Carb Help!!!

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calgee

calgee

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I'm at my wits end with a carb for my motor. Im running a mild 340 and initally had an 800 cfm Edelbrock on it. I know, way to big. I picked up a used Edelbrock 600 CFM , bolted it on and it was pouring fuel out of it so i decided to "attempt" a rebuild. Took the carb apart, cleaned everything, all new gaskets, floats etc. Buttoned it all back up and bolted it on.No leaks but I cannot keep the thing running. Its almost like someone is throwing a switch and cutting the fuel off. If i turn the ide screw all the way in ,it will fire up and idle at about 2700 RPM and as soon as I touch the idle screw and back it off it immediately dies. If I start it and keep the engine rev'd it will stay running for 10 seconds or so and then it cuts off. I adjusted the floats and from what I could tell they were really close to the 7/16 but maybe not. I am not a carb guy and thought instead of buying a new one or paying someone I could try and learn something but I am kicking and screaming. Any help would be appreciated. Thanks!
 
are you sure you put the correct gaskets back in it? you may have a vacuum leak somewhere. did you have instructions when you rebuilt it?

the 800cfm carb isn't too big for a340. what was the matter with it?
 
I thought the 800 CFM was to big as it ran so rich. It almost smelled like fuel coming out of the exhaust pipes. I did put new springs in it, played with the timing, adjusted the mixture screws but it just seemed to big. Maybe I am totally wrong and it needs to be tweaked, again no carb expert here by any means. I did rebuild using instructions and bought the edelbrock rebuild kit for the 600. The gasket matched the old one I took off.
 
Too much fuel pressure?

Even thought instruction might say 7 psi, I've rarely seen one that handles more than 5.5 psi without some kind of issue. I tend to run ede carbs at 5 psi max.

Look and see if when it's running you have fuel dripping in from the boosters.
 
I didnt notice any excess fueld dripping into the carb and the big problem is I cant keep it running long enough to really tell whats going on. I'm running a stock fuel pump so hopefully i would be ok there. I took the 600 off the car and put the 800 back on and it fired right up and idled fine at 850 rpms. Def something going on in the 600 carb. Could it be the float adjustment???
 
Did you put the 1/2 pipe plug back in the rear? Fuel pressure will cause it to idle then gurgle, cough and die with gas fumes everywhere. Turn both mixture screws all the way in, then out 1 turn. The idle screw should be just touching the throttle, forget the choke for now. Get it started and feather the throttle so it warms up, then start messing with the idle screw and mixture screws. An edelbrock can almost idle with the top off if you could hold the rods in the jets. Also check your floats, weigh them and see if you got a sinker. rotate rod covers to side and see if the rods stay sunk at idle, shouldnt bounce. Get yourself a vacuum guage and a tach and a partner to read it. Set to idle and then adjust mixture screws until the vacuum climbs, lower idle back to where it was with idle speed screw and continue to adjust to get highest vacuum at SAME idle. Carters are pretty easy to get set up. But they did make over 500 variations and like thousands of rod variations for the AFB.
 
I made sure I had the 1/2 plug in the back,tried turning the idle screws all the way in and then out a turn and still the same thing. Since the 800 runs fine could it still be a vacuum leak or to much fuel PSI? Why would it run fine with the idle screw all the way in turning 2700 rpm's but then cut off if i back the screw out any ? It doesnt chug like its trying to die or struggle to stay running. Its literally an immediate cut off like fuel is cut to the carb. Im running 9 degrees BTDC aon the timing as well.
 
The 2700 rpm idle means you're pulling a bunch of air someplace. Primary or secondary blades not seating properly. Did you remove them from the shafts?..and if you did, are you sure they were reinstalled in their original orientation?
 
Could try running your mix screws out 3-4 turns and if it runs somewhat better you have a huge vacuum leak if worse you are getting too much fuel.You couls jet the 800 down about 2-3 sizes to see if that clears up the excesive fuel thru it.But keep in mind a 800 cfm will need a bigger jet than a 600 cfm for it to have the right A/F ratio,dont lean it out too much.
 
Turn the initial timing up to ~15* and DO NOT drive it until you find out where your total timing number falls. 9* is not enough initial timing on a 340 unless you are taking it to a smog test.

You should see no fuel dripping in from the boosters at idle. If you do, that's a problem.

Take the carb and baseline it to whatever ede says to set the idle mix screws, etc.

Something is definitely not right if it won't run below 2700.

If the 800 ran OK, put it back on.
 
