98 5.7 vortec 1 7/8 crimped - hurting power?

[michael hurd]

40 hp and 50 ft lbs at the rear wheels is nothing to sneeze about, if you factor in driveline loss, that would be closer to 46 hp and 57.5 ft pounds at the flywheel in a manual transmission truck.

 

[skylark]

Stock exhaust on a half ton is like trying to breathe through a coffee stir stick. It truly does need better exhaust from the y-pipe to the tip. If you drive a three-quarter ton version that is equipped identically to a half ton version, gears, transmission and weight it will drive like a different truck. It almost feels like the difference between a 305 and a 350. Owning over 40 of these damn things has proved that to me.

 

[slowburb]

Stock exhaust on a half ton is like trying to breathe through a coffee stir stick. It truly does need better exhaust from the y-pipe to the tip. If you drive a three-quarter ton version that is equipped identically to a half ton version, gears, transmission and weight it will drive like a different truck. It almost feels like the difference between a 305 and a 350. Owning over 40 of these damn things has proved that to me.

So wait a minute, are you saying that even though the L31 has the same shortblock, same cam, same heads, same rocker arms, same intake manifold, same computer, same exhaust manifolds, and even the same power output numbers at the crank, THAT WITH DIFFERENT EXHAUST, THE ENGINE MAKES MORE POWER?


Get. The. ****. Out.

 

[Justin S]

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[michael hurd]

According to an article posted the L31 for 2500 / 3500 has a single angle valve job with inconel seats. I haven't seen any flow numbers of these heads vs. L31 heads for the 1500's, but it is likely the 2500 / 3500 have slightly less flow with the single angle valve job and the protrusion of the seat, compared to the induction hardened seats in the 1500's.

 

[skylark]

So wait a minute, are you saying that even though the L31 has the same shortblock, same cam, same heads, same rocker arms, same intake manifold, same computer, same exhaust manifolds, and even the same power output numbers at the crank, THAT WITH DIFFERENT EXHAUST, THE ENGINE MAKES MORE POWER?


Get. The. ****. Out.

Yep.

 

[GMRedline]

So wait a minute, are you saying that even though the L31 has the same shortblock, same cam, same heads, same rocker arms, same intake manifold, same computer, same exhaust manifolds, and even the same power output numbers at the crank, THAT WITH DIFFERENT EXHAUST, THE ENGINE MAKES MORE POWER?


Get. The. ****. Out.

Because GM gives the same output numbers for the 1500 and 2500 on paper it must be true!?!?

He's giving a real life example and you're being suborn.

The point that a lot of people are missing is this.

It truly does need better exhaust from the y-pipe to the tip.

It's not just the about the y-pipe. The factory cats on the 1500 are a joke. Not to mention the school bus muffler.

Will changing the Y pipe make a big different on a stock 1500 L31? Not Really.

Will changing the Y pipe and cats make a big difference on a stock 1500 L31? Probably not a lot.

Will changing the Y pipe, cats, and muffler on a stock L31 1500 make a big difference? Not a BIG difference but a noticeable difference.

If your going to argue on the internet at least be clear of exactly what you're talking about.

 

[slowburb]

Because GM gives the same output numbers for the 1500 and 2500 on paper it must be true!?!?

He's giving a real life example and you're being suborn.

The point that a lot of people are missing is this.

I could have stated what I stated differently to more clearly state what I was trying to state. The point is that the engine is going to make what it is going to make. Then, when connected to two dramatically different exhaust setups, why, how could anyone think it would have the same output? I wasn't being suborn, or stubborn, I think you just misunderstood. YMMV.

It's not just the about the y-pipe. The factory cats on the 1500 are a joke. Not to mention the school bus muffler.

Will changing the Y pipe make a big different on a stock 1500 L31? Not Really.

Will changing the Y pipe and cats make a big difference on a stock 1500 L31? Probably not a lot.

Will changing the Y pipe, cats, and muffler on a stock L31 1500 make a big difference? Not a BIG difference but a noticeable difference.

If your going to argue on the internet at least be clear of exactly what you're talking about.

Muffler's the same for 1/2 ton and 3/4 ton. One piece of the Y has one cat, and the other piece of the Y has the other cat. I think you probably know this.

 

[GMRedline]

Okay.

Maybe the muffler case size might be the same but the inlets are different.

I just did a full exhaust on my Vortec 1/2 ton 350.

http://www.gmt400.com/threads/finally-installed-my-custom-3-exhaust.35081/

I can tell you that it doesn't fall on it's face (as bad) through the mid range and high RPMS like it did with the stock exhaust. But what do I know?

 

[slowburb]

I know what you did; I posted in your thread. That's why I said "you probably know this". I've also recently completely replaced the exhaust system on my Suburban. It was done with a number of other performance mods, so I can't remark to the affect of the exhaust alone, but all the mods together gave my 'burb more balls than Spalding. I'm now running 2.25" headpipes, no cats, a DI/SO 18" magnaflow, then 3" pipe exiting at factory location.

Previously, a muffler swap to two generic turbo mufflers did nothing but change the sound. Also previously a muffler swap to two 2 chamber thrush mufflers yielded nothing but a sound change. The restriction in the half ton exhaust system is the headpipe diameter and converters. This has been common knowledge for like 20 years, yet for some reason it's being discussed here as if it's uncharted territory.