Sport Side

iTrader: (6)

When we talk about smoggable camshafts on the most part, once you approach a near 225 degrees of duration @ .050 we approach an unsmogable camshaft. This is just comparing alot of the vendor sold camshafts. My assumption may be off, but besides the point of my topic.

I don't quite understand the requirments of a smog camshaft. So, what standards must it meet to fit the category? Also, does cubic inch play a role in what is considered smogable?

For ex.
Thunder's 224 @ .050, I've heard passes smog test's in a 346ci LS1. Would it pass in a 325ci LM7?

Any insight?

Hysteria

I would not go over 224 at .050 lift and no tighter than 114 lobe separation angle on a 346 inch LS1. The larger the engine the more you can get away with. The larger the engine the more cam it can use and still be passable. My rule of thumb is for every 30 inch gain use a 2 degree larger cam. Also the tighter the lobe separation angle the cam can have when going larger in engine size, rule of thumb is every 30 inch gain use 2 degree tighter lobe separation angle. Say you have an 346 engine that passes with a 224 cam that is cut on a 114, when you go to a 382 you probably can run a 226 cam cut on a 112.

z98

I'd play it safe and go for the B1 or the TR220.

But that's just me. And people have gotten great power out of both of those cams.

Also, a stealth II has made 430 RWHP with stage 2 LS6 heads through an auto.

Z28Venom

iTrader: (13)

This is how Predator-Z explained it to me.. pretty exact..

224 would be the maximum duration on should go, because with more intake valve being open the bigger the charge the more the unburned fuel residue.
Now comes the lsa:
A 220 or 222 or 221 on a 114 would have a better chance to pass
224 would be better on a 115+ lsa.
It has to do with valve overlap (the time both valves are open together and therefore exhaust is contaminated with unburned fuel.
The more negative degree is the better your chances of passing.
To calculate degree of overlap is simple:

((int DUR+ exh DUR/2)) - 2 x lsa = degree of overlap

EXPL: ((224+224)/2) - 2 x 114 = 224 - 228 = -4 for the cam you've given me.

You could make use of the ramp rate to make the same power (XE-R or similar)
Some cam Examples are the MTI Stealth cams

PREDATOR-Z

basically, a cam with more negative (-) degrees of overlap at .050 has a better chance to pass. This directly involves lsa as bigger lsa will induce more negative overlap. This is the reason LS1/LS6 stock cams are in the 115>>117.5 lsa range.

IMO and it has been done before, 224/114lsa will pass emission if properly tuned for that purpose.

John B

iTrader: (10)

It really depends on your goals and objectives. If you want a year round smog legal cam go with what is recommended above. If you just want to pass emissions with a cam, you can go quite a bit bigger by tweaking your set-up just prior to testing. I passed the sniffer with a mid/low 230's duration cam!

z98

John B, how much does your car weigh?

Sport Side

iTrader: (6)

im sry guys, i didn't even know anyone posted. thanks for your help. let me catch up.

Sport Side

iTrader: (6)

ohhh ok. thats it. sorta the whole overlap feature, i'm catching on.

I wasn't looking for a cam that will pass smog, i was just looking for an explanation of how one passes, or why one wouldnt

thanks for your help guys.