Smog Test Truths/Myths

[1BADC10]

I posted the sale of my 216/220 cam on several sites. One site's user responded quickly, then changed his mine b/c he was told by (what he said) "others" that he would have smog issues if he swapped cams? Is this or what? I would think the type of exhaust (header, cat, and muffler selection) would dictate the level of emissions output he receives. I would also think that proper tuning can minimize excess fuel flow, thus rich-running motors. I may just be assuming too much.

Anyone have EVIDENCE of truth to this?

[RedHeartbeat]

Any time you change the engine it can affect the smog readings in the engine if the tune doesn't have the ability to compensate for the change. Some states have very strict smog laws. Some guys are too cheap to get a tune. You just have to deal with that crap when selling parts. I know, I hate it too.

[chrisj6]

It all depends on the engine, exhaust, intake and tune combo. The efficiency of the cam has alot to do with it, and any cam in any motor, if not tuned right will not be emissions friendly. The more aggressive the cam, the harder it will be to meet emissions standards.

Chris

[misterp]

When it comes to cams it's the overlap that is the biggest factor as to tailpipe emissions; to get a better idea you need to know the LSA of the cam as well as duration, that duration on a 108-degree LSA will certainly not pass emissions where on a 114-degree LSA it probably will, assuming the tune is dialed-in. Anther factor is whether the cam is right-sized for the crank stroke and displacement, a cam that is domesticated in a large stroker can become very rowdy in a 5.3L. FWIW of what I've read on the f & y body forums a 216/220 cam on a 114-degree LSA in a 5.7L-6.0L is the largest recommended to pass california emissions and will need a very good tune...

Mr. P.

[NITROUS]

I'm running a 220/220-581/581-115 cam and it passes with no issues thanks to HPTuners. There's no way in hell my truck would pass without it due to other mods. We tried the test without the tune and it failed. We tried again with it and it passed with no issues. As long as you can keep the MIL off you'll probably be alright.

[1BADC10]

Well, as ya'll know I pulled my old cam, and posted it FS. The individual that made the first offer decided to decline. His reason was due to smog concerns (Southern CA area). I thought nothing of it, but did suggest (assuming he had the capability) tuning to meet smog restrictions. The inspections place I went to said he'd have to check the emissions as well as other things on my truck to pass. I didn't watch him do it, but I'm assuming it passed cuz I have a nice new Emissions Test sticker on my windshield. The area I live in is known to check EVERYTHING (as if I was living in CA). I was always told not to have it inspected in my area, but had no choice. Here's the kicker... the exhaust has NO CATS!

Under my carport, you can tell there's something up with exhaust, but it's not noticeable in the open. I've leaned the tune out as much as I'm comfortable with at idle speeds, but righteously richer on up the RPMs. It's not as bad as before, but the rich scent is still present. That'll happen as long as there are no cats. Sometime next year, I'm going to cut the exhaust, and get it redone with high-flow cats installed. Hopefully, that'll eliminate the rich scent a bit more. Of course, having turn-downs in a semi-enclosed area doesn't help dissipation of fumes much, huh?