help with exhaust

[johnleewilson]

hi, im new to this board (well to message boards in general) but i have been reading on it for a while.. so, i own an 85 silverado 4x4 its get alot of new parts but its fair share of old ones too. anyways... The old exhaust setup was a Y-pipe, then the cat, then a 1-in 2-out muffler. The cat started coming apart and rattling around so i decided to look at new exhaust. I went to the local muffler shops and got some prices. I only found one that would remove the cat, and he was pretty spendy, so i went ahead and bought one of them 150 dollar dual exhaust kits out of LMC catalog. It had two glass pack mufflers and all the pipe needed. I also bought a set of 2 year old headers off of a friend for pretty cheap and put those on. the truck has all the egr crap on it but i dont have to do emissions where i live, so im removing all of that as soon as i put a new intake manifold and carb on it. the old exhaust sounded decent, it was real quiet and the cat rattled but it was ok. I took of the entire old system and then just put the new one on. I plugged up all the emissions lines as i was told too by some friends of mine, and then fired it up and it sounds like crap! at an idle it is nice and low but as soon as i rev it up it sounds like a big fart, real choppy like. it seems to run alot rougher too. i dont mind loud exhaust i just want it to run smooth. i checked and seems as though i have all the emissions lines plugged. any help would be appreciated. i am by no means a mechanic i just try and save money by doing work myself and screwing it up. err anyways thanks.

[apstguy]

I would check those vaccum lines capped and capped correctly. Otherwise it might have a vaccum leak and idle rough. Do you know what engine you have? If it is a 305, they don't sound that great. I was just running the original cat - no muffler for a while and it does sound ok at idle, but reving it up didn't sound great. It would be useful to put your location in your profile so we know which state we are dealing with. The law is (at least in CA) your cat has to have 50,000 miles on it or be damaged to be replaced. If your having trouble finding a shop to do it, I suggest you beat the hell out of your cat or saw it of, then take it to a shop. They should have no reservations about replacing it then. My cat started shooting out the pebbles inside so I had to replace it.