haven't taken car out yet, but verry loud. fresh 402 and headers off road y no cats, and loudmouth, going to take out car in spring and try it out. may be considering puting cats on, anybody have dyno results of before and after cats, and does it make mutch different in sound and smell.

 

Why don't you get rid of the loudmouth and get a better muffler.

Go with a magnaflow muffler or two in-line and never look back.
Straight through design and they are pretty damn quiet.

 

i have replaced the empty chamber with a resonator type bullet even before i started the engine, only enough room for 1 .

 

Cats will make it noticeably quieter and make a big difference in the smell. You probably wouldn't be able to feel the difference with a good hi flow cat.

 

Ive tested a 500hp engine with and without a set of Dynatech cats. It was only 3-4hp difference. Get the cats!!

I didnt have the money to put them on mine, but I will add them in time!! I can do without the gas smell and quieter is always better.

 

put a good muffler on the back, and just put an electric cutout in front of it to make some noise when you want to and close it if you get pulled over.

 

Yeah my tuner told me with my setup cats cast me 5 rwhp max. I wouldn't think it would be much more for you.

 

thats not so bad, easy trade off for noise level and smell for 5hp

 

I cut my cat off (wish I hadn't because it was a highflow CATCO aver 300) It sounds much better but has a small rasp when you rev it hard and let off. I am pretty much all stock and I didnt feel any difference. I like the cutout Idea TransAmatt99 mentioned. Thats the best of both worlds.

 

Yeah for sure your numbers won't really be effected if you get a cutout, but i'm running true duals with a 408, 1-7/8 LT's, an a 660 lift cam.... lol The cops love my car it's hilarious to see a cop giving you thumbs up. I've been thinking about piecing together a CME with the BMR panhard relocation bar so 3 inch will fit through.

 

not interested in installing cut-out, it's just when i started it is smelled real bad, mayby after the tune it will get better, or should i instal the cats first before tuning.

 

If your cam has much overlap it will still smell strong after the tune and you may still want the cats. Big overlap causes an inefficient combustion process at low rpm and raw fuel getting in the exhaust....

 

cam is 236-242 648 lift and 112

 

what cats would you use to put in y pipe for most clearence?

 

Yup, I have very little overlap and no cats and my exhaust still has the smell of gas, even if Im idling at 15-16:1 AFR...