Intake backfire

What causes an intake backfire? I ran my truck for the first time tonight for a few mins, hit it with the timing light and saw it was about 10* BTDC so I moved it down to about 6* BTDC. I thought 6* was the stock timing but I dont have my Haynes manual anymore so I couldnt remember for sure. Anyways, it wont stay running and it backfires through the Weber carb. I have a header and a Weber 38. Its not a LOUD backfire but enough to hear and with the hood off I can see a puff come out of the filter of the carb. Is it just timing or is this a case of something else?

HERE YA GO MY MAN, CHECK OUT THIS LINK,

When I first saw the topic title I thought timing . 6 Deg is corrrect at correct idle. But you already Knew that. Maybe it's running rich or is not delivering consistent spark. Not sure, but maybe this thread will open up.

It was a simple timing problem. Was a short fix. I tend to ask questions late at night when I get tired of working and have something on my mind.

Nytrydr24 you kick ass. Ive had that link saved for a while from the Mazdatruckin site...its great.

On a side note....whats the stock spark plug gap setting? Again, no manual anymore so Im not sure if I remember. Is it .32 or .36? Those numbers are what comes to mind..

this is what parts america sells

NGK Spark Plug: Plug No. BPR5ES
Standard Plug; BPR5ES; OE Plug ;@ Gap .032 @

it may be different if you run a hotter or cooler plug tho.......


have you got her running yet?

Yes, she is running. Finally. Now I can put the front bags on sometime this week and hopefully have time to weld in the 4 link and bag the rear next weekend.

kool beans, glad to hear she's running! good luck w/ the baggin!

bout time you got it running. now just bring tha biitch over here and bag it

Jesus Christ (was a good man) I hate this damn motor. She cranks, runs FINE while warming up (2k rpms just like ever since i got the weber) and then after a min when she decides to idle down she just shuts off completely. Then if I try to crank her she starts backfiring through the carb. As in an orange "poof" and wont run for shit. Timing is 100% correct. Made sure of that about 30 times so far with the timing light. Is this carb fucked up somehow or what? Im going to blow the truck up soon.....hopefully.

check the intake adapter for the weber, sometimes the nuts work themselves loose and give you a good sized vacuum leak, which will be ok when the choke is shut and the engine is rich anyway, but will cause all sorts of warm problems.

I've also seen carb installers overtighten the nuts on the carb base and warp it! After a few weeks it gets a intake leak there and its the devil to try and figure out. I had a BMW 2002 I bought with a weber carb, had an intake leak, backfired through the carb, ran lean and subsequently hot on the two center cylinders. I tried everything, new carb gaskets, rebuilding etc. Then when I had the carb off for the hundredth time, I happened to set it on my workbench and noticed a gap between the base and the table. I took a THIN layer of permatex and put it on the carb base gasket (yes I am aware Weber says dont use gasket sealer, but what choice did I have?) and the car ran like a striped ass ape.