Just curious. Does anyone have any evidence to support that single cats w/headers produce more power (less restriction) than dual cats w/ dual-cat headers?

Why do you suppose that GM went with dual-cat headers half way through 95-96/97?

 

I've had both SLP's single cat and dual cat headers. I got a set of dual cat headers first but never installed them. When I compared them to a set of their single cat ones there was no question which one should perform better. The d/c's had much shorter primaries, one of the primaries was almost non existant, it was like 1/2" long or something. I have no doubt that the singles produce more power than the d/c's. No offense to anyone with the d/c's, it's just plain as day to see if you compare the two designs.

Most likely for better emmissions, I really don't think it was done for any performance increase.

 

Claude, I haven't had any problems with them. They are stainless, uncoated. Plug access is not so good, but only one or two plugs are hard. The others are ok. Running new wires through them is the bitch. I would recommend the SLPs to anyone, it's a nice set of headers.

John

 

I have two sets both coated. Of all the headers I have seen I like the SLP's the best. Like others have said plugs are no big deal except for 5 and 6. Special short socket took care of that. Had to raise the drivers side motor to get header in, no sweat take out motor mount bolt and use a wooden block and a jack 5 minutes. I previously have RkSports on one of my cars. I hated them they rubbed my ac box and the steering shaft at first. I had to beat the shaft further up.
My theory on the power situation is: The 94-95 style make 20 rwhp. The 96-97 style make 10 rwhp but with the obd2 y-pipe you allegedly started out 10 rwhp ahead anyway. So it sort of evens out. My 2cents.

 

I must be the only guy here that have the d/c headers and don't have a problem with them.

I put them in 2 years ago, back then everybody was bitching and complaining about how they sucked or didn't make the power but I proved them wrong. I haven't had any problems with mine at all, I did the install during the winter of 2000/2001 when my car was stored. I had the patience and took my time and the results are what I have now. I don't have leaks, they work as promised and when I'm driving the car nice I get the mileage and reliability all there.

Power's not a problem either. Look at my engine mods and I dyno 305hp/320torque @ the wheels (Sept 2001) when the mods were freshly done. Last year in Aug. at a different dyno location I dynoed 300hp/318torque @ the wheels. All emissions legal. The chart for that dyno session is here:

http://community.webshots.com/photo/...49791802kUJbbf

Here's what I know about SLP dual cat headers: They work as advertised but the key is the installation. If you rush and try to hurry to get them in so you can drive your car Monday morning, sorry you're going to be babysitting them when issues develop.

Use fel-pro ex. gskts instead of the ones that come in the kit, the fel-pros are much better.

Make sure your collector flanges on the header and your dual cat y-pipes are true. Scrap off all gskt. residue on the y-pipes and check both surfaces with a precision straight edge. Notice also that the collector flanges (on the header and the cat y-pipes) are not perpendicular to the tubes they join, there is an angle to them. Make sure the two surfaces that join together have the same tilt angle to each other. That will ensure a good seal with the gskts. If they don't meet up right and you tighten the bolts too much you will warp the flanges and that's the majority of the leak problem people have.

I make it sound like these things are picky AFA install procedure but to me it's just simple common sense when modding a vehicle. A few simple checks and taking your time to do it right the first time will guarantee trouble free operation and performance.

Granted, I too would go with LT's if I had the option but I don't. The car has to meet emissions here in Ontario. I also didn't like the fact that I should go with single cat headers when my car came with dual cats from GM to begin with. To me that's like going backwards, and I do have to dispute those people that say single cat headers make more power than d/c headers, that BS. They will make as much or more power than single cat headers all things being equal. My car is proof of that.

It's too bad old posts don't stay around too long. I've done my fair share of posts regarding this issue before and I'm in no mood to revisit the topic again. I only did this one to shed some light yet again on this topic to enlighten those that are dead set on a certain type of performance part when another item is more suitable and up to the task of performing to the owner's expectations. There's no need for them to have to spend extra amounts of money for "said" type of performance part (which is not really designed to fit the vehicle in question) to make them work on the vehicle. Take my post for what it is.

 

I run my 96-97 DC SLP's with the Random 2 cat y pipe which flows 10% better than the stock setup and has a much better balanced exhaust note especially when backing off the throttle.

Together probably 20 hp over the stock setup.

 

I like my slp shorties, great sound and performance. no leaks so far. I did have to replace my starter and put a heat shield on it because of them though.

 

You can avoid pulling the oil filter if you take one bolt out of the brakelinesetup on the drivers side, not sure what you call it exactly, it's late and i just finished a cam swap.

I picked up 3 MPH and .3 sec with DA corrections. Very happy with them, but i do have one beetch. What the hell where they thinking when they put the drivers side O2 sensor hanging down as the lowest point on the car? mine is shaved down and next time i bottom out i'm affraid i'm gonna lose that O2 sensor. Still love em and recommend them because you don['t havec do deal with clearance, emmisions, or a custom Ypipe like longtube guys do and you get nearly the same gain. Oh yeah, plug wires are fine in the stock location with a lil heat sheildimgn.

