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 Technical - wedge shaped heater foam

What is the purpose of the wedge shaped piece of foam at the outlet of the heater box. When I took the heater out there was no sign of this so assume that the PO did not include it when he reshelled the car. Should I try to fabricate this or can I leave it out?
Steve Church

There is plenty of discussion about this part. It is there to provide a seal between the lower part of the heater and the rear outlet panel which is part of the cockpit bulkhead. Some believe that air will still leak out every-which-way and they may be right. However, I've measured the gaps and am reasonably confident that a seal will be formed so that all of the air intended for the screen and/or feet will get there.
The reason the PO may have left it out is that it makes the installation of the heater, with this bit attached, a very difficult exercise. Search this site for other comments and how-to-do-its.
Richard Coombs

Early cars did not have it -- instead they had two plastic tubes. I'm not sure when this changed, but '69 definitely did not use them.

What year is your car?
Rob Edwards

The car is 1968. I have the two tubes you speak of between the heater box and a plate on the transmission tunnel with two right angled vents on. Seems like I can go ahead and install then.
Steve Church

On my 69 produced roadster (late 68 body) the wedge definitely did not provide an effective seal between the front and rear lower heater compartments. You could drive a B through the gaps. I left it out when I refurbished the heater unit and I get good heater air flow when switched on. I do have the two tubes fitted to direct the air flow to the screen vents of course.

I should add that there was no evidence a wedge had ever been fitted in my car, though I cannot rule out a PO having removed the heater and not bothering to refit the thing. My attempts to fit the wedge (before I established that it would have been a useless 'seal') were fruitless - it just was not going to fit without significantly deforming the operating cable and inhibiting operation of the heater flap.
Roger T

http://www.chicagolandmgclub.com/photos/b_heater/ shows how to modify the hole the air direction cable comes through so as not to mangle it when refitting the heater unit. I understand later shells had a similar modification from the factory.
PaulH Solihull

My '69 B and '69 CGT both show no sign of the heater ever having been out before I touched them, and the foam was not fitted -- only the tubes....
Rob Edwards

None in my 67 GT and when I tried to fit the Moss foam, it just would not go. Then I found that they did not have them in the early cars.
Bruce Cunha

My '72 roadster has the large rectangular hole shown on the Chicago photos. Do you think this was introduced when the factory fitted the rubber wedge, circa 1970?
Richard Coombs

Quite possibly.

I can't lay my hands on my parts books at the moment, but as I recall, the Sept '76 edition of the MGB book lists /only/ the rubber block, for all cars. The ca. 1970 edition of the MGC book (MGBs and MGCs use the same parts in this area) lists /only/ the plastic tubes. It seems as though the factory superseded the tubed with the block.

I also can't quite remember the details of the interior anatomy of the heater system, but I recall concluding at the time I was doing my heater box that in my car at least, the foam block would do nothing. It was useless without the tubes, and the tubes didn't need it so it made no difference to leave it out. The tubes alone did the work of conveying the air to the demister ducts....

HTH!
Rob Edwards

This thread was discussed between 23/08/2010 and 25/08/2010

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now