holley accellerator pump adjustment

kalli · 09-09-2009, 09:43 AM

Hi all,

i did a rookie mistake when mounting the carb.
I turned out the idle screw after i changed from ported vacuum to manifold vacuum.
i never adjusted the accellerator pump ... and surely off-idle hesitations like mad.
stupid me never thought of that until today (2 weeks later)

So i adjusted it, job done.
Let my mistake be a lesson for anyone else out there fiddling with a carb
when you adjust idle speed the next step has to be accellerator pump linkage
I adjusted so that I had no play in it anymore and on WOT (engine off) i can still squeeze a bit of petrol out there moving the pump arm with the finger nail

anyway, no that I now what bad off idle hesitation feels like I'm very sensitive to it now. there's still the slightest hesitation left but drives like a different car now.
i have the black cam on #2 position and will try different cams now. probably red next

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Stepman · 09-09-2009, 02:04 PM

Come set mine up when you get it down...I don't have much patience for carbs. Are you using ported now or, did you go back to manifold vacuum?

urban_cowboy · 09-09-2009, 03:54 PM

I have never played with the pump linkage. You just adjusted the height from the pump lever to the screw so there is zero lash?

67mustang302 · 09-09-2009, 05:33 PM

Idle circuits are a good place to fix off idle stumbles. Sometimes(like mine did) they need an idle feed restrictor change. But off idle problems are IRRITATING on daily drivers, since you ALWAYS have to deal with it a lot of the time.

kalli · 09-09-2009, 06:57 PM

stepman: i'm at manifold vacuum. kinda makes more sense to me. but you need to adjust ignition and carb for that, so it's not as simple as switch the pickup port. if you pay for the flight ticket from ireland I'll call and give it a try ;-)

Urban: that's how I understand it. otherwise it will not kick in until you press the throttle so far til lash is gone. and that's exactly where that problem is most annoying. On the other side you cannot adjust to make it longer to the end as when you are at full throttle you still have to have a bit of way for the pump. to make sure you don't jam the pump or bend something, or even worse the linkage might jump over and you'd be stuck at WOT. don't know if it's possible, but if misadjusted like made i think it could happen

67M302: i never heard of idle feed restrictors. have to read on it.
I changed the jets from 58 to 60 and changed the pump cam from black #2 to orange #2
, but that made it even a bit worse. the orange one was used before but i really thought it would put down more fuel. any recommendations on what color to try next?

Kalli

67mustang302 · 09-09-2009, 07:17 PM

The idle feed restrictors are basically the jets for the idle system. After the fuel goes through the main jet into the main fuel well, some of it is diverted into the idle system, where it passes through the idle feed restrictor then mixes with air from the idle air bleed before it goes down to the transfer slot and idle mixture screws. That's why jetting has 0 effect on the idle system, it's controlled with the IFR and IAB. Another reason I got my Quick Fuel, it comes with screw in IFR's, most carbs don't so what you get is what you get.

kalli · 09-10-2009, 07:10 AM

thanks for explaining that. if i can't get the off-idle right (yes. it is irritating like mad) using cams and adjusting the pump i might even look into the QF carbs. why not treat myself ...

67mustang302 · 09-10-2009, 12:46 PM

That's why I got mine...I got tires of trying to work around other problems that you couldn't tune out.

boogerschnot · 09-11-2009, 01:25 AM

great thread Kalli, Im going to check on mine this weekend.. Today I was actually paying attention to my off idle and did notice a little bit of stumble when I would go straight into it, hopefully I can get it with the pump linkage.

kalli · 09-12-2009, 03:43 PM

HA !!!! the blue one was the business for off-idle. installed it this morning and no problems anymore with that crap. it seams a bit lean shot at higher revs, but i'll check on the cam specs again if I can find one with same start rate but more overall and i'll be golden. if that doesn't work I'll just put in a bigger nozzle and start over.
Anyway it's complete gone just off idle. so i can drive off a light without revvinng and switch to 2nd very early with no hoppining around on the throttle :-)

nice ! I'll be getting there. I know it