TOPIC:

Chances are if it's firing back through the carbs, you've got either tight intake valves or more likely a couple of high tension wires crossed. Check your spark plug leads first.
One coil (top coil)should be feeding cylinders 1 and 6,
second coil (right side coil) should be feeding 5 and 2 and
the third coil (left coil) should be feeding 3 and 4.

If the leads are all going to the right plugs, then I would check the firing order. Pull all the spark plugs and attach them to the high tension leads and place the plugs on top of the cylinder head to ground the plugs. Then ignition on and hit the starter button and hold it on. You should see the left side plugs firing 1-3-2, 1-3-2. your eyes and brain will prefer to see it as 3-2-1,3-2-1 same thing. Then look at the right side cylinders and you should see 5-6-4,5-6-4 or as your brain wants to see it 4-5-6,4-5-6, same thing. If they're not then the coils are plugged into the wrong ignitor feed wires. You could simply move the high tension leads around to get the firing order right or alternatively change the leads from the ignitors to the coils to achieve the same thing.

If the firing order is correct then you'll have to pull the cylinder head cover and check the valve lash. You may have tight valves holding the valves open and that will cause backfiring through the carbs, but if it's backfiring out the exhaust too, then you more than likely have wires crossed. Still, if you haven't checked the valve lash, I would most definitely confirm that as well. tight valves become burnt valves and that's not good.

If ALL that's good then check your ignition timing. If it's off a lot (like 30 to 40 degrees) then it will run and fart and back fire like stupid.

Hope this helps,
KB

Many say I am crazy but a quick flick of your finger across the chromed pipe will tell you. if it is slippery its hot and if there is a slight resistance its cold and not firing.I have been doing it for more than 50 years and never a blister or even a tingle. A black painted pipe wont work but the shiny chrome or stainless does not conduct the heat quickly enough to burn you just feel it is slippery or not.

RickG wrote: Many say I am crazy but a quick flick of your finger across the chromed pipe will tell you. if it is slippery its hot and if there is a slight resistance its cold and not firing.I have been doing it for more than 50 years and never a blister or even a tingle. A black painted pipe wont work but the shiny chrome or stainless does not conduct the heat quickly enough to burn you just feel it is slippery or not.

We could open a whole new topic on "How to tell if your cylinders are firing" I envision a multitude of "different ways" of checking the exhaust pipes for heat. Laughing so hard I can't type anymore.

I've used an infrared thermometer with laser pointer guide to check the temperature of the headers but it just makes me wonder why there is such a difference between the outer most cylinders and the 4 behind the radiator- Can't remember the values though

zed_thirteen wrote: it just makes me wonder why there is such a difference between the outer most cylinders and the 4 behind the radiator- Can't remember the values though

Yeah right, that's what prompted me to ask the question - Number 6 cylinder was getting very hot very quickly (I didn't check number 1) There is no way of leaving your hand there for a one second without burning you, where 3,4 and 5 cylinders I could comfortably touch - Luke warm I'd describe it.

Kawboy wrote:

RickG wrote: Many say I am crazy but a quick flick of your finger across the chromed pipe will tell you. if it is slippery its hot and if there is a slight resistance its cold and not firing.I have been doing it for more than 50 years and never a blister or even a tingle. A black painted pipe wont work but the shiny chrome or stainless does not conduct the heat quickly enough to burn you just feel it is slippery or not.

We could open a whole new topic on "How to tell if your cylinders are firing" I envision a multitude of "different ways" of checking the exhaust pipes for heat. Laughing so hard I can't type anymore.

It's Like dipping your head in a bucket of shit, don't knock it till you try it.