Just wondering what exhaust upgrades are best on these things? I've got a V8 and would like to let it breathe a little better.

Are there any legal headers, high flow cats, etc besides just catback systems? Anyone know what power gains are to be had? Lastly, any of this legal for smog testing?

 

There are no direct options for headers on the Alpha due to frame/4wd clearance. You can get the colorado V8 thorley headers and modify them abit to work and thats fine since many people who instal headers that are direct fit endup having to caress them into place!
But you will loose the upper cats which will affect emmissions!

 

Can duals be run or is there simply no room? Maybe high flow cats and 3" pipe is all that can be done.

 

Im running high flow magnaflow universal cats inplace of the stock manifold ones (mine were done) and removed the secondary cats (under the front doors area, they were also done). As for a true dual, you can cut the part where the driver side crosses over and merges with the passenger side and run dual pipes (true dual) with an x/h or straight pipe.

Check this

 

Best bang for the buck is a MAGNAFLOW CATBACK. The thing that helps most is that it replaces the restrictive “flattened” stock crossover under the transfer case. That alone is worth measurable hp in addition to 3” diameter from the collector, the zero restriction resonator and well designed muffler. Because the full diameter crossover is closer to the transfer case tailpiece, not a bad idea to wrap it in header shield held in place with stainless zip ties.

 

Excellent stuff guys, thanks!

 

x2! Not to mention the entire system is stainless steel, gives you twin exhaust outlets, and sounds great (at least on my Alpha)

 

Interesting! The magnaflow sounds like a much better setup than the gm performance exhaust I bought years ago (which is also the borla one) as it onlu starts right after the merge section. Ever since my LS swap and my exhaust sounds terrible at idle and I blame it on the fact Im running 2.5" tubing all the way down and Ive read I need 3" for 500 hp!

 

I failed to mention in my earlier post that I met a fellow who claimed to have been deeply involved in the H3 ALPHA project. He said that the ONLY reason the ALPHA was rated at 300 hp. instead of 315 hp. for other 5.3’s such as the SIERRA was the restrictive exhaust. He emphasized that the the “pinched” crossover was the major contributor. If you carefully inspect the stock system, it makes sense!

 

Its probably true but keep in mind the H3 Alpha has 4 cat converters which contribute significantly in lowering performance. 15 hp because of a crossover is an over statement. I saw on youtube people testing headers on an LS engine after beating the **** out of them (bashing with a sledgehammer) and they barely lost power conpared to when they were in perfect condition.