help? spitting carb
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Junior User
Joined: Aug 2005
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help? spitting carb
I just swapped out my edelbrock 750cfm carb with a holley street avenger 600cfm on my 390. My edelbrock was spitting or like a backfire noise when I would accelerate when it was cold sometimes this would cause it to die. I let my truck warm up for about 15 minutes and drive it for the first half mile or so it will spit when you accelerate. After a while of driving it will just start running right. Other symptoms include thick white smoke coming out of exhaust when warming up with the edelbrock it was black smoke. My choke is opening up all the way. I thought the edelbrock might have been to big and caused the spitting. I also here alot of noise from valvetrain at around 60mph. I have an edlebrock intake and headers and that is about all i know about the motor. I am getting ready to rebuild the motor but would like to make sure when i get it together this will be fixed. If anybody has any ideas on what is causing this I will greatly appreciate it. Thanks. Let me know if more info is needed.
Lead Driver
Joined: Feb 2003
Posts: 8,140
Likes: 4
From: Oak Harbor, OH
Please clarify... Does it still do it with the new carb? When you say you hear a lot of valvetrain noise is it like spark knock or more serious? What kind of oil pressure does it carry? White smoke is usually coolant/water not good. It may also be that it's too lean now.
Posting Guru
Joined: Oct 2005
Posts: 1,235
Likes: 2
the intake's been changed, could be getting water into the system there to give you the white smoke-steam- from your exhaust... valvetrain noise and backfires sounds like valve timing.. stuck valve, lifter, or maybe a cam going flat... do you got a vacuum guage? if so, get a manifold vacuum reading at idle...
Posting Guru
Joined: Oct 2005
Posts: 1,235
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not a bad lobe, but if it's a sticky lifter the oil may thin out enough at operating temps to get it working a bit...
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Postmaster
Joined: Jul 2005
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Pull out one spark plug wire on the distributor cap at one time and rev the engine. Continue this process untill the spitting of carb quits (backfire through carb), then you have isolated the cylinder creating the backfire. Remove the valve cover on side of the cylinder creating the backfire, and check and verify if the rocker arms for this cylinder is moving up and down with engine running.
If rocker arms are rocking like the adjacent pushrods then checkfor a bent pushrod, this will also create spitting of the carb. Check for a bent pushrod by removing the pushrod for this cylinder.
If rocker arms are rocking like the adjacent pushrods then checkfor a bent pushrod, this will also create spitting of the carb. Check for a bent pushrod by removing the pushrod for this cylinder.
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From: East Bend, Carolina, U.S
Before you start taking the valve covers off or anything check the ignition a bit more. If there is condensation under the distributor cap it will cause the exact same thing. The problem does go away after an engine is warmed up enough to cause the condensation to evaporate.
Also if the sparkplug wires are old or cheap this can cause some strange problems like this as well. In the dark some night with your engine cold start the engine and open the hood and take a close look. If you see what appears to be small sparks jumping around the sparkplug wires then that is part of if not all of the problem.
Only after checking the ignition out would I take the first bolt out of my engine.
Almost forgot to add that if a carburetor is running lean it will cause a backfire while accelerating.
Also if the sparkplug wires are old or cheap this can cause some strange problems like this as well. In the dark some night with your engine cold start the engine and open the hood and take a close look. If you see what appears to be small sparks jumping around the sparkplug wires then that is part of if not all of the problem.
Only after checking the ignition out would I take the first bolt out of my engine.
Almost forgot to add that if a carburetor is running lean it will cause a backfire while accelerating.
Last edited by Purely Ford; Nov 16, 2005 at 12:02 PM.