Vapour lock in a 49 BL.

[Larry LewisParticipant]

On hot summer days my 49 would stall if sitting in heavy traffic. I found out that it’s vapour lock. Sit with the bonnets up for 15 minutes and all was well until the next time. Do the Solex type 35 carbs have a tendency to do that? I drove the car today after installing a re-cored radiator and the temp went no higher than 80 so I’m hoping I’ll be OK.

[BernieParticipant]

In my experience, vapour lock in a 4-cyl tends to occur only if the rad and/or block are not in best condition, i.e. clean and deposit-free.

I have only experienced it myself on an engine which I later found to have about 25mm of solid deposits in the bottom of the block.  Quick roadside cure is to throw a wet towel or similar over the fuel pump and pipe to the carb.

The six is a different beast with a reputation for overheating.  My ’48 15/6 block and head were completely cleaned when I rebuilt the engine in 2017 but I found it still overheated in high temperatures and heavy, slow traffic.  I therefore fitted a newly recored rad. which, until last week,  solved the problem.  However, on the trip to the Polish ICCCR, we were stuck in a traffic jam for well over half-an-hour with an ambient temperature around 30°C.  When we finally moved off it suffered vaporisation but was almost immediately sorted by switching on the auxiliary electric fuel pump which I normally only use for priming a cold engine after standing.

B…..

 

[Larry LewisParticipant]

Thanks Bernie- I’ve not done that wet towel trick, just waited for the engine to cool off a little. But the fuel pump never seems to get very warm. Also, there is no heat deflector for it as I’ve never thought it was necessary. I do have heavy foam insulation on both sides of the bonnet that I installed for quietness so I wonder if that is keeping the heat in the engine bay?

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