FUEL EVAPORATION OVERHEATING CARBURETTOR

I HAVE RECENTLY PURCHASED A TA 14 AND THE FUEL IN THE CARB EVAPORATES ONCE THE ENGINE GETS HOT, CAUSING MISFIRE AND EVENTUALLY STOPPING ALTOGETHER. I HAVE HAD A HEAT SHIELD FITTED, BUT IT HAS NOT HELPED, ARE THERE ANY OTHER WAYS TO SOLVE THIS PROBLEM? Posted by Faylen 31/08/2015 16:45:05

Terry,  My two bobs worth for what it is worth.  Is the shield an identical copy to the original and fastened as such? I am trying to eliminate a shield that is failing to play its part as planned? I own a TA21 with a single Solex and it was originally fitted with a thick heat insulating gasket between the carburettor and inlet manifold. Over time this was replaced with a standard gasket resulting in fuel boiling in the float chamber. To that end is a thick gasket fitted to the TA14? If not try an thicker one. I know that an old 1960's gasket kit that I have for my TA21 also included a pair of thick mounting gaskets for the later fitted twin SU's.  With respect to the motor in general do you feel that it is running hot? Where is the temp gauge sitting? If side engine flaps are fitted are they open? Is the cooling system up to spec?  Is the timing correct? All these things can result in reaching a tipping point where the below bonnet temperature causes havoc.  Regards Richard Melbourne Posted by RichardWallach 02/09/2015 08:52:20

Maybe I can contribute.  Having last year returned a TA14 to the road, this year I have had fuelling issues over the summer.  I have been hard put to decide if they were due to blockages or vaporisation, I suspect both!  I have been blaming much of this on the ethanol now added to our petrol which I believe loosens old sediment causing blockages and also lowers the vaporisation temperature,  I don't know if it is true but I was informed that old 4 star used to vaporise at around 100 degrees centigrade but modern 2 star does so at 50.  So this is what I have done: Flushed out the petrol tank with Marine Clean from Frost. Replaced the fuel line. Fitted an aluminium heat shield between the manifold and the carburettor. Wrapped the exhaust manifold and downpipe in fibreglass tape insulation. Fitted an HP (pusher) SU fuel pump at the rear of the car next to the fuel tank and removed the one on the bulkhead.  The theory here is that a higher pressure in the fuel line, especially within the warm engine bay will reduce the chance of vaporisation.  The set up is thus like that on an MGB among others. Changed to using "super unleaded" which I have been informed has less or even no ethanol. Also in the interest of good cooling I have flushed the radiator and block and opened the bonnet side vents.  Things do seem improved though the bulkhead filter is still trapping some crud from the tank and I will keep an eye on that. If things stay OK I will revert to the LP (sucker) pump on the bulkhead and see how that behaves as I would rather have the car as Alvis intended.  It may be of interest to note that at about the same time this year my daughter's Morris Minor started to show just the same symptoms and I tried out much of the above on that car first, in particular the heat shield, exhaust wrap and disconnecting the SU pump on the bulkhead above the exhaust and using a HP one next to the tank instead.  It was the fact that I had the same problems at the same time time with two cars which made me suspect the increased ethanol as the underlying cause. Posted by OldBodger 03/09/2015 16:15:16

Is ethanol free, or "recreational" fuel available in the UK?  It is in the USA, in many States, particularly near marinas, as boats use it exclusively.  I use recreational fuel whenever possible in my old cars. Posted by johnlayzell 04/09/2015 13:44:03

As an aside, a 10% ethanol blend is available in Australia. I think the octane is around 95. I deliberately don't use it preferring the lowest grade which is 91. We also have  95 and  98 RON available too. The TA21 was designed for "pool" petrol back in 1950 so the car runs quite happily on 91 octane petrol. Summer temperatures are regularly in the high 30's and the Alvis shows no sign of boiling either with respect to water or fuel. I really feel that the thick gasket between carburettor and manifold made all the difference.   Richard Melbourne Posted by RichardWallach 04/09/2015 22:55:42

Thank you all for your vary useful advise and comments. Posted by Faylen 12/09/2015 17:10:20