So I have been doing lots of cam research in the last weeks...I am building a new motor for my z28 and the major restriction is that it must pass smogg in california. Now we have built 383 ltx's which must pass smog before and the LT4 hot cam was used, it just barely squeaked by on the emissions and dyno roller test(no lope at 20mph in 1:1). I am asking for Bret's adivice as to whether the XFI lobes look good for this purpose. Build specs are as follows...

Callies crank 3.75"
Manley rods 6.0"
Mahle pistons -5cc flat tops - But I can stick them in the CNC and make whatever dish I want....
Trick-flow LT1 heads - will be ported...62cc+ chamber 75+ cc exhaust port will flow real well.

Must run on 91 octane...was thinking 11:1 static.

I was considering a cam similar to these lobes

3014 268 218 .570" INT
3035 276 224 .565" EXH w/ 1.6" rocker

LSA seems to have a significant effect on smog, so ? 112 ?

 

i have the XE 230/236 112 LSA and if I ever even thought of trying to pass emissions I would go sell the car right now. I dont have a tune, but dont see how something w/ more lift, duration, and same LSA will ever pass emissions personally... but maybe with the more cubic inches it is possible? Just my thoughts

 

You know how I am with cam specs man....

My advice would be to get the most aggressive ramps you can on that cam to cut down on the overlap area without screwing up the valve events.

Compression is your friend in a emissions motor since the centerlines are so wide to cut down overlap. Which makes the IVC later no matter the duration.

I'm suprised that the Hotcam barely passed in CA, that's suprising.

Bret

 

My shop is deap into SCCA road racing engines, and local roundy-round track stuff, so not too many motors that have to deal with the complexities of smog. So my R&D time with those kind of apps is really low. I guess I will throw something in there and see how it does.