I just went to look at a '90 rx-7 gxl with a rebuilt engine and gutted cats, it ran damn nice but it backfired when i let off the gas after hitting the redline. Is that normal??

 

it could have an exhaust leak, mine did that when i had an exhaust leak, but im not sure, it could hav to do with the cats but i dunno

 

No big deal. Its normal for that to happen with modded or leaking exhaust.

I kinda like it

 

You probably threw a flame or two out the tail pipes.

Gutted cats + redline + sudden relief of load = flames

 

Maybe you lucked out and hes got a testpipe on it.... i wudnt complain tho, my friends dads truck shot 4 foot flames out of the back when you let off the gas, good ole sierra classics lol

 

Normal without cats and redline in a rotary engine

 

my cats still on and i backfire, dunno about flames though. only started to happen when new bov was fitted ?!

 

That is because the BOV is venting to the atmosphere, resulting in a momentarily rich condition. Puts lots of fuel into the exhaust, and then "bang".

 

That's exactly what gutting the cats were intended to do.

 

Ya, you got some flames more than likely. I got some 6 footers the other day

 

Fu*kin Shweet Man!!! Gotta love the flames!

 

with any engine haha, I used to have an old '80 f-150 that I beat to hell offroad... jumped it and broke the exhaust, so I cut it in front of the cat... open pipes, sounded badaaaaaass lol

but yea, it'd shoot flames when I came off the redline.