Stumped and Frustrated with a Holley 670 Hesitation

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This thread is getting a little long now, and there's great advise coming in. I just want to take a moment to thank all these great members for trying to help out.....That's what makes this site so great, and we can all learn things from situations like this. :thumbrig:


As far as the accelerator pump arm, once the timing is set and the idle speed is where you feel comfortable, then adjust the pump arm to "zero" clearance.....not loose, not tight, but as close to zero as possible. This gives you the most pump shot with the original pump cam that is reasonably mild, but is usually sufficient for anything other then a seriously modified engine. The .015" clearance at full throttle is to make sure you don't bottom out and damage the diaphragm or bend the arm.

I do agree that the Street Avenger's tend to look lean out of the box, but it's hard for me to think that it's causing the dying off at full throttle like you are experiencing.

At this point, I'd like to hear your feedback from double checking your adjustments, and confirming that the ignition side is up to speed?

Good Luck! I'll try and keep in touch with the thread and add anything I can. We're going to get you goin' somehow, count on it...:thumbrig:
 
I appreciate everyones input on this thread as well. I will be working on these adjustments starting this evening and into the weekend. I will touch base with everything that I have done and its results. Thanks a ton guys!
 
Ok fellas, I've had some time this past week to check a few things. First was the float level. The Primary side was set high and I had fuel pour out of the hole. I readjusted it and got it just so it was at the bottom of the hole. The secondary side was a titch low so I adjusted that one up. So this brings up a question, if the primary side was high how does that affect the carb? Is it like flooding it out?

Second, I checked the accel pump lever. Like I said before it was very tight and hard to move. I had to really crank down on the nut to shrink the length of the bolt and now its set so its just touching, but not loose on the arm. I didnt think about it until afterwords, but I should had measured with a caliper the difference I moved it. It does seem however that the amount of movement in the arm is about the same, but at least its set properly now, I also dont believe it was bottoming out on the diaphragm. Still seemed to have plenty of room to go.

3rd, I threw in my 69 jets on the primary side. Since many of you mentioned it seemed the 65 jets were a lean.

I was going to take it for a drive, but noticed that my throttle was hanging up a little, and wouldnt back down on rpm. I dont want that while Im trying WOT so I pulled it back in the garage. Im running Lokar cables and it was extra long for the 1" spacer. It has a pretty good bend in it now so I have to remake the cable so its a straighter run to the carb from the fire wall.

So what do you guys think of what I have found so far?
 
You'll only know when you drive it with the changes. My only other thought as I read through this for the 1st time is that there may be something hanging up the secondary butterflies; if so, the pump shot would be gone by the time that the delayed secondaries opened and it could bog. Having the throttle hang now might be a symptom of that. And the whoosh you heard upon throttle close could be the secondary hanging open.

I'd disconnect the secondary vacuum pod from the secondary butterflies and check for free secondary action very carefully. Then pull the pod off and check for free, smooth operation of the rod with a vacuum applied and relased. (Sukcing a vaccum by through a piece of vacuum hose will work.) Pretty easy to do.
 
The high float would likely have caused the boosters to start sending gas early, makng it rich ,, if not out and out flooding..

The short pump shot likely would cause some kind of hesitation, or bog,, prob like your's..

hope it helps..
 
I stuck my bone stock 670 (? on specs) on my 360 that has a bigger cam and an eldebrock intake manifold and have no hesitation problems...
 
Grrrrr! Things just didnt go well for me this weekend. I was shortening my throttle cable and broke it... So needless to say I never got to take the car for a drive. My new cable is on order. Thanks again everyone, I'll keep you posted!
 
Update on my crappy *** carb!

When I go WOT either rolling or from a stop the whole gurgling thing is now gone and it doesnt seem like its going to die. So that is a step in the right direction. I still have the hesitation or delay what ever you want to call and and I still have that whistle as I let off the gas from WOT. Seriously it sounds like a turbo whoosh or whistle. I dont get it.

