Backfires. Need help

Just for reference re: 34-PICT-3:

http://www.aircooledtech.com/34pict3_modification/

In all honesty, I have very little experience with stock, 34 carbs.  BUT!  What little experience I do have has always been to get a rebuild kit and do a complete rebuild on them, including blowing out every passage I can find with about 40 PSI of compressed air before I put them back together.  They have always worked perfectly whenever I do this, provided that the throttle butterfly shafts aren't excessively worn and leak at the housing..  If I just try to blow a little air here and there and "try to clean things up", it never works and I just end up doing a full rebuild, anyway.  The good news is that a complete rebuild takes about an hour with a beer break.

Given all that, it kinda-sorta sounds like an intake manifold leak, especially if you're running a vacuum advance disti, but I would still either rebuild the carb or pop on a new one And replace both manifold gaskets in the process.  Yes, that's shotgunning it, but Carlisle is a week away.......

Thanks, guys.

Scott: I'm not running a 009, but a SVDA disty. Even so, that link gave me an idea about my timing specs that I had not considered.

Gordon: The carb is pretty much new--maybe three seasons old. Throttle shaft is not oval yet & carb seems to be working just fine. But, right. She IS acting like a lean-out is happening, isn't she? I might just have a dude bring me a 30 PICT to swap over at Carlisle for testing purposes.

I suppose the good news is that there will be a dozen vendors selling stock intake/carb gaskets in the vendor area.  Maybe you can get Danny P. to do a 34 rebuild??

On The Samba there was a tread about backfires and the general consensus is a small exhaust leak is to blame. 

i think you are on the right track with exhaust gaskets. Be careful to not over torque the flange bolts. Also, you may consider using copper high temp silicon to ensure leak free exhaust joints. Post your results!

Yeah, looking more and more like one or both of the front pipes. Tried my timing theory this AM--re-timed to 5 after TDC at idle and then reset the carb idle and there was no change. Well, maybe a tiny slower off the line, but who can know. The backfire is still exactly as it was.

I'll pull the tins tonight and jack her up and crawl under with a light to see what's what.

Tonight I climbed under to look at the front exhaust pipe connections. No sign of a leak there but--hey!--lookit these donut connections! The driver's side was nicely blackened and the donut actually broke in half when i took the clamp off it.

Thinking it was maybe leaking there a bit.

I actually have a couple donuts, but not the rest of the many gaskets, nor the patience to reinstall the muffler tonight. I bought some RTV Copper gasket stuff and stuck the donut back together with that, then buried it in the stuff and put the clamp back on snug. Coated the other donut too, for good measure.

Tomorrow morning I'll cinch-up both sides a little more and, weather permitting, take a ride. If the situation is changed at all I'll know where the problem is, I think.

Maybe I'll get lucky and the thing will be cured! And then maybe all the little clamps and dohickies will come via FedEx, and I can enjoy the weekend completely reinstalling my muffler. This time, liberally coated with that high-temp RTV.

Wish me luck.

Edsnova - just as food for thought, consider taking your car to the local muffler shop and have them replace that exhaust slip-joint/clamp thing and weld on flanges (with gaskets available at any muffler shop).

Here's a pic. Not my engine and not a great pic, but its the best pic I could find for a quick response to this thread.

Even HI-Temp RTV won't last long at exhaust temps.... Plan on replacing those gaskets. Soon.

Thanks Jim and Leon. Def. want to get this done soon. My parts aren't here yet. I do have a muffler guy and this might be the way. I'll see if he's around today.

GOOD NEWS UPDATE: The RTV worked. Almost no backfiring now. I can make it backfire only by revving way up and getting off. Even then, not every time and more of a "poot" than the old sound, which was like the report of a 9mm Glock on the firing range. The new sound is more like a misfiring spud gun.

BUT this (Bad news update): took her the long way around the block, driving a little spirited to try to make the backfire, and she died on me again just before I made the turn to my street.

