Home Forum Gallery Support  
Register FAQ Advertisers Search Today's Posts Mark Forums Read

Go Back > >

GT40 Tech - Fueling, Electrics, & Engine Cooling Petrol, Electrons, & Water

Thread Tools Display Modes
Old 3rd September 2017, 04:16 PM   #1
johnny cobra's Avatar
johnny cobra
4 Tenths
United Kingdom
Join Date: Jun 2015
Location: Essex
GT40: Tornado GT 40.
Posts: 427
Rich and lean ....

Hi all . another Question for you clever people ..

I am running a 600 Holley and doing the final settings and I cant for the life of me remember ... is it screw the air screws in to richen the mixture and screw out to weaken ?

Thanks guys John..
Tornado 40 330 BHP IVA passed ........
johnny cobra is offline   Reply With Quote
Old 3rd September 2017, 06:37 PM   #2
blueovalz's Avatar
Skinny Man
United States
Join Date: Aug 2008
Location: Arkansas
GT40: An orange car
Posts: 2,128
Re: Rich and lean ....

Depends on the model you have. The early or "traditional" Holleys lean as the screw is turned in (cuts off fuel when screwed all the way in). The later emissions had a nylon thingy on the screw, and they were opposite. Long story short:

There are two different types of idle screw circuits used in our Holley carbs.

The regular type we are aware of, are FUEL screws, in leans out, out richens. These screws have the same outer diameter their entire length.
The "reverse" type is an AIR screw, in richens, out leans, to a point. These screws have an enlarged head with serrations at the outer end of the screw, and are usually covered by a plastic limiter cap over the end of the screw.

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
blueovalz is offline   Reply With Quote
Old 4th September 2017, 05:16 AM   #3
MikeP's Avatar
Gold Supporter
United Kingdom
Join Date: Dec 2005
Location: Oldham
Posts: 1,477
Re: Rich and lean ....

I first set the carb level when the car is level using a wedge plate. As my engine is slightly nose down and the Edelbrock manifold is angled the other way i use a 5 degree wedge plate to get the carb level. My Holley is the type where the mixture screws adjust the fuel flow and hence in is leaner and out is richer. Set the fuel pressure to 6psi.
I then set the fuel levels on both sides by adjusting the float screw. With the fuel pump running to maintain fuel pressure remove the sight level screw. Have a small container or a rag ready to catch the fuel if the fuel level is way too high and a lot runs out. Loosen the big slot screw and the adjust the float level nut until the fuel only just weeps from the sight hole. Then retighten the big slot screw and replace the sight plug. Be careful not to damage the very thin washers on the level nuts. They are very thin so I have some spare just in case I mash them.
Turn the mixture screws fully in but only very lightly and then unscrew 1.5 turns. This should be near enough to get it running well enough to get the engine warmed up. Then adjust both the mixture screws 1/8th of a turn in or out until the best idle is achieved. Or attach a vacuum gauge to the inlet manifold and adjust for maximum vacuum.

MikeP is online now   Reply With Quote
Old 4th September 2017, 07:30 AM   #4
jac mac's Avatar
jac mac
I Have No Life
New Zealand
Join Date: Dec 2005
Location: Gore, NZ
Posts: 4,373
Re: Rich and lean ....

With regard to setting the carb pad level, take a closer look at your Holley and you will find the fuel level sight screw plugs are slightly lower on front and higher on the rear float bowl to allow for the nose high engine attitude on virtually every production car they are fitted to.
AMGT Rep Steel Mono x Plans, FE328 T44R.
[email protected]
jac mac is offline   Reply With Quote

air, guys, john, remember, screw

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

All times are GMT -4. The time now is 11:12 AM.