Subject: [Fot] need help w/40 DCOE 151 carb setup

From: "J.C. Hassall" <[email-masked]>
Date: Mon, 20 Aug 2012 19:25:19 -0400

Gurus, I need some help with my Webers.  I have a matched pair of 151s 
with the following configuration: 55F8 idle jets, 1 1/2 to 1 3/4 turns 
on the idle mixture screws, idles nicely at 1K RPM with ~ 1/2 turn on 
the idle speed screw.  Accelerator pump jets are 40s, the pump exhaust 
valve hole soldered shut (the ball valve still works).  Main jets ranged 
from 150 to 120, with various combinations of air bleeds from 150 to 
190.  The plastic float levels have been set to 14.5 and 22mm, to reduce 
fuel in the well.  The problem is that above ~2K RPM the AFR drops to 
high 10, low 11, so of course the engine runs like crap.  One more bit 
of info: fully closed the throttle plates are mid-way in the first 
progression hole.  One Weber parts distributor said that was correct for 
151s, another said that the carbs must be binding because the 
progression holes should be clear at fully closed throttle.  Hmmm.  The 
throttles have no binding that I can feel (linkage disconnected).

I took a set of main jets and filled the fuel hole with JB Weld, 
thinking I'd start really small and work up.  As a baseline test I made 
a run with the hole still closed and the AFR was still ~11.5.  Ah ha!  
That tells me that it's not the main circuit which is the problem but 
rather the accelerator pump circuit.  I noticed that at 2100-2200 RPM a 
ball of fuel forms on the jet, then drops into the venturi; that seems 
wrong to me, but I've not found any info in a myriad of Weber books on 
what might be wrong in the accelerator circuit .

Falling back on my Army career, I'm tempted to implement my mantra that 
"there's no problem that judicially placed high explosive can't solve".  
Before I start shopping for C4, anyone have any ideas?  Any and all 
advice gratefully accepted.

Tnx!

jim

-- 
Jim Hassall
Blacksburg VA
'63 TR4 in autox preparation
99% finished, 90% to go
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From: "Walter Hollowell" <[email-masked]>
Date: Mon, 20 Aug 2012 18:31:44 -0600

My TR6 racecar with triple Weber 40 DCOEs runs well with the following
setup. I am running at 12:1 compression, lots of porting and bigger valves.
A very strong camshaft but not full race. 
Also, I am at 5,500 feet above sea level.

Main Jets		130
Air			200
Emulsion Tube		F7
Idle jets		55F9
Acel pump Jet		40
Bleed off set to		Zero
Idle mix screws set to two turns

Walt Hollowell
Albuquerque, New Mexico

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of J.C. Hassall
Sent: Monday, August 20, 2012 5:25 PM
To: fot
Subject: [Fot] need help w/40 DCOE 151 carb setup

Gurus, I need some help with my Webers.  I have a matched pair of 151s with
the following configuration: 55F8 idle jets, 1 1/2 to 1 3/4 turns on the
idle mixture screws, idles nicely at 1K RPM with ~ 1/2 turn on the idle
speed screw.  Accelerator pump jets are 40s, the pump exhaust valve hole
soldered shut (the ball valve still works).  Main jets ranged from 150 to
120, with various combinations of air bleeds from 150 to 190.  The plastic
float levels have been set to 14.5 and 22mm, to reduce fuel in the well.
The problem is that above ~2K RPM the AFR drops to high 10, low 11, so of
course the engine runs like crap.  One more bit of info: fully closed the
throttle plates are mid-way in the first progression hole.  One Weber parts
distributor said that was correct for 151s, another said that the carbs must
be binding because the progression holes should be clear at fully closed
throttle.  Hmmm.  The throttles have no binding that I can feel (linkage
disconnected).

I took a set of main jets and filled the fuel hole with JB Weld, thinking
I'd start really small and work up.  As a baseline test I made a run with
the hole still closed and the AFR was still ~11.5.  Ah ha!  
That tells me that it's not the main circuit which is the problem but rather
the accelerator pump circuit.  I noticed that at 2100-2200 RPM a ball of
fuel forms on the jet, then drops into the venturi; that seems wrong to me,
but I've not found any info in a myriad of Weber books on what might be
wrong in the accelerator circuit .

Falling back on my Army career, I'm tempted to implement my mantra that
"there's no problem that judicially placed high explosive can't solve".  
Before I start shopping for C4, anyone have any ideas?  Any and all advice
gratefully accepted.

Tnx!

jim

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Unsubscribe: http://autox.team.net/mailman/options/fot/[email-masked]

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