Stumped and Frustrated with a Holley 670 Hesitation

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straightlinespeed

Sometimes I pretend to be normal
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Hi fellas, Im about ready to pull my hair out. I've been struggling trying to figure out why I have a hesitation on my secondaries when I go WOT.

Here is the set up

LA360, Air Gap, Holley 670 street Avenger, stock jets, 6.5 power valve, 31 squirter, XE268 Cam, 3:73 gears, 2800 stall converter, HEI ignition.

I do know my secondaries are opening but like stated there is a hesitation. I tried swapping all 3 of the springs and nothing made a difference. I was running a 1 inch carb spacer, I could go WOT and the car would nose dive then the secondaries would open and it would take off. If I eased into WOT there was no hesitation at all, but I couldnt just stomp on it.

I decided to remove that 1" spacer and install a 5/16" insulated Eddy spacer. I got everything back together took the car out for a drive. I opened it up to WOT and the car almost died, almost sounded like gurgling from the engine. I let off the throttle and eased into it like I did with the 1" spacer, it seemed doggier but they would open. Then when I let off the throttle to coast I heard a woosh of air. It was fast so I did it again and sure thing a woosh of air. It was high pitched almost like a turbo woosh.

The only thing I changed was the spacer and back to the stock spring that came in the carb. I bought this carb as a reman from Holley and Im wondering if this is the reason someone else may have returned it, but Im willing to try any suggestions that you guys may have for me.
 
Is this from a standing start,, or from speed..??

Initial timing??

The secondary springs are color coded, and there's about 7 diff strengths,, which do you have..?? By the sound of it, you need a stiffer spring.. or you may need to change accel pump cams to a longer stroke..

White - Lightest
Yellow (Short Spring)
Yellow
Purple
Plain (Steel grey)
Brown
Black - Heaviest

hope it helps.
 
Is this from a standing start,, or from speed..??

Initial timing??

The secondary springs are color coded, and there's about 7 diff strengths,, which do you have..?? By the sound of it, you need a stiffer spring.. or you may need to change accel pump cams to a longer stroke..

White - Lightest
Yellow (Short Spring)
Yellow
Purple
Plain (Steel grey)
Brown
Black - Heaviest

hope it helps.


From either a standing or rolling its the exact same.

I have 20* initial and 35 total timing.

I have 3 springs, Yellow, Plain, Black. I've tried all 3 with the 1" spacer and there was no difference. With the 5/16" spacer Im currently trying the plain. Figure I would start over since I changed spacers.

I have seen the accelerator pump squirt into the primary side when just standing over the carb so I know that is working, but the pump shot may need to be changed like you mentioned. Someone awhile back mention the air bleeds may be plugged. Is this a possibility?
 
Dont know if this will help or not but here is what I went through with my 770 Street Avenger. I bought mine used so I knew nothing about it. Put it on my 360 and it wouldnt run for crap. bought a rebuild kit for it and proceeded to take it apart only to find out the coating on the inside of the fuel bowls was literally peeling off in chuncks. Called Holley to try and order some parts only to find out Holley wanted that carb back and they sent me a brand new one. This probably wont help you but it might be worth taking a look at your fuel bowls. Food for thought.
 
From what I've read so far, this is not a secondary problem. You're either going lean in the primary or your timing/ignition is acting up at the hit/load. That #31 nozzle should be plenty, so I have to wonder if you're running a vac advance hooked to the manifold vacuum? Even being a little lean on primary jetting shouldn't cause it to dump at low speed full throttle? Is the primary float level consistent?

Anything else you can think of may help. Either the carb is bad, or we're just missing something? I'll keep thinking on it...
 
Dont know if this will help or not but here is what I went through with my 770 Street Avenger. I bought mine used so I knew nothing about it. Put it on my 360 and it wouldnt run for crap. bought a rebuild kit for it and proceeded to take it apart only to find out the coating on the inside of the fuel bowls was literally peeling off in chuncks. Called Holley to try and order some parts only to find out Holley wanted that carb back and they sent me a brand new one. This probably wont help you but it might be worth taking a look at your fuel bowls. Food for thought.

Wow! your not the only one I have heard of this happening to. I doubt I could be that lucky.

From what I've read so far, this is not a secondary problem. You're either going lean in the primary or your timing/ignition is acting up at the hit/load. That #31 nozzle should be plenty, so I have to wonder if you're running a vac advance hooked to the manifold vacuum? Even being a little lean on primary jetting shouldn't cause it to dump at low speed full throttle? Is the primary float level consistent?

Anything else you can think of may help. Either the carb is bad, or we're just missing something? I'll keep thinking on it...

