Holley 750vs lean spike

[Lit549]

I recently installed a holkey 3310 (750vs) on my 355 vortec with a comp xr270hr cam.Headers,msd,edelbrock eps..
I have a afr gauge and its pretty rich and it spikes lean anytime i transition off idle circuit causing a momentary hesitation.Ive installed a secondary block to have changeable bleeds as the plate was WAY to rich at wot.Ive got secondary pretty good(12.5:1).I have the pink cam on acc pump (30cc),secondary has next to the lightest spring.Ive went all the way up to 42 squirter and it didnt effect lean spot at all..So i went back to a 37.I was at 72 primary jet and i went up to a 75 which almost cured the lean spike,but now im too rich on that circuit.I was at 14:1 with 72's,now at cruise its around 12.8:1 ,and it STILL spikes lean on transition but not as bad.So ny question,how do i fatten up the lean spike without richening that circuit?Ifr's?Iab's?Enlarge the idle well??Heres my numbers before and after jet change.
idle - - 13.5:1
cruise- - 14.5:1
Wot- - 12.5:1

After jet change
idle 12.7:1
cruise- - 13.3:1
wot- - 12.5:1
Any carb gurus that can point me in the right direction??
Lean spike was going from 13:1 to 20:1
now after jet change it goes from 12.8:1 to about 15:1 which is great but now im too rich ..

[squirrel]

I've played with a couple Holleys with an afr gauge, and decided that they work just fine when it's way rich (according to the gauge)....ignorance is bliss. Set it up so it runs good, and if it's leaner than 11 under most driving conditions, it's working pretty much as designed.

Not that I'm a pessimist, or anything....

[Lit549]

hey i appreciate the reaponse..I agree but im so OCD i want it perfect,but i know its not going to make a big mpg difference.I had a QF 680 hr on it that was pretty good but i just had to have a 750vs,lol..I coukdnt ever get the Qf to idle right..So in your experience,im ok with how rich it is (judging from my posted afr #'s)??
72 jets was perfect on cruise but was spiking lean..Maybe itss just too big for my application?

[anotheridiot]

Isnt the lean spike just a function of the accelerator pump if it goes away again?

[squirrel]

The numbers look a little lean, compared to the Holley's I've played with that ran good.

[Lit549]

Cool,thanks Squirrel..It dam sure dont smell lean,lol..No mosquitos though..Another Idiot- Thats what i thought but ive tried EVERYTHING on that circuit to no avail. I read on another site that this one carb shop fixed this lean spot by enlarging the idle circuit?I also seen other fixes like Ifr's..Idk but the only thing that has made it better is jetting up..And it STILL does it when its cold..When it warms up it doesnt do it but its pretty rich..

[squirrel]

try a smaller carb

[Lit549]

try a smaller carb

Thats about to be my conclusion!I had a qf 680 on it,shpuldve kept it!

[cstmwgn]

you didn't mention what dash (-) number you had. If its a newer one with the straight booster they may not be picking up the signal as well as the older downleg booster. You also didn't mention where the throttle blades were in respect to the idle transition slot. Most folks can't change the booster so the next thing you could check would be the throttle blade position. If you have had to raise the blades to get the idle correct and therefore have used up too much of the transition slot, then the old method of fixing that was drilling small holes in the throttle blades - if you decide to go this route be VERY CAREFUL to not drill them too big! There was also an old shade tree fix of bending a small diameter wire in an "V" and putting it into the idle feed restrictor in the metering block.

[Lit549]

3310- 6 ,2790 under that..

[Lit549]

[cstmwgn]

Yeah, those look like the straight boosters to me. Like I said, most folks can't change them (special tools required). I didn't ask and it is very hard to tune over the internet but when you changed the jets and the idle mixture richened up, did you attempt to use the idle screws to lean it back out and get it back to where it was before the jet change?

[Lit549]

yes,i set them lean best.Still too rich at idle..Hell,they used yhis carb on the comp cam i have,on dyno sheet (cam card)

[cstmwgn]

If the carb is responding to the idle screw changes then further restricting the channel may not help. Can you look at the transfer slot to see how much is used up at idle?

[Lit549]

If the carb is responding to the idle screw changes then further restricting the channel may not help. Can you look at the transfer slot to see how much is used up at idle?

The screws are only about a half a turn out,i cant tell on the transfer slot,i took it off awhile back and it looks squared..