Weird Knock after BBK LT and cat H-pipe install!

[USMCracing]

I just installed BBK Long Tubes with a BBK Cat. H-pipe on my 96 Cobra. At first I thought I had a exhaust leak. But I don't, I used Stage 8 Locking headers bolts on the headers. I got under the car and at the pass side cat. I can hear a knocking or rattling sound coming from the cat. I can tap on the cat and the sound would stop for a few seconds. I'm thinking that the stuff inside the cat is lose and rattling around in side there.

My Check engine light came on today. I thought that it only goes off if you have Off road pipe? I"ve drove the car with the headers for about 300 miles now and the light is just coming on? WHY?

How much HP and TQ am I losing from the stock catback?
The only other MODS I have is a C&L MAF with K&N and a Fluidyne RAD. I haven't made it to the the track or Dyno yet. What kind of times should I hope to get?

Thanks

:beer:

 

[Wildpony]

I'm not sure if you have a "tune" on the car but you may need to have a tuner burn a chip for the car. Between the C&L and the BBK's/diff. flowing cats could cause the engine to throw out engine codes.It could also be that one of your 02 sensors on the H-pipe are not working right. You said you drove it for 300 miles-maybe the 02 wires caught something while driving. (I had to "wire tie" my wires up out of the way for fear of ripping them off)..

As far as times you could be anywhere from mid13's-14lows.(gears would help out in dropping ET)

The cats aren't going to make you lose a "ton" of power-maybe 10-15hp. If you go to a blower and have the car tuned rich on the A/F(ie.SAFE), the cats will plug up quicker causing a more of a power loss.

 

[USMCracing]

I checked the O2 wire right after the check engine light came on and they were all fine. I let the disconected the battery for about a hour and the light went off. I'm thinking about going back my stock MAF, I have noticed that I'm getting some duration even with 92 oct.
I've only been to the track once and that was right after I got the Cobra in Aug. I made three passes and keep in mind that this was my first time behind the wheel of a fast car (I've been driving 4wds since I've joined the Marines, its a long story). I ran a first 14.4 at 98, then a 14.3 at 100, and my last pass was a 14.2 at 99. Each run I was trying diffrent things lunch RPM/shifting points. I think that I could have gotten into the 13s with a few more passes. My brakes started scrapping after the last pass. I can't get any traction because the lady that owned the Cobra didn't see the need to by the good tires, she got some kind of no name cheap RAGE h rated tire. They do not hook at all. Tiree, gears, and shifter are the next items I'm going to get. I'm hopping to make it to the track this Sat. I'm hopping for a mid 13 run. It was really hot in Aug. at Firebird raceway, 100 plus. I've gotten a Fluidyne Rad now and its nice temp outside in Az. Thanks for the help.

Later

 

[Wildpony]

Those are pretty good times for that year Cobra w/no mods. With the tire/traction problem you have try launching around 2500-3000 and not powershift it too hard(you will prob. just break it loose). Once you get a new set of rubber-say Nitto Drags,some better gears,etc. you will be in the 13's easy-maybe low 13's...
There have been alot of bad posts about C&L mass airs. The stock meter is fine for what you have in your setup. (I run a re-cal. stock M/A on my car at almost 500hp)..

 

[USMCracing]

I tried lunching at 2000 and I looked like a top fulie doing a burn out and ran the 14.4. The 14.2 I lunched around ldle and shifted at around 6800 getting the 14.2. If I get to Phoenix this weekend I'm going to take my old MAF meter and change them out and see which is better. I have a stock K/N too. I've read all the bad post about C&L but that was after I got it. That damn knocking sound is drive me crazy. The check engine light didn't go off on the 30 mile drive to work this morning. I'm thinking about gutting out the cats. I wanted a OFFROAD pipe anyways. I got the catted H-pipe from Brothers for $100, it was in their used parts section and I think I found out why it was only $100. Later

 

[USMCracing]

OK, The damn check engine light came on again on the way home from work. And the damn knocking is getting louder and driving me nutz. I'm going to gut the cat this weekend. My Cobra sounds like it has something really bad wrong with it, but I know that it is just the CAT making the sound. What does the MIL elem. do besides turn off the Check Engine light? How do they work? If I don't get them will it hurt anything? I have a friend with 02 GT with offroad H-pipe and he says that his car isn't running right and drinking more gas cause he doesn't have the Mill elems. yet. Should I just gut the cats and get some MIlls? Later

 

[USMCracing]

I took the H-pipe of today and I found that I was right. THe stuff inside the cat had broken up. The pass. side cat back had two big cunks of the blocking the whole pipe. I pulled them out and gutted the rest of the cats. I'm going to need to get some mils now. Thanks for the help.