With our cars being so old, I keep finding threads from around 2002 recommending parts that aren't made anymore. I've been trying to read up, but I'm a complete newb at this. I'm much more at home working on my Jeep.

I drive a '91 Z28 5.7L with the N10 RPO dual cat setup. My PO lied about a lot of mods, and I got ripped off pretty bad when I bought it. I don't even know what stock looks like, so I'm assuming he lied about everything. I plan to keep the Camaro pretty mild for the foreseeable future while I build the Jeep, but I have an exhaust leak, and I can't install my passenger-side Spohn SFC until I change my exhaust setup.

Easy questions.
How do I know if I have factory manifolds or aftermarket headers?
If aftermarket, how do identify them?
Is 3-3.5" single pipe a good size for a stock(?) L98?


Exhaust questions.
I'm looking at Hooker 2055 headers and Y-pipe with '98-02 SLP LM2 cat-back. I don't need a cat cause I'm emissions-exempt, and I drag my current ones over the speedbumps in my apartment lot.

I understand I can run the 4th gen cat-back with 3rd gen headers and Y-pipe, using the 4th gen hangers. I also understand this requires an S-pipe to mate the two halves of the system. I don't have a local mandrel bending shop, so is there a certain pipe I could buy online, or will it have to be custom?

Also, I've read I'll need to remove my AIR setup with that header. It's simply a matter of pulling it all out, and it won't trigger any codes. Then I install a 91.5" belt without the AIR pulley, and I'm good. With AIR gone, would there still be an O2 sensor or anything else that would need to be added to the new system?

Thanks in advance, all.

I'm attaching a few pictures in the next post so you helpful people can tell me if anything stands out as aftermarket.

 

Here's the list of modifications I was given by the seller:
58mm Throttle Body, SLP 51010 Roller Cam, 5.1 Roller Rockers, 91 Corvette Aluminum Heads w/stainless steel valves, SLP Headers, SLP High Flow Intake Runners, Edelbrock High Flow Intake, Timing belt was replaced with Gear Drivin, Transmission Shift Kit (Summit), MSD ignition High Fire and the SLP Headers go into a 3" Full Flowmaster Exhaust from Summit.


Here we go:

 

Looks like a few of the mods you list are definitely there... headers, runners, heads, etc. One thing with the heads though is the valvecovers are incorrect which lead me to believe you have something else besides Corvette heads. It's hard to tell in the pic but I can't really see aluminum either which Vette heads are AL construction. Definitely ditch the catback. That's killing any kind of power! Check out the hooker catbacks. No reason to do a 4th gen setup. Plenty of 3rd gen options available. Does the car run decent??

 

Should be able to remove all the AIR stuff at your descretion. O2 sensor will have to remain as computer uses it for air/fuel correction.

 

I knew about the runners, but I wasn't sure about headers. Any way to identify the brand? The car DID have aluminum Vette heads, but there wasn't much left after the previous owner blew up the motor. My dad currently has an expensive piece of aluminum back in his shed in Cleveland. As far as I know, the current heads are OEM.

Everything I know about exhaust, I've learned from reading over my last two night shifts. I found this video (LINK), and I really like the sound. That's the only reason I was leaning to SLP cat-back. Would you suggest this one? It says 305; does it matter?

The car is running great aside from the exhaust leak and high oil pressure. The L98 has a new block and half the top end has been replaced. I just got it back on the road in July, currently 33k on the body and 5k on the motor. Next major project will be a new transmission. I got one out of a Monte Carlo to get the car back on the road, but it's starting to slip.

 

Well I don't think it's currenty vette heads as the valvecovers should be centerbolts and your setup is using perimeter bolts. OEM Camaro head of this year would be centerbolt as well.


The Hooker catback would actually be my first choice! They are very very good systems for the money...Great sound and performance! SLP is good too!


Good luck!

 

Right here.


https://www.thirdgen.org/forums/engi...er-2055-a.html

 

Well apparently I don't have factory manifolds. I wasn't sure. Is there any way I can identify the headers that are on mine currently? If they aren't any good, I'd be looking for a replacement within a month or two.

 

IDK. But yours are rusting.

 

Try taking more pics of the headers at different angles and try to include the collector area as well.

 

Looking at your pics you really do have a bunch of the external mods. Those headers don’t look like SLP headers, but I suppose that they might be. We’d need better pictures of them to tell for sure, pics of the collectors and y-pipe would help. SLP headers were 409 stainless, which turned rust colored but didn’t really rust, yours look like they’re rusting.

Judging from the valve covers (I don’t think your posts are clear, are the heads aluminum? I’m betting they’re iron) you have mid 80’s or older heads on there. I really wouldn’t be surprised if someone just stuck all the external mods on a goodwrench replacement 350, basically a low compression truck engine. They run OK and with the TPI, headers and the right cam you should hve way more torque then most of whats on the road, so it should at least be fun to drive from a stoplight. Back in the day putting some ported vette heads (which are lighter and raise compression significantly, but don’t flow more than old school iron 350 heads without some port work) and the right cam on that setup was a popular way of getting a cheap >350hp engine.

 

factory manifolds look like cast iron logs, not like tubular headers, so you definitly don't have those. That cat back looks like a flowmaster muffler, but I don't think that they came with crush bent pipes. I'm not a big fan of flowmaster so I'd probably ditch that.

3" is plenty for even a pretty well built 350 tpi, assuming it's a good 3" (read- ditch the flowmaster muffler if nothing else).

As far as mating things up 2 ways to deal with things:
order some mandrel bends in the correct size and cut and weld them to make whatever you want, or use crush bent pipes one size (typically 1/4" up), like if you needed 2.25" mandrel bent pipes, 2.5" crush bent will flow about the same. The crushed part is typically on the inside of the bend, and the flow tends to "stick" to the outside of the bend, so as long as the overall cross section remains the same it works fine.