Carb Question
 

Carb Guys, Education needed on 1150 Dom.carb adjustment. E85 race carb shows lean for first 2-3 ish seconds after launch off trans brake on O2 reading. Car runs 9.0 on motor and is plenty rich at top end (110 jetting). Carb is 3 circuit with external adj. screw on metering block,set 1 turn out.
What adj. can I make to richen carb after launch,or is this normal? Thanks, Rich

Does the secondary side have jet extensions? Sounds like its leaving hard enough to uncover the rear jets.

yes

Lean but may or may not be on all cylinders. Hard to tell when you only have one Ox sensor.




What’s your fuel pressure ?

The G force of a lunch taking a car deep in the 9s hads been shown to back out .3 lbs of pressure per ft of fuel line after the pump if it’s back around the tank area.

Float levels up? Maybe go to a smaller air bleed on the intermediate circuit?

fuel 6.5psi, fuel level 5/8 in glass.
not sure what to do with 3rd circuit, has screw on side of metering block in fuel and .028 air bleed on top of carb.

also big fuel pump with return reg

Have you trimmed the rear metering block whistle about .400" on the length and then copied
the previous opening shape of the whistle on that shorter length on the rear of the carb????

Tom V.

did not, what does whistle do?

Whistle provides the entry of atmospheric pressure into the Carb Bowls.
All Dominators should have been built with One Whistle on the front metering block
and One Whistle on the rear metering block.

The fuel "runs away" from the entry opening on the Front Whistle.

The Fuel packs up on the back wall of the Rear Bowl Whistle on hard acceleration,
the fuel moves forward and seals the Whistle's opening with fuel.

No atmospheric pressure on the rear bowl and the fuel stops moving thru the metering block passages. Then you have a lean "hole" in the acceleration until the fuel settles back in the bowl and the atmospheric pressure is restored to the rear bowl again.
It can stop the fuel flow for a couple of seconds.

So the "fix" can be sometimes: Make the rear vent whistle about .400" shorter so that the fuel moving upward in the rear bowl and forward, will not block the opening for atmospheric air to enter the rear bowl properly.

Tom V.

Thanks, Will look into that today at the track

Tom V, You're information was dead on! I took the rear bowl off and shortened the whistle approximately 3/8". I took the front bowl off and was reminded that at one point the whistle fell off metering block and jammed the float, flooding the carb . I left off,not knowing better.
I installed a whistle and made a run which made an 8.98, AND a flatter afr at the beginning 0-3 seconds. A slight rise in afr was present after the shift of the PG Trans, which I think is the job of the 3rd circuit adjustment. I would welcome more explanation of the 3rd circuit if you care to. My metering block has a needle valve between the air bleed/fuel jet. Much Thanks for you're information! Rich

You can mess for stuff for years and not figure out what was wrong with carbs.

OR you can go to a guy like Shaker455 who I have sometimes helped with carbs (He does all of them).
a very good friend. Recommend him to build carbs for members.

Or you can ask a Holley question and I can sometimes provide a small amount of info on the carbs I
have played with over the years. Glad I could help you out.

Tom V.

I'm always learning something on these boards. Thanks Tom! Now my challenge is to remember it!!!!

Steve

You are welcome!

Tom V.