LT1 Metling Cats with CC503

[96'bowtie]

The engine is: 355, Dart Heads, Long tubes, Comp Cams 503 (224/230 112), 11.0:1 CR.

At idle after a minute or so the cats start to get hot enought o begin to glow. My suspision is the overlap in the cam is pumping air and fuel out of the
chamber and is combusting at the cats?

I did not think this is a wild enough cams to have this sort of problem, so something is definetly off. I cannot seem to cut the fuel at idle enough with LT1 edit either.

I had a scanner on the car and at idle I seem to to register misfire counts on cylinder 1 and 2. Not sure if it is actually a misfure at idle or the choppy cam causing an
eratic crank speed at lower RPM. As soon as you come off idle, there misfire counts go to zero for all clyinders.

Am I missing something in the tune? or something mecanically? I tried reducing the timing at idle to possible make the 02 see a rich mixture and cut fuel, but that did not seem to work either.

If anyone would like any other information about the tune to bring this into context, please let me know, need to do something before car melts.

[meissen]

I have a 357, stock heads, cc503 build also. My tuner put the idle tune at like 18:1 and said "it's OK, you don't have cats..." So maybe the idle is too lean, not rich.

[96'bowtie]

Thanks for the reply, if that were the case, how would you change that with LT1 edit?

[bigtoyz]

correct if I am wrong but if the cats are getting that hot is because it is burning up the fuel that is in the system. So I would say you are running rich. If your software tells you what the A/R is I dont know, or else you can use a wideband o2.
I have 224/230 but it isnt the 503 but a custom boost grind. But pm me your email and I can send you my tune to use it as a comparison tool. I have it tuned for NA atm so it might give you some idea where to go with it.

[BLK95-Z]

Are they stopped up?

[96'bowtie]

Based on my understanding I would agree there is combustion at the cat.

What is really confusing if the source of the fuel at idle that would be causing such a rich condition to have enough excess fuel to make the converters flow? My thinking was the overlap in the cam was
allowing the fuel to pass though and hit the cat?

The topic of the plugged cats came up, maybe they need to be cut-out, however we holding off on that as they are new. The exhaust system was just made up? Still a possibility.

Thanks for the help bigtoyz, i'll pm you. Maybe I am missing something in LT edit.

Thanks,
Vic

[bigtoyz]

No problem just give a yell, glad to help out. I know when I rebuilt my 88 t-bird turbo coupe the timing was off and really raised hell on the cats. Just thinking out loud here, to give
yeah idea's.