Lars-need carb help
Thread Starter
Racer
Joined: Jan 2001
Posts: 334
Likes: 1
From: Averill Park N.Y.
Lars-need carb help
Need help setting throttle plates per Lars instructions.
Background: I have a 670 Holley Avenger on a ZZ4. I have had idle problems right along. It idles way too rich so I decided to set the throttle plate per Lars. I set the plates showing .020" of the transition slots on both the primaries & the secondaries. Now it idles at about 1500 rpms and I can't slow it down. Also note that I cannot close the primaries plates any further. Seems like something is binding. Please help.
:confused:
Background: I have a 670 Holley Avenger on a ZZ4. I have had idle problems right along. It idles way too rich so I decided to set the throttle plate per Lars. I set the plates showing .020" of the transition slots on both the primaries & the secondaries. Now it idles at about 1500 rpms and I can't slow it down. Also note that I cannot close the primaries plates any further. Seems like something is binding. Please help.
:confused:
Safety Car
Joined: Jul 2002
Posts: 3,770
Likes: 3
From: St Louis MO
Re: Lars-need carb help (Ken74Conv)
You should take it back off and re-adjust the throttle plates to get about .006-.008 of the transition slot showing. Note that this does not change the idle mixture...that's done by the idle mix screws or changing the amount of air the idle air bleeds into the mix or changing the amount of gas fed through the idle ports in the metering block.
Brett :thumbs:
Brett :thumbs:
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
Re: Lars-need carb help (Ken74Conv)
You've ruled out a timing issue - is your initial timing set too advanced? If your vacuum advance is connected to manifold vacuum try to connect it to ported vacuum so that at idle the vacuum advance does not advance your timing. Just something to rule out. :cheers:
Thread Starter
Racer
Joined: Jan 2001
Posts: 334
Likes: 1
From: Averill Park N.Y.
Re: Lars-need carb help (Boofers)
Thanks, but the timing is at 36 deg. full advance. Distributor rebuilt by Lars.
Vacuum advance is ported so there is not advance at idle.
:confused:
Vacuum advance is ported so there is not advance at idle.
:confused:
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Lars-need carb help (Ken74Conv)
Ken -
On the Holleys with 2-corner idle circuits, the secondary transition slots are higher up in the throttle bores than the primary slots. If you set the secondary throttles to expose .020" of the transition slot, the idle speed will be too high. Instead, do this:
First, set the primary side as you did to expose .020" of the transition. Then, hold the carb up to a light and look up the bottom of the carb: Set the secondary throttles to create the same "light gap" around the secondary throttle blades as you see around the primary blades. This will get you the same throttle opening at all 4 corners.
Once done, bolt the carb back on and test the idle speed. If you have to adjust the primary side speed screw more than 1/4 turn, pop the carb back off and make an equal adjustment to the secondary screw. Repeat as necessary to obtain the proper idle speed while keeping the primary and secondary throttle openings identical.
On the Holleys with 2-corner idle circuits, the secondary transition slots are higher up in the throttle bores than the primary slots. If you set the secondary throttles to expose .020" of the transition slot, the idle speed will be too high. Instead, do this:
First, set the primary side as you did to expose .020" of the transition. Then, hold the carb up to a light and look up the bottom of the carb: Set the secondary throttles to create the same "light gap" around the secondary throttle blades as you see around the primary blades. This will get you the same throttle opening at all 4 corners.
Once done, bolt the carb back on and test the idle speed. If you have to adjust the primary side speed screw more than 1/4 turn, pop the carb back off and make an equal adjustment to the secondary screw. Repeat as necessary to obtain the proper idle speed while keeping the primary and secondary throttle openings identical.
