MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Factory V8 Carbs

My carburettor adapter (balance pipes/plenum) has a bolt on top that is not shown in the parts list, Clausager or the David Knowles V8 book. I unscrewed it for a repaint and was surprised to see that it had a UNF thread and not UNC which is on the rest of the alloy castings. When attempting to replace it I discovered there is no thread in the casting - or if there is it is bunged up with a sealant that was used to 'glue' an undersized bolt in. Looking underneath there is a pin-hole in each of the passage-ways that connects with this bolt hole and is definitely part of the casting process. Anyone else got this bolt? If so what thread it should be? And what it is used for?

I have posted two pics with the bolt and pin-holes arrowed at:

http://www.ph012b2086.pwp.blueyonder.co.uk/v8e001.jpg
http://www.ph012b2086.pwp.blueyonder.co.uk/v8e002.jpg
Paul Hunt

Paul,
I have my adapter off right now, I'll check it as soon as I get home from school. I dont recall seeing that bolt on mine but it does have the passage between the two chambers. Maybe its for a vacuum gauge? I think I remember seeing John Bourke's adapter that he fitted with a vacuum gauge and pulled the reading from right there. Here is the page where you can see, the adapter in the pics doesn't have that bolt yours does.
HTH
Jake

http://www.mgcars.org.uk/v8_conversions/files/engine/sucarbs.html
Jake

Interesting!!!!!!!

My Clive Wheatley duplicate has the passage between the 2 chambers and where this passage is drilled from the outside, there is a roll pin to fill the outer hole.

Hope that makes sense.

What is the bolt that does not hold the throttle cable for??

cheers
Ian G Buckley

I've just received my carbs (original as far as i know) back from being refurbished, and have had a look undeneath the plenum chamber and I also have the same hole between the two chambers within the dimples, as per your photo no. 2. So presumably this is original to your chamber as well, could this hole be for keeping a pressure balance between the two chambers? But I do not have the extra bolt hole as per photo 1.
Mark
Mark Bushby

I checked mine this afternoon, also absent is that top hole you have. The one bolt on top aside from the two that hold the accel cable bracket is, I assume, to hold down the vacuum advance line with a P clip. That is what I have seen on other V8's anyways.
Jake

Interesting indeed. An original balance passage and a PO vacuum gauge take-off were my thoughts, but if the external hole were fitted with a roll-pin wouldn't that leak? The other bolt hole on the adapter is shown in Clausager etc. and is unused. The vacuum pipe P-clip bolts to the inlet manifold proper, right beside the thermo fan switch position.
Paul Hunt

I just went to the 'motashed' and had another look at the plenum. The hole I said is filled with a roll pin, which would of course leak, has something similar, perhaps a cut off threaded bar there.

Also there is a flat on the left side of the plenum which appears to be just for this purpose. Have you noticed that?
Ian G Buckley

This thread was discussed between 14/03/2003 and 19/03/2003

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now