[Healeys] Vapor lock gas

Michael Salter michaelsalter at gmail.com
Fri May 7 06:59:33 MDT 2021

*re: "Methanol[sic] lowers the boiling point ..." Typo?*

Have I got that wrong Bob?

*"Following the crude oil price shocks of the 1970’s, methanol blends for
use in the onroadvehicle fleet began extensive studies in the later 1970’s
and the 1980’s. Based onthis early research, methanol blends containing up
to 15 vol% (M15) were successfullyoperated by automakers or oil companies
in a number of large vehicle fleet trials (~ 1000 vehicles each) in Sweden,
Germany, New Zealand and China during thattime. Also during that time
period, methanol gasoline blends containing as much as 5 vol% with
co-solvent alcohols werecommercially introduced in Europe and the U.S.A.
Because carburetted fuel systems with older elastomer parts were part
ofvehicle fleets on the road at that time and had limited ability to
handled high oxygen content in the fuel, the fully commercialmethanol
blends were generally limited to 3 to 5 vol% of the gasoline blend with
some co-solvents also added to provide fuelstability. However, with today’s
modern pressurised fuel injector systems using feedback control loops and
also using moreadvance fuel system materials, current experience suggests
that methanol blends as high as 15 vol% (M15) of the gasolineblend with
adequate co-solvents and corrosion inhibitors can now be successfully used
in today’s more modern vehicles inuse today. Many provinces in China have
been commercially using M15 blends as early as 2005, and China’s M15 use
hasbeen expanding because of very favourable economics compared to higher
cost petroleum fuels."*


On Thu, May 6, 2021 at 11:03 AM Bob Spidell <bspidell at comcast.net> wrote:

> re: "Methanol[sic] lowers the boiling point ..."
> Typo?
> On 5/6/2021 6:51 AM, Michael Salter wrote:
> 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
> pump.
> 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
> problem.
> For the most part neither of these modifications are visible and I have
> found that fuel delivery issues, although not completely eliminated, are
> manageable.
> 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.
> M
> 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
>> assumptions
>> Correct on heat causing the issue.  Could today’s quality if gas be a
>> issue?
>> I recall reading this was a common issue for 100’s to have vapor issues.
>> Ken
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