[TR] Fuel percolation-Opposite effect

[Alex]

Here's a flip side issue with my TR3A that no one has been able to come up 
with an answer for except a Mini owner who said he had a similar problem due 
to the witches blend.

My 59 TR3A is running su's (earlier model su's) with a stainless heat shield 
between the exhaust manifold and the carbs. This is the standard shield 
available to all. Quite honestly, I installed the shield because it makes me 
nuts to have these carbs directly over a hot manifold. That's another story 
that has to do with my TR6.

Anyway, what happens with my car is there is an ENORMOUS build up of of 
water droplets that form all over the intake manifold and carb bodies. 
(condensation) At one point it was so severe that it flooded out the car. 
When people see this, they cannot believe it. The carbs and intake manifold 
are so cold they feel like they were packed in ice.

I actually thought about taking off the heat shield to help warm up the 
situation. Debating on which is better. But still no one has ever seen this 
or can offer an answer or suggestion.

Alex Manzo
59TR3A
72 TR6



----- Original Message ----- 
From: "Terry Geiger" <tgeiger at geigergarage.com>
To: "'Randall'" <TR3driver at ca.rr.com>; <triumphs at autox.team.net>
Sent: Friday, June 10, 2011 11:22 AM
Subject: [TR] Fuel percolation


> I've seen percolation on several cars over the last year.  I agree with
> Randall, I think it is a result of the fuel they are selling now; the
> addition of the ethanol lowers the boiling point of the fuel.  I've seen
> fuel literally boiling in the jets of an SU H6 equipped TR4 recently. 
> This
> tends to happen after the car sits for about 15 to 20 minutes after 
> shutdown
> and the heat has enough time to "soak" the carb bowls and jets.  The TR4 
> in
> question did have a heat shield and we had rerouted the fuel line away 
> from
> heat sources.  We were also running a low pressure electric fuel pump in 
> the
> boot so vapor lock in the pump wasn't the issue.  We also had a TD (SU H4,
> same design as the H6 used in TR3/TR4) that was doing this recently (which
> has a heat shield).  We insulated the fuel bowls and the bottom of the 
> jets
> which did help the situation but did not entirely cure it.
>
> We haven't seen the problem on MGBs and big Healeys, but they have that 
> nice
> big heat shield with the cancer causing asbestos insulation to help keep 
> the
> carbs more insulated from the heat.
>
> Regarding the heat shield, is there any insulation or is it a bare metal
> shield?  I can see where an insulated heat shield would be work better, 
> the
> bare shield would tend to radiate the heat once it gets hot.  If you could
> get your hands on some flat brake lining material and have it riveted or
> bonded to the heat shield that might help.  Jet coating the exhaust 
> manifold
> I think would help.  Also, fiberglass wrap is used on exhaust components 
> by
> the racers to keep heat down under the bonnet.
>
> Cars with fuel injection wouldn't have a problem, the fuel is under 
> pressure
> which raises the boiling point.  Also, unburned fuel is returned to the 
> tank
> which cools the fuel.  My 1982 Porsche 911 has the Bosch CIS mechanical
> injection and we haven't seen any issues with the new fuel.
>
> Terry Geiger
> www.GeigerGarage.com
>
>
> -----Original Message-----
> From: triumphs-bounces at autox.team.net
> [mailto:triumphs-bounces at autox.team.net] On Behalf Of Randall
> Sent: Friday, June 10, 2011 9:25 AM
> To: triumphs at autox.team.net
> Subject: Re: [TR] BAck again - and with a question
>
>> I thought vapor lock was starvation due to the fact that the fuel pump
>> can't pump vapor.
>
> Me too.  But lots of folks confuse percolation (fuel boiling in the carbs)
> with vapor lock, and it has become a common problem due to the witch's 
> brew
> they sell for gasoline these days.
>
> And even just high underhood temperatures can cause mixture problems,
> especially if your mixture is already on the rich side.
>
> Tell us more about the heat shield.  Is it between the carbs & exhaust? 
> Did
> you set the mixture on a hot day?
>
> -- Randall
>