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Heat-related carb issue on BN1

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matt78

Senior Member
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Hello knowledgeable people.

Here is my topic of the day : my BN1 (with 2 H6 fitted by the previous owner) runs well, but last summer I experienced some issues :
- difficult restart after a short stop - approx. 10 min, at the gas station for example,
- when in a traffic jam for, say, 3 or 5 min, the engine tended to stall when idling or at low revs, needing to be helped by accel action.
I can't remember the engine temperature then : it was hot, but not alarming. The main issue really was the engine behavior - unable to keep idling.

I guess that this was a vapor-lock matter. As the car was still equiped with the original BN1 H4 heat shield (don't know how it could be a shield for anything, due to its very small size !) and 4-blades cooling fan. Of course, spacers are fitted between the intake manifold and the carbs.
So, I bought a 6-blades fan ("tropical"), but, due to temperatures being not high enough, I could't really check the gain provided yet - only noticed the increased noise :(

I think that the second step could be to use the large 100 M heatshield sold by AH Spares, but I remember having had a VERY hard time to remove the carbs 2 years ago (access to some of the carb's flange nuts drove me MAD), so I wish to be sure that this will solve my problem with a reasonable chance of success...

Am I right ?
Thank you in advance for your help, and take care of you and your beloved ones.

Matt
 
Matt
i have not had stalling issues but the car does seem to be harder to start if shut down for a few minutes.
i am trying two new things this year to see if it helps. So far it seems good but i have not had any hotter temps than 80 so far this spring. my two things:

1) i wrapped the fuel line with that fuel line insulation from Napa. they have a tubing and a 2" wide wrap (i think that is the size). i wrapped the line where it comes close to the exhaust manifold from the frame up past the heat shield. i also made a little shield below the fuel pump. just slides in behind the fuel pump mounts and bends under the fuel pump to help deflect heat from the exhaust. (keep in mind my car is a tri-carb)
2) i built a little cold air box for my carbs. idea being when i go to restart the car it will be getting cooler air in sooner. the bottom of my air box is also covered with a heat insulation. i have drilled a hole in the side big enough to stick a meat therm in there just to check air temp but have not had a chance to really check it. will know more once the weather gets warmer.
 
Ok, thank you for these interesting suggestions.
I'll check the behavior as soon as temperatures rise, and if necessary apply some of them. I'll keep you posted.

Matt
 
Though not a problem on my Healey my Elva Courier suffered badly from "heat soaking" and was extremely difficult to restart after a run on a hot day, sometimes requiring 10-15 minutes for things to cool-down--which often presented problems during a race restart, etc.

I solved the problem by running a 1/2" ID hose from the cockpit to a nipple on the intake manifold with a simple 90 degree valve close to hand under the dash. On hot days, etc. I would open the valve while I cranked the engine and the blast of cool air would allow the car to start instantly. I had to be careful to close the valve immediately as otherwise the revs would climb rapidly.

It may seem a bit unorthodox but it worked.
 
Don't forget to check the fuel pump! Had same issues on my BN1..new fuel pump fixed it......
 
Also check the carb adjustment. I had similar symptoms when one of the carbs was running way too rich on my BN1. The jet adjuster was spinning and not winding and so before I noticed this issue I assumed heat soak and went through the process of lagging the exhaust manifold and building a proper heat shield!
 
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