car stalls at full throttle????

68chargerboy · July 22, 2009, 09:29:12 PM

off the line the car rocks at quater to half throttle, but if i bury the pedal from a dead stop it backfires and dies

i am pretty sure its a timing problem but should i advance it or retard it? or am i wrong and is it the carb? thanks

Zach

Ghoste · July 22, 2009, 09:40:18 PM

Going lean at WOT. How is your acceleration pump and what kind of carb?

68chargerboy · July 22, 2009, 10:30:00 PM

its a holley street avenger 770

Ghoste · July 22, 2009, 10:56:12 PM

Was it working properly before and just started this, did you change anything?

68chargerboy · July 22, 2009, 10:57:27 PM

only about 20 miles on the build so i guess its always done it lol

Ghoste · July 22, 2009, 10:59:06 PM

Is the carb new, is it properly tuned?

68chargerboy · July 22, 2009, 11:20:42 PM

the carb is new and i do not believe it is. i tuned it untill i had the highest vacuum possible at idle then backed it off a little bit and thats it

Ghoste · July 22, 2009, 11:24:41 PM

I'd start with the accelerator pump then. Check which cam it has and that it's properly set up. Even though it's a new carb I'd still check the float levels too.

68chargerboy · July 22, 2009, 11:27:20 PM

alright so richening it up would not help at all? also it has the vacuum secondaries maybe i should change the spring in that???

SeattleCharger · July 23, 2009, 01:29:09 AM

Quote from: 68chargerboy on July 22, 2009, 09:29:12 PM
off the line the car rocks at quater to half throttle, but if i bury the pedal from a dead stop it backfires and dies i am pretty sure its a timing problem but should i advance it or retard it? or am i wrong and is it the carb? thanks

Zach

does it only backfire and die when flooring it off the line? how about if you are moving while at higher rpms and you floor it? does it stall out then? or work fine? what is your intake manifold? what's your rear differential? approximate tire size? cam size?

Ghoste · July 23, 2009, 10:44:19 AM

I don't think fatter jets or secondaries opening sooner are the issue. If it's dying as soon as you stomp on it from a dead stop I tend to think it is in the accelerator circuit. With the car not running, look down in the carb and work the throttle quickly to WOT and see if there is a good strong jet of raw fuel coming out of the squirters. If there isn't, you have a big problem. I suspect there will be a good shot but it either isn't enough or isn't timed long enough.
But I'm no expert so this could all be a waste of your time too.

TylerCharger69 · July 23, 2009, 12:38:08 PM

I dunno...but I'm leaning toward a timing/cam issue. At WOT, the backfiring, to me, seems like the valves aren't opening at the proper time. Vacuum advance could be wrong....I dunno.....is it backfiring through the exhaust, or backfiring back up through the carb??? I could be wrong, of course....and maybe it's getting too much fuel at WOT and flooding out. But I'm still leaning toward a timing issue....I'm curious to see what the problem is....keep us posted!!!

68chargerboy · July 23, 2009, 12:41:33 PM

well it's back firing through the carb. im goin to do some driving tests to see exactly when it does it. time to open up the 440

68chargerboy · July 23, 2009, 12:52:47 PM

so i just took it out and it runs like a champ if i roll on the throttle but if i goose it, womp it, hammer, it, etc it cuts out? any guesses?

SeattleCharger · July 23, 2009, 01:22:24 PM

too big of carb and or carb/intake combo for the cam type and rear gears and stall combo. That's my guess without knowing anything about your car,

68chargerboy · July 23, 2009, 01:25:49 PM

its a 770 carb, the lift is a 484 in/ex has a 3.23 rear with at 2200 stall. 10.8 comp 30 over bore

SeattleCharger · July 23, 2009, 01:52:35 PM

cool. must be pretty fast car.

dual plane or single plane intake manifold? sounds like you probably have aluminum heads with that compression, huh?

