Engine heat shield/baffle plate

[Mckorkins]

My 1962 Morris Minor convertible suffered from the effects of being in a traffic jam on a hot summer's day recently and nearly stalled. It was only by pumping the throttle that I managed to keep it going at all. To stop in a line of traffic on the A48 outside Carmarthen without a hard shoulder was unthinkable. Fortunately, there was a 'B' road which we took off to the left and the car kept going and didn't miss a beat from then on.

Looking at the proximity of the carburettor float chamber to the manifold, I guessed that it could be a problem with excess heat in certain situations, leading to evaporation and therefore caused the engine to misfire/cut out. I thought about putting a heat shield between the float and the manifold that might alleviate the problem and to that end have just finished a modification today. A photo of the installation fitted to the carburettor is attached: [frame][/frame][frame][/frame]

[jagnut66]

Hi,
This looks like a good idea, it would be interesting to hear how she copes in a similar situation, now she has the heat shield fitted.
Best wishes,
Mike.

[bmcecosse]

The real problem was the high mounted fuel pump struggling to suck up fuel from the low mounted tank - in hot weather the fuel can start to vapourise in the line and the pump struggles. Any additional (completely unnecessary) filter added in the line makes the situation worse - and of course if the filter inside the pump is blocked....that doesn't help. Some pumps are worse than others - probably depends on the length of stroke set on the pump. Sure fire cure is to mount the pump lower down -or convert to the mechanical pump if your engine has a removable plate on the side to allow the pump to be fitted.

[Trickydicky]

The heat shield does look like a good idea. Also reading this article maybe we should be rerouting the fuel line to the carb away from the manifold?
http://www.classicandperformancecar.com ... ation.html

[bmcecosse]

It is the fuel line that picks up heat - especially when there is little fuel demand (idling in traffic) and little or no flow of air...

[philthehill]

A new take on an old problem.
Advert from Minor Matters July/August 1995.[frame][/frame]

[bmcecosse]

Your shield is very well made and v neat - it certainly won't do any harm! But as Phil's crib shows - Grumpy did have the right idea and shielded the fuel pipe.

[philthehill]

As regards the carb heat shield it may be worth considering using a cut down MG Midget 1967 > 1275cc twin HS2 heat shield
Pt No: 12G1460 (MOSS) at £13 plus P & P.
The uplift pipe to the pump does need to be protected from the heat.
I used to own a 1200cc Cortina which when hot would not start. Come back 20 min later and it would start first time. Never got to the bottom of why it suffered from fuel evaporation/starvation. At all other times it ran perfectly - So problem not just confined to Minors. And it was fitted with a mechanical fuel pump.
Whilst not necessary on your car performance cars often wrap insulation around the exhaust manifold to reduce the heat in the engine bay and especially under the carb(s).

[MarkyB]

The exhaust wrap I used on my friends car advised not to wrap cast iron manifolds.
Just wrapping the pipe reduced the under bonnet temperature significantly.

The only difference I've notice Between that car and mine which is fine in traffic is the proximity of the petrol and exhaust pipes above the back axle.

[philthehill]

MarkyB
You are right in that you do not wrap cast iron manifolds because they will get too hot and crack. I was thinking more of tubular multi branch manifolds when writing the above post.
Wrapping the Minor exhaust after the exhaust manifold clamp is a good idea. Anything to reduce the temp in the engine bay is a good thing especially on a hot day.
Even on my modern car with electric fan if I notice the engine temp rising I open all the car windows and turn up the heater on full blast; it soon brings the engine temp back down. Use to do that regularly on my Series 2 when stuck in traffic jams.
As an aside - the colder the air around the carb and entering the engine cylinders the denser it is and the more fuel it will carry - so better performance. That is why some cars perform better on damp days and which has led to the development of water injection directly into the manifold.

[Mckorkins]

A lot of good ideas here. Thanks all!

I didn't realise that there was a commercially-made heat shield (Grumpy's) and thought I was being innovative for a while! I now know the problem of overheating the fuel is an endemic factor on these old cars and others like them without an electrical fan. My neighbour, who's and ex-mechanic, pointed out that he used to deal with Morris's with such problems and he used to retro-fit electric fans to them. Hmmm...not sure about that one.

Wrapping the exhaust below the manifold is quite a good idea, especially since my system is a stainless steel one and therefore rust is not an issue. I'll try the heat shield first to see if that makes a difference before embarking on that. I do think that the fuel line on my car could be moved over slightly so that it is not directly over the manifold, however.

The thing is not to get stuck in traffic jams in the first place and so overheating issues won't arise, which is more easily said than done these days!

[bmcecosse]

Some cars never suffer the problem - no matter how hot the day or how bad the traffic. An electric fan is unlikely to be 'the answer'. Mounting the fuel pump lower - so it has (almost) flooded suction from the tank is an absolute cure.

[jaekl]

A heat shield without air flow behind it will only provide protection from short duration of direct radiation or general hot air. You have neither, no movement of air and the entire under bonnet will be virtually the same temperature. A heat shield and a fan may do the trick. I also see your fuel line from pump to carb is closer to the engine than it needs to be. You don't mention whether your fuel pump is pumping a lot or not. Vapourization, which is most likely on the suction side will cause the pump to go crazy. If the vapourization is on the pressure side, in theory the line will be pressurized, thus satisfying the pump but as soon as the float allows some fuel past, there will be a bubble, so the pump needs to pump more since the bubble is vented out through the bowl. Vapourization between the bowl and the jet has the same effect of increased demand more fuel. Based on your assumption that it is fuel delivery problems, the bowl is getting bubbles constantly. So again, is the pump going erratic?

How's your ignition coil? Overheating will push a marginal coil over the edge.

[Mckorkins]

I have moved the fuel delivery pipe away from being directly placed over the manifold and it is much more in line with the pump/carb. I have also ordered a heat-reflective tape to shield the fuel delivery pipe where it runs past the exhaust (there is a Velcro equivalent available in the US, but apparently not here in the UK), which I hope it will prevent it overheating. See link:

http://www.ebay.co.uk/itm/Heat-Barrier- ... OC:GB:3160

I was interested in the article that suggests fuel companies change their formulas at least four times a year. This might have some bearing on how to tackle the problem of overheating of the fuel, especially when boiling points vary so much. The Morris is mainly used on minor roads (no pun intended!), so overheating is not usually an issue, as normally it behaves itself impeccably. I always use premium-grade fuels (BP, Esso etc.) and not supermarket stuff.

I have not heard the pump working hard, but there again one can't hear the thing working above the engine noise, so I don't know whether it has been struggling to supply enough fuel in these situations! The coil doesn't seem to be an issue and I carry a spare in the car in case of failure anyway.

[bmcecosse]

Hah! It's NEVER the coil..... The heat problem is in the fuel suction pipe to the pump - not the delivery pipe.

[Mckorkins]

As I said, to that end I've ordered a roll of heat-proof tape to wrap the tank-to-pump pipe in!

[jaekl]

I find it hard to believe you don't know if you can hear the fuel pump. Sure, when it's on normal duty, it may be easy to ignore. It's like your heart, you know when it misses a beat or in this case throws in a few extra especially when you say you are stuck in traffic. Even with my fresh diaphragm it'll throw a couple extra strokes once in a while. In my years of Minoring and plenty of pump issues, the pump goes crazy long before there are any drive-ability problems especially if it's only vapourization. A hole in the diaphragm which only shows up when the pump warms up is another thing.

As I've reported before, I've seen the vapours form in my plastic fuel line. As the pump tries to pull the fuel up to the pump at higher ambient temperatures, the pressure drops enough to create vapours. I say a heat shield will only save one from the mildest of cases and may allow you to limp along on the worst cases, but stuck in traffic, it may give you a minute or two. I've consider adding a back-up pump in-line back at the tank to get through the worst ones.

Also you mention pumping the throttle keeps it running. How does that work with poor fuel delivery? Does the increase in vacuum across the jet actually pull the fuel from the bowl before the piston has a chance to rise much? On the other hand I have no idea what pumping the throttle will do to help an ailing ignition.

You have to be hearing that pump banging away.

[Trickydicky]

Just been ordering some other carb related stuff and found that ESM stock the Grumpys heat shield kit.

http://morrisminorspares.co.uk/shop/pro ... 1f36926f85

[bmcecosse]

Pumping the throttle will indeed not do anything useful....unless of course revving up the engine flows air through the engine bay with the fan (although I would expect it to be hot air..) and the additional fuel consumption allows some fresh cool petrol to run along from the tank.... R

[Ufudu]

I see on the ESM site Grumpy's heat shield is painted black, this should in fact be painted a bright (silver) colour.... that will maximise the reflection of radiated heat from the heat source and minimise the re-radiation of the shield's own heat onto the petrol float chamber or fuel pipe.....

It would be far better to use sheet aluminium as above ^^^