1998 K1500 exhaust upgrade

[JeremyNH]

I have a 1998 K1500 5.7L with a marine intake and cam with Gibson coated stainless shorties. Presently getting the 4L60e swapped to a 4L80e. Next and final upgrade will be exhaust in the Spring. Plan is to get a direct fit cat and catback for a K2500. Looks like there are two avenues for the cats both of roughly equal cost: (1) Walker OEM which has 3-3/8 aluminized non-mandrel bent head pipes to stainless cats which neck to 2-1/2" at the cats or (2) Bosal/Magnaflow which is stainless throughout, mandrel bent pipes, but 2-1/2" the whole way. Catback I would go Walker OEM or Gibson single-side. Gibson is stainless vice aluminized and likely superior on all counts but much more expensive ($150 vs $650).

So the question is thoughts on (1) vs (2) and is there much to be seen for the Gibson given the hefty price spread?

 

[Schurkey]

Do you have to meet emissions regulations/inspections in your area? Any movement by Elected Criminals or Appointed Dirtbags to cause you to have to get the vehicle inspected?

When it was me, I bought famous-name aluminized steel cat-back exhaust for my '88 K1500; and when it rotted-out, I fixed that mistake with stainless steel. But if your plans are to dump the truck in the next 5--7 years, you might get by with aluminized.

Single catalyst, single exhaust behind the cat? My truck is 3" from where the Y-pipe comes together, through the cat, muffler, and to the end of the tailpipe. 2 1/2 would not be my choice.

 

[JeremyNH]

Plan is to keep the truck through it's life or mine. It was my dad's who bought it original in 98 and came to me by inheritance having 123k rust-free Utah miles on it. I put undercoating on it when I brought it to NH 3 years ago and don't drive in during the winter. So won't be selling it. I had decided on the stainless route last night after looking further into it. Walker lists their pipe NID as 3-3/8" but they list their NID for the 1/2 ton kit as north of 3" and that pipe is known to be 2". Stock 1/2 ton is 1-7/8" non-mandrel bent so crimped pretty good on the driver's side 90 degree bend. Walker must be listing the NID as the flange to header diameter which ain't cool. The 3/4 and 1 ton trucks are 2.5" off each header through separate catalysts in separate pipe which meet at the muffler. Muffler is a 2-in-1-out design. Stock is 2.75" tailpipe. Gibson uses 3".

 

[JeremyNH]

Also, in NH you age out of the sniffer at 20 years so technically cats are not required on my truck. That being said I have no interest in deleting them.

 

[slovcan]

Do you have to meet emissions regulations/inspections in your area? Any movement by Elected Criminals or Appointed Dirtbags to cause you to have to get the vehicle inspected?

When it was me, I bought famous-name aluminized steel cat-back exhaust for my '88 K1500; and when it rotted-out, I fixed that mistake with stainless steel. But if your plans are to dump the truck in the next 5--7 years, you might get by with aluminized.

Single catalyst, single exhaust behind the cat? My truck is 3" from where the Y-pipe comes together, through the cat, muffler, and to the end of the tailpipe. 2 1/2 would not be my choice.

I ordered the famous-name cat back. It is a stainless steel (but painted black) dual in/single out 3 chamber muffler (50 Series Big Block) with the 3" aluminized tailpipe. I was really looking at the Gibson and that is surely better quality and is ALL stainless, but I think it will be louder and is triple the price. I compromised.

It's a long lead time for mine, though. The seller in Canada won't get it to ship to me until Dec 1st. It seems it has to be made in the USA and sent to the seller, then to me.

Cheers,
Glenn

 

[Schurkey]

Also, in NH you age out of the sniffer at 20 years so technically cats are not required on my truck. That being said I have no interest in deleting them.

Catalysts (emission control devices) are required by FEDERAL law, not state or county regulations.

 

[JeremyNH]

Catalysts (emission control devices) are required by FEDERAL law, not state or county regulations.

Fair enough. I've seen folks on the forum talk about cat and egr deletes and presumed it legal but I have no interest in it even if it were. I could probably get away with it since the state inspector no longer checks for emissions. Getting the egr to work on the marine intake was the most difficult part of the swap (I have a bag of various brass fittings bought in failed attempts to resolve it) but it was important to me to make it work. Ended up with a remarkably simple and stock-looking solution. But you had asked about cats and the answer is that the state doesn't care.