So again I changed the primary float level so it wasnt so high, brought the secondary float level up slightly, changed to 69 jets on the primary's, and adjusted the accelerator pump level.

I did a couple checks when I got home. First the A/F screws. I turned them both in one at a time and the car wanted to die, then re-set them. The next thing was the plugs and they were black! Sooty Black! The only ones that had some color to them were 7 & 8. 7 having more of a tan color than 8 did. Now please keep in mind this was not after a WOT and shut down scenario. Just taking the car for a drive opening it up and bringing it home. I know black plugs are not good, but Im not sure where to go from here.

Last thing I wanted to ask about is this.. Sometimes, not all the time, when I start the car the start will drag. Is this a symptom of timing?
 
Whats dragging? Bendix? slow starter?


I dont know if this helps.but my 4150 has a whistle at idle and it has never ran as good as this. I could be way wrong but I was hoping that was a good sign?


Change plugs and make another pass?

Try the pink pump cam (longer squirt beter transition) and or next size down on acell discharge nozzle? (may help stumble on WOT same affect as the pink cam)
Are your cams in #1?
any slop in acell pump screw to pump diaphragm arm? (remove any to .015 at WOT) Hold throttle wide open and check with fealer gauge.


If you truly do need more fule and have zero vaccum leaks than look to a 50cc acell pump diaphragm, hollow discharge screws and 40+ acell discharge nozzels...

Are you running a drop base aircleaner? If so it may need some hammer love to clear the throttle an kickdown linkage... mine hung up bad an now I test that the pedal snaps back before any fire hits the engine..
 
Well I am glad you did the jet change as for sooty plugs, 69 are not going to do that IMO ,what is your vacume reading at idle in gear if you have an A T may your power valve is to blame,but you said turning in the mixture screws in it would die this is what you want,any chance your breather lid is to close the the bowl vents .Have you talk to Holley tech about this problim.
 
Snake said:
Well I am glad you did the jet change as for sooty plugs, 69 are not going to do that IMO ,what is your vacume reading at idle in gear if you have an A T may your power valve is to blame,but you said turning in the mixture screws in it would die this is what you want,any chance your breather lid is to close the the bowl vents .Have you talk to Holley tech about this problim.
Click to expand...

Funny you mention this. Im currently on hold with them as I type this. Im going to see what they have to say. I'll report back after I talk to them.
 
Well after a 40 minute wait time, I got to talk to Holley tech support. The gentleman I talked to said it sounds like my accelerator pump nozzle is sized to small and I should increase it from a 31 to a 35.

As for the whistle sound, he said that is caused from a carb gasket hanging over and in the air stream. Said it didn't hurt anything, but that is whats happening. So I have a question about that. Im running the edelbrock 5/16" heat insulator gasket and I also installed a paper gasket on the top and bottom of that. It didn't say to add them or leave them off so I added them. Should I take them out?

So off to the local carb shop to pick up a bigger pump nozzle and trying that. I hope that is all it is.
 
Hey, had the same problem. Its your accelerator pump squirter, you don't have enough fuel to handle the hand off of from the jets to the power valve. when you go wot the transfer circuit takes time to hand off the duties form just jets to jets and power valve this is the duty of the accelerator pump and squirter. I had to go up to a 40 on my 750 to get rid of the hesitation and move my screw on the pump cam to the second hole. The spacer gives more plenum volume that has to be filled with fuel air mix this also will require more accelerator pump shot. The problem is a lean condition at wot due to insufficient pump shot.
 
I'm still tryin to dial in the 670 as well. Went from a .031", to a .032", then to a .035" squirter. It helped some but still a slight hesitation off idle. Running a 4 speed as well. I even played w/the initial timing a bit, now up to 16 degrees from 12. Drawing 15 inches and the power valve (6.5) is working. Using ported vac. adv. too. Ordered the holley pump cam kit and time to experiment w/them. Looked at the profile and chose the black one for a trial. Readjusted the acc pump and worked pretty good. Ran the car to a cruise yesterday, 1.5 hour run each way. Still have a slight hesitation but its better than before. Gonna experiment w/different cam profiles and hope one corrects it. Once I get passed the hesitation off idle, no other issues are present. Worked like a charm cruising and WOT.

