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TR7 BFH#41 - Zenith carb mixture

To: Triumphs@autox.team.net, british-cars@autox.team.net, tr8@mercury.lcs.mit.edu
Subject: TR7 BFH#41 - Zenith carb mixture
From: Eganb@aol.com
Date: Sun, 31 Dec 2000 01:42:41 EST
Cold enough for you?  

I've only put 100 miles on my rebuilt engine so far, but it seems to be 
running fine.  I'll keep my fingers crossed.  The problem is that it is so 
?!X#$ cold outside, and the heater isn't working yet...

Since everything else in the engine compartment has tended to be "uniquely" 
set up by the previous owner, I'm now turning my attention to the twin Zenith 
Stromberg carbs.  

Luckily, the automatic choke seems to work fine.  I already have a carb 
synchronizing tool from the days with my dad and his MGB/SU carbs, but I need 
to order the mixture adjustment tool for the Zeniths.  

Meanwhile I read an interesting email on the WWWedge mailing list about 
setting the mixture, if you don't have a gas analyzer or colortune spark plug.

The trick was to use an unlit portable propane torch to force propane down 
the carburettor throats.  If the rpm went up, the carb was lean, if it went 
down, rich.  What you were shooting for was a brief increase of 25-50 rpm.  

Can anyone confirm this as a poor man's approach to adjusting mixture, and 
that it won't lead to blowing up the car?  And how about an explanation of 
the logic?

In my VW days I would simply look at the color of the plugs -- black was 
rich, white was lean, and gray was just about right.  Doesn't that still give 
you a general idea of what's going on?    

And what about simply leaning out the carbs until the RPMs drop, and then 
backing off a couple of flats on the adjustment?  

As usual, thanks.  

Bruce
Actually Running 1980 Inca Yellow TR7 5-speed convertible
Chapel Hill, NC

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