Exhaust Question For Motorhome

[TallPaul]

Subject vehicle is a 2000 Chevy one ton van cutaway chassis motorhome, 28 feet long. WB approx 15 ft. Engine is 7.4L. Exhaust comes in 3" OD pipes from each cylinder bank, through cats, to a Y into a single 3" OD that runs several inches then enters the muffler (7"x9" by 24" long), then proceeds a considerable distance through 2.5" OD piping until behind the axle where it goes through another muffler or resonator (4" by 20" long) then out the tail pipe.

 

1) How restrictive is the muffler (the big one just behind the Y)?

 

2) How restrictive is the resonator (the little one behind the axle)?

 

3) How restrictive is the 2.5" pipe behind the muffler?

 

I figure that the big muffler is the main restriction and that the resonator is more likely a straight through with sound absorbing perforations around the inner tube. The 2.5" pipe may not be a problem, assuming the hot exhaust gasses cool enough after they work their way through the muffler that they have condensed and take up less space.

 

Main problem is the big muffler does not have much ground clearance. I am considering taking to a muffler shop to have it turned so it stick upward more to get more ground clearance, but on the other hand, it might be easier to put an aftermarket muffler in it's place to get the ground clearance and improve exhaust flow for more power. Will this work? Or will the freer flowing muffler then need a larger pipe that the 2.5" that follows the muffler.

 

Suggestions? Should I just turn the stock muffler or upgrade? Would like to keep cost relatively low, so just replacing the muffer is cheapest.

 

Thanks

[redvett]

If the muffler is the OEM & welded in the pipes i wouldnt mess with it because getting it too close to the underneath of body could cause heat & fire problems .

[TallPaul]

There is a lot of clearance above this muffler. Heat should not be a problem or fire hazard. Problem is low ground clearance and potential damage from road hazard, which already got the generator muffler, which was about just as low.

[Steady Eddie]

 

Paul--

 

Since the invention of the Vortec Engine Series in 1996, the OE exhaust

systems have been quite free-flowing. Your injection and engine need

SOME backpressure to work correctly. Most Owners that opt to change the

OE set-up have no idea what it is worth ($$$). I have a 1998 P12 Chassis

with the Vortec L21 454 and an Allison. the single SS Muffler for it is listed

at over 470-bucks at AC Delco. I think you'll find your pipes are SS, too.

If your system is rotted out (unlikely) then, of course, you'll need new.

Mr. Goodwrench can check your exhaust system's backpressure in about

the minimum Shop Time fee of one hour. Money well spent. And, you'd find

out if it was within OE specs.