Joshs68 · July 24, 2009, 12:33:18 AM

where is everything set?
set the mix screws one and a half turns out from bottomed,
unhook the vacuum advance, and set the total timng at 34*, I leave my advance capped and dont use it, but use it if you want to.
check for vacuum leaks. do you have play in the accelerator pump arm/spring? it should be just touching no slack. sounds like its not getting fuel fast enough when you crack the throttle. when you roll the throttle it is , lighter spring in the secondaries? I dont know much about vacuum secondary carbs but it sounds like the secondaries are not coming in fast enough

68chargerboy · July 24, 2009, 01:08:21 AM

Quote from: SeattleChargerDog on July 23, 2009, 01:52:35 PM
cool. must be pretty fast car. dual plane or single plane intake manifold? sounds like you probably have aluminum heads with that compression, huh?

thanks! i enjoy it. but it is stock intake and heads. looking for a new intake though

68chargerboy · July 24, 2009, 01:09:17 AM

Quote from: Joshs68 on July 24, 2009, 12:33:18 AM
where is everything set?
set the mix screws one and a half turns out from bottomed,
unhook the vacuum advance, and set the total timng at 34*, I leave my advance capped and dont use it, but use it if you want to.
check for vacuum leaks. do you have play in the accelerator pump arm/spring? it should be just touching no slack. sounds like its not getting fuel fast enough when you crack the throttle. when you roll the throttle it is , lighter spring in the secondaries? I dont know much about vacuum secondary carbs but it sounds like the secondaries are not coming in fast enough

i will check these things over in the morning. what is the advantage of using or not using your vacuum advance?

SeattleCharger · July 24, 2009, 02:34:48 AM

hmm, well, I don't know about your carb tuning. A couple things come to mind. -(separate issue- that is high compression for iron heads, aluminum heads would fix that. 440 source aluminum heads are identical to eddy rpm heads, 64cc etc., you need to get better valve locks on em, search for thread about those. you use octane booster and 93 octane gas?)
another thing, a 770cfm carb is pretty big. oversize carb will act like that on any car. you gradually put on throttle and the engine handles being floored fine once rpm's are up, but when you try and floor it off the line, it bogs down and wants to die. So its getting enough fuel, your pump and lines etc. are fine. Perhaps your heads and intake are the problem, not sure. if you tune your carb to perfection, and it still does it, you probably want to go with an eddy rpm intake or other aluminum dual plane intake, and aluminum heads will probably help. that isn't that big of a stall either, and your rear end gears are freeway gears, all this is adding to it somewhat. I hope you figure it out, and others chime in here with help. I only know a little and just offering guesses at possible problem.
Nate

68chargerboy · July 24, 2009, 08:31:32 AM

Quote from: SeattleChargerDog on July 24, 2009, 02:34:48 AM
hmm, well, I don't know about your carb tuning. A couple things come to mind. -(separate issue- that is high compression for iron heads, aluminum heads would fix that. 440 source aluminum heads are identical to eddy rpm heads, 64cc etc., you need to get better valve locks on em, search for thread about those. you use octane booster and 93 octane gas?)
another thing, a 770cfm carb is pretty big. oversize carb will act like that on any car. you gradually put on throttle and the engine handles being floored fine once rpm's are up, but when you try and floor it off the line, it bogs down and wants to die. So its getting enough fuel, your pump and lines etc. are fine. Perhaps your heads and intake are the problem, not sure. if you tune your carb to perfection, and it still does it, you probably want to go with an eddy rpm intake or other aluminum dual plane intake, and aluminum heads will probably help. that isn't that big of a stall either, and your rear end gears are freeway gears, all this is adding to it somewhat. I hope you figure it out, and others chime in here with help. I only know a little and just offering guesses at possible problem.
Nate

you called it with the fuel mix, and i have a couple holley 650 double pumpers laying around, do ou think that carb size would be a better fit on it?

SeattleCharger · July 24, 2009, 09:04:39 AM

that's possible, I don't know how hard it is to swap them, but that would be one way to trouble shoot this.
you floor that 770 and a lot of gas goes into engine, a different intake and bigger heads might increase flow the engine can handle, that might be your choking off point in dumping in all that gas. if you get new heads and intake, the 770 should work fine, but for now you can try the holley 650, then when you change it up to the new stuff, it won't be a lot of extra work then to switch the 770 to the new intake, you would have to do this anyways,
I don't know much about tuning carbs, but if you know one of the 650's is tuned pretty good, your car will launch better off the line probably. other option is to keep trying to mess with timing and tuning the 770 before you do this. There are some mopar clubs around here that meet once a month at a pizza joint, if you hooked up with some people they might have some carb tuning guru guy that could take a look at your setup

