Gibson Headers and 6.5 Diamond Eye Diesel Exhaust on 454

Thanks to some fine folks here I have my exhaust all figured out, special shout out to member Crazeydavez28 for posting up his thread for me to stumble upon, below.

https://www.gmt400.com/threads/6-5-diesel-exhaust-on-454.40793/

This install will start next Monday, more completion pics to follow.

My Tahoe has a 4" diamond back tailpipe and a Corsa dual 3" in single 4" out muffler with Thunderbolt 3" metallic core spun cats.

Do it now. I wanna know the before and after.

I just put a new exhaust on my truck, 305 tbi. It started out as a factory take-off from a duramax truck around ‘06 I think. I got from the turbo flange back and there is only a giant muffler in the pipe. It is all 3.5” pipe. I cut it up and welded it all back together to fit as a cat-back. It is as quiet as stock(which I wanted) and should last much longer than the parts store stuff while flowing much more than the factory rated 175hp could use. I’ll put up some pics when I get a chance.

gibson headers, gibson y-pipe, are installed and cut as needed and plumbed into flowmaster y-collector.

its insanity level loud with the flowmaster y-collector dumping right at the second level of seating under the trauck and without the rest of the exhaust attached, but that will get finished tomorrow, but none the less the header music wont go away

i will say the motor performs dramatically different already, revs so much more freely, and is really snappy.

unfortunately we all love to fantasize about documenting change and benchmarking upgrades, total fail here, i didnt even get before video on the factory exhaust let alone any other comparison notes performance wise, nor did i even weigh the parts to understand weight savings, but i can say that the factory stuff is heavy as F while diamond eye parts are basically just pipe with a straight through muffler, the factory suitcase muffler that has a cat attached if i had to go off feel weighs more than entire diamond exhaust, but in all fairness i have not yet order a cat as i need to understand dimensions of available space once the complete exhaust is hung but i have a full year to install it.......sweeeeeeeeeeeeeet.......before my next emissions test. in all fairness to the factory, the exhaust came off at 136,000 miles and appears to have been able to support another 100k plus miles or more if needed, AZ truck

whole thing has been a bit more of the pain in the arse then i had hoped for but everything fit for the headers without issue. the only beating i had to do was on the passenger side as there is a bracket on the frame rail supports the hard line rear heater lines, it was an easy peasy beating session with a 3lb sledge.

i will try and figure out how to get a video to youtube with this current stage and complete exhaust

Diesel vs gad blah blah!

When did the mandrel down pipe the low end grunt got better and yet way quieter. Better 3" to 4" adapter also helped make it quite.

On my Tacoma V6 the header was the only thing that made it quieter

Put the first miles on the exhaust last night. Was super fun driving home from my buddies shop to the house, was like driving my Vette but in truck form, super low throaty note, very loud under full throttle.

Then put 50 miles on it towing 4k lbs boat, so it was just weight with no excessive wind resistance. The drone at cruise is unhealthy, the overall volume going down the road is very obnoxious.

Soooooo.... I love the mandrel bent fit of the pipe but will be considering an alternate option for a muffler. Cat has not yet been installed but