Using flat tappet. THe cam is a 351, and I already switched the wires to a 302 order just to make sure that wasn't it. After doing that, I replaced the plugs just to be sure it wasn't something like that. I'm still using a stock ignition for now - yeah, I know...young racer on a tight budget :cry:

It did start doing it while in park and revving the motor.

It's only flaming out the pass. side of the front of the carb. I pulled the cover off that side, and everything seems to be working fine.

...was it a new cam and lifters ?

Yep, new cam and lifters. What I don't get is if I just gradually rev it, it doesn't do it. Only when revving it quickly, or when taking off in drive. Guess I'm gonna have a beer and call it a night. I'll try to remember my camera and maybe put a video link up.

So confused.

Thanks for all your help so far! I Really appreciate it.

A lean mixture can do it, so can a bad distributor cap. Vacuum leak also can. If you have a vacuum gauge, and can hook it to manifold vacuum, put it on and see what it reads at an idle. Valve lash set too tight?

could be any of afore mentioned, but i am thinking lean condition, float level too low, air/fuel mix, etc... what type carb are you useing?

backfire's under a load
 

Do you have a msd box??? If so, does the timing mark jump around when you check it w/ a light? How much lift do you have on the flattappet cam & did you break it in w/ just the outer spring's first. Check the plug's first to see if if they are burning lean. example: do they look the same as they did when you first installed them(white)?

Low voltage defiantly could be the problem. If you have a 6al or better make sure you dont have a 3000 chip installed. Some of my buddies use to think that was funny to put a 3000 chip in when someone just built a new engine.


If you really want to know what the true firing order is,

Start with number one. Make sure both valves are closed.

make the dampener t.d.c. mark align up with the pointer.
then
just rotate crank with a wrench one quarter of a turn,
whatever the cylinder is that both valves are closed,
it the next cylinder that is supposed to fire....
it is probably #5,
or #3 and so on........

I'm using a holley 650 double pumper carb that I bought after it was rebuilt (after giving the guy my engine specs, it was supposed to be able to bolt it on and go HA HA) So far, I had to reset the floats - fuel level just at the bottom of the sight glass. Haven't checked the jets or anything on the carb yet.

No msd ignition, and it's still running single springs on the heads. All the lifters are still moving like they should, and I double checked the firing order one more time.

Ever feel like one of Dr. House's patients? :lol:

How did you adjust the idle mixture, did you use a tach, or a vacuum gauge? Did you adjust the Idle mix screws? It sounds like it could be lean, Usually a low voltage can cause a miss, but I'm in no way saying it couldn't cause a backfire, If it's already lean at idle, and you crack the throttle, especially under a load, that could cause a lean backfire through the carb.

Have you pulled the plugs and checked the plug wires yet ?

Double checked timing again ?