Didn't remove the blades from the shaft. I didnt remove the secondary jets when I did the rebuild. Could they be clogged or dirty and cause this? I just put new floats, gaskets, needle, seats etc from the edelbrock kit you can buy your local auto parts store.
 
You should be on the idle circuit, secondary jets shouldn't have anything to do with this issue.

At 2700 rpm you aren't close to the idle circuit.
 
Did you spray all the orfices out with compressed air,when you had it apart ?
You could have some dirt or a small pebble blocking the flow.
I would take it apart again on a clean bench/ towel. Take your time.
Once apart,blow all the orfices,jets,ect,out with compressed air. Double check the float level.Put it back together. Turn the A/F screws all the way in (do not over tighten)and then,back them out 2 turns. Start the car and set the idle to 900 rpm's.

This is all with the understanding that you have the proper gasket/gaskets under the carb,and no vacuum leaks. And the rest of your car/engine is in order.

Refer to an Edelbrock manual for proper tunning of the carb. If you don't have one,you can look it up on their website. YouTube also has some good videos on how to tune an Ede carb.
 
the primary boosters will go in the wrong way around . the tiny brass vent tubes sticking out the tops should be toward the rear [secondary]side of the carb . check for this durning disassembly ,make sure your float settings are to soec. float height and float drop . good luck
 
Thanks for all the feed back guys I really appreciate. I guess im going to take her apart over the weekend and see if I can get it to work. If I decide to put the 800 back on what suggestions do you have to make it not run so rich? Timing? I dont mind using the 800 but my wife and kids dont like riding in the car because the gas fumes are so bad. It literally burns your eyes! Also with the timing, I timed it at idle with a timing light and the mark bounces between 9-10 BTDC. Is this correct or incorrect way to time it? I have a stock timing chain cover on it so the timing marks only go to 10 I believe. These are two areas I am totally lost on. Thanks again and hope I am not asking totally ridiculous questions here!
 
Timing FIRST!!!

Search "hillbilly timing tape", mark it like that and you can get all the way to your total number. Never have to worry about timing tapes falling off. don't need a dial back light, just a base cheapo model.

If you reach in, give the distributor a light counterclockwise twist and your engine picks up rpm, it's not timed correctly from an initial timing standpoint.
 
For all around usage,the total timming on a Chrysler small block should be 34 degs.
Don't worry so much about your initial. Set your total to 34 degs,tighten it down.
Then check your initial. Your initial will probably end up between 12-16 which will work well with your mild 340.
 
Not gonna bother...

There's the right way and the lazy way, make your choice and live with the results.
 
calgee said:
Thanks for all the feed back guys I really appreciate. I guess im going to take her apart over the weekend and see if I can get it to work. If I decide to put the 800 back on what suggestions do you have to make it not run so rich? Timing? I dont mind using the 800 but my wife and kids dont like riding in the car because the gas fumes are so bad. It literally burns your eyes! Also with the timing, I timed it at idle with a timing light and the mark bounces between 9-10 BTDC. Is this correct or incorrect way to time it? I have a stock timing chain cover on it so the timing marks only go to 10 I believe. These are two areas I am totally lost on. Thanks again and hope I am not asking totally ridiculous questions here!
Click to expand...


The 800 does NOT necessarily have to be richer than the 600 at part throttle. If the carb is tuned properly, you would see zero difference between the two just cruising around town.
You tune the low speed fuel mixture by changing the drop rods (metering rods) and the springs that are under the vacuum cylinders. The rods are tapered with a step. The larger part of the taper is your idle/low speed, and pointy end is your load/high speed. The lighter the spring, the less fuel your engine will see at smaller throttle openings.
This is the Carter/Edelbrock version of the Power Valve as used on Holleys.
 
By the way, I ran an 800 Eddy on my 500hp 408 stroker. I love the Eddy carbs. It was too much carb for my motor. I went back to a Holley 750 DP and I have to adjust that damn carb all the time. The Eddy was set and forget. The 600 Eddy is just fine, and once you get it built right and adjusted you will be very happy.
 
Ok so I set my timing at 15 BTDC and reinstalled the 600 Eddy after I reajusted the floats again. I did not hook up the electric choke and it fired right up and ran perfect. I shut it down and hooked up the choke and it did the same thing as before, just immediately die after a few seconds. I took the 3 screws out and rotated the housing forward towards the front of the car and it fired right up again. As soon as the choke opens the butterfly on the top of the carb the car dies immediately. Any ideas or suggestions?
 
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