Don't mean to steal your thunder but seems (we, and most) have similar issues w/this carb. The pump shot arm is also resting on the pump cam, not on the wound spring, like some 670's were.
 
hughesboysvaliant said:
Hey, had the same problem. Its your accelerator pump squirter, you don't have enough fuel to handle the hand off of from the jets to the power valve. when you go wot the transfer circuit takes time to hand off the duties form just jets to jets and power valve this is the duty of the accelerator pump and squirter. I had to go up to a 40 on my 750 to get rid of the hesitation and move my screw on the pump cam to the second hole. The spacer gives more plenum volume that has to be filled with fuel air mix this also will require more accelerator pump shot. The problem is a lean condition at wot due to insufficient pump shot.
Click to expand...

So glad Im not the only one with a issue with these carbs. I planned on picking up a few different size squirters tonight on the way home. I asked about moving the pump cam to a different hole and the Holley tech suggested not to. Said it was probably all a squirter issue.

pntastar69 said:
I'm still tryin to dial in the 670 as well. Went from a .031", to a .032", then to a .035" squirter. It helped some but still a slight hesitation off idle. Running a 4 speed as well. I even played w/the initial timing a bit, now up to 16 degrees from 12. Drawing 15 inches and the power valve (6.5) is working. Using ported vac. adv. too. Ordered the holley pump cam kit and time to experiment w/them. Looked at the profile and chose the black one for a trial. Readjusted the acc pump and worked pretty good. Ran the car to a cruise yesterday, 1.5 hour run each way. Still have a slight hesitation but its better than before. Gonna experiment w/different cam profiles and hope one corrects it. Once I get passed the hesitation off idle, no other issues are present. Worked like a charm cruising and WOT.

Don't mean to steal your thunder but seems (we, and most) have similar issues w/this carb. The pump shot arm is also resting on the pump cam, not on the wound spring, like some 670's were.
Click to expand...

Wow, your timing seems low to me, but Im no expert on timing. I just know my car likes the 20* that I have in it. I sure hope this fixes my issue I will tell you that. Would be nice to drive the car and have fun with it.
 
Ok guys, here is what I did. I picked up 2 squirters a 35 and a 37, I also picked up some 70 jets just to have (incase). I decided that I might as well make a big jump from my 31 and installed the 37. For ***** and giggles I checked what jet size I had in the secondaries and they are 68's. I got the 37 squirter in and took it for a drive. The car seems much more responsive if I lightly open the car to WOT. Although now when I go from cruise to WOT the car picks up for a split second then bogs down, then picks right back up.

Is this a symptom of to big of a squirter or just not quite there and I should go bigger yet???
 
straightlinespeed said:
I asked about moving the pump cam to a different hole and the Holley tech suggested not to.
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This ^^^^^^^^^^^ is one of the things I can actually agree with the Holley tech's on. I've been holding back on posting here again, but there's no way you need a #37/#40 nozzle on a mild engine with a dual plane. That and the potential of needing a big jump in primary jet leads me to believe there's another issue somewhere. Where? I don't know at this point, but you've got to be getting rich on the low end with these mods, and I believe that's what we're trying to clear up at this point? The vacuum secondaries are a completely different issue to me right now. I've actually recommended the 670 on occasion, but I have to wonder, at this point, if you didn't get a bad one?


That carb on your combo, with a proper tune, should need nothing more then slight jet change, and a little lighter secondary spring.......I've run several combo's like yours, over a single plane, with nothing more then a #31 nozzle, one jet up, and a short yellow spring! They were very drivable and ran like a bat out of he!!...
 
