[Mg-t] Too high idle speed

[Dan]

Listers, 

 

I have done all the homework I can, and now at wit's end, I need your
expertise.  Sorry for the length of this request, I am trying to include all
relevant info.  

 

Though I have driven my '54 TF more than 500 miles since engine was
partially rebuilt by a factory trained (back then) mechanic.  Top end only,
and I am not sure of each and every thing he did, but it included a good
used stock cam, and new valve guides at least.  Each cylinder compression
reads right around 140 psi.  Carbs were rebuilt by another veteran of
similar vintage whose TSO ads you would be familiar with.  These gentlemen
are well experienced, so it seems unlikely they put things back together
wrong.  I have thus assumed the jets are properly centered (they come down
with a "clunk" when lifted and let go).  The idle adjustment screws were set
with the connecting rod loosened so that each adjustment screw was
independent of the other.  

 

After many tries at tuning, I finally took the car to the local LBC shop
(which restores and maintains many British and special sports cars).  They
corrected the timing, re-balanced the carbs and adjusted the mixture.  It
runs much better, and after 100 miles last weekend, the plugs are light tan,
all of them.  

 

Here's the problem.  The idle speed is still 1200 - 1300 RPM and the
adjustment screws as far out as they will go without actually removing them.


 

Having reviewed Mr. Old's articles on tuning from The T Series Handbook (did
my homework as best I could), I am concerned about his paragraph saying the
most likely cause of inability to adjust RPMs to the desired 800 - 900 is an
intake air leak.  I tested this with an unlit propane torch, but was unable
to perceive any change in engine speed or performance.  I am concerned
because of Mr. Old's admonition that with an intake leak the car might idle
OK, but will suffer from a wrong mixture as the engine is revved up under
driving conditions.   He says that bad things can happen then.  I also
reviewed the archives, and I really don't want to get into removing the
newly rebuilt carbs unless I have to (Lawrie Alexander's instructions to a
TD owner.)

 

Is my only option to change out the intake / exhaust gasket to be sure there
is no leak?  Is there any other way to understand what is happening, or to
make this adjustment?  Should I stop driving the car until this is solved?
Or, should I quit worrying and drive the car with the idle at 1200 to 1300?


 

Any help appreciated.  

 

Dan

TF Car # 3563