Acceleration Problem
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Senior User
Joined: Feb 2013
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From: Southern Cal Desert
Acceleration Problem
What can cause for lack of better words, a stumbling when you lightly tap on the gas peddle using the primaries before opening of the 4 barrel. You just get going, truck accelerates, then as I said you give it just a tad more gas but it sort of stumbles. Its not a miss, just is not accelerating properly. The motor is a 390, with new Edelbrock performer, and new Edelbrock Carburator, and new HEI. Any thoughts?
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Senior User
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From: Southern Cal Desert
It doesn't seem to help. When the engine is still cold, 2 min of warm up, you can idle away. If you step on it a bit, it stumbles, or even backfires. Once warm, the backfire stops, but you still don't feel a smooth acceleration.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Issues at cold could be choke setting. Tighten and revisit. Lack of power at warm could be timing- should be around 6* advance- or lean jets. Run if for awhile and then look at a plug. White is lean.
The metering rods are easily changed on these carburetors from the top. Try going one size smaller to richen. One size does not fit all on this carb as it comes in the box.
And remember, putting the accelerator pump on the outside hole lowers the squirt. Go to the hole closest to the body to get more squirt.
Come on back in and tell us what transpires.
The metering rods are easily changed on these carburetors from the top. Try going one size smaller to richen. One size does not fit all on this carb as it comes in the box.
And remember, putting the accelerator pump on the outside hole lowers the squirt. Go to the hole closest to the body to get more squirt.
Come on back in and tell us what transpires.
Cargo Master
Joined: Oct 2011
Posts: 2,251
Likes: 304
From: Kenner,La.
stumble
Make sure that the harmonic balancer has not moved and giving you the wrong timing degrees.
What was on the engine before, did it run smoother ? Also if you have dual exhaust without a balance pipe can also cause this symptom.
What was on the engine before, did it run smoother ? Also if you have dual exhaust without a balance pipe can also cause this symptom.
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Senior User
Joined: Feb 2013
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From: Southern Cal Desert
We replaced the standard dizzy with the HEI. The timing is spot on. I do have dual exhaust with an H pipe. I think its in the carburetor.
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Lead Driver
Joined: Jul 2011
Posts: 8,679
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From: On the Edge of the Desert
I had a 2100 that was FUBAR and causing me all sorts of problems. Stumbling, leaning out, Mis Fires, coughing back. I rebuilt that thing 3 or 4 times and even machined and re bushed the throttle shaft. Still was bad. I replaced it with a edelbrock 4 barrel and the thing ran great!
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Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
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From: Raphine, Virginia
Engine off, look down throat of carb, pull accelerator, you should see fuel nozzles squirting immediately. Adjust linkage accordingly. I have also seen the nozzles clogged due to trash left in carb during manufacture.
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Senior User
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From: Southern Cal Desert
Going to play with this some more today. I will do just that. These were all new parts placed on this engine. I even began to second guess myself whether a 390 can handle this 600cfm Carburetor. I know it can, however the thing should run good basically out of the box and it doesn't.
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Going to play with this some more today. I will do just that. These were all new parts placed on this engine. I even began to second guess myself whether a 390 can handle this 600cfm Carburetor. I know it can, however the thing should run good basically out of the box and it doesn't.
I've had good luck with the Edelbrock's right out of the box, but did have trash in one from factory. I "believe" they come tuned for sea level. I have to run them at least one step rich around here on a 302ci. The optional metering rod/spring and jet kit is nice for fine tuning, and easy to work on. Kinda suck offroad though. Don't like off camber situations. Your 390ci should have no problems with 600cfm.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Lou, the 600 cfpm Edelbrock has been put on a million small blocks and FEs and will work just fine.
There is a forum for carburetors with a lot of smart guys. Why don't you poke a look and do a search? Or start a discussion with your problem.
There is a forum for carburetors with a lot of smart guys. Why don't you poke a look and do a search? Or start a discussion with your problem.
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Senior User
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From: Southern Cal Desert
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