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Lately I've been noticing a hesitation if I try to take off with a little speed. If I ease on the throttle and accelerate slowly everything works fine. If I give any more than about 1/4 throttle I get a hesitation, nothing too terrible but enough to be annoying. I've checked the timing, its at 12* initial (where I left it last). I moved the vacuum advance from timed to full to see if it had any effect on the hesitation, and it didn't. I tried moving the accelerator pump stroke to the upper hole to see if it affected the hesitation, and it didn't either. I'm getting 18" of vacuum like I always have. I messed with the fuel pressure, nothing changed. The problem tends to get worse as the car warms up. I've been noticing gummy looking stuff around the top gasket of my carb though, so I'm wondering if its going bad. Its only 3 years old, but its been sitting a lot lately. Any other ideas?
 

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Remove the air cleaner, and with the engine off, open the throttle while watching inside the front venturis for a stream of gas. It is best to try to get as directly over the top of the carb as possible so you can see inside, which is why you don't want the engine running. It sounds like your accelerator pump went bad. If you don't see a good squirt, than that is most likely the issue.
 

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yea I'd say time to freshen up the carb. Throw a new accelerator pump, blow out the passages and new gaskets.
 

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Do you have a spacer underneath the carb? If the problem gets worse when the car warms up, it might be that the fuel in the carb is percolating......


http://www.jegs.com/p/Mr.+Gasket/743823/10002/-1


I have this on my set-up and so far, so good.


Sorry, I had to re-read your post and I saw that you mentioned that the carb has been sitting for a while. You might have an internal gumming issue that is causing this hesitation. As posted already, its time for a complete tear-down and clean-up.
 

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Not sure about the Edelbrock but the Carter AFB that the Edelbrock is based on has a ball check valve in the bottom where the accelerator pump sits and that might be sticking shut also if you are not getting a shot out of the boosters as 72Green Rally mentioned. This is quite common to be stuck not allowing fuel into the accelerator pump if the carb has been sitting dry for a while. The varnish that forms from the eveporated fuel is what sticks it in its seat. This ball has to be in place for the accelerator pump to shoot the gas into the carb but when stuck does not allow fresh fuel in after the pump does its thing.
 

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If you have a manual choke close it off a little and try it if it drives fine again its the pump, not sure on mine but i think mine has the same problem, it runs great with the choke slightly closed but i know the rods/jets are close, let me know what yours does if you try this.
 

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I would go through it and check everything out. Might just need a good cleaning and the gasket kits are cheap. But I'm with the others, sounds like the accelerator pump. Also check to see how much play is in the arm. If it seems loose, try bending the rod a bit to tighten it up. (I know, but that is what edelbrock suggests, :eek:. Kind of crude isn't it...? )

I was never able to get my edelbrock carb to run as good as I wanted it too. Always a little hesitation or stumble. I was a die-hard fan of them because they are so easy to work on, but then Big Al showed me the light :). Holley
 

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Discussion Starter #8
I am getting pump shot. Unfortunately I think this may be more than a carb issue because I took the car for a drive today and got pretty bad noise from the valve train for about 4 min or so after starting it. I was sure I'd wiped a cam lobe or something but the noise went away after (and I am ashamed to admit this) revving it hard.:confused: Basically I was sure the thing was done for and I'm (slowly) building a 406 to replace it, but it started driving normally and no hesitation tonight:confused: It was cooler tonight so maybe this is a fuel percolation issue cause it was HOT yesterday.
 

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Lately I've been noticing a hesitation if I try to take off with a little speed. If I ease on the throttle and accelerate slowly everything works fine. If I give any more than about 1/4 throttle I get a hesitation, nothing too terrible but enough to be annoying. I've checked the timing, its at 12* initial (where I left it last). I moved the vacuum advance from timed to full to see if it had any effect on the hesitation, and it didn't. I tried moving the accelerator pump stroke to the upper hole to see if it affected the hesitation, and it didn't either. I'm getting 18" of vacuum like I always have. I messed with the fuel pressure, nothing changed. The problem tends to get worse as the car warms up. I've been noticing gummy looking stuff around the top gasket of my carb though, so I'm wondering if its going bad. Its only 3 years old, but its been sitting a lot lately. Any other ideas?
Mine is the opposite. When I start off slowly it hesitates for a second or if I'm cruising along and I'm barely giving it any throttle it will have that little hiccup. It's a Carter AFB not an Edelbrock which is the same thing. If I really stab the pedal it doesn't do it. I bought it used not new but it appeared to be in good shape. I took it apart, cleaned it, and put a new accelerator pump in it. I also moved the linkage arm down to the bottom hole but it didn't make any difference. I haven't tried the top one but that's the next thing. My dad has a 750cfm Edelbrock on his Corvette and loves it. The only problem he's ever had is the little ball would stick if he went very long without driving it.
 