68chargerboy · July 25, 2009, 12:02:04 AM

ill have to try that i am going to a cruise night tomorrow, ill ask around for someone who knows what they're doing when it comes to tuning. as for the new heads and intake, that kind of sounds like a lot of money for such a stupid problem $:-\$ so hopefully i can fix it without ay of that or i can get a good deal on at least an intake

SeattleCharger · July 25, 2009, 12:20:09 AM

Quote from: 68chargerboy on July 25, 2009, 12:02:04 AM
ill have to try that i am going to a cruise night tomorrow, ill ask around for someone who knows what they're doing when it comes to tuning. as for the new heads and intake, that kind of sounds like a lot of money for such a stupid problem $:-\$ so hopefully i can fix it without ay of that or i can get a good deal on at least an intake

with aluminum heads you can run pump gas without issue. also lots more power with an intake and aluminum heads. the 440source eddy copies were 900 bucks. an dual plane edlebrock or whatever, ebay for 125-150,
if you don't have headers though, its almost not worth doing all that. what goes in, has to go out, you might be better off with a holley 650, don't know, have fun cruisin your charger

firefighter3931 · July 25, 2009, 06:36:18 AM

A lean bog is tunable by adjusting the accelerator pump circuit as mentioned by Ghoste. The carb may need a larger squirter to increase the pump shot.

Ron

SeattleCharger · July 25, 2009, 10:50:45 AM

these guys know a lot, so if they are routing you to carb tuning, then that's probably the problem, hope you find someone at the cruise to help or that can point you to a local mopar club or something

68chargerboy · July 25, 2009, 11:41:59 AM

well i tried a stiffer secondary spring..... no luck with that so im going to mess around with the accelerator pump today to see if i have any luck with that. ill keep you guys posted

Zach

Purple440 · July 25, 2009, 12:38:00 PM

Zach I had the same problem with my 800AVS and I tuned it out by tightening the secondary spring. The carb is too big which is probably why that worked. I had to keep tightening until I found the sweet spot, and not only did it solve the stalling, but it all around is much crisper on the throttle.

g/l

Ghoste · July 25, 2009, 12:47:55 PM

There are some links in this thread that may be of some help.
http://www.dodgecharger.com/forum/index.php/topic,59697.0.html

Although 770 and 800 cfm are on the large side, they are not extremely large for a stock 440 and without mechanical secondaries, the secondary circuit shouldn't be a major contributor to your troubles unless it's way out. That's major contributor, I am not trying to downplay it's importance or the size of the carb in any way. I don't want to oversimplify this but if the secondary opens too quickly, the other thing that is happening in addition to stalled airflow is a lean condition, that is why a lot of the symptoms are the same. Try tuning the pump a little and see if it changes, it may not or it may but it will be one more thing to check off the list.
(needs more gear and higher stall

)

68chargerboy · July 25, 2009, 12:59:50 PM

Quote from: Ghoste on July 25, 2009, 12:47:55 PM

(needs more gear and higher stall )

hahaha i would love too and plan too the only thing holding me back is i have to save some money up first. so i fiddle with the pump and not too much change. i dont have any new cams in my garage so that may be why its hard for me to tune it right. but ive been hearing alot that the carb is most likely too big for my motor so should i just put on one of the 650 (its a double pumper too so i think the lean situation would be worked out as well)? thanks

Zach

Ghoste · July 25, 2009, 01:04:21 PM

The less airflow can go a long way to clearing up a lean spot. You could go the other way too with the dp (although Ron is on a mission to see that all Mopars are equipped with dp's

).
Get to it and have fun.

68chargerboy · July 25, 2009, 01:10:18 PM

puttin the dp on now

68chargerboy · July 25, 2009, 01:24:39 PM

should i use my 1'' carb spacer or no???

b5blue · July 25, 2009, 01:43:44 PM

One less thing to adjust.

firefighter3931 · July 25, 2009, 01:53:04 PM

Quote from: 68chargerboy on July 25, 2009, 01:24:39 PM
should i use my 1'' carb spacer or no???

Zach, what type of spacer are you using....4 hole or open ?

What is your timing set at ? How much at idle and how much total ? Are you using vac advance and if so is it using ported vacuum ?

