Exhaust sys.

K35 · December 27, 2003

Current exhaust sys is about to expire (factory single).

Have thought about duals but have been told to be careful since they can rob low-end torque. I cannot afford that loss.

The truck is a 98 Chev K3500 HD RC (C/K silverado) w/ a 5.7Vortec (350cid/330lb T@2800rpms/255hp@4400rpms. Snow-plow pkg & tow pkg. 4L80E with cooler etc..

Thought maybe walker mufflers on a cat back design? Not interested in sound etc. It is a work truck that needs all the grunt I can get, especially down in the low rpms since I push snow and pull a small flat bed with various equipment on it..

Not interested in high-rpm performance such as racing or top end. (4:10L G80 diff).

I've heard you cannot go above .225'' in dia on duals in order to keep original torque specs??? I'm sure several of you 350ci chev guru's can advise me of a good system. If in doubt I'll replace with a single factory.

Thanks in adv!

Joe

TarheelZ · December 28, 2003

Well, Joe, I'm definitely NOT a guru but I'll tell you what I've learned from a local guy who is (a guru, I mean). If you're not interested too much in the sound of a dual exhaust, then maybe it's the appearance that appeals to you. If that's the case, then you probably want to stick with 2.25 pipes with maybe 3" tips.

For what it's worth, I've always heard that dual exhaust straight out the back aren't recommended if you tow often. Duals out the stock location would probably work better for towing.

According to the guy who did mine, the best set-up for power is a free-flowing muffler with a single 3" pipe, mandrel-bent (in the stock location), and a 3 or 3.5" tip.

Good luck!

DSZ71 · December 28, 2003

You are correct about being cautious about the size of the tubing when trying out dual exhausts. If you go too big, or large of a diameter, you will decrease the torque becaue the extra area will increase the exhaust velocity too much. What most people recommend is go with a sinlge in / dual 2.25" out type muffler. If you are truely worried about the low end, at the same time you are replacing the cat-bask sytem, also look into some longe tube headers, which will help out the lower end power.

K35 · December 30, 2003

Thanks guys for the quick response.

:
"I've always heard that dual exhaust straight out the back aren't recommended if you tow often. Duals out the stock location would probably work better for towing."

[unquote] Good idea.

Appearance really isn't that important with me

:
"What most people recommend is go with a sinlge in / dual 2.25" out type muffler."

I'll probably not go with the headers since I'm not wanting to spend more than necessary on the truck. If I'm able to maintain 'the big T' (torque) I'm happy. If I get better mileage so much the better. If upper performance is enhanced (better breathing etc) Ok too. For the most part this truck rarely see's the other side of 70.

TarheelZ I like your suggestions. Yours too DSZ71. Thx again...Thanks for taking the time to help !

Joe

Gilbert · January 10, 2004

"If you go too big, or large of a diameter, you will decrease the torque becaue the extra area will increase the exhaust velocity too much"

Not true, definitely not true.... DSZ71.

All engines love to breath, ALL ENGINES. The only engine that likes a little back pressure (timed back pressure) is a 2-Stroke. Ask anyone involved any motorsport racing. From Kart to Formula One, all engines love to breath easy.

Straight pipes out the back is not a good idea because the air turbulence behind the tailgate can create a hazard. And you'll also be spraying unspent combustion debris all over your trailer.

However, if you like your neighbors and you like being able to hear you should install a muffler, maybe 2, if you decide go with a dual system. DOT's typically require the exit tip(s) occur behind the rear wheel(s). The only exception being factory vehicles (e.g. Cobra's, Lighting's, Viper's, etc.).

piratebaseball · January 22, 2004

I would go 2.5 inch duals. I've made many swaps going from factory size to 2.5 inch dual pipes and have never experienced any decrease in low end torque. Header size really changes low end torque more than the cat back exhaust because the exhaust velocities are greater there. Personally I'd go with one 3" pipe out the factory exit with a good free flowing muffler. The 3" will make more power over duals unless it is a highly modified engine. Magnaflow also says this on their website.