Bad plug Big problems?

[Motorhead350]

This isn't about the Maruader but I was hoping someone would know this. If I have a bad spark plug in a carbureted engine will that cause it to back fire? The engine is a 350 Chevy small block. It used to be fuel injected, but now it's got a carb. It backfires when accelerating sometimes and even while shifting gears. (it's automatic) I also hear a ticking sound and this all just started today. I know I have one bad plug and will get it replaced tomorrow, but can this one bad plug cause all of this? I just had all the plugs and wires replaced less then a week ago. The lifts are only a few months old too. :mad2: :mad2: :mad2: :mad2:

[CBT]

I had that happen to my 77 'vette, it has a 350 also. I had 2 plug wires going to the wrong place. I put them in the correct order, reset the timing, problem went away.

[Motorhead350]

could a common Chevy dealer do this? I have a time set up for tomorrow and did u have a ticking sound too?

[CBT]

As I recall there were ticking and pinging sounds, probably from the plugs trying to fire when they shouldn't and vice/versa. I recommend pulling them and see if any are saturated with gas. Hell, just replace them. I eventually replaced the cap, rotor, module and had the carb rebuilt just to be safe because I ran the dang car a couple hundred miles that way. It would quit at stoplights, it was a mess just because of two plug wires being crossed.:mad2:

[Motorhead350]

I'll have the firing order checked again, but everything is new. Cap, plugs and wires are all 2 days old. Wish me the best. We'll see what happens tomorrow.

[RF Overlord]

IIRC, the firing order on a SBC is 1-8-4-3-6-5-7-2...cylinders 5 and 7 are right next to each other and it's an easy and common error to get the plug wires reversed at either the plug end or the distributor end...it's worth a check...one misfiring plug (assuming the firing order is correct) will not normally cause the symptoms you describe...

[89VERT]

I'd always check the easy things first , like the timing .

[Motorhead350]

I got it checked out and the firing order was fine and changing the plug didn't help. The bill was $90 for changing one plug and nothing happening! :mad2: :censor: It was at a chevy dealer and I couldn't do it myself because I don't have my tools on me plus it's a clearance problem for me because it's blocked by a header. Now I heard the lifters could be the issue because the engine cought on fire a week ago. Thats what could be causing the ticking sound and the backfiring. Does this add up to anyone? :depress:

[MarauderMark]

either the wires are mixed or the timing needs adjustment.heck maybe both.either way Let us know ..

[Krytin]

If the firing order/plug wires/timing are all in order (double check your timing - initial & total advance) - the next thing I would check for is a burned/warped intake valve. It could be out of adjustment or sticking open. If this goes unchecked it will burn (the valve that is)!

Edit: I missed that comment about the engine fire - also double check all vacuum lines and intake manifold gaskets for leaks!

[Motorhead350]

Thanks for the help. I will get it serviced on friday. Lets hope for the best. Will have have to pay for this? The engines under warranty for another year. The people said it was Edelbrocks fault that the carb cought on fire. Something isn't right. And if the lifters or anything is damaged because of the fire whos fault is that? :mad:

[Krytin]

A back fire in the intake can and OFTEN does set fire to the carb! If someone put the engine together wrong, ie. incorrect timing, crossed plug wires or incorrect valve adjustment, and a back fire occured setting the carb on fire, they would be the ones responsible. In the long run it may be difficult to determine what happened first. I don't think a carb fire would damage the lifters - I fire hot enough to damage lifters would probably melt the valve covers off!
Good luck and keep us posted!

