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MG MGB Technical - Heat shield replacement

I have a 1980 roadster & am in the process of replacing the leaking seals on the tappet covers.I have carefully removed the asbestos heat shield that just about gives me enough access & view to complete the task without removing the manifold.The original heat shield is just OK to re-use but would have preferred to go down the metal route.I have been advised that the previous metal version for H I F carbs up to 1976 will not fit with the latter style H I F carbs as used on my car.If that advice is correct does anyone know where I could source a metal one that has the profile of the asbestos version?
Many thanks
Charles
Charles9

Charles, looking at the parts catalogue and the normal suppliers you would need part No CAM1194 heatshield HIF Carbs Sept 1976 on. The MG Hive is showing this part number, see weblink

MGB CAM1194 12H3607 HIF4 RUBBER BUMPER HEATSHIELD 1974 ON

http://mgbhive.co.uk/product/16-mgb-cam1194-12h3607-hif4-rubber-bumper-heatshield-1974-on/

It does say 1974 on, but it is the right part number, so maybe worth a call to them to check?

Andy

Andy Robinson

Does plain metal work? I would have though it would radiate almost as much heat as it picked up from the exhaust.

I was under the impression that later models used a one-piece moulded non-asbestos insulation board - CAM1194, in place of the earlier metal panel (12H3607) with the asbestos pieces, as in this picture from Clausager. Why the earlier rubber bumper one one wouldn't fit I don't know, as it uses the same carb and cable arrangements as later.

There are versions around that seem to use a metal panel with non-asbestos pieces rivetted to it, although you have to be careful as some places show both part numbers for the earlier item without the choke cable support, and others show the earlier number as being suitable for all rubber bumper cars.

You could try for used from the likes of Welsh MG and Andy Jennings.



paulh4

Charles, If you want to go down the route of using the earlier heat shield I can't see there being a problem with the HIF's or the inlet manifold. Some adaptation of the throttle cable and choke mountings, may be necessary but doubt whether there is much involved there.
Allan Reeling

Thanks Guys for your assistance. I have been in touch with Mgbhive & ordered the one highlighted by Andy. This does have some insulation on the rear. (Paul I was always intending to affix some sort of insulating factor to the rear which is mentioned by many of our fellow members in the U.S.My original heat shield looks very like asbestos rather than some moulded product & the original part no describes it as asbestos but NCA unsurprisingly).I asked the guy at Mgbhive if there was a difference between the earlier & later H I F carbs & it was his view that the bodies were the same with differences on the jets etc..
The metal one I have ordered does include the hole framework at the bottom for the accelerator & choke cable return springs. (One additional bonus is that it saves me cleaning up the old heat shield & in particular the remains of the old gaskets)!
Thanks again
Charles
Charles9

Does it have the second support at the top for the choke cable as well as the accelerator cable? The one they show doesn't, with both old and new part numbers. That could be because they supply the two types but have only pictured one, or ...

Clausager sez that the change in UK HIFs for the 77 model year (he thinks) were so-called 'tamper-proof' versions recognisable by the shorter necks on the external cover. However the only change in the Parts Catalogue is for the 18V846/847 engines i.e. rubber bumper cars, and the pictures in Clausager for both pre-77 and post-76 seem to have the same external cover, and pictures of supposedly the later carbs seem to have the same length neck! V8s had the short neck.
paulh4

Hi Paul,
I have just rec'd the shield & have done a quick fit check as need to deal with tappet chest covers first... The shield does have a second support at the top although i may have to bend the shield in at the top as the support hole doesn't quite line up with the hole on the choke & accelerator bracket. Alternatively i could drill out the support hole to make it into an oval which should then fit.The accelerator guide hole seems fine.
In all other respects the shield seems to be reasonably made.
At the bottom of the shield there are holes similar to the original fibre shield for cable return springs & further up attachment lugs as alternatives
Cheers,Charles
Charles9

I am very cheap. I cut a piece of sheet metal to the correct shape and affixed layers of heat tape to the back. Looks OK and works
R LEARY

Charles - thank for that.
paulh4

Paul,
In '76 I bought a new midget, fitted with "tamper proof" SU's. There was no difference as far as I can remember, apart that is, from the plastic covers to stop the owner from adjusting the mixture!
Allan Reeling

Guys,
Following removal of manifold to one side to deal with leaking tappet chests I have now got back to the stage of fitting the new heatshield which after making the hole on the choke cable / accelerator plate slightly oval I managed to align the fixing bolt to the heats held as per the attached.(I also used the opportunity to tidy up the paintwork on that side of the engine bay)!
Here's hoping the tappet chests don't leak when I eventually get the engine going again.
Cheers, Charles


Charles9

Allan - alloy on the ones I'd seen, but still easy enough to dig out!

I'd imagined the cable bracket was part of the heat shield as it is with HS carbs, hence more complex. Being separate it's strange replacements are not more freely available, there can't be that much difference between the two types. I'm not surprised you had to modify it from that source!
paulh4

This thread was discussed between 24/10/2017 and 01/11/2017

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