swaped my auto fore a 5sp ,now when i slow down with it in gear it makes a poping noise sounds like the exhaust back fireing
i have edelbrock headers,3in exhaust all the way to the flowmaster,and no cat. any ideas thanks rob

 

oh yea its prettymutch all stock 305 with small mods

 

anybody

 

You're probably running a little rich, with the manual it pulls your engine RPM down consistent with roadspeed on decel, with an auto the converter lets the engine "slip" on decel so it doesn't keep the RPM/load as high for as long.... You might also have a small exhaust leak, theslight vaccum created in the exhaust system on decel might be sucking in some outside iar, providing your rich mixture with enough 02 to ignite- backfire. If you want to fix this, put the stock manifolds back on and run a cat. ;-)

If its really annoying, and LOUD (sounds like a grenade going off under the car/shoots flames out the exhaust, you might want to replace your header/collector gaskets (Percey's Dead-Soft Aluminum are the ONLY ones worth anything).

Good Luck,
JK

 

thanks for the info, i do have a little leak were the cat was i,ll try that first and go from there,, the noise is not that loud but it is bothering i,ll fix it this weekend. thanks again
later rob

 

If you are using EFI, did you replace the PROM with the correct one for the manual tranny? The auto and manual PROMs act a bit different and that could be the problem.

Just a thought.

Dale

 

yea i have a 90 rs with the 305 tbi, and no i did not change the chip i heard u didnt have to

 

The computer still works fine with the auto PROM but the manual one will change things to better suit the tranny. I am not sure if it will solve your problem, tho.

My V6 does a little of the popping even after I swapped the manual chip in. I like it actually. Makes my car sound like it has a pair

Dale

 

see if the a.i.r. check valves are all in good shape-first-when the miles get up there leakage happens and backfiring is the result should only flow 1 way.