SPG

iTrader: (3)

I have a 402, 59cc ffhp stage 2 ls6 style ls6 castings, LT's, cats, very free flowing exhaust, Ls6 inlet, TB & MAF, and a need to pass these emmissions here in the UK.............

Fast idle 2500-3000rpm

CO no more than 0.3%

HC no more than 200 parts per million

Lambda between 0.97 and 1.03

Normal idle 450-1500rpm

CO no more than 0.5%

I am looking for solid midrange, good road manners, no quarters, occasional track days, but mainly road use. I don't want to spin the motor hard to gain every last HP! compression ratio is likely 10.9 or 11.3 depending on gasket. this is going in my shelby cobra replica, t56, 3.23 rears, 1800 lb

Where should I start with cam choice, I need some experienced comments from people that have tuned for emmissions on this type of motor. I am not interested in max dyno numbers.... but want what will really work on the road

thanks for any help

steve

71CamaroLS1

With catalysts, those are not very difficult targets to hit, especially if you're allowed to idle as high as 1500 RPM. If you're using a factory ECM, the lamda number should take care of itself as long as you're still running closed loop part throttle. Big cams will tend to increase HC more than CO, but 200 PPM at 2500+ RPM is pretty generous (I had a carbureted non-emission 502 big block that made less HC than that).

You could go pretty big on cam, but you might not want to in such a light car. With a very light car, presumably with serious traction issues, a very flat torque curve, extended RPM range, and minimal part throttle surging would seem to make for a better driving experience. All of that would point to a cam with modest duration and wide LSA. MTI uses a cam on their "Devil Ray" 427 stroker called the DR1, with 228/232 duration, .588/.574 lift, and 116 LSA. This goals of this cam in a GMHTP article were described as "retain driveability, dependability, and pass emission tests" as well as "idle great and maintain a very fat torque curve all across the powerband". Sounds like a winner to me.

SPG

iTrader: (3)

I can run tickover wherever I need at emmissions test, and I have the cats built into the sidepipes so they have to stay really...in any case they allow the removal of almost all other silencing so total flow is not restricted too drastically. I think the dB limit on road is 101, most tracks here are 95 or so...

I do have a unused 224/224/114 570 lift cam sitting in the garage that I was considering using, but wondered if it was just too small.......

I have had cammy cars in the past, and whilst this is not a daily driver, I do use the car most weekends and often for a week or two as a dd, so I want to stay away from cams that would make that too harsh to live with.
the other issue with such a light car, with the engine relatively firm mounted, is that a really lopey cam shakes the car around so it gets kinda uncomfortable!

thanks for the advice

FDLS1

iTrader: (2)

https://ls1tech.com/forums/generation-iii-internal-engine/311937-395-rwhp-na-factory-manifolds-cats-catback.html

Maybe this will help! Just trying...