so when shifting out of any gear it back fires, somtimes wont at lower rpms, and seems like if i shift fast enough it wont do it but the higher the rpms the louder. it started doing this after the catalitic convertor was cleaned out. It doesnt seam to have any leaks from the weld job. What could cause this?

Unburnt fuel in the exhaust. Turbo cars run a little rich. Put a cat back on it.

no turbo on this. ea81 i bought a new cat with y pipe and all and it plugged in 200 miles, so i cant afford another 200 bucks for a new cat to have it plug again

duh me, I am post lagging. I was mixing post titles. Check your carb, you are running hella rich then. especially plugging new cats.

If your engine is running rich, it will clog the cat. Amazingly enough, if the engine is running rich, you will also experience backfiring.

 

I say, your engine might be running rich??? That or the timing is off.

You have exhaust leaks or bad air injection valve reed's.

 

GD

i think ya oughta throw a cherry bomb on it, throw some stickers in the window and really make a statement! i like the whole backfire thing.....! brrrrrrrrrrrrrrrrraaaaaaaaaaaaaaammmmmmmmmm............. bloaw!!

 

really though, runnin rich/timing ^^^^ these guys are right i'm pretty sure..

While richness and timing may be part of the problem - without oxygen there can be no combustion in the exhaust. He has leaks that are allowing in fresh air which mixes with the unburnt fuel and ignites in the exhaust.

 

Typically the backfireing can be solved simply by eliminating the ASV's - either by blocking them with a quarter or by welding up the holes in the spacers.

 

GD

i think ya oughta throw a cherry bomb on it, throw some stickers in the window and really make a statement! i like the whole backfire thing.....! brrrrrrrrrrrrrrrrraaaaaaaaaaaaaaammmmmmmmmm............. bloaw!!

 

really though, runnin rich/timing ^^^^ these guys are right i'm pretty sure..

 

I used to drive a 74 VW Bug, UNBAFFLED Stinger (megaphone) Exhaust, Dual carbs ect. I would come down an off ramp, hit 2nd and you would think you were in a shootout! BBBRRRRRUUUHHHMMMMMMM.....POW....POW....POW..POW POW POW!!!

 

BWWWAAAHAHAHAHAHAHAHAHA!!!!

 

:lol::lol::lol::lol::lol:

 

The two times cops pulled me over, I would just say "My baffle fell out the other day". Never was written a ticket

what do you mean by ASV's I would like to fix it, i have had some people almost fly off the road thinking they are getting shot at

The ASV is the Air Suction Valve. If you look at the exhaust ports on the heads you will see a spacer with about a 3/4" diameter tube running out of it. Follow that up to the ASV. Unscrew the valve from the tube you just followed and put a quarter (yes - $0.25) inside the valve body and screw the tube back on. Do this to both sides if you have two valves. That will cure your backfireing.

 

GD

thats a pretty trick quick fix, and very affordable too! i will have to remember that cause i've actually run across this problem on several of the cars i bought in the past and never knew that....