Another Carb Question...WTF!

[gunner_vincent]

Alright fellas, Truck was running fine yesterday, but this morning, i went driving down the road, and it backfired in the carb and it kept doing it. I just had it "professionally" tuned about 3 weeks ago. I am in the process now of checking all the plugs/ wires. There is a definate smell of fuel, like it is burning rich...could this cause the backfire? Also I believe i am gonna have him recheck the timing tomorrow. You guys have any Idea on how to adjust the mixture on a Holley? It should be the screw with the spring on it right? Your inputs would greatly be appreciated! /forums/images/graemlins/peace.gif Rock ON!

 

[pauly383]

[ QUOTE ]

BACKFIRING

It is nearly impossible for a carburetor to cause a vehicle to backfire. Make sure that the spark plug wires are properly attached and that the distributor cap is free of any carbon tracking. Check the ignition rotor to make sure that it is In good condition, Set the ignition timing to manufacturers specifications. Check the manifold vacuum with a vacuum gauge. A bad vacuum leak can lean out the mixture enough to cause an engine backfire. Check the engine compression. A leaking, burned, cracked, or stuck valve could be the cause. A worn camshaft lobe or bad timing chain could also be at fault. Check the choke operation. If the choke comes open too quickly the engine will be lean when cold and backfire

[/ QUOTE ]

I got this straight from a major remanufacturers site . http://www.rockauto.com/ref/Tomco/Trouble.html

 

[mrk5]

Is it backfiring through the exhaust or the carb?

 

[pauly383]

I was thinking I should of said that , retarded makes backfire out exhaust , advanced makes backfire in carb /forums/images/graemlins/k5.gif /forums/images/graemlins/k5.gif

 

[NerdBoy]

And, backfiring through holly carb = blown power valve.

 

[grundy99]

[ QUOTE ]
And, backfiring through holly carb = blown power valve.

[/ QUOTE ]

Not on the newer ones,
The newer Holleys i would say within the last 5 years or so have power valve blowout protection.
[ QUOTE ]
You guys have any Idea on how to adjust the mixture on a Holley?

[/ QUOTE ]
If you are looking at the carb from the front of your truck, there are two air/fuel mixture screws that are on the sides toward the front of the carb. Do a google search for "How to tune a holley" and you will find plenty of pics of this. Good luck