Just got the new 350 to start up. It is backfiring every 3 seconds and I can't get it to go away. It will get faster or slower depending which way I turn the distributor but to far and the engine dies.

I have headers the carb was set for a stock 305 that ran at +6 advance and I don't have the air cleaner on.

What do I do?

Check your firing order i had the same issue, scope out my thread http://www.elcaminocentral.com/showthread.php?t=43664

Yea, sounds like the plug wires are on wrong.

I will check again later but the firing order is already burned in my head, enough for me to say that isn't the problem.

18436572 double check it twice.
did you have to adjust the valves??:texas:

fire it up and pull each wire off the plug one at a time till it stops,then u know which cylinder it is..

if its not the wires/firing order,,
pull the valve cover and check the valve lash on that cylinder,,
look at the rocker nuts and the threads above the nut on the stud,,they should all be about the same ~
if u see one with more threads?? thats probly the one..

if its popping out the exhaust?? check the exhaust valve..
if its popping out the intake?? check the intake..

check it out and let us know J..:texas:

I'm dumbfounded, had it running smoothly 8-6 before tdc played with the air/fuel mix rev the engine it would still detonat in the exhaust like to much fuel (I'll assume I have an exhaust leak). Let off the throttle it dies, then doesn't want to start, twist the dist a little( I really do mean a small amount not anywhere near 1 plug off difference) and now its running 10 after tdc.

did you use the balancer off the 305??
for now just get it running,,
and adjust the distributer/timing for the highest idle,,
that will probly a little too much advance for it to start without kicking back on the starter
then retard it a little (clockwise)so it starts ok..
check for vacuum leaks,egr,retorq the intake,,check the idle mixture..
are u running the computer and same carb or not ??did u change distributers??

the wires are right??both ends?? i know..
if it wasnt a new motor id say a tight or bent exhaust valve??? compression test would tell..
check the cat also,,if its rich and backfiring..:dontknow:

did you use the balancer off the 305??
for now just get it running,,
and adjust the distributer/timing for the highest idle,,
that will probly a little too much advance for it to start without kicking back on the starter
then retard it a little (clockwise)so it starts ok..
check for vacuum leaks,egr,retorq the intake,,check the idle mixture..
are u running the computer and same carb or not ??did u change distributers??

the wires are right??both ends?? i know..
if it wasnt a new motor id say a tight or bent exhaust valve??? compression test would tell..
check the cat also,,if its rich and backfiring..:dontknow:

New balancer, no egr, no ECM, edlebrock carb, changed distributo and no cat.

Should 1 fire before or after tdc. What's weird is how it changes between starts. It will run fine then it won't start...

the mechanical and/or the vacuum advance may be sticking,,
check the mechanical weights and springs under the rotor,,
and the vacuum advance plate under the module,,test the diaphram..
that may explain the weird timing,,maybe the no start,,but not the popping in the exhaust..

double check the tdc mark on the ballancer,,with #1 piston up on the compression stroke..
just to be sure its for the new timing tabs,,there is 2 styles 12:00 and 2:00..

yes the initial advance should be 8 to 12* before tdc..
that would be above or to the left of the tdc mark on the timing tab..

with the edelbrock check that its not flooding from too much fuel pressure..:texas:

What JJLT1 said...good call....

It shouldn't be fuel pressure, I have the edlebrock fuel pump for it. I checked the dist advance stuff seems its all fine nothing sticking at least, vacuum budged when I pulled air. I'll do the thumb on the hole trick and see what it shows tomorrow. May end up pulling the rotor and shifting 1 plug over. I'll let you know ASAP, tomorrow is my last chance to work on it. I'm heading out on business for a week.

i guess u can get an edlebrock pump that puts out more pressure than there carb can handle,,
there carbs. dont like more than about 5 psi..

I'm a dumbfounded too..:dontknow:

are you runnin any kind of ignition/spark box?? msd,malory??

Where are you taking your vacuum advance from, ported or manifold. Modern engines (enviro) say to use ported vacuum, BUT, you are much better off using manifold vacuum, as vacuum is always there, and it isn't on ported.

The vacuum is off ported, my tran is running off manifold. I can probably change it to manifold with some careful tube work.

She runs :):nanawrench:
Header bolts needed a good tightening(could of sworn I cranked them before) got rid of the ping.
The damper 0 is for a 12 o'clock tab and I have a 2 o'clock tab. The damper is 8 inch and is marked from 0-10 so needless to say I can't find true 0. It would run at this false 0 then choke on a rev and die so I set it further up, raised the idle screw and found the spot the engine didn't shake or backfire on a rev. The rotor wasnt playing nicely so I moved every spark plug around the cap to get room to play with timing.

Anyone with an idea on finding the mark I need for the timing?:beer:

pull the #1 plug,,roll the motor over by hand,,get the #1 piston up to tdc on the compression stroke,,
get it as close as you can to tdc and re-mark the damper to match the timimg tab,,
it wont be perfect but it'll work..:texas:

get the 2 o clock pointer and bring #1 UP AND MARK THE BALANCER