Carb Help Please

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Punisher66j

Punisher66j

Dart Swinger
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Sep 6, 2014
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Location
Iowa
I have been trying to get my 74 dart to run right with this new engine. I recently installed a 360 magnum that I have carbureted. Engine has a 750 willys (Holley Double pumper) and a dual plane intake. I have the timing at around 14 before top dead center. I tuned the carb and set the timing with a vacuum gauge. I adjusted them so I had the most vacuum. I did timing so I advanced it to highest vacuum first then retarded it and inch and a half. I checked it with a timing light but since factory timing cover only goes to 10 it is hard to tell. I can see the line a little above 10 degrees before top dead center, looked around 14 degrees. I timed it at idle warm and then after I had it adjusted I started tuning the carb. It has the holley double pumper built by willys with no choke horn. I screwed idle screws all the way in and then backed them out to 2 and a half turns. I kept tuning and tuning but the highest vacuum was with the car richened up quite a bit to around 4 1/2 turns out each. If I put it in gear it sounds almost cammed where you can hear it hitting on the cylinders. I have tried retiming it multiple times and it always does this. The more I work at it the better it runs but will bog with quick acceleration. I currently have the exhaust coming from manifolds and dumping at my feet. I am trying to get it tuned in decent enough to drive it to get the exhaust done but I can't get it to quit sputtering. If I accelerate slowly it will run with very little sputter. If rev it in gear it will squeal tires. If I accelerate quickly it will cut out and sputter. If I stomp it to the floor like the dirty ***** it is acting like it screams....I am at a loss. Carb was rebuilt but power valves weren't, ANY help is appreciated.
 
if there is nothing wrong with the carb and it's close to baseline holley tune, then i'd imagine you need to be less than a full turn on each idle mix screw.
probably around .75 turns out. start at one turn out on each of them
then go around the car turning them in 1/16th turn until it starts to idle down slightly, then turn each one back out 1/16th of a turn...

you should be able to get it to where, after they're all adjusted correctly, you can turn one screw in close to all the way and the motor will want to die.
 
What pv is in it, if they are old the rubber gets hard and they don't work right. How much
vacuum do you have at idle?
 
I don't think they are that old, it was on a drag car last summer or the summer before. Has around 21 pounds of vacuum.
 
can you drive it with the vacuum gauge where you can see it, what is the vacuum when it falls on it's face, the power valve might not open and your not getting the extra fuel you need.
 
You are RunningOutOf. fuel.
Check with garage for fuel pressure.
Put a manual gage under hood rht be fore the carb fuel fitting.
Good luck
 
I do have a fuel gauge under the hood and at idle I have a gauge reads 6lbs of pressure. I will try upping it.
 
I have a electric in line Holley blue pump with a regulator. My regulator is at 6lbs.
 
I don't think it's fuel pressure, its more like pump cam, nozzle size, power valve.
 
Not trying to sound ignorant but what is a pump cam do per say? I know it works the accelerator pump but this thing if you snap the throttle quick it will squeal tires but it won't continue.
 
pump cam is on the throttle shaft and has 2 screw positions, they make a bunch of different cams to pump fuel at different rates & time. The nozzles have different size holes, so say you have a 30cc pump no matter what nozzle you still get 30cc's of fuel,
the smaller hole gives you a smaller but longer squirt of fuel, the large hole gives you a big squirt for a shorter time.
Holley%20Cam%20chart.JPG
 
Im thinking about saying screw it and getting a edelbrock back on it but when I did I had the same issue. I thought the carb needed rebuilt and I bought this Willys used and rebuilt it and put it on.
 
I just had a thought will slant 6 factory line be too small on a v8 360? I upped my fuel pressure to 6.5 pounds. I went out and drove it. If I stomp it just in the primaries it would go like hell for around 5-10 seconds then sputter. If I got back in it right away it'd continue to stumble. As soon as I would stop as if to let the bowl fill up the car would go fine again like a bat out of hell until it would seem to run out of fuel again.
 
Last edited:
Possible issues:

Carb no good.....advance timing?.......bigger accererator squirt nozzles/cam as suggested.......in line filter......... vacuum advance issues..... vacuum leak or combination of any.
 
mycuda said:
Possible issues:

Carb no good.....advance timing?.......bigger accererator squirt nozzles/cam as suggested.......in line filter......... vacuum advance issues..... vacuum leak or combination of any.
Click to expand...
Carb should be good. I used a edelbrock 650 first and now this 750 willys and same problem. My timing is at 14 before top dead center and was up further but it had a hard time starting that high. It does fine when you first stomp it but sputters out after its initial squirt. I will have to check in line filter, I have two of them on it one before and one after the pump. Everything is new as far as that goes. 2 brand new in line filters, new holley blue pump, and rebuilt carb. Vacuum advance isn't hooked up right now. I had the same problem hooked up and not hooked up. Not sure where would be a good place to hook to because the ports on the carb have vacuum at idle. I will have to check for vacuum leaks.
 
get a long vacuum hose hook it to the intake vacuum and run the hose up to the windshield and tape a vacuum gauge to the glass so you can see it while driving down the road, what is the vacuum when it has the problem.
 
the other thing you need to check is the spark, how far will the spark jump if you pull the coil wire out of the dist cap and hold it close to a ground, 1/4", 1", 2", if you don't have a good spark it will run but not good.
 
Looks like I have good solid spark. I haven't driven with the vacuum gauge on yet because I don't have enough hose. I had been testing it without the vacuum advance hooked up. I decided to hook it up and try it and the symptoms were way worse. I couldn't accelerate very good at all. I checked my port I can plug into on the carb always has vacuum. It is making me think my timing is jacked up.
 
did it ever run good or it just one day started running bad
 
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