Help "bending" my LT Dpipe

[84ttype]

Well I just installed some poly motor mounts and now I'm on to the DP, which I'm sure is what is tripping my KR gauge. The thing rides along the firewall about 1/2 inch from it. and at the bottom it almost rests against the lip of the heat shield for the cat. I plan I going into the low 12's E.T. so I know I'm going to need this DP. Is there any tricks to bending it or some other way to adjust it?

 

[cool 84]

Remove the heat shield. If you're not running a convertor and just a test pipe you'll never know the difference. Mine hasn't been on in 10 years.

 

[84ttype]

I do have a convertor installed, car wouldn't pass without it . I was going to cut out a piece of the shield where the DP connects to the convertor though. as far as the firewall I thought about just denting it in but I can't get a hammer in there between the frame. has anyone else had this problem before?

 

[Jerryl]

If this is a LT unmolested DP, you may want to look a bit closer at other things before you cut that pipe. Some may throw egss at you if you cut that pipe.

 

[84ttype]

Update!! Decided to "bend" the firewall instead with an airhammer, helped a little but I still get knock, also noticed that my cat convertor is touching the heat shield, theres no gap between them Took it out after beating the firewall in, results are: From 30 MPH, floored it Knock gauge went into yellow, disappeared after shifting, then went to the third green light. DS recorded worst KR at 4.8 degrees. next test held the brake and revved to about 2500 RPM and took off, gauge pegged immediately! DS recorded 66 counts of knock, but no degrees KR at all???? anyone got any ideas?

 

[Jerryl]

Update!! ......... From 30 MPH, floored it Knock gauge went into yellow, disappeared after shifting, then went to the third green light. DS recorded worst KR at 4.8 degrees. next test held the brake and revved to about 2500 RPM and took off, gauge pegged immediately! DS recorded 66 counts of knock, but no degrees KR at all???? anyone got any ideas?

What happens when you "ease into" the throttle?
FP keeping up with boost? What are the O2's @ WOT? How much boost are you running and what timing?

 

[84ttype]

The cars only at 7lbs. right now because of the knock, o2s are around 830, the timing is around 25 degrees when cruising goes down to about 20 when I floor it. Not sure about FP its a rail mounted gauge.

 

[Jerryl]

The cars only at 7lbs. right now because of the knock, o2s are around 830, the timing is around 25 degrees when cruising goes down to about 20 when I floor it. Not sure about FP its a rail mounted gauge.

Is the car smoking or burning any oil?

 

[84ttype]

nope. smells a little on the rich side though. reg. is set at 42lbs.

 

[BRAD_PADGETT]

I had a a problem with my 2 1/2 downpipe banging on the A frame. My mechanic heated up the pipe and bent it so it would not cause knock. The real message is that you can test for this false knock on your driveway in my case. I have a knock gauge and reved up the engine on the driveway and the downpipe created the false knock. My scanmaster could'nt pick it up. After the downpie was bent the false knock was gone while testing on the driveway. This was also confirmed on the road. Just my experience. Brad

 

[Lee Thompson]

Before you butcher the pipe

How about enlarging the 4 holes in the first section (the one that bolts to the tubo) which will give you some more clearance. A slight amount @ the top will be a bunch @ the bottom.

 

[84ttype]

Good idea. I have some room between the firewall now but doing that might help push the cat down away from the shield.

 

[boosted84]

id be willing to take that dp off your hands to help you get rid of the knock problem