[Healeys] Vapor lock gas
healey.nut at gmail.com
Thu May 6 23:13:44 MDT 2021
Did you replace the teflon bushes around the throttle shafts on your HD8s?
If these are old or worn, air will start leaking into the carbs when they
get hot and you idle will become erratic, it can seem like vapor lock but
it might be simply a matter of fuel mixture getting too much air when the
car is hot.
On Thu, May 6, 2021 at 11:13 PM <fsufan1952 at yahoo.com> wrote:
> Hi All ,
> I have a 67 BJ-8 . And when I did a frame off restoration I lived in
> Mass. Well me and my Healey are now living in central Florida. And my mods
> are a set of headers from Dennis Welch along with his matching 2 inch
> exhaust system. I had the headers ceramic coated and I wrapped them with
> header insulation tape . I completely used fuel line insulation wrap from
> mid way on the car all the way up to the carbs . I installed a neat set of
> fuel bowl insulated coozies from Joe Coutu. Along with a new radiator from
> AH Spares and a electronic fan mounted to it . My next mod was a new intake
> manifold , also from AH Spares , there newly designed system with round 2
> inch ports . I also had this ceramic coated . I still install the original
> Healey heat shield . I installed an electronic ignition system and a new SU
> electronic fuel pump .
> Well running around Florida it runs strong . But every time I come to
> a stop light , then pull away I always have vapor lock problems. Stopping
> at a stop light I get no air flow around the carbs . Looking back
> installing those fender rally vents I’m sure would help getting rid of some
> of the engine heat . None of these mods have stopped my vapor lock
> problems. My next attempt at solving the fuel vapor problem is I just
> insalled a cooling fan from Chill Out , a company that specializes in race
> car cooling systems. It’s a 3 inch fan about the size of a beer can . I
> mounted it next to my brake reservoir with ducting on the intake side
> pulling in air from in front of the radiator, then duct work on the output
> side blowing onto the carbs . Unfortunately I ran out of time to test it
> as I’m now back in Mass for 3 weeks. When I get back to Florida I’m
> looking forward to 🤞 seeing if this helps . I can supply pictures of all
> the above mods if anyone is interested.
> Wish me Luck 👍🏻 Don
> Sent from my iPhone
> On May 6, 2021, at 10:03 AM, Alan Seigrist <healey.nut at gmail.com> wrote:
> I have found that having the header and miniature heat shield to be
> ceramic coated makes a huge difference in the engine bay but then transfers
> heat to the exhaust, so it’s only good if you have an SS exhaust system and
> then you need to insulate around the pump as Michael has said. i just wrap
> header tape around the exhaust pipe in that area and that is also effective,
> On Thu, 6 May 2021 at 9:52 PM, Michael Salter <michaelsalter at gmail.com>
>> Hi Ken, yes I think everyone with a 100 has encountered fuel delivery
>> issues with modern fuels. Methanol lowers the boiling point of petrol to a
>> point where it becomes a problem.
>> With the 100 there are 2 distinct issues.
>> Firstly, because the fuel pump and its associated lines are directly
>> above the exhaust pipe, hot air heats them. The fuel in the suction side of
>> the pump has, effectively, a lower boiling point than it would at
>> atmospheric pressure. This fuel tends to boil if there isn't sufficient air
>> circulation to keep the pump and lines cooled, as occurs while stopped in
>> traffic on a hot day. True vapor lock occurs because the pump will not
>> pump sufficient volume of vapour to exceed the rate of its production by
>> the boiling process.
>> Secondly the carburetor float chambers and the small fuel passage to the
>> jet are very close to the exhaust manifold.
>> The manifold radiates lots of heat which heats them. Again when the car
>> is moving at a reasonable pace the incoming air through the grille and
>> around the radiator is sufficient to maintain the carburetor at a low
>> enough temperature to prohibit boiling but, again when stopped in traffic
>> this doesn't happen.
>> I have managed to eliminate the first problem by installing a insulating
>> sleeve from a modern car's AC hose over the fuel line from the tank to the
>> For the second I have made small heatshields from 24 gauge galvanized
>> steel to shield as much as possible of the carburetors from the radiated
>> heat. This has helped considerably but not completely eliminated the
>> For the most part neither of these modifications are visible and I have
>> found that fuel delivery issues, although not completely eliminated, are
>> I am considering installing a small blower and duct sourcing air from
>> behind the grille to see how much difference that makes but if course that
>> will be visible.
>> Hope that helps, others may have found better solutions.
>> On Mon., May 3, 2021, 2:58 p.m. Ken Fleming, <ahmg at aol.com> wrote:
>>> Michael , I thought you maybe have experience this ans have a solution .
>>> On my Bn1 which is M spec with carbs, advance distributed, LeMans Cam and
>>> Pistons has always suffered from what I call vapor lock of gas. Especially
>>> in hot weather .
>>> I am assuming the heat is from
>>> Manifold and it placement near carbs or fuel pump/ battery near exhaust
>>> play a role but I could be wrong . I have asked other owners and they seem
>>> most of them not to have same problem. I do have a heat sheild added with
>>> little result.
>>> I am at a loss as to
>>> What to do
>>> Next , but have you experienced this and have any suggestions. Are my
>>> Correct on heat causing the issue. Could today’s quality if gas be a
>>> I recall reading this was a common issue for 100’s to have vapor issues.
>>> Sent from my iPhone
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