[Land-speed] Carb Lean Out Help Needed.

[Ed Van Scoy]

It could be a lot of things, but the most obvious would be a jetting problem.
maybe go up a few numbers. Also an over-looked tuning aspect is the air
bleeds.... high speed bleeds in this case. The high speed air bleed or also
referred to as the "main bleed" correlates to the main system. The high speed
air bleed controls how much air is fed to the emulsion channels of the
metering block. The emulsion channels distribute that air further to different
parts of the main well where it mixes with fuel and ultimately goes to the
booster. The high speed air bleed is generally located closest to the squirter
when looking at most race carburetors. In my case, once you get the bleeds
right, I leave them alone, but I chase the tune at Bonneville by changing carb
main jets..... In his case richer might help.
Ed
-----Original Message-----
From: Larry Mayfield [mailto:drmayf at mayfco.com]
Sent: Sunday, February 9, 2014 05:25 PM
To: land-speed at autox.team.net
Subject: [Land-speed] Carb Lean Out Help Needed.

Not for me, of course, I run EFI. But one of my associates in the SunbeamTiger
world races his car on circuit tracks and is having a lean out issue.He runs a
Holley carb not by choice but by rules. He has a small hood scoopwhichis
forward facing and is about 8 squares inches in opening size. And itis sealed
to the carb or the carb is in a box, so to speak. This is on aFord 289 motor.
It is built. He uses an Innovate AFR wide Band system tomonitor his fueling.
He says that when he launches in low that AFR is low12, maybe 12.0 or so.
Second, it starts to lean out, ditto third at around140 mph, it is running
more than a full point leaner, a tad more than 13.0.So he is either getting
more air or less fuel, but he does say that his fuelpressure is rock solid. I
asked him about the appropriate size of the powervalve and also if he might
have a vacuum leak that manifests under load. Hesaid he didn't think so. So, I
am asking, on his behalf, the folk who run a carb on the salt or EMand no
other power adders, if they have experienced anything like this, andif so, did
you find a solution that I might pass along to him. Or anyadditional trouble
shooting ideas. He is not a noob at this so I am sure hehas checked all the
normal rational things. Any help out
there?mayf_________________________drmayfWorlds Fastest Sunbeam,
period.204.913 mph flying mile210.779 mph exit
speed_______________________________________________Land-speed at autox.team.net
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