Oldmanrick, ya i have given up on the secondary side and thinking this is all the primary side. I'm starting to think at this point its junk also. The more I research online the more horror stories I read about these. I guess that is what I get buying a refurbished carb from them. Its just to bad I have no idea what's wrong with it and I don't know if rebuilding it would be worth it? I wish I had a spare carb just to try. I've been looking at new carbs but I have no idea what to get at this point. Grrrrr
 
Many say the Street Avenger series is Holleys worst design ever.
I had one, and was in the same position as you. I threw part after part at that thing, and could never get it to run right. Was it operator error, or just a bad carb ? I will never know, but I couldnt get rid of the thing fast enough. Found a like new Eddy 600. Put it on, turned the a/f screws out 1.5 turns, and burned rubber down the street. Not here to bash Holley carbs, but if you do a search on the Street Avengers, you will see alot of unhappy folks.

I have finally settled with a Ede Thunder Series 650 avs, on a mild 360. The carb works flawlessly for what im doing.
 
You're busy changing the big things,, but it's something small causing your prob..

Have you actually looked at the squirters and moved the throttle to see what's going on,, cuz you should be able to see what you are experiencing,.. There is a pause,, just a small gap where that squirter doesn't work..

I found it to be things like the needle under the squirter doesnt seal,, and the squirter circuit drains a litlle, causing a hesitation,, the metal strap that holds the check-ball in the pump cavity is loose, and allows 10* of throttle movement to close the check-ball, causing a hesitation,, a tiny bit of slack in the linkages, cause a hesitation,.. Something is causing a slight pause in the squirter shot,, you find that,, and you'll cure your hesitation.. Study it,, watch it's opperation, AS soon as you move the throttle, there should be an INSTANT and Continuous shot of fuel till you stop moving the throttle.!!!,

And that whistle is a gasket sucking air somewhere at high manifold vacuum,, check all the carb screws, baseplate screws, make sure the carb to manifold gskts don't leave a gap somewhere where they barely overlap..

hope it helps
 
Well, I talked to the gentleman that runs a local carb shop. He has been working with me also to try and figure out this situation. I informed him today that the nozzle increase didn't help. He offered to build me a carb suited for my car to try, hoping that what he builds me will solve all my issues. He said if the carb works he will work with me on a good price. If it doesn't work he will keep working on one that does.

This guy has already spent couple hours under the hood of my car helping me out trying to narrow things down, and hasn't wanted a penny for his time. I've tried paying him and he refuses. I have to say that his offer to build me a carb, not just grab one off the shelf and sell it to me and not guarenteeing it works is quite nice!

So I have to get ahold of him Friday and I believe I should have some new results for you all this weekend. I'll keep you guys posted.
 
inertia said:
You're busy changing the big things,, but it's something small causing your prob..

Have you actually looked at the squirters and moved the throttle to see what's going on,, cuz you should be able to see what you are experiencing,.. There is a pause,, just a small gap where that squirter doesn't work..

I found it to be things like the needle under the squirter doesnt seal,, and the squirter circuit drains a litlle, causing a hesitation,, the metal strap that holds the check-ball in the pump cavity is loose, and allows 10* of throttle movement to close the check-ball, causing a hesitation,, a tiny bit of slack in the linkages, cause a hesitation,.. Something is causing a slight pause in the squirter shot,, you find that,, and you'll cure your hesitation.. Study it,, watch it's opperation, AS soon as you move the throttle, there should be an INSTANT and Continuous shot of fuel till you stop moving the throttle.!!!,

And that whistle is a gasket sucking air somewhere at high manifold vacuum,, check all the carb screws, baseplate screws, make sure the carb to manifold gskts don't leave a gap somewhere where they overlap..

hope it helps
Click to expand...

I have to agree with you to a point. The only thing is I had this same guy that runs the carb shop go thru the carb. He has done this with the carb on his bench and on the car running. He has not seen anything that has made him say, yep this is the problem.

Like I said In the post above. Im curious if a different carb fixes this. It will be a good true test to see if I did get a bad carb.
 
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