Holley 750 dp, way rich at idle.

[falkenracing]

Did actually check for straightnes when I hade it apart.
Going to do somthing a little different and ask, does anybody have an other double pumper of the older vintage, or a vac-secondary, and would like to check the index of the air bleed in that one? Just for fun, and as a guide for what holley have provided earlier.

Guess this carb is set up to work with fairly low vacuum at idle, and that it could cause it to run seemingly richer on this kind of mild build. Could I be right here?

[jhaag]

take the carb off and turn it over. look at the throttle blades in relation to the idle transfer slot. both front an rear. my guess is throttle is open too far. close the primaries so you cannot see any of the transfer slot below the throttle blades. open the rear until they are in the same position. rear are adjustable by small set screw on passenger side of carb. put it back on and run for awhile. idle screws should be more responsive. If still rich you need to drill a 1/16" hole in each primary throttle blade. still rich..drill holes in the secondary blades. holes should be on the same side as the idle transfer slot. engine is telling you it wants more air. this is the best way to do it.

[falkenracing]

Ok, good tip there. Should check it out.

[falkenracing]

Ok, this starts to have me confused. I'm still contemplating playing with the air bleeds, but looking at this link: http://www.jegs.com/i/Holley/510/126-71-10/10002/-1?parentProductId=#moreDetails
It kind of looks like they are saying jet is .071" While this drill kit:
http://www.jegs.com/i/JEGS-Performance-Products/555/150110/10002/-1
kind of confuses me, because the smaller the number, the lrger the drill. Or dose the numbers of this chart have nothing to do with the bleed size they are represnting? Still seems odd thou, to hav smaller numbers for larger holes, but that's just me.

Starting to figure things out in the idle department (I think) so going to try some easily retracable stuff this friday and measure with the co-meter at work. If idle co comes down about normal level, the wideband O2 sensor goes in sunday and time to fine tune the entire curve.

[Strawdawg]

Larger the number, the smaller the hole. Strange but true

Steve

[falkenracing]

Sorry, cant get my head around that as I can with my bare see that my 71 primary IAB is signifficantly bigger than secondary 28 IAB, so it doesn't hold true when i check what i have now. Or am I beeing stupid over here?

[Strawdawg]

Sorry,  I was referring to wire drill sizing

Steve

[falkenracing]

Sorry, I was under the misconseption that the drill kit I found was specially for drilling Holley-bleeds, and as such was labled with the same number as would the bleed. You learn something every day when your a little stupid

[Strawdawg]

just find the wire drill that fits the bleed, and then go to the next larger bit and drill it out.  Don't use a drill...use a pin vise and do it by hand

That's not stupid....just inexperienced...

[Chryco Psycho]

I have a set of # drills used for drilling natural gas jets , they have a hex shank so they lock into a drill OK

[falkenracing]

Well, looking thru the tool collection I hav found a .79 drill (2mm), and out of curiosity, i might just do that leap, as there's nothing that can't be reworked and back tracked by just buying a set of smaller bleeds.
Thoghts on that? Either that or a more radical restriction in the IFR to get the idle to lean out properly (tried with out the fron IAB. mounted yeasterdy, idles ok and the stink goes away, but does'nt want to rev up properly, go figure  and falls flat and almost stallls when you let the revs down again)

Once the idle mixture is in a better place I will hook up the wideband O2 and start fiddling with the main system. Just afraid I will foul the O2-sensor with this overly rich mixture at idle right now.

[Chryco Psycho]

not much to lose by trying it

[falkenracing]

Ok, hade some incourraging talks with a fellow muscle car driver, and he told me to go ahead and install the wideband and not to worry about it fouling up due to my rich mixture. So I did. 
On first start up AFR showed at about 12.2:1.
Today I went ahead and jetted down signifficantly from 73 to 69 main on the primaries (secondaries are disabeled for tuning purposes right now)
AFR on idle is down to 13.7 (ish) at idle now, but due to bad weather conditions I did'nt take it for a drive to se wath it would look like under load. Thats what I will be going about tomorrow.

To be continued

[bandt]

Your primary jets shouldn't effect your idle AFR. The idle circuit is the only thing that controls the idle mixture. Unless you inadvertantly changed something else while swapping out the jets.

[Strawdawg]

Your primary jets shouldn't effect your idle AFR. The idle circuit is the only thing that controls the idle mixture. Unless you inadvertantly changed something else while swapping out the jets.

I would agree...sounds like the blades are too far open at idle as suggested above?