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Exhaust System Advice

Gmcfan1974

By Gmcfan1974
in Ask A GM Technician

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Gmcfan1974 Enthusiast

Gmcfan1974

Posted
Posted

I am working on a 85 GMC Sierra long bed. I am installing Summit long tube headers with 3" collectors.

 

I currently do not have an emission inspections in my area, but I was planning on putting a high flow cat for possible future changes in the law for my area.

 

The advice I am looking for is should I run a single Cat back to a single muffler with dual outlets or should I run true dual lines from the headers back with dual CAT and dual mufflers?

 

What would the advantage be from one to the other?

 

 

Chris Senior Enthusiast

Chris

Posted
Posted

If you do use cats always do one or in the case of my truck in California 2 cats ber bank. So you would run dual cats then a y-pipe or keep it dual.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Just MHO ... I would never waste money on a cat for anything built before '96. It's a useless device as far as your concerned - you want the truck to perform.

Gmcfan1974 Enthusiast

Gmcfan1974

Posted
  • Author
Posted

Jsdirt thanks for the input again. You helped me out on the vacuum setup I was having. I went with a Edelbrock 2701 intake and I was able to pick up a Summit racing carb (600cfm) for $150. I am still putting everything together, hope to have it running again soon. The stock exhaust manifolds just did not look right so I ordered the headers they should be here by the 8th.

 

Would you go with true duals from the headers back or put in a Y-pipe then back to a single in and dual out muffler?

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Cool, glad I could help. :cheers:

 

 

 

In the old days I'd have said straight duals all the way back ... but these days I prefer a Y pipe. Reason being, is for all-out top end power and big dyno HP numbers, you can go duals. But, for low & midrange grunt I prefer manifolds with a Y pipe. Not going to see big numbers with that setup, but driveability is AWESOME once it's all dialed in - just my personal preference.

 

If I could have a choice between a 400hp engine that screams to 7,500rpm ... or a 250hp engine that makes 400 ft.lbs., I'd take the torquer any day. If I had the patience I'd put diesels in everything I own. :lol:

 

But, if your set on headers, might as well let it breathe, and go duals all the way back.

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