Did timing, still backfiring.. 84 GL Wagon

[seattlelegacy]

Now I'm perplexed. Here's what I think I may need to do next:

 

Replace manifold gaskets? (there is a small amount of carbon, maybe like a half inch on the pipe, looks like a little exhaust is getting out..)

Adjust valve gap clearances?

Run about a bottle of Seafoam through the carb?

Run it down the freeway at 70 in 2nd gear?

 

The carb is nice and tight on the intake manifold, but the exhause does smell like its running a little rich. No idea how to adjust that as this is my first carbed car ever... even the timing was a new experience for me.

 

Hmmm.... any ideas? Of the above things, which would you try first?

Oh, and emmissions are due:dead: , so no ripping vacuum lines off the carb.... yet:lol:

 

I did find this thread... http://www.ultimatesubaru.org/forum/showthread.php?t=48834&highlight=reed+valves Perhaps its the anti-backfire valve? Let me be more specific... The backfiring occurs after shifting at about 4000 rpm, sometimes less, like 3000 rpm. Its the "loud" backfire, not the "grumbling". The kind that makes people duck. Also of note, if sitting in neutral, and you punch the throttle, there is a terrible low end hesitation. If I think of more symptoms, I'll edit again.

 

Thanks,

Jordan

[seattlelegacy]

Bump and some additional notes.

 

I located the "backfire valve", took it off, cleaned some crud out (with the trusty carb cleaner) and replaced it. Also found some very loose vacuum line going into the softball sized saucer under the left hand side of the air filter and tighetened that up a bit. Sprayed some carb cleaner down the throat of the carb. None of this helped.

 

So, now I'm thinking more likely an exhaust problem, or a carb tuning problem. When this think backfires, it BACKFIRES. Its a loud, exhaust destroying type, none of this pansy rump roast gurgling as I'm going down a hill. I also found in HTKYSA alive manual and the Haynes how to adjust the mixture. I could try that if someone here thinks that a potential problem. At this point I'm thinking about the old saying... if it aint broken, don't fix it, so speak up if you think this is an issue. Still entertaining the seafoam idea as an easy fix.

 

I should probably pull the plugs and make sure each one is getting spark too (???).

 

As far as the hesitation when punching the gas, I noticed that if I hold the choke upen, and have someone punch the throttle, the little "accessory jet" doesn't do squat, so that probably explains the hesitation issue.

 

I'M STUMPED ON THE BACKFIRING ISSUE.

 

 

Jordan

[GeneralDisorder]

Your backfireing is due to leaks in the exhaust stream - either in the y-pipe, or from the Air Suction Valves. Block then off (quarters work well) or fix the leaks in the pipe. You are introducing fresh oxygen into the exhaust stream and it's mixing with unburnt fuel in the rear of the exhaust. The hot muffler will ignite this.

 

GD

[mbrickell]

Your backfireing is due to leaks in the exhaust stream - either in the y-pipe, or from the Air Suction Valves. Block then off (quarters work well) or fix the leaks in the pipe. You are introducing fresh oxygen into the exhaust stream and it's mixing with unburnt fuel in the rear of the exhaust. The hot muffler will ignite this.

 

GD

 

Excellent call.

[seattlelegacy]

Your backfireing is due to leaks in the exhaust stream - either in the y-pipe, or from the Air Suction Valves. Block then off (quarters work well) or fix the leaks in the pipe. You are introducing fresh oxygen into the exhaust stream and it's mixing with unburnt fuel in the rear of the exhaust. The hot muffler will ignite this.

 

GD

 

GD, Thank you for the info. I'll probably defer this one to a muffler shop, as I don't have a welder (yet). But, this also brings another matter to the table.... why do I have unburnt fuel in the exhaust? Seems like a mixture adjustment will be in order in the near future... THANK YOU.