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MG MGB Technical - Seal, bonnet rear channel - 72 Roadster

I have a seal for the rear channel of the bonnet (Moss part number BHH2270). Can anyone tell me if it sits in the bottom of the channel, so the bonnet closes down onto it, or should it be stuck to the channel rear vertical edge, so that the rear edge of the bonnet compresses it rearwards?
Richard Coombs

Mine was in the bottom of the channel....Worked fine...
This is the closest image I have...
No longer have this car...
Edward

E.B. Wesson

Richard. On my 79, with the original factory weather strip, the strip fits on the vertical section towards the centerline of the engine compartment. The seal, which is formed in a figure 8, is split along the bottom and fits over the upright lip. Edward's photo seems to show some type of seal which both fits over the raised lip and fits into the channel surrounding the lip. My car shows no evidence of any form of seal ever being in the channel, so it may be that the replacement seals are different from the factory weather stripping.

Les
Les Bengtson

Richard, I think you're referring to the 40-inch strip of closed-cell foam (15 x 6mm x 1metre).
I bought one recently from Moss, and it looks identical to the original on my 1980 B.
It should be stuck to the bottom of the channel.
Brian Shaw

Where does the rain go if you block the channel at the back of the opening? I have no seal there as it helps to get heat out of the engine bay on my V8.
Mike Howlett

Gentlemen. I also checked my 68 BGT to see what form of seal was involved. Again, only the figure 8 seal fitted to the upright ridge. No seal along the inside of the channel as shown in Edward's photo. Clausager, pages 63,65,66,67, 68, and 69 all illustrate the figure 8 seal with nothing in the channel next to the seal. Thus, I suspect that only the figure 8 seal was applied at the factory.

Les
Les Bengtson

My 1970 BGT had a foam seal in the bottom of the channel. It was in bad condition so I removed it. Unfortunately I do not know the history of the vehicle, but the seal looked very old.

Ronnie
RA Potter

It would appear that the foam seal BHH2270 was fitted to all MGBs - see Clausager p.59 which shows an early 1962 car, also c.1964 model on p.61.

The other seal, which pushes onto the vertical edge of the engine bay aperture (all along the rear edge and halfway along the sides) was fitted to later cars (from Nov.67) - see Clausager p.144 ("new rear bonnet seal, which goes round corners of bonnet aperture flange"). This probably obscures the foam seal on some of the later Clausager pictures, but it can just be seen on the p69 photo.
Brian Shaw

My (early) '67 just has the seal in the rear channel. Stuck to the lower surface.

Dave O'Neill2

Early cars just had the foam seal stuck to the bottom of the channel, later ones had the rubber seal that sits on the edge of the channel and extends part way down the side channels, as per Clausagers 69 and later cars. According to the Parts Catalogue the change occurred for Mk2 cars in 67. A pal has a Mk1 with the rubber seal, and for whatever reason it sticks up higher than either my 73 or 75 and the rear edge of the bonnet doesn't close flush with the panel behind it.
PaulH Solihull

Thank you all. I guess I should have done more to describe the seal than with just the part number and Moss pictures as this doesn't explain it well. There are three under-bonnet seals sold by Moss. The main one extends along the rear edge and halfway down each side and is the figure eight cross section (sort of) some refer to. The one shown on page 59 of Clausager seals the bonnet to the radiator diaphragm. The third one, and the one I was trying to reference, sits in the very rear section of the channeling which runs around the rear and two sides of the engine bay.
The consensus appears to be that it should sit in the bottom of the rear channel which surprised me as I would agree with Mike H that this might impede water flow. Paul S says it may not even be fitted to a car as late as '72 although Brian S has one on his '80.
I'm fitting the bonnet tomorrow so I'll see if that helps with the answer.
Richard Coombs

Richard,
I also have a '79 B. It had the BHH2270 seal when I bought the car in 1980.
Brian Shaw

"I also have a '79 B. It had the BHH2270 seal when I bought the car in 1980."

Anyone buying my 75 V8 would say the same, as I added the foam seal thinking it should have one, and only subsequently realised it was either/or. Parts Catalogue info attached.

PaulH Solihull

Done it again.

It looks like Mk1 cars only had the foam seal between radiator and diaphragm panel, the rubber seal from diaphragm to bonnet appears to have been added for Mk2 cars. My 73 came with just the rubber seal, it was quite a few years before I got round to fitting the foam seal as well, and was surprised how much difference it made to cooling.

PaulH Solihull

Paul, it looks like both BHH2270 and BHH209 seals were fitted to late Bs.

Copy of BL microfiche attached.

Brian Shaw

Unfortunately, I no longer have the car in my previous photo,(above), but that seal was used in place of Moss #282-815...
This seal has an "L" cross section, and still allows water to channel around to the front, while making a tight seal.
The radiator support seal is from Moss.
Edward

Edward Wesson 52TD

I believe the Moss rear-channel seal, is a figure "8", to allow water to channel around to the front, while any water that gets under the seal, will also go to the front of the car, and down the side channels.
Edward
Edward Wesson 52TD

My '71 B/GT has both the seal on the ridge as well as the
one in the rear channel.

I am very much sure that they serve to help prevent hot fumes
and gases from leaving the engine bay and getting sucked
into the cockpit via the windows and heater/vent air intake.
Daniel Wong

Brian - the catalogue for the later models does indeed show that, hadn't noticed it before, most peculiar. After adding the foam seal I did notice it was better at keeping fumes out of the cabin than the rubber alone.

Some people recommend removing those seals altogether to give better engine bay ventilation, they don't seem to mind fumes and heat getting from there into the cabin.
PaulH Solihull

A while ago, I too was trying to identify the correct rear bonnet seal for my English assembled 1966 MGB. After much searching, I discovered that the seal used seems to be determined by the shape of the opening at the rear of the engine bay. Earlier cars had quite a defined square shape at each corner, whereas in later cars (67ish?) the corners were radiused to accept the rubber seal that mounts on the flange and comes forward on each side.

I have seen earlier cars, with the squared corners, with that later seal and the seal really doesn't take the sharp corners very well and doesn't look right.

Take a look at a few photos of early and later engine bays and you'll see what I mean. It's quite a subtle difference, but does seem to determine the seal type.

Phil
PG Crowell

"Earlier cars had quite a defined square shape at each corner, whereas in later cars (67ish?) the corners were radiused to accept the rubber seal that mounts on the flange ..."

The implication is that one or other of the panel at the base of the screen, or the wings, if not both, *did* change from Mk1 to Mk2 with the change of seal.
PaulH Solihull

Now that we have sorted that out - beware seals anywhere at the rear of the engine bay - when we removed the seal on the edge of the channel on our roadster, we found the metal had totally disintegrated. The bodyshop had fun re-building it. Both our cars now have a short strip in front of the ventilation grill only. The only fumes come from the tailpipe of the cars in front.
Roger W

This thread was discussed between 08/02/2013 and 19/02/2013

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