Some co-workers and I were discussing CA-emissions friendly mods (lame emissions I know). Since I don't know of any "friendly" test-only stations, I can't have LT's, and the consensus on this forum is that shorties don't do anything. A co-worker mentioned having the stock exhaust manifolds extrude honed. I never heard of it (I know what it is now), but I want to know if there are any performance gains to be had/noticed?

 

on an lt1 or ls1?

 

Lt1.

 

What about mid length headers? Better ground clearance too.

Or r&r lts every 2 years

 

Any headers that move the cat and I will fail smog test. Remember this is Cali.

 

Ya but I'm sure you can find someone that will overlook the visual part. Do you have to take your car to a test only station? If you do then you're hosed. If not, then go with mids and just hit up the ghetto when smog time comes to have someone overlook the cat being moved (if they notice at all). If you know anyone with smog legal headers, have them get you a carb sticker and you're good to go.

 

Yeah, I have to use a test-only station.

 

lol... ok. You think shorties don't "do anything"?

Seriously, extrude honing stock manifolds will have WAY less flow than shorties would. It's an option for those with no cheap header option (rare engines/chasis), or for those who insist on orginal numbers-matching castings... but cost per hp its pointless for our purposes.

I think you should look into shorties more seriously.

 

Well I guess that's my only option.

 

I think there used to be maybe one or two midlenth headers that didn't move the cat for the LT1's, but I think they are hard to find now/they don't make them anymore. I had smog legal mids on the V6.

I don't share the opinion that shorties are worthless. But yes, they are pretty much your only option.

 

compared to stock lt1 manifolds, shorties are an improvement.

the real "shorties are pointless" arguement pertains to the later model LS1 manifolds.

 

If he's talking about the 97 SS, than ANY headers other than shorties will move the cat. 96-97 cars have 2 cats.

 

Yep, that's why I didn't even address mid-length headers.

For 1, I only know of AS&M mid-lengths for the LT1 (which I have), and 2) all the AS&M headers are single-cat now... so you have to convert to a 94-95 style path/cat-location.

AS&M's obviously won't pass visual inspection in the Republik of Kalifornia.

At one time I belive AS&M actually HAD a dual-cat design for 96-97 cars... but demand was low since the single-cat version flowed better and they dropped it many years ago... and I belive it was only a mid-length on the passenger side, with the driver's side being a shortie-style keeping the cat up top near the stock location.

Go with SLP shorties and be happy with your new-found plug access and hp gains. Besides... once you go turbo you'll need shorties anyway.

 

AS&M had a set of CARB dual-cat headers, but they had major problems with the heat melting everything in the engine compartment, becasue of the way the driver's side primaries had to wrap up over the valve cover to keep the drivers side cat in the stock location. I think that's why they stopped making them.

A buddy of mine bought a used set of the AS&M dual-cat headers for his 97 Z28. They came with a complete firewall heat shield pad. We added shiedling to the heater box. They still melted stuff in the engine compartment, like the plastic dipstick handles.

The guy pulled the AS&M's out, and junked them. He contacted a friend at SLP, and bought a set of extrude honed LT1 exhaust manifolds. I think SLP had them made for the LT4 97 F-Bodys (not sure if they actually installed them). He was very happy with the extrude honed stockers, but I don't think he ever dynoed them.

 

Good to hear, I guess its still an option.