Same basic thing as the other day--power just fades, and then nothing. She'll start but not run, then not start at all.

Then in a minute she's all better.

Checked my wire to my idle cutuff solenoid again: it's good. Connections are snug. Could the solenoid itself be going bad?

OR... am I seeing/causing the dreaded carb icing maybe? This seems to only happen when I "test drive" around the block, running the rpms up, getting off, testing acceleration and backfire propensity. I felt the intake under the carb--very cool to the touch there, and some sweating condensation had formed.

What say youze?

the orange high temp will last as long as the car will, and some of the blue will work on exhaust also. I had a bracket that had to mount onto the ceramic header tube, it was stainless and formed to fit the tube, about 3"x3" area, I didnt want the ceramic effed up so I coated the back side of the bracket with blue rtv and severail years lator off it came not a scratch, no burns nutten.yes ceramic does get as hot as the non ceramic coated but it dosent raidiate heat like non coated.  and for the old race cars& stret cars befor these great copper header gaskets came out I would totaly cover& work in the orange hightemp rtv into the gasket,(no not globed all over but a good thin coating on the entire gasket & edges) and the gaskets would last extreamly long and be reusable when needed. I also use rtv in the header slip jounts. rtv is far better than any other exhaust sealer, and in my openion is best suited for exhaust usage over any thing else......execpt for using on the ends of intake manifolds to replace vally gaskets on V8 engines.

change your fuel filters, make sure all fuel hoses are good and clamps are tight.next time it does it pull off the air cleaner and see if it's dripping fuel down the throte of the carb, might need to readjust the float drop&level, might need new nedel&seat also.or might be something else...like loose nut.....behind the wheel skeering the car. or could be a wire moving & shorting something or not connected good.(at coil or dist.)

Thanks, Mark. Took it to my muffler guy and he's not going to be able to do anything this week with her. I'm going to bring a couple spare donuts and the install kit (assuming it gets here by Thurs), plus the tube of copper gasket, and hope she holds out for the week at least. Seems to be doing OK.

And. . . found another exhaust leak that may also explain the stalling. Turns out one of the bolts through the right hand carb heat tube flange had lost its nut. There was some blackening on the number 2 exhaust pipe. I gummed it all up with more copper permatex and tightened it all back up. Gonna let it cure before test driving but feeling pretty confident I did something good this morning.

Progress is good! 

OK, I got this thing licked. Took her for a ride this evening and the car is quieter than it has ever been. No more burbles on decel (I'll kinda miss that). No more backfiring. And I can hold a conversation in the car at 60 mph. That has never been possible.

Also, doesn't stall. Idles much better than it ever has since I got it. Carb heat is apparently a good thing. Who knew?

Thinking this Permatex will probably get blown out on the way to Carlisle, or while there auto-crossing. But I know now what the car is supposed to sound like and, like I said, I got a whole kit of exhaust gaskets heading to my house. So with a couple hours of gritty nastiness I should be able to make a permanent fix pretty soon.

Thanks for all the advice and encouragement.

Rock on dood. Glad you got it sorted and see you soon.....

Thanks, David. Looking forward to talking to you. I made a deal yesterday for a '95 Legacy with 83,000 miles on the clock. Need to tow her home this week (brakes totally gone). But I think you know what's coming next. We need to talk intake manifolds and such.

You're a funny guy, Ed. I almost had orange juice coming out my nose! Al

There will be at least five different booths selling VW exhaust gaskets at the show.  If we need to, we can do a full exhaust rebuild in the hotel parking lot.  

No Problemo!!

Thanks, Gordon. I will hold you to that.

I love the copper header gaskets, there kinda soft&conform well, and cant blow out. gladd you atleast got on track of what the issue is, that makes it a lot easyer than just changing parts till youve spent way too much for something simple.

Got all my exhaust gaskets in the mail today. And the steering coupler (rag joint). Also an oil change gasket set ('cause I still have the screen).

Also the Legacy with 83,000 miles on an EJ22.