leaning out a Holley HP at idle

[antmnte]

He's trying to lean it out, putting a wire in the air bleed would effectively make the hole smaller which would richen up the mixture not lean it out.

I was talking about the tiny little holes with brass inserts in the bottom of the primary metering block not the bleeds in the top of the primaries.

[Scott Liggett]

He can do that too. But if his car has changeable air bleeds, thats a better solution.

[Cyclone03]

I have found the idle/transition circuit is very much in play at low ,sub 2000rpm cruise. I do agree if the mixture screws can be turned all the way in you have either a blown power valve (unlikely on the HP because it has backfire protection IIRC) or the IFR is too big. I would lean the IFR first. The IAB will lean the idle mixture but it will also lean the transition circuit by "cutting it off" sooner and possibly creating a lean "hole" prior to the main jet coming in. Most likely the IAB is a .073 or .070" much larger than .073 will most likely require a larger IFR and open up more tuning to make work.
Drop your IFR .002" and retest,your life will be easier.

[antmnte]

He can do that too. But if his car has changeable air bleeds, thats a better solution.

Scott, the carb tuning article you did shows adding the piece of wire to a different hole. I was wondering what would be better?

[Scott Liggett]

Doing this, I was able to bring up AFR's by two points.

[Falcon67]

As above or get some IABs same size as stock and drill them out .001 at a time and test. Better it to stick some #14 stranded wire in the IFR and re-test. Quick and easy to see if that gives a better response with the idle screws. Also, I've yet to see a "blown power valve". What I do see - a LOT - is ethanol flavored fuel deteriorating the PV gaskets and allowing them to leak. I'm also seeing sealing issues with blue gaskets and stock metering blocks. Everything has to be clean/clean during assembly.

[Huskinhano]

FYI, I just bought a set of micro drill bits from 61 to 80 with a hand held collect to my door for $7.82. Got them on fleabay. I'm going to tune my snow blower carb so it runs half way decent.

[malc]

If I have carb issues the first thing I do is install a new power valve, then take it from there.

[Scott Liggett]

As above or get some IABs same size as stock and drill them out .001 at a time and test. Better it to stick some #14 stranded wire in the IFR and re-test. Quick and easy to see if that gives a better response with the idle screws. Also, I've yet to see a "blown power valve". What I do see - a LOT - is ethanol flavored fuel deteriorating the PV gaskets and allowing them to leak. I'm also seeing sealing issues with blue gaskets and stock metering blocks. Everything has to be clean/clean during assembly.

According to Holley's carb reps which came by the company I work for, all gaskets are now designed to withstand ethanol use.

There is no leaks with the wire because the wire gets pushed into the gasket upon tightening the bolts. They do not extend past the gasket leaving a trail for gas to follow. That carb has been on my car since I made these modifications in June of last year. No leaks anywhere. Throttle response and gas mileage both improved. Hot idle AFR's are 13:1.

[Techmarcb]

sorry for my lack of activity, my engine developed a light knock. i have remedied that and i figured while i had it all apart i would check the transfer slots on my carb. the secondary transfer slots were totally covered up on the secondary throttle plates. i have set that to about an 1/8th inch exposed. i also dropped jet sizes and i will report back after i get the car back together this weekend.

basically anything over 2000 rpm light load it would run stupid rich. under WOT the AFR was in check 12.6~ or so all the way up the RPM range through all three gears.

[Techmarcb]

Doing this, I was able to bring up AFR's by two points.

is that affected cruising AFR or WOT? or perhaps even both?

[malc]

sorry for my lack of activity, my engine developed a light knock. i have remedied that and i figured while i had it all apart i would check the transfer slots on my carb. the secondary transfer slots were totally covered up on the secondary throttle plates. i have set that to about an 1/8th inch exposed. i also dropped jet sizes and i will report back after i get the car back together this weekend.

basically anything over 2000 rpm light load it would run stupid rich. under WOT the AFR was in check 12.6~ or so all the way up the RPM range through all three gears.

Instructions for my 750 Demon told me the secondaries should be covered and the primaries just open enough to make a "square."

[BigAL]

Instructions for my 750 Demon told me the secondaries should be covered and the primaries just open enough to make a "square."

That carb has the idle adjuster where the carb stud is, so your not really adjusting the idle with the throttle blades. It works for this carb but not for Holley's that don't have the center idle adjuster. If you have a 4 corner idle carb all the blades should be set like the primaries in the pic above. Though on larger cammed engines you may have to open them up a to get the engine to run. Also if I remember right you don't want more than .060 of the transfer slot to show, more than that and it'll start pulling off the main circuit. Basically if your have both front and rear throttle blades open to where .060 of the transfer slot is showing and the engine still won't run you have to drill holes in the throttle blades to get the added air through.

[Techmarcb]

i got it all back together over the weekend. i need to pull the carburetor back off and readjust the secondary throttle plates, i couldnt get it to idle happily under 1500 rpm, pulling 13 inches of vacuum. i have too much transfer slot showing on the secondaries, i was able to shut the primary throttle blades all the way and still have the car idle at 14-1500 rpm. too high, although AFR reading was in the 15's at that engine speed.

[milner351]

One of the things I dislike about holley carbs - to adjust the secondary throttle plates idle position - you have to remove it and flip it over, hopefully you only have to adjust it once.