Trailbeast mentioned I should eliminate my HEI being the issue by hooking up 12v from the battery to my coil and taking it for a drive. Basically saying that if the problem still persists then we can assume that its not a voltage drop at the peak load time.

So even though the problem got worse when I removed the spacer your still leaning towards the possiblility of being lean on the primarys? I do have bigger jets, but they are 4 sizes bigger than the stock ones.

My vac, advance is hooked to ported vacuum, not the manifold vacuum.

I've checked my floats a couple times, but never with the car running. I didn't feel like I wanted fuel dumping on the manifold. I had the fuel set just so it was weaping out of the hole, (basically level with the bottom of the hole). I can double check that again.

I honestly cant think of anything else. However I can double check my timing and get back to you all with those numbers.
 
I had a Holly act all weird on me like that. I took the rear bowl off to find the float was filled half way with fuel and had a hole in it..... Super sporadic miss is what I had until I put my foot to the floor.
 
I had a Holly act all weird on me like that. I took the rear bowl off to find the float was filled half way with fuel and had a hole in it..... Super sporadic miss is what I had until I put my foot to the floor.


Interesting! I think this may require me to take the carb off the car and give it a good once over.
 
With that black spring in the secondary,, they prob shouldn't have been opening till 3500-4000 rpm,, when was your hesitation,, did it change rpm with the different springs..??

Also, if your accel pump is adjusted way too far,, you may be getting a short squirt, cuz its only getting 1/2 a "pump".. adjust accel lever till it just touches the pump arm and takes out any slack....
 
I've checked my floats a couple times, but never with the car running. I didn't feel like I wanted fuel dumping on the manifold. I had the fuel set just so it was weaping out of the hole, (basically level with the bottom of the hole).

I have always adjusted the floats running,, you can put a cloth under the carb to catch any spillage.. You could simply be running outta fuel cuz of low float level.. ?? .. jmo
 
With that black spring in the secondary,, they prob shouldn't have been opening till 3500-4000 rpm,, when was your hesitation,, did it change rpm with the different springs..??

Also, if your accel pump is adjusted way too far,, you may be getting a short squirt, cuz its only getting 1/2 a "pump".. adjust accel lever till it just touches the pump arm and takes out any slack....

My hesitation is thru the entire throttle range. It really does not matter what speed or RPM Im going. If Im at a dead stop and go WOT it bogs. If Im cruising at 30mph 1400 rpm and kick it down the car bogs before it takes off, then goes like a bat out of hell. If Im cruising at 60mph 3k rpm the car acts the exact same way as I just said. Really it does not matter what Im doing with the car it just bogs.

I did look at my accel pump tonight and it does seem to be tight on the arm. I can back it off a little bit so that its adjusted like you said.

I still think the stock jetting of 65 is way to lean,just me.

You just installed one of these on your car right? Is your set up similar to mine? Like I said I have some bigger primaries jets I think they are 69's. I could install them.

I guess what is are some of the first things I should be checking for. I have a lot of suggestions so far or should I just try them all? I dont always think that is a good thing because if your on track with one thing that is improving it then you should stick with that until you no longer have options. Then move onto the next one, otherwise you just get overwhelmed.

So what are some of the initial adjustments I need to check? Float levels, accel pump lever, crap in the bowls, complete tear down?
 
I have always adjusted the floats running,, you can put a cloth under the carb to catch any spillage.. You could simply be running outta fuel cuz of low float level.. ?? .. jmo

Well that is simple enough, I guess I was thinking it would just come spraying out of there. Ok, that is for sure one of the things that I can make sure is correct first.
 
nope, it'll just sit there (and dribble out the bottom of the hole when it's set right and you give the car a little shake) same as when it's off.


Awesome thanks, Oh and I will also try that 12v to the coil to make sure Im not having a voltage drop issue, as starters also.
 
Holley makes plastic replacement caps to check the float levels with the car running.
No mess
I don't recommend them as a permanent replacement for the steel ones.

Double check the pump shot from the squirter in the front, sounds like the arm may be adjusted too loose, you need to check the gap with the throttle wide open,

Holley's are easy to work on and tune, but I also had one a few years ago that with the help of everybody here it was just JUNK and it was a fairly new used one.

OldmanRick is super knowledgeable on Holley carbs, he actually taught me alot from his posts here. And I have run holleys for 30 years.
 
Holley makes plastic replacement caps to check the float levels with the car running.
No mess
I don't recommend them as a permanent replacement for the steel ones.