Ron

68chargerboy · July 25, 2009, 02:17:26 PM

Quote from: firefighter3931 on July 25, 2009, 01:53:04 PM
Quote from: 68chargerboy on July 25, 2009, 01:24:39 PM
should i use my 1'' carb spacer or no???

Zach, what type of spacer are you using....4 hole or open ?

What is your timing set at ? How much at idle and how much total ? Are you using vac advance and if so is it using ported vacuum ?

Ron,
its around 18 initial and 37 total. it did have vacuum advance untill i put on the 650 dp. talk about a night and day diffrence, still a slight bit hesitant but my floats are way out of wack. im having a total brain fart today which way do i turn the screw to add fuel to the bowl? and i am using a open spacer.
Zach
Ron

68chargerboy · July 25, 2009, 02:22:40 PM

dont know why but the new stuff i said was also in the quote somehow??? idk lol

b5blue · July 25, 2009, 02:56:38 PM

The nut adjusts height not the screw.Counter Clockwise = up

68chargerboy · July 25, 2009, 02:58:57 PM

ok so i adjusted the floats, thanks for that help. nowww if its not one thing its another. now i am having exhaust pops i know its when its ideling for sure but not too sure about under load, under load it seems good but pops when its sitting idle in my drive way. what is the caused by???

b5blue · July 25, 2009, 03:10:01 PM

No snap or crackle....just pops....

like in backfire?

68chargerboy · July 25, 2009, 03:45:57 PM

DONT YOU JUST LOVE A HARD LAUNCH!!!!!!!! finally!!!!!

for whom ever is interested it turned out to be too big of a carb for the engine combo. 770 is evidently to big for a mild 440 the 650 works beutifully. as for the exhaust pops spent a little more time tuning and setting my fuel pressure and all the other goodies and the pops disappeared. finally i have what i wanted for sooo many years lol thank you every one for all of the help on this thread as well as many others that i have had over the years during my process

ps its a muscle car so im sure ill have many more problem threads to come hahaha

Zach

SeattleCharger · July 25, 2009, 04:34:28 PM

awesome, just in time for your cruise tonight, keep her between the lines

maxwellwedge · July 25, 2009, 05:58:21 PM

In my experience over the years a 780 vacuum is a perfect street carb for any 440 if adjusted properly. On a properly tuned carb the secondaries aren't coming in until the engine wants it and may never open fully depending on the spring. 440 cubes is a lot of cubes that pump a lot of air. Sounds like accelerator circuit trouble to me. GM put 780's on small blocks all day long.

firefighter3931 · July 25, 2009, 06:58:37 PM

Quote from: 68chargerboy on July 25, 2009, 02:17:26 PM
Ron,
its around 18 initial and 37 total. it did have vacuum advance untill i put on the 650 dp. talk about a night and day diffrence, still a slight bit hesitant but my floats are way out of wack. im having a total brain fart today which way do i turn the screw to add fuel to the bowl? and i am using a open spacer.
Zach

Good work Zach....timing is perfect for that cam profile....good work !

You beat me to the next question regarding vacuum advance.....blocking it off was going to be my next suggestion.

It sounds like you've got it pretty much dialed in....the open spacer will help compensate for the smaller (650cfm) carb so i'd leave it on there.

Ron

Purple440 · July 25, 2009, 07:41:16 PM

Quote from: Ghoste on July 25, 2009, 01:04:21 PM
...(although Ron is on a mission to see that all Mopars are equipped with dp's ).

Yes he is! lol

Nice work Zach! Glad to hear it's running great now.

b5blue · July 25, 2009, 08:11:10 PM

Great news!

Ghoste · July 26, 2009, 11:41:42 AM

Great to hear it's running good now.

(although I still think the 770 could be made to work well since less airflow from smaller carb plus more fuel from double pump = no lean spot

) With the 650 you should have great throttle response now too.

68chargerboy · July 26, 2009, 06:11:42 PM

Quote from: Ghoste on July 26, 2009, 11:41:42 AM
Great to hear it's running good now. (although I still think the 770 could be made to work well since less airflow from smaller carb plus more fuel from double pump = no lean spot ) With the 650 you should have great throttle response now too.

ohh yea makes it way more fun to drive stop light to stop light on the way to my cruise nights

News:

car stalls at full throttle????