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

Justin S said:

For a stock 350, I bet there would be a less than a 3hp gain from swapping the skinnier Y pipe and exhaust. Same with shorty headers. However, if say it was a modified engine and long tube headers were installed, dented or not, it would definitely make a difference, so to put this in better terms, headers CAN make a difference, just depends on what they're going on. Stock, not so much, modified, absolutely.

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Jrgunn5150 said:

Impossible, everyone "knows" engines "need a little backpressure" to run lol.

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michael hurd said:

A properly placed expansion ( muffler, convertor, resonator ) in the system can greatly increase the scavenging of an engine, like a two stroke pipe.

I recall reading about David Vizard making more power with smaller diameter primary headers on a healthy small block than common practice would have dictated. He was running 1 1/2, when others would typically run 1 3/4 or 1 3/4 to 1 7/8 stepped. IIRC, the key was having catalytic convertors directly off of the header collectors, this expansion prevented reversion pulses from pulling exhaust back into the cylinder when overlap occurs.

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michael hurd said:

With the same 1999 vortec L31 engine, stock compression ratio, albeit more camshaft, Brian Harrris at Harris Performance Inc, picked up 40 hp and 50 foot pounds at the rear wheels on a dyno, changing from the factory y-pipe ( same shorty headers for both tests ) to 2.5 inch pipes off the shorties going to a flowmaster Y. Both set ups used the same 3" thunderbolt catalytic convertor.

The project was called 'Black Magic' and details are on his website.

With an absolutely stock 350, you aren't going to pick up as much, but I would wager it is going to be noticeable. 8600 GVW systems are going to flow much better than the 1/2 ton exhaust.

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