I heard that the 96-97 SLP headers don't make as much power (noticeable) as the 94-95, because of runner length. Is this also true of the MAC headers?

 

You mean primaries? The dual cat primaries are rather contorted because the cats are so close.

SLP does offer 1 3/4 and I'm not sure that MAC is not 1 5/8.

So I guess if a MAC header has a longer, less contorted primary but a smaller diameter if that would make any difference.

The bottom line for those of us who can't mess with the cats (location or number) is that we need to either go with the SLP type or risk the wrath of the emissions cops.

 

I don't know much about MACS, but my 1 3/4 SLP shorties gave a noticeable gain. I've only heard bad about MAC. Well, performance wise, I hear they are good, but that they wear out REALLY quick. I've seen pictures of MAC headers that were already rusting real bad for the amount of miles they had been on. If you go with MACs, I would get them Jet Hot coated first.

 

Mac headers are 1 5/8. Get the 94-95 SLP. You feel a good hp gain. The only thing better about the MACs is the plug access.

 

I have the SLP 1-3/4 set on my 93'......unfortunateley i didnt opt at the time to get them coated, which has resulted in a couple of wire cooking incidents from the extreme under hood temp....i did notice a good HP gain from them , off the top of my head id say a solid 10 ......however , the install was a bitch and a half.......and it didnt exactly make the plugs easier to get to.......

but all in all im happy with them....

 

my slp shorties felt like a 12-15wrhp gain.... 2 years later i saw the error of my ways and went with long tubes which felt more like 25wrhp with the off road ypipe.. good for 3 more mph in the quarter.

 

I used to have a chart that told what header primary size was best for what size engine. If i remember right....
1 5/8 was for a 350 CU motor making 250-350 HP
1 3/4 was for a 350 making 350- 450hp or a 400 making 300-400 hp
as you increase displacemtn the size has to go up even with the same HP because you are pushing more air out at once.

as far as primary length i sat down and did the calulations (there is a big long formula) Mine came up to 34 in primary, but no matter what #s I put in it seemed like every header on the market for our cars were too short, even for stock cars, LTs are barley long enough. so, the longer the better.
I had mac shorties, I liked them and plug access was great. If you are just gonna throw a few bolt ons on the car I reccomend them. if you plan on doing heads/cam in the near future the SLPs may be better.