1997 gmc k2500 burban

[yevgenievich]

Reason for not as expected performance under good load. Over 4 psi back pressure in exhaust revving engine up in the driveway.

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[Erik the Awful]

About twenty years ago I did an engine swap in my RX-7. I went from a stock-ported 12A to a half-bridgeported 12A - like going from a stock TBI motor to a .650" lift cam race motor. I had a header and an aftermarket exhaust, but the engine wouldn't rev over 5000 rpm. I rejetted it, tweaked the timing multiple times, and even drilled my own larger carburetor jets, and I got it to rev up to 6000 rpm. It had a serious lack of power for such a hot motor.

Finally I took it to an exhaust shop. They pulled the aftermarket exhaust and built a dual 2" exhaust all the way out. It was waaaaay too loud, but as soon as I romped on the fun pedal the tach swung around to 10,000 rpm (redline was 9,000), and I hung the rear sidways. Fun stuff.

What's your plan?

 

[yevgenievich]

Stock ported intake might have been just fine and it was just the exhaust keeping pressure on the engine. Currently planning on dual cats from 2008 topkick(8.1l) and follow with two 2016+ 1 ton stock mufflers. I prefer to keep the noise down and running one large muffler per bank hoping it will run good.

I did check the pressure months ago when I had the other intake but use a 0 to 40psi gauge and it did not show any change. Might have just been a bad gauge. I cheated when added a port, exhaust pipe is thick enough that I just drilled a hole and tapped for npt threads. Then plug it back when done testing

 

[Christian Steffen]

Great work, looking forward to the results!

 

[yevgenievich]

Great work, looking forward to the results!

Thanks, really looking forward to it being fully sorted.

 

[yevgenievich]

Mocking up cats and mufflers.

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[yevgenievich]

This was a pain to come up with. Next time will likely just take it to exhaust shop.

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[OutlawDrifter]

Looking good! We'll be needing a sound clip/video when it's finished up.

 

[GrimsterGMC]

This was a pain to come up with. Next time will likely just take it to exhaust shop.

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Exhausts are never as easy as we think they are going to be, but nice workmanship all the same.

 

[yevgenievich]

Thanks. I might have outdone the quiet part. Mechanical fan becomes the loudest thing around 2k rpm. Maybe the other set of straight through mufflers might have been okish to use, but will see tomorrow how it is under load