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It sounds to me like you might have a vacuum leak. Try spraying some carb cleaner around the gasket between your carb and intake. If the RPM's change at all, then that is where your problem lies. I had the same problem after I added a spacer on my 75. Hope that helps.
 

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Take it off, flip it over and fill the venturies full of jb weld and use it as a door stop. I had two 1406's and changed springs, jets and metering rods. never changed the off idle issue. even changed fuel pumps....:eek:
 

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It sounds to me like you might have a vacuum leak. Try spraying some carb cleaner around the gasket between your carb and intake. If the RPM's change at all, then that is where your problem lies. I had the same problem after I added a spacer on my 75. Hope that helps.
Were you replying to my post or heavy7DchevY?
 

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Actually you both should try it. A vacuum leak is the easiest thing to check for.
When I had my hesitation problem, I tried everything people were telling me to do. Timing, fuel/air mixture, accelorator pumps. In the end it turned out to be a simple leak around the carb gasket. Luckily I didn't sink a whole lot of money into trying to fix it before I found the real problem.
Do either of you know how to tune your engine using a vacuum gauge? If not, you should google it and learn how. It's not too hard, and once you learn how, it's the fastest way I've found to get your engine running the way it likes to be set.
Hope it works out for ya.
 

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No I haven't put a vacuum guage to it yet but I will. It might have something to do with it. The Carter manual for it talks about the intake and discharge check when trouble shooting the accelerator pump. It says that if the discharge check is not seating properly on acceleration air would be discharged before solid fuel is delivered to the pump jet causing a stumble or hesitation. I'll just have to keep fooling around with it. I don't really need to buy a new one right now.
 

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I'm still trying to get rid of this stumble on acceleration. It's a Carter AFB 9635SA 625 cfm. I didn't know when I bought it that it is an emissions carb or I wouldn't have bought it. I've moved the pump linkage up to the top hole so it would get a quicker shot from the pump. I had to put a new vacuum advance canister on my distributor because I ran the adjustment bolt out of the internal plate and it wouldn't screw back in. It's supposed to stop when you run it ccw all the way but mine didn't. Anyway, I've got my initial timing set at 12 deg. BTC
and the HEI distributor adds another 10 - 11 degrees by 1500 rpm. It came with medium springs installed. Right now I've got the vacuum canister set at about 10 - 12 degrees according to chart that came with it and the number of turns in. It's an Accel brand. I had more but I was getting some pinging on hard acceleration. I hooked a vacuum gauge up the back of the intake manifold and I'm getting 15" at idle and then I hooked it to the manifold vacuum port on the carb. It has absolutely no vacuum at idle and steadily comes up as I give it throttle. When I hook it up to the timed port it idles at around 5" to 7" and steadily increases as I add throttle. I thought I was supposed to have vacuum when I hooked it to the manifold vacuum port on the carb and little to no vacuum on the timed port. Is this not correct? With the engine at idle and the breather off, I can make it stumble at the exact spot every time if I give it throttle real slow just like it does when driving. If I stab the throttle real quick it doesn't do it. The pump is squirting two good streams of gas into the carb when you really hit it hard and barely any at all when you ease into it. It stumbles at exactly the same spot every time. It's really aggravating me. Maybe I should get another carburetor.
 

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Tider- Have you sprayed around all your gasket areas with carb cleaner? Try that first. That will tell you if you have any vacuum leaks that you need to fix. I messed around with ignition timing and different springs for almost a month or so before I figured out that was my problem. If that doesn't fix it, then go to this article and read all about tuning with a vacuum gauge.

http://www.centuryperformance.com/tuning-with-a-vacuum-gauge-spg-148.html

After I read that article and did what it said, I can't get so much as a single backfire out of my car. I drove it 2500 miles across country without a care in the world. From sea level, up to 8 or 9,000 ft elevation.

Hope all this helps you figure out your problem. I know it's extremely frustrating when you car won't produce power on demand and you can't figure out why. Good luck.

Comic
 

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Well I sprayed carb cleaner around the base gasket and it didn't have any affect on it. I just figure it's something with my carburetor. I guess I'll get another one as soon as I can. I would take it off, tear it down and let it soak in cleaner if I thought it would do any good but I doubt it would. As I said before, I can make it stumble while letting it idle and slowly increase the throttle. It will do it at the exact same spot every time.
 

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It's all in the name, I personally hate their carbs so much i refuse to put anything with Vics name on it on my car,,, of coarse i will be the first to admit that Vic senior did alot for our hobby
 

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Well I messed with my carburetor some more and somethings got to be wrong with it. There is absolutely no vacuum at idle at the manifold vacuum port on my carb. It's acting like the timed port in that vacuum will only come on as you give it throttle and it doesn't matter which port you plug the vacuum line into the rpm doesn't change. Shouldn't the manifold vacuum port on the carb have the same vacuum as the port at the rear of the intake? When the vacuum line is plugged into it the timing should be advanced at idle shouldn't it? Anyone run into this with a Carter or Edelbrock before?
 
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