-brent

 

I have the 94-95 jethot coated single cat shorties on my car as well and been pretty happy with them now over a year since theyve been on my car. the only downside is plug access on #5, #6 isnt too great at all but thats really about it... i guess they are pricy too.

 

CMan, great post! You are absolutely correct about being careful on the install and using a quality gasket. That is time and money well spent. You also provide a very informative post about SLP headers. I just have one exception.

About your thoughts on the 96-97 headers being equal to the 94-95 design. I can't agree there. For SLP to accomadate GM's awkward placement of one cat nearly in the engine bay the the exhaust flow is routed in a such a way as to be suboptimal in my opinion. SLP simply could not correct GMs flaw layout and keep the exhaust "legal". When I saw my oem 97 headers and y-pipe uninstalled and laying next to the SLP 94-95 headers and the custom dual (Random) cat y-pipe, I was convinced of the much better flow of the 94-95 header design....and especially with a custom dual cat y-pipe. I would agree that the 94-95 style header will not be as efficient with just a single cat. But the 94-95 header can be made to flow better than the 96-97 design, IMHO.

This work was done in 98 and I remain pleased that I (with the strong advice from others) chose this header and cat design exhaust. It flow s well and it will pass for being legal (except if I get some **** inspector that was abused as a child).

 

Thanks for all they response regarding the plug access guys. My car is lowered and I currently have coated Grots LT on the car and was thinking of mabee going with SLP 94-95 style headers when my coating wears out and starts showing signs of rust but that should not be anytime soon. I dont really have any issues with ground clearance with the long tubes but only over big Speed bumps but I do drive my car every single day

Also I was curious about the Stainless steel headers without the coating because I have a friend that had an SLP set on his 3rd Gen Firebird and after 3 years of everyday driving in NJ (including on salty winter roads) those things never showed and significant rust. The 94-95 Stlye headers looked very similar to the ones on his 3rd gen which seemed almost like a mid length header. So other than cooler under the hood temps, I would see no reason why one would want to coat a set of stainless steel (Unless they were coated inside and out), I heard the inside coating is good for another 2-3 HP.....Woopie

Thanks,
Claude

 

Since this post is up, I've got a question. I bought my car and the previous owner installed SLP shorties. What I don't know is if I have a stock Y pipe. Can the SLP's use the OEM Y pipe? It looks original, but not sure. I'll need to know b/c I'm needing a new cat back.
Thanks

 

More than likely it's the SLP Y-pipe if they are single cat headers. SLP includes their y pipe with their 93-95 single cat headers. I'm not sure if you could install them with the stock y also I don't know why anyone would do that unless they got the headers used without a new y.

Here is what their single cat y looks like. It could very well have some light surface rust on it after a few years making it appear older, mine does.

 

The stock Ypipe flange will not bolt up to the SLP headers if you have the single cat style.

John

 

Hey Don, been a while since we posted on a thread eh??

You made some good points but I want to add a little bit more to what you're saying.

Only the great minds and engineers at GM knew what they were doing when they did the dual cat setup the way they did them on 96-97 F-cars. They had to meet strict OBD2 parameters and I guess the setup they chose was the way it was going to be. There's nothing SLP can or would be able to do to change that so they had to make the header to accomodate the design. FWIW, I would have to say they did the best they could. Do I like the dual cat setup done by GM? Not really but that's what my car has and it was going to have to do in my case. I've posted before about the extra amounts of money needed to be spent if I did go with the single cat header with a high flow dual cat layout, for me I didn't see the need to have to spend the extra $$$$'s. Compared to our Mooshtang counterparts, we are at a serious disadvantage what it comes to parts avail. to do mods and the pricing of them.

I still stand by my thoughts about single cat vs. dual cat headers AFA power production. You threw in your "Random Tech dual cat y-pipe" with your single cat headers as being better than dual cat headers with the stk. dual cat setup. I did mention in my above post about all things being equal. A SLP single cat header with its corresponding y-pipe vs. SLP dual cat headers with its stk dual cat setup would be a more fair comparsion. I have no doubt in my mind that either setup will produce the same #'s on each vehicle, ALA both vehicles are in identical states of tune and have the same mods done (with a slight variance of course due to production tolerances)

Being ********, I mean technical for a sec. even you yourself admit that your setup isn't "legal" visually if some smog inspector (who was abused as a child and has nothing better to do that day you are getting checked) decided to give you a hard time whereas my setup is totally legal eagle.

Anyways, all I'm going to say about this is untimately, it's YOUR car, YOUR money, YOUR parts that you are buying to put into your F-body. Research throughly, spend wisely, and patience, patience, patience during the install. Good luck to all!!!!!



Tony