I finished my rebuild about a month ago on my 93 lt1. i threw in a hotcam kit and pacesetter emissions headers with y pipe going through a high flow cat and dumping into an slp loudmouth catback. the car seems to run extremely rich and is desperate need of a tune, but something tells me a tune isn't going to cure my horrendous exhaust smell that fills the cabin. it seems to get worse when the heat or air is on. i used the search function and it seemed like most people with this problem traced it back to a leaky exhaust manifold. I don't think thats the problem in my case considering they're brand new don't sound like they're leaking, and all bolts are in place and tight(just checked). I'm really at a loss here, any suggestions? thanks in advance for the help

 

mines doing the same thing i have pasesetter lt's too let me know what u find im going to change the gaskets in spring

 

You said emissions legal you might check the hoses on them and make sure all that is tight and double check all the header bolts. All of your connections if the exhaust is bolted or welded just check for leaks. If it's running very rich and it's dumped anywhere near the cab it could be from that but if it's dumped behind the diff. I wouldn't think that would be it. Getting it tuned might help some though.

 

mine does the same thing, especially when air/heat is on. i have pacesetter midlength headers tho and no emissions on my car. also no tune yet. its kinda sick but once you roll the windows down and start crusin its not so bad

 

i'm going to check the y pipe bolts since i've already checked the header bolts and hoses running from the emissions hookups on the headers. I'm kind of doubting i'll find anything simply because it doesn't sound like the exhaust has a leak, it doesn't tick when i'm on the throttle, so i'm up in arms this seems like too common of a problem to be left undiagnosed

 

You could always plumb up a nitrous system to spray in the interior, then you won't notice the exhaust smell

 

i cant believe nobody else posts this as a possible cure, but my car was running extremely rich, i replaced the engine coolant temp sensor (the one in the waterpump) and most of the problem went away, not saying its a cure, but for me when i did this it wasnt running nearly as rich. i am assuming the rest of the rich on my car is from running without a tune. but for $8 its worth changing. put plastic or something over your opti if you do it and keep ALL coolant off your opti!! its like a 10 minute swap.

 

Keep a window down,fix the leaks,route the exhaust where it gets out from under the car, get a tune.

 

You need to tune for the larger cam...Anytime you add a bigger cam you need to tune for it. Remember, though even with a proper tune you'll still have more fuel smell at idle...Its just the nature of the beast...

--Alan