Dual Exhaust Question

[Schurkey]

a bit concerned about the restriction from stock 2.75" dual inlets down to 2.25" dual inlets.

You should be concerned. No way I'd use that muffler.

Are you saying my stock muffler is so restricted inside the box?

Fairly certain his was dual-in, dual-out. His was terribly restricted internally--I think he said that the internal tubes were 2".

I don't know about YOUR muffler.

My '97 had a totally-blown-out aftermarket muffler in place when I bought it. I therefore haven't seen the OEM muffler with my own eyes.

On dyno the x pipe is only one makes a power difference usually above 5000. H didn't do much at all

Kinda depends on the engine, the rest of the exhaust system, overall system backpressure, location of the "H" or "X", and probably a dozen more variables.

Nicest thing about a crossover--any crossover--is that it tends to quiet the blat-blat-blat of a dual exhaust with no crossover (except the little one across the intake manifold.) Makes it easier to USE the horsepower you have without attracting attention from hand-wringers, busybodies, and Law Enforcement.

 

[PlayingWithTBI]

On dyno the x pipe is only one makes a power difference usually above 5000. H didn't do much at all

Hmmm, I wonder why NASCAR Craftman series trucks used this setup with such a wide spacing "H" pipe? Note the Tri-Y headers too.

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[DavidAlan]

I bought my truck used and guy before me, used it to haul a camper on it, like so many out there, if you have stock or duals, its all up too you, my truck has headers and dual cherry bombs, with separate exhaust ,and let say if like that fine, I am 60 and still am a kid ,my wife hates riding in my truck for that purpose ,am old school and if have duals, then go for it, but I also get a different cam, and tune the motor,to make worth the fun, Make engine more powerful then,get dual exhaust.

 

[Dahead76]

I’m running duals on my 93. It’s a 305 with hooker headers, dual 2.5 inch pipes, no cats, thru two black widow venom 250 mufflers with turndowns at the rear end. No H pipe or X pipe. One problem I have is not enough back pressure. I get an EGR code everytime I drive it.

 

[Schurkey]

You probably have a negative-back-pressure EGR valve. I wouldn't expect a lack of back-pressure to be a problem.

Things might be different if you had a positive-back-pressure EGR valve.

Follow the official diagnostic procedure in the service manual. I bet that EGR code is entirely fix-able.

 

[b454rat]

I ran full duals on a lot of trucks, some TBI, never had check engine light come on for EGR, or anything for that matter. H or X pipes do help, H pipes will help on drone. My Tundra has one, and is quiet, when it had full exhaust there was none, but when they rusted off, with no pipes off the muffler, it was bad. Put some cheap pipe/turn downs, and now nothing.

 

[badco]

Hmmm, I wonder why NASCAR Craftman series trucks used this setup with such a wide spacing "H" pipe? Note the Tri-Y headers too.

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Nascar is a different application than any one on here is talking about. They need to be at high rpm for long periods of time.

On a nhra stock eliminator 69 camaro 350 low compression engine a 1 1/2 for 8" then to 1 5/8 for 11" lastly 1 3/4 into a 2 5/8 merge collector made 471hp and a 1 3/4 to 1 7/8 with merge made 451 hp and 50ft pounds less tq. We have done 100s of header tests getting to these results. These engines are stock type bottom end, stock lift cam, stock heads, no port work, stock cast intake and qjet carb.

 

[b454rat]

471 horse ona stock 350?!? Where’s the BS flag...

 

[Postmech]

Stocker cams are a special grind. They may have stock lift but you can move LSA angles and LCL around. Plus they are ground with very aggressive ramps, or at least that's what I remember. Also everything else is optimized to the limits of the rules. Valve angles, spring pressures, chamber volumes are perfected. Back in the day, you might flow dozens of heads to find the best pair. Of course this is all old, obsolete sh#@, from the 70's, lol. Check some of the times they run, it's amazing.

 

[CNRED]

X pipes or H pipes are necessary to scavenge the exhaust and prevent condensation within exhaust system. The crossover prevents rapping back on deceleration (some folks like it). You might look at Engine Masters on YouTube and catch the episode where they are testing for horsepower and torque. Westech Engines and Brule know their stuff.