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Home » Public Forums » GMCnet » Mufflers, crossover and gas mileage (How much restriction matters)
Mufflers, crossover and gas mileage [message #307526] Wed, 21 September 2016 08:07 Go to previous message
Tilerpep is currently offline  Tilerpep   United States
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma:
Senior Member
The last thing on Jim K's bad gas mileage fix list is blocked mufflers. I have indication of exhaust restriction on my intake manifold crossover passage, as the paint is definitely overheated.

Banging on the mufflers with a rubber hammer only sounds like rust scale, no loose plates or baffles. They look good from the outside.

So, looking to replace, reading on the forum, saw Walker 18425 muffler as an option. Crawled under coach and hit the pipes with a micrometer thing.
2.2 inch OD pipe going into each muffler (original config two mufflers, Y after). One muffler pipe is 2.2 coming out, other muffler is 2.0 coming out, and welded to the 2.2 from the other to make the joiner/Y. I wuould assume this is some local shop's solution to a cheap muffler system?

Question is: is that enough difference to unbalance the sides, and push exhaust through the crossover? This input matters because if I can figure out how to put two new 18425's on myself it will be under a hundred bucks. If I need a new Y to get the flow right, it will be at a shop anyway and I'll just let them do mufflers and Y



1975 Glenbrook, 1978 Royale rear bath Raleigh, NC
 
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