brake servo fitted under the dash on the passengers side. Works well and completely out of sight|
|Following an earlier conversation I bought a pair from the 'Steve's guy in the US'. That was all fine but I almost certain that when I got them the packing said they were 'made in UK'. I don't think I have packaging so don't know how to source in UK but may be worth trying although as Dominic says probably not for this application.|
|Well, how about positioning the servo behind the front grille? I think it would be visible and scupper the already poor airflow. I think behind the dash on the passenger side is the place to go; it gives a nice route to pick up on the firing order stud for the vacuum too.|
|Behind the dash may work on a RHD car, but would be a pig on LHD.|
One of the firing order plate mounting holes on the inlet manifold has a hex plug. when you remove this, you have the same tapping as is used on a B or A-series Midget for adaptor 12H1405 for the anti-run-on valve, which is a suitable bore for a servo vac take-off.
As the photo shows, (damn. File too large to load up) there was no plug on my inlet manifold. I guess I can remove the stud and drill as large as possible hole through it, or drill into the end plug and tap into that.
|Here's the absence of a 'plug'
|and here is the unit mounted behind the dash. It does not tilt downwards (that is just photographic illusion)
|See here for item 38 |
Maybe Colyn has a "foreign" inlet manifold
My 1500 manifold is the same as Colin's.
|Thinking further on where to attach the brake servo vacuum hose, would welding a hose connection to the rear air filter (similar to the rocket cover hose connection on the front air filter) provide sufficient 'suck' for the servo hose?|
|No, it's atmospheric pressure, more or less|
|Here's a suitable manifold |
|and another - much cheaper|
|I am not sure when/why the change of inlet manifold took place but there are certainly the 2 types as I own both. This caused me confusion when I was fitting the early B crankcase breather set up as the one I had on car didn't have the hex take off just 2 studs, but then I searched my boxes of bits and found one with it that I used. Incidentally the thread was extremely tight when I fitted there B adaptor from Moss.|
|The pictures on Barney's site is of my car. On a standard intake manifold I drilled out the back of it in the plug like a water plug found on a engine block so it can be replaced back if needed. I went to a speed shop and had the vacuum line made with proper fittings to do the job correctly. The brake servo is in the front fender wheel on the passenger side of the car. The vacuum hose was adapted to also have a cruise control.|
|Not for a brake servo but here is my set up which is relevant to vacuum takeoff although in my case for a different reason. The manifold fitted to the car has the larger tapped hole and the takeoff is the standard MGB part for the purpose that I am using it for so you could use this part for a servo takeoff. Note also there is a screw in the middle of this manifold which is presumably from some earlier attempt of some kind. Also sitting on top is the other version of manifold which is just drilled and tapped for a stud. Comparing the 2 types of manifolds I think they are identical castings just drilled/tapped differently in the back hole. When was the change?|
Not trying to restart the drum vs disk debate but I will pass on the following view. Talking to a friend last year who owns 3 MGAs with the 3 different braking systems and all with servos, hidden under wings, he said his preference is drums with servos. I think the reasoning was that drums are the most progressive system but there slight lack of stopping power is fixed by the servo. Clearly drums are a bit more difficult to keep in balance but its a view.
This thread was discussed between 24/05/2017 and 14/06/2017
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