[Motorhead350]

ok thank you. I will let you know what happens. It will be serviced friday and I'll post the results by monday at the latest. :coolman:

[Wagonmaster]

This isn't about the Maruader but I was hoping someone would know this. If I have a bad spark plug in a carbureted engine will that cause it to back fire? The engine is a 350 Chevy small block. It used to be fuel injected, but now it's got a carb. It backfires when accelerating sometimes and even while shifting gears. (it's automatic) I also hear a ticking sound and this all just started today. I know I have one bad plug and will get it replaced tomorrow, but can this one bad plug cause all of this? I just had all the plugs and wires replaced less then a week ago. The lifts are only a few months old too. :mad2: :mad2: :mad2: :mad2:
Motorhead,
I concur with Krytin. If you've had a recent engine fire it is likely that you burned up an intake manifold vacuum line, thus causing a lean condition when you hit the accelerator, hence the backfire. In addition, you mentioned one of your source's stated the fire was Edlebrock's fault. I'll presume you are using an Edelbrock or similar AFB style carb then. Check the back of the carb near the intake manifold, there should be a large threaded plug in the baseplate of the carb.
Often people forget to install the plug. The engine will idle fine, but when you hit the gas, bang! backfire! due to another lean condition......much like the missing vacuum line or a leaking intake manifold gasket.

Furthermore, if the "squirter" in the carb is too small then you will not get an adequate "shot" of fuel when you hit the accelerator. They make squirters in several different sizes, ie. .050" .060" ect. You may need a larger squirter. If the squirter is too small you will lean out and backfire, if the squirter is too big then it will bog and fall on its face.
In closing, keep in mind that a worn of flat camshaft can cause this condition as well, however it usually backfires through the carb, not the exhaust. Your engine may be newly rebuilt, but if the cam was not properly broken in, then it may have a worn/flat lobe. A worn lobe is unable to open the exhaust valve, thus it "exhaust's" through the carb. Hope this helps.
GT

[Motorhead350]

Motorhead,
I concur with Krytin. If you've had a recent engine fire it is likely that you burned up an intake manifold vacuum line, thus causing a lean condition when you hit the accelerator, hence the backfire. In addition, you mentioned one of your source's stated the fire was Edlebrock's fault. I'll presume you are using an Edelbrock or similar AFB style carb then. Check the back of the carb near the intake manifold, there should be a large threaded plug in the baseplate of the carb.
Often people forget to install the plug. The engine will idle fine, but when you hit the gas, bang! backfire! due to another lean condition......much like the missing vacuum line or a leaking intake manifold gasket.

Furthermore, if the "squirter" in the carb is too small then you will not get an adequate "shot" of fuel when you hit the accelerator. They make squirters in several different sizes, ie. .050" .060" ect. You may need a larger squirter. If the squirter is too small you will lean out and backfire, if the squirter is too big then it will bog and fall on its face.
In closing, keep in mind that a worn of flat camshaft can cause this condition as well, however it usually backfires through the carb, not the exhaust. Your engine may be newly rebuilt, but if the cam was not properly broken in, then it may have a worn/flat lobe. A worn lobe is unable to open the exhaust valve, thus it "exhaust's" through the carb. Hope this helps.
GT
The thing only back fires sometimes. I can't do it on command so it's like something is kicking on and off. It will do it usually everyday and start up can be a problem. I'll start it and then it will instantly die. I'll fire it up again and it stays on. I think my choke needs to be reset or something. :mad:

[SergntMac]

The thing only back fires sometimes. I can't do it on command so it's like something is kicking on and off. It will do it usually everyday and start up can be a problem. I'll start it and then it will instantly die. I'll fire it up again and it stays on. I think my choke needs to be reset or something. :mad:
Just guessing here...Pushrod engine...Backfire at start up? Ticking?

Sounds like valve train...Ever consider a collapsed/lazy lifter?

Just guessing...

[Motorhead350]

It has lifters less then a month old, rockers too. But this all came back after the engine fire. The ticking especially. :bigcry:

[Motorhead350]

The problem was the plugs wouldn't work for this type of carb. I still think this is a load of crap, but thats what the problem supposly is. :bs: Also I will be getting a MSD distributer. Lets hope this works. :o

[Paul T. Casey]

I'm still with the others who are saying vacuum problems. Leaky vacuum lines, could cause no advance at wot, hence the backfire through the carb. If they're all good (lines), then lean toward the lifter/valvespring or worse yet camshaft area. Just because they're new doesn't mean thet're good or properly installed. Just my $.02.

[Motorhead350]

Thanks I'll mention that. :argue: