Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Vapor Lock issue TR Powered +4

I have a 1965 TR Powered +4

So I recently replaced my radiator with a high capacity aluminum unit, and also installed the plastic 6 blade puller fan from Morgan Spares.

The car is cooling beautifully now...175 degrees or lower at the block - even in 90 degree Houston heat!

Unfortunately I'm having bad vapor lock issues since replacing the radiator. If the car sits for 5 minutes after a 10 minute drive, it won't really start unless I open the hood and let things cool for 5 10 minutes. I assume the problem in that engine bay temps are now increased by all the heat dissipation by the new radiator and fan. The fact that the fuel line runs right in front of the thermostat housing certainly doesn't help!

I wrapped the metal fuel line in a thicker, split rubber fuel line...no change.

I assume the problem is at the carbs, when I spray the Strombergs with water to cool them, the car starts right up.

I'm wondering what the best solution to fix this problem is:

1) Buy a Stromberg heat shield? (I doubt this would work, since the problem is hot air from the radiator, not excess heat from the headers...)

2) Wrap the Headers? (might help cool the carbs - but see #1 above..)

3) Install a Facet electric Fuel Pump?

Any advice appreciated...

Would something like this help you . Commonly fitted to racers.

I had vapour lock issues with my TR4 on hot days in traffic. I had standard rad and big cast iron exhaust manifold.
Additional of stainless steel shields below the carbs cured the problem, so might be worth trying that first as a simple mod,
plus bonnet spacers as suggested.

Years ago I had a Worsley 6/110 it had the exhaust manifold under the carbs, it was a bugger in hot weather.

So I didn't have this problem last summer with the stock Radiator, though the car was running very hot 200 degrees+ at the block.

But when I changed to a new, efficient Radiator, reset the timing to 30 degrees advance at 3000 RPM, and added a six blade, plastic "puller" fan, that's when the problems started...

I guess that's why I'm skeptical that the problem is heat from the headers - though perhaps the addition of more heat under the bonnet + hot headers was enough to boil the fuel in the float bowls...

It seems that wrapping the headers would be the cheapest option to try first...and I will probably try that...

As an owner of two Plus 4's (1955 and 1968)

I'd advise the following.

I) Ditch the engine driven fan and go to a thermostatically controlled electric fan. My preference for a fan which pushes air through the rad.

2) Make sure the heat insulation blocks are fitted between carb and manifold.

3) A heat shield is a good idea between manifold and carb but then the risk is that the reflected heat will cook your starter motor.

4) Another tip but one which is not on topic is to relocate your ignition coil from the engine block to the inner wing to as heat cycles and engine vibration are not good for the windings

Arwyn

Depends which side you put the pusher fan I suppose Arwyn but neither seem ideal. On the inside it will suck hot engine air and oppose flow from any forward movement. On the outside the fan housing and blades will mask natural flow.

Apologies if I'm missing something.

Thanks Arwyn - always appreciate your expertise...

I think you're right about the electronic fan...the one big change that came about between the old radiator and the new one is that I deleted the electronic pusher fan and went with the 6 blade pully mounted puller fan...I'm wondering if the pathway of airflow was simply changed enough to overheat the carbs...food for thought...

Personally I would try the bonnet catch extensions as a cheap and simple option. Allowing the hot air to escape the engine bay quicker has got to help.

Andy

Not sure if it's relevant, but I have had a similar issue with my MGB on twin SU's.

Can't remember the exact science, but it goes something along the line of the hot underbonnet air is different to cool air, and it make the fuel mixture richer. Leaning the fuel mixture corrects it.

MG had been running fine for ages, but was taking a while to warm up in the morning so thought I'd richen the mixture slightly. Straight away the hot running problem started again, so reverted back.