Double check the pump shot from the squirter in the front, sounds like the arm may be adjusted too loose, you need to check the gap with the throttle wide open,

Holley's are easy to work on and tune, but I also had one a few years ago that with the help of everybody here it was just JUNK and it was a fairly new used one.

OldmanRick is super knowledgeable on Holley carbs, he actually taught me alot from his posts here.


I've seen those caps, but now knowing how simple it is, Im not worried about doing it with the car running.

I was actually thinking the squirter is to tight. I cant even wiggle the arm or lever from the accel pump. There seems to be a lot of tension on it. How do you check the gap with it WOT? I wouldnt think there would be any gap at all.
 
What do the plugs look like? They're the best indicator of whether it's lean or rich. My initial thought is the floats are too high or too low, but I wouldn't mess with anything until I knew for sure. You need to verify whether it's a fuel or ignition problem. High secondary resistance in the ignition system will cause hesitation problems. (problems can occur if on the primary side also) Check your car & rotor real good for any signs of burn through. I've seen many rotors burn through & cause the voltage to short right to the distributor shaft. initially the problem will only happen under load.
 
What do the plugs look like? They're the best indicator of whether it's lean or rich. My initial thought is the floats are too high or too low, but I wouldn't mess with anything until I knew for sure. You need to verify whether it's a fuel or ignition problem. High secondary resistance in the ignition system will cause hesitation problems. (problems can occur if on the primary side also) Check your car & rotor real good for any signs of burn through. I've seen many rotors burn through & cause the voltage to short right to the distributor shaft. initially the problem will only happen under load.

Its been a long time since I've pulled the plugs. Im not sure if now is a good time to do so or not, since its not running right. If you think it couldnt hurt, I could take it for a drive and open it up then shut it down and pull the plugs to look.

Checking the ignition system the way I mentioned is the only way I know how to unless you have another way? I had the dizzy out about a week ago to change the intermediate shaft because I had a lot of excess play with it. The cap and rotor and all the parts looked good and no appearance of arcing or jumping of the spark.
 
...I was actually thinking the squirter is to tight. I cant even wiggle the arm or lever from the accel pump. There seems to be a lot of tension on it. How do you check the gap with it WOT? I wouldnt think there would be any gap at all.
You can only check the accel pump gap with the butterflies closed (idle speed). There should be somewhere around a .015" gap between the pump arm and where the screw/spring contacts it.
 
You can only check the accel pump gap with the butterflies closed (idle speed). There should be somewhere around a .015" gap between the pump arm and where the screw/spring contacts it.

That's what I thought. I for sure don't have any clearance right now. I'll readjust that gap tomorrow.
 
too lean ... mine wanted 72 pri..also make sure there is no clearance at the accelerator pump... [cant move arm freely up and down] should be .015 clearance at WOT [ENGINE OFF PLEASE] ONLY!..simply so you are NOT BOTTOMING OUT ACCEL PUMP!... forget springs etc in secondary..THIS IS A PRIMARY PROBLEM... might pull pri bowl to make sure there is no flakes in it as they will clog jets OBV.. keep us posted..
 
I know this might sound simplistic but I suggest blocking the secondaries closed and run it on the primaries only to see whats what. I run 72s up front on my 360.
As to the "whoosh", hmmmm. Do you have power brakes? I wonder if the diaphram in the booster is perforated.
 
What's your vacuum at idle? Your power valve is a 6.5 you say. Your PV should be roughly 1/2 your vac gauge number. ie if your vac gauge is reading 13 inches then a 6.5 PV is about right. Something just to check that's easy/quick. Also an easy thing to check is if your PV is blown out. Turn your idle mix screws in. If the car dies your PV is not blown.

I would add too that I'm running a very similar setup to you but with a little bigger cam in the Hughes Whiplash with a 4150 750 DP with a 4.5 PV and 71 primaries. My vac at idle is right around 10-11". If runs phenomenal, pulls like a bear and blows the tires off when you stab it.
So I'd check your vacuum and make sure it corresponds with a 6.5 PV or change it and put those 69's in the primaries and see what happens.

Good luck! Carb tuning is just a lot of "one at a time changes" and adjustments then test. It seems like your just not getting fuel and it's going lean and falling on it's face. Had that issue with some vac secondary carbs before.
 
Here's a coupla vids by Holley on adjusting floats and another for adjusting the accel pump..and other vids are avail..

[ame="https://www.youtube.com/watch?v=ge-mIk6nEYQ"]How To Adjust Fuel And Float Level On Holley Carbs - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=k-Nx5HEzvlY"]How To Adjust The Accelerator Pump On Holley Carburetors - YouTube[/ame]
 
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