Art Brock

I recently added a new Holley Avenger 570 to my 302. (I also added a new Summit Racing dizzy, new plugs & wires).
I have been following Kallis thread lately & we seem to have the same or at least a very similar problem.
My car runs fine when I nail the throttle, with no hesitation or bog, even with the lightest long yellow spring that came with the carb. But I am using the plain spring now, just to eliminate that as the cause of my prblems.
But leaving a stop light, or gentling accelerating from a low cruising speed, I get a bad hesitation. I have to give her more pedal than I should have to just to get her moving. Trying to leave a stop light at a normal pace & the car just jump & lunges after a hiccup or two.
Timing is about 12 degrees, all in by 3500 (34 degrees). Vac in gear is 14-15 pounds.
WOT feels fine. Dring at 30-40MPH & flooring it & I have no hesitation at all.
So I'm thinking accelerator pump. Should I order some cams & try swapping it. Or should I try getting bigger squitters? (or maybe drilling mine out a little bigger, I think they are .031 now). I did read in a old Holley manual that if you have an auto tranny you may need bigger squitters than what comes stock.
Help please!!!!!!! I look like I'm trying to drag race every time I leave a stop light now.

kalli

very familiar :-)
after way more driving I figured that it sometimes happens more and sometimes less. Just because it happens sometimes I adjusted my driving and then found that occasionally (i usually only try if noone's around) it actually works normal (no hesitation off idle).
I realised that sometimes I have air in my fuel filter and I guess it's the same as with a brake. If air is in there then there's no way to actually get a solid fuel pressure. no matter what the pump does it'll just compress the air in the line. (Think float level!)
I don't run out of juice anymore. it's not that bad anymore since I put in the rubber spacer gasket. But it's either my carb getting warm releasing air into fuel line or the fuel line sucks air somewhere when hot. I'm still investigating this and probably will re-route the fuel line going into engine compartment. Away from headers. I'm thinking about ditching my fuel pump and get a gerotor design. Holley black with int regulator or the mallory. I'm so sick of the noise in the back. whhhhhhhhhhhhtthwhwhwhtthhwhhhwtwhhhtwwww ... car squeaks enough already as is, no need tto add more noisemakers :-)

That said for the hesitation I'll check first off all on what cam I actually have in the pump. that's step 1. I'll order 2 powervalves (9.5 and 10.5). If changing the cam and playing with PV does not resolve the issue I'll drill a hole into the firewall to attach a vacuum gauge ....

Good luck. I'll keep reading your post as well. Maybe I cna get ideas from there.


Kalli

boogerschnot

Wow.. I guess I just got lucky with my 670 holley, its perfect on my 351. The only adjustments I have made thus far are the fast idle.. It was at about 2200 RPM when I first started, now its at about 1200 until it warms up and back down to 750. And I adjusted the fuel mixture to bring my vaccume up to right at 19-20.. Which is great.

Maybe you do need a different cam for your pump just to get a little more of a shot so you dont bog off the line.

JMD

This MIGHT provide some insight. Ever since I had seen Kalli's p0ost about this issue I have been trying to remember where I saw this info... just remembered.....

1965screamer

A few years back I had the same problem and it turns out that the motor mount was broke causing one side of the engine to torque up and down on takeoff creating a bad hesitation. This probly isnt your problem since it has just occured since the carb swap but anythings possible.

67mustang302

Try a pump cam with a faster ramp rate, like the orange, or maybe the blue or green. It might need more timing curve or more vacuum advance, or it might need the power valve to open sooner.

kalli

JMD: that's how I understand it as well/. if you feel the secondaries opening then there's something wrong. power increase ya, but no bog and no jump :-)
thankfully this is sorted so I'll go down the route of changing the accellerator pump cam to see what happesn. hope a friend of mine has a set. if not I'll order weekend

Art Brock

I think I have solved my low speed stumbling problem. I checked the vacuum advance on my new distributer & it was adjusted almost all the way in the direction of less advance (can't remember if that was CW or CCW right now). Anyway, I kept adjusting & test driving until I started getting a little spark knock then I adjusted about 1 turn in the opposite direction. My hesitation seems to be gone & acceleration is nice & smooth now. I apologize to my Holley for thinking it was the problem.

kalli

nice one :-)

trashline

lol BAD HOLLEY!!!