Fuel vapourisation remedies

[Matt Cotton]

Hello all.

My car has always suffered from fuel vapourisation in hot weather (1500). I know it is common as Richard Old's cars also suffer with the same symptoms and we are often together when it happens!

Has anyone found any benefit with some of the 'heat resistant' wraps/tape that are on the market?

Modern fuels don't help granted, but it would be nice to improve matters if anyone has had any success?

Kind Regards

MC

[Carledo]

You can get a stainless steel heatshield for 1500 Spitfire from a number of sources. Goes between carbs and manifold. It's also a good idea to reinstate the cold air induction pipes from the air filter that are nearly always missing! And a bad idea to fit aftermarket air filters or trumpets that draw air from under the bonnet, rather than the great outdoors.

The culprit is entirely down to modern ethanol added fuel, which doesn't react well to carbs and high underbonnet temperatures.

A quick and effective trick is to pull the bonnet release when sat in traffic as this lets the hot air escape and the fan can push more cold air through. A more permanent and elegant solution is to get some louvres cut in the bonnet above the carbs, it ain't cheap though and the bonnet will need repainting afterwards!

Steve

[mbellinger]

Matt,

Another vote here for the Spitfire heat shield as mentioned by Steve. Incidentally, the rather bling highly polished ones sold by certain sellers on ebay are actually nowhere near as effective as the original BL type, which has a sort of (I assume) asbestos sandwich material on the side facing the exhaust manifold.

I have the same problem with my Healey and wrapping the manifold made a tiny difference (and I already have a louvred bonnet)!

I would go with the heat shield first. Popping the bonnet on the catch in extreme situations is also very effective.

[xvivalve]

Vermiculite board would be a good substitute for the OE, if you can get it thin enough without its brittleness causing problems, particularly if you faced it with aluminium foil glued to the manifold side. The OE was brittle itself and if they still exist are generally in at least two halves...I have a pair somewhere if you'd like a pattern?

The original insulated against radiation, conduction and convection, but as a particularly good conductor of heat, the aluminium on its own, once it is warm itself, fails on one fundamentally and a second partially.

[SprintMWU773V]

You could add some aluminium heat shielding to the back of your flat heat shield. The material encourages air flow and heat transfer as is very effective. This would give you the look as well as making a difference.

The material in question is called Nimbus heat shield and you can buy it from numerous places including Demon Tweeks. Though it may be called something else from other suppliers. It cuts and bends really easily and can easily be attached to another flat piece with rivets or even small nuts and bolts.

[Triumph1300]

Alternatively, electric fuel pump, which is the route I went down with KAC a number of years ago

[Matt Cotton]

Many thanks gents for the replies and some good advice there.

I will have a ponder on this one. My heatshield was replaced a few years ago, although isn't stainless steel. All the rest of the set up is original.

Regards

MC

[Carledo]

Alternatively, electric fuel pump, which is the route I went down with KAC a number of years ago

I wouldn't have thought an electric fuel pump would help much! I have this problem as a hardy (summer) perennial with a customers Rover V8 powered Stag - which has an electric pump as standard and a massive and correctly set Kenlowe as well as an uprated rad. The car keeps it's cool on the guage under all conditions but 5 mins in traffic has the engine spluttering like an apoplectic hippo and me reaching for the bonnet handle. It's entirely down to modern fuel which has a lower vaporisation temperature and the fact that, with a carburetted system, fuel actually sits in the carb float chambers long enough to get up to it's (reduced) evaporation temp. My customer flatly refuses the louvre option, somebody before his time has expended considerable time, effort and lateral thinking to get the Rover carbs under the stock bonnet and we are now investigating EFi as a permanent cure, which should be fairly easy with all the old EFi Range Rovers etc that are around!

Steve

[cliftyhanger]

Some modern cars have fuel coolers fitted, not investigated where they are placed in the fuel system, but it means a real issues does exist.
Modern cars have a huge advantage in EFI,so the fuel never sits in one place, most fuel doing a circuit and returning to the tank. add to that it is sitting around 3bar pressure which will raise the boiling point by about 30 degrees should there be any localised hotspots (but I don't think the higher BP is requied, otherwise the fuel would vaporise after the PRV)

I have wondered if it is possible to set the carbs up to have a return fuel line. Probably more complicated than it sounds as you don't want to pressurise the float chamber at all, and you can't really use gravity for the return line. Not sure a suction pump would work either...

[SprintMWU773V]

Some modern cars have fuel coolers fitted, not investigated where they are placed in the fuel system, but it means a real issues does exist.
Modern cars have a huge advantage in EFI,so the fuel never sits in one place, most fuel doing a circuit and returning to the tank. add to that it is sitting around 3bar pressure which will raise the boiling point by about 30 degrees should there be any localised hotspots (but I don't think the higher BP is requied, otherwise the fuel would vaporise after the PRV)

I have wondered if it is possible to set the carbs up to have a return fuel line. Probably more complicated than it sounds as you don't want to pressurise the float chamber at all, and you can't really use gravity for the return line. Not sure a suction pump would work either...

No this is far too much effort. I'd personally concentrate on reducing heat. The 1500 engine will always have the problem of having the inlet manifold right over the exhaust. If you can reduce the effect of heat soak on these areas it will help. You could zircotec the manifolds but this isn't cheap so I'd stick with better heat shielding and even go so far as to try and find fuel with a lower ethanol content, though this can be tricky.

[AlanH]

There is an original type of shield here.

https://www.ebay.co.uk/itm/Triumph-Spit ... xyuGFRztDW

Why not buy one of those and wrap the exhaust manifold.

Quick and cheap, should improve things even if it doesn't cure it completely.

[Toledo Man]

I was going to suggest getting the manifold coated with the Zircotec treatment or suchlike but Mark has confirmed that this would be costly. Is there a DIY version or could VHT paint be used instead? If this isn't feasible how about making a heat shield from the heat shield material that is fitted on modern cars?

[marko]

Look on page 19 of this month's magazine. I did a similar thing with aluminium as it dissipates heat quicker. I riveted a small bit of angle onto the flat bit that folds underneath my HIF38s, then a expansion spring and it's perfect. I can't post photos here but I'll put some on Fb.

[Matt Cotton]

Excellent Marco. It dropped through the door today, so I will settle down with a pint of Hobgoblin and have a read!

[AlanH]

I was going to suggest getting the manifold coated with the Zircotec treatment or suchlike but Mark has confirmed that this would be costly. Is there a DIY version

Yes - heat wrap.
https://www.ebay.co.uk/itm/15M-TITANIUM ... 0005.m1851

Combine that with the heat shield as I suggested above all for less than 20 quid (just).