Need Holley Adjustment info

[Larry E.]

Hello:

We just bought a nice #4555 carb for the LT-1 engine. Those 2 little screws on
top of the carb just below the model number have been changed from the factory
setting. I'm told the factory set these and put some type of putty on them so
no one would reajust them. Well mine have been moved. Any idea on how to set
them? Carb is not on the engine. Believe the screws are to set idle mixture.

Thanks; Larry

[John H.]

Re: Need Holley Adjustment info

Larry -

Connect a vacuum gauge to a full manifold vacuum source and work back and forth between the two idle mixture screws (adjusting the idle SPEED screw as necessary) to achieve the highest steady vacuum reading. If the idle mixure screws have been disturbed, 1-1/2 turns out from lightly seated is a good starting point.

[Larry E.]

Re: Need Holley Adjustment info

John:

Just want to make sure we are talking about the two tiny screws that face up
right by the top of the air horn. These are not the screws that are on the side
of the carb. I noticed that not all carbs have these screws. This perticular
carb is a new remake from Holley for the #4555. Thanks for the help.

Larry

[John H.]

Re: Need Holley Adjustment info

Larry -

Got your e-mail - send me a photo if you can; don't know what the "tiny vertical screws" might be, unless they're removable (vs. pressed-in) air bleeds.

[Clem Z.]

Re: Need Holley Adjustment info

those are final adjustment for emissions at idle.i am at the PRI show this week and i will ask the guy at the holley booth who i get my info from

[Clem Z.]

Re: Need Holley Adjustment info

these were set on a air box and there is no way to duplicate the setting.best bet is to check the same carb/engine combo that did not use these adjustment screws and use the same air bleed/jet combo and block these adjustment passages.