fuel avaporation 401

[mikesay]

Having now returned to the fold after tricky medical period I am tackling a long list of items on my 401 restoration.
One of my earlier problems related to the Solex carbs which I could not get to balance because of much wear etc and as a result I took the plunge and had them rebuilt - wonderful job - heavy on the bank account.
Whilst discussing matters carburration with rebuilders they mentioned that there was an historical problem with heat rise from the inlet manifold leading to fuel evaporation on switching the engine off.
This problem was noticed when using the Solex carbs on Mk 2 Jaguars and was resolved by placing a 3mm neoprene type gasket between the body element of the Solex - the part which faces directly to the inlet manifold - and the next section of the body - it is held by four M5 cheese headed screws. The only problem is that you need some slightly longer screws to cope with the additional thickness of gasket and the longer M5 screws are not readily available since the thread pitch is .75 (point 75) - typical of the French.
Does anyone have experience of this possible mod for the Solex on the Bristol 2 litre.
Regards
Mike Say

[Geoff Dowdle]

Mike,
I assume you have been talking to a Jaguar specialist as Bristols even in sunny Australia don't have these problems where air temperatures can reach regularly in summer 35 - 40 degC or more . Remember Bristol Solex don't sit on top of nearly 500kg cast iron, steel & cast alloy like a 2.4 Jag

If you want some new longer screws and used so called insolators I have both . These fit between the carby body & throttle body of the Solex .

I suggest while you have the carbs off the engine , you remove the carburettor adapters which sit between the head and the carbs . Remove the two studs in each and either file or mill the top surface flat . Over the years the upward tension of the studs tend to pull the alloy upwards around the studs and the gaskets won't seal properly. THIS IS IMPORTANT if you ever want the engine to run properly.

Geoff

[GREG]

I am trying to put two 401's that lost their drive trains many years ago back on the road. I now have engines but I will need two sets of Solex carburettors. I would be very grateful if anyone has spares laying around that they can sell me, even if they need a rebuild.

[Hydroglen]

I have had very similair experiences with my 400 and SU carbs. I see Geoff has answered but I will pass this on......
My carbs get very hot after a 10 minute shut-down and the fuel evaporates. When I say hot I can't hold on to the fuel bowls for more than a second or two.
I "fix it" by opening the bonnett a little when I park the car!
I posted this problem on other sites but it seems I am the only one with this issue. I wanted to put in the spacer as Geoff mentions but no room with SUs and in any case nobody else seems to need them.

On our Rolls Royce forum we have had much chit chat over modern fuels and the fact that some fules start bubbling at around 30c. Keep in mind that some 80% of cars on the road are fuel injected, so not a problem for them.

Originally Posted by mikesay

Having now returned to the fold after tricky medical period I am tackling a long list of items on my 401 restoration.
One of my earlier problems related to the Solex carbs which I could not get to balance because of much wear etc and as a result I took the plunge and had them rebuilt - wonderful job - heavy on the bank account.
Whilst discussing matters carburration with rebuilders they mentioned that there was an historical problem with heat rise from the inlet manifold leading to fuel evaporation on switching the engine off.
This problem was noticed when using the Solex carbs on Mk 2 Jaguars and was resolved by placing a 3mm neoprene type gasket between the body element of the Solex - the part which faces directly to the inlet manifold - and the next section of the body - it is held by four M5 cheese headed screws. The only problem is that you need some slightly longer screws to cope with the additional thickness of gasket and the longer M5 screws are not readily available since the thread pitch is .75 (point 75) - typical of the French.
Does anyone have experience of this possible mod for the Solex on the Bristol 2 litre.
Regards
Mike Say

[mikesay]

My thanks for the responses.
Geoff you are right vis a vis the Jaguar although the high Australian temps are ambient and the heat rise from the block is very direct and much higher hence possible fuel evaporation regardless of ambient temp.
I remember when I served Queen and country in the middle east that we never suffered from fuel evaporation with tanks and armoured cars as well as soft skinned vehicles - this being a pretty warm environment as well.
I realize of course that the Bristol head is aluminium and disperses heat more rapidly than cast iron
I have some "gaskets" and also an appropriate die and have prepared some longer M5 bolts, but thanks for your kind offer.
The BODA group have considered an idea that you could also provide two gaskets of something like Tufnol Carp between the inlet manifold and the carbs either side of the throttle control bar.
I checked with Tufnol and they quoted me circa gbp 1.15 per gasket (1.5mm thick) on the basis of a 1200 mm sheet producing some 300 gaskets - rather more than I met need!
I will check levels before refitting the carbs - thanks for the tip.
Kind regards
Mike Say