Backfire through carb during acceleration
 

The issue vehicle is my 75 K10 pickup that I got back in August. First thing I did when I got it was pilled the engine for a rebuild. New crank, cam, pistons, intake manifold, rockers, springs, carburetor list goes on... buddy of mine built the engine because I got sent off for work. Newly reunited with the truck and I have my issue. Truck starts great and runs fine for the most part. While in park I can rev the engine just fine. While accelerating from a stop or under load it feels under powered if I time it right and floor it I picks up power otherwise it will sputter and backfire through the carb. Up hill with the power demand sometimes if I give it the right amount if throttle I will do it then. Carb is an edelbrock performer series 600. Nothing special about the hei distributor. Haven't gotten around to getting a new one. New plugs and wires plugs gaped at .045. Any help on this will be greatly apprechiated. Tomorrow I'm going to check the vacuum advance on the distributor, check the cap and rotor, adjust the carbuerators accelerator pump and whatever you all suggest thanks again in advance.

I'm just thinking out loud here...

Cracked Distributor Cap...
Loose Rotor...
Leak in the Diaphragm of the Vacuum Advance...
Vacuum not dropping on the Vacuum Advance (bent tube/stopped up)...
Centrifugal Advance is stuck in retard position...

You using a stock Cam ?

Pulled the vacuum advance line from the distributor and idle didn't change so I think i found my culprit. Or something that needs to be fixed anyway.

No it not a stock cam and I don't remember off the top of my head shock one my old roommate put in either I'll get ahold of him and get back to you

He said he believes its the Comp Xtreme 4X4 #12-235-2 1000-5200 rpm 210/218 duration at 50 .447 .462 lift. any way new vacuum advance no joy.

If air can be blown through that Line, and you can ear the Engine sucking vacuum when it's disconnected, then since you put a new Diaphragm in it (I think that's what you meant) the Plate must be stuck for some reason. If you feel up to it, you might just pull the Distributor and go through it completely. (with the Diaphragm disconnected, the plate should rotate back and forth about 10-15°)

Also, you might check with the Mfgr of the Cam, and see if they have any recommendation about how much advance timing to use with it, and, if they want the timing set with the Vacuum Tube connected or disconnected.

Is that Distributor single or dual points ?
Do you have a Dwell/Timing Meter/Light ?

thanks for the assistance. nowadays same truck new engine and problem

https://chevroletforum.com/forum/eng...35/#post284445