Street Avenger issues

Z06killinSBF · Apr 3, 2010

New Holley Street Avenger 670 problems consist of:

1) won't smoothly idle below 1k. Wants to maintain idle around 1100 or else it surges then dies.

2) Bogs really hard upon tip in or WOT. I installed the black vacuum sec spring to no avail.

3) decides to have random idle/throttle hangs on it's own.

The one and only vacuum hose is fine, carb is bolted down snug, no vac or fuel leaks. I went from a 600 Edlebrock that has a slight hesitation while cruising to this. NOT HAPPY

woodsnake · Apr 3, 2010

Sounds to me like a vacuum leak, even though you said there isn't one.....

blown65 · Apr 4, 2010

You can check how the butterflies on the secondary are too. Mine came with it open too far, where the primary side had to be closed too far. Wouldn't idle for crap and would lean out.

I'm not sure though if the secondary's on those are adjustable or not.

restomoded66 · Apr 4, 2010

Hi! did you adjust the idle mixing screw using a vacuum gauge, set the float level and I thing the secondary butterfly screw is set 1/2 a turn open. What is your engine and cam? If you have a stock cam vac should be around 20" at idle, more duration less vacuum at idle and more duration higher idle is recommended to. My 351w with 224 230 duration @ 0.050" idle best at 1000-1100 at 800 way to lopey.

Z06killinSBF · Apr 4, 2010

Cam has 262 adv duration and 108 LS I will re check for any vacuum leaks in case I missed it. It seems to like A LOT more fuel from the idle screws but starts running fat. I thought these carbs were supposed to be about spot on out of the box.

S-Car-Go · Apr 4, 2010

The days of quality and pride in workmanship are long gone. Check everything. I have a 670 SA in a box that a friend gave me because he couldn't get it running right. The transfer slots were machined wrong (one is a lot longer thant the other). As Blown 65 pointed out, check thier position. There is a small slotted screw underneath to adjust the position. Make the slots square.
Did you set your floats?

D.Hearne · Apr 4, 2010

Z06killinSBF said:
New Holley Street Avenger 670 problems consist of:

1) won't smoothly idle below 1k. Wants to maintain idle around 1100 or else it surges then dies.

2) Bogs really hard upon tip in or WOT. I installed the black vacuum sec spring to no avail.

3) decides to have random idle/throttle hangs on it's own.

The one and only vacuum hose is fine, carb is bolted down snug, no vac or fuel leaks. I went from a 600 Edlebrock that has a slight hesitation while cruising to this. NOT HAPPY

Sounds like a vacuum leak to me as well. Are you using a spacer under the carb ? What intake is it sitting on ? What's your timing set at ? The black spring is the stiffest one, so nothing short of your letting it pull hard to 6000 rpms is going to open the secondaries on a 289. The 670 is really more carb than you should have chosen for a 289. The sticking throttle sounds like a linkage binding to me, you may need a stiffer return spring. And finally, what ignition system are you running with it ?

blown65 · Apr 4, 2010

Z06killinSBF said:
Cam has 262 adv duration and 108 LS I will re check for any vacuum leaks in case I missed it. It seems to like A LOT more fuel from the idle screws but starts running fat. I thought these carbs were supposed to be about spot on out of the box.

Good luck being spot on. Unless you buy from a custom carb shop and even then they usually need slight adjustments. Hell, our Demon carb was 6 jet sizes off, too big running super rich.

Check everything, float levels, mixture screws, transfer slots on the primary and secondary. Vacuum leaks also like has been mentioned.

Z06killinSBF · Apr 5, 2010

Sticking throttle I think is the fast idle cam mis-adjustment. I doesn't like to let out sometimes. I am running a 1" 4 hole spacer, I disconnected the vac advance and tightened everything. I also put the yellow vac sec spring in. Not sure what the timing is but I bumped it up a little and it runs smoother. I re adjusted the air mixture screw to 1-1/2 turns out. The spring is plenty strong and is not binding or catching on anything. Intake is an RPM Air Gap and I'm running a unilite ignition. It still has a bog when going to WOT unless I roll into it.

D.Hearne · Apr 5, 2010

Ok, now try adjusting the slack out of the accellerator pump arm linkage. Check the timing with a light, that's a must. The bog could still be from retarded timing as well as the pump linkage. Is that 4 hole spacer a stock Ford unit ? If it is the factory 4 holer with the PCV passages under it, that's going to be your vacuum leak. These will not seal on an aftermarket intake flange with their bare bones flanges. Must be a solid spacer to seal on an aftermarket intake.

Z06killinSBF · Apr 6, 2010

No slack at the arm and the spacer is some aluminum one I picked up long ago. I think it's a Mr. G. Will check timing with light tomorrow. What's a good range? I always seem to run a lot more timing than most people. I know on my 5.0, I would run 16-17 deg when most were running 12-14. Seemed to run crisper.

D.Hearne · Apr 6, 2010

I set em the same way, any where from 10-18* BTDC. I checked one at the track after a few runs and it was bumped up into the 20's. Never seemed to hurt it though.

Bluesman · Apr 7, 2010

i had the basically the same issues with a 3310 years ago. would still race with both mix screws bottomed out, spitting gas, burping through the air horn, idleing at 1500 RPM. whole garage stinking of gas.
i struggled with it for a week, called summit for an RA # returned it got another one 3 days later and it ran fine right out of the box and still runs fine today.

some times you just get a bad one

Z06killinSBF · Jun 13, 2010

Well, after checking and adjusting everything I could and having my dad who knows a lot about tuning Holleys look at it, I could never get it to run right. It felt really sluggish driving around and every time I would give it just a little more gas it would fall on its face. So, I put the old, reliable Edelbrock 600 back on and was instantly greeted with crisp throttle response and tire frying power (well, for a mild 289 at least). Much happier!! Holley.....wtf?

D.Hearne · Jun 13, 2010

Want to sell the 670 ?

Z06killinSBF · Jun 13, 2010

Not really. When I have time and when I rebuild the motor, I want to go through the carb and try to reuse it.

Jermsjunk · Jun 13, 2010

accelerator pump too big or wrong accelerator pump cam profile? Might be the carb is too big for the motor in general.

Z06killinSBF · Jun 13, 2010

I ran a 780 on it years ago for about a month and never had these issues. The carb was brand new.

blown65 · Jun 13, 2010

Jermsjunk said:
accelerator pump too big or wrong accelerator pump cam profile? Might be the carb is too big for the motor in general.

or it can be too small of an accelerator pump. Mine was too small, had to go to a 50cc pump with larger squirters to make it work. Plus because of my cam drill the butterflies to keep the transfer slots in relation to the butterflies correct.

Street Avenger issues

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