I am getting my L98 swapped out for a ZZ4 and while doing so I am getting subframe connectors welded on. Two different places told me that there is just NO room for the SFC's with the dual cats and that I need to switch to a single highflow 3'' cat and then they will fit.

But now, the guy who is swapping my engine is telling me that I need to buy single cat headers now... that my dual cat headers wont work. If you ask me... shorty headers are shorty headers are shorty headers and then only difference between single cat and dual cat headers is the Y pipe they give you... right? So who is right, do I need to buy new $600 SLP headers again for a single cat this time????

 

I thought the ZZ4 and L98 were both gen1 engines and manifolds/headers should be the same. So if everything fit before the swap, everything should fit after the swap. Your signature indicated dual cat SFC's from Spohn. Call them with your question. Sounds like they're specific for your car.

 

Thank you... but I think you missread... or quite possibly, I posted ambiguously (too lazy to read it over tho )

My question is... why does the guy who is swapping my engine tell me that I need to order new headers AS A RESULT OF switching from a dual cat to a single cat system. He says that the actual headers are different and my headers which are for dual cats can not be used after I switch to a single cat.

I thought if you ordered dual cat headers they gave you one kind of Y pipe and if you ordered single cat headers you got another... but in either case the actual headers are the same. Who is right, and who is wrong???

 

That is such crap! I have sub frame(not on currently) and they will fit with my dual cat system.

When I was looking for sub frames, I contacted most of the manufaturers and they all told me the same thing....they are inteneded to to work with dual cats unless noted. Call the company that makes yours and see if they can be used with duals. If anything, you may have to modify your current system a little so the tubing will clear the pipes.

 

OK....

But what I am asking is, plain and simple... are the dual cat headers the same as single cat headers... I belive its just the Y pipe thats is different, correct? That is all I am asking.

 

The headers shouldn't be any different.

 

SLP said that the headers are the same... just as I thought. Shorty headers are exactly that... short! So how would the actual header itself be any different. Its the pipes after the headers that determine whether they are dual cat headers or single cat headers so I am going to go ahead and convert to a single 3'' high flow cat.

 

Spohn has SFCs for either single or dual cat (and they are different).

Keep the dual cats. They're better than single. Spohn will be taking orders for SFCs again next month, order them from him when he's taking orders.

Dual cats, Spohn SFCs is a better combo than single cat, anybody's SFCs.

 

I have dual cats, I have dual cat headers, and I have dual cat SFC's.

However, two different places looked under the car and said that the cats sit exactly where the SFC's get welded and there is no way I can retain dual cats.

 

Why would Spohn advertise them as Dual Cat SFC's if they dont fit with dual cats? I've got Alston's and they fit just fine with my stock y-pipe. Then when I put in an custom y-pipe it was fit around the SFC's. Just have your exhaust shop do the same.

 

People always say that not every car is exactly alike even though they may be the same year with the same options and same mods...

Trust me... I would LOVE to keep my dual cats. However, two different places have looked and said that MY cats sit EXACTLY where the SFC will go. This is two different places.... maybe it is something with my car, but I have no idea.

I wish there was something I could do. Any other suggestions or ideas?

 

The Sphon SFC's for dual cats and SLP headers are the same thing. The clearance issue is where the Y-pipe runs, NOT the dual cats. The Sphon SFC slopes from a box frame to a flat bar in this area. I don't have pics but if somebody does or if you decide to order them you will clearly see what I mean.

Any mechanic that tells you that you need to replace dual cats with a high flow one in order for this Spohn SFC to fit is full of $hit.
However, you will probably have to remove the Y-pipe in order to properly weld the SFC in place at this location.

 

i had the same problem with a 2.5" single cat!............the only way is to make your OWN sfcs! most aftermarket ones won't fit without modifying the Y-pipe....it's a shame,but the coolest sfc's i ever saw were made from round 1.25" pipe with flanges attached out of the way,the right side just "snuck" along the frame rail,undisturbed by the y-pipe......to bad my car had already been stolen and destroyed by the time i had learned of such a simple,yet genuis solution!

BTW...they didn't look like much,but they did the job!

 

I got a 90 firebird with the L98 and duel cats. I ordered the Spohn box sfc duel cats version the main pieces fit except for the little bar that goes from the passenger side of the sfc to the transmission tunnel area. The cats are in the way, but all the other parts fit fine, had to cut the front driverside one a little for a bolt to screw in but that's normal I hear. Spohn SFCs was well worth it. I also got the powder coated version, which in my opinion is well worth the money also.

OH by the way I'm running Edelbrock TES headers with the duel pipes to the cats.

 

yep, you need new headers, and then you need to sell me your current ones for real cheap cause they won't work on my dual cat cars .
No, really, I'd be surprised if you'd need to go to a single cat, I have two 2.5" hi flows under my 90 with spohns dual cat sfc's. I had the sfc's put on first then had a shop modify the y-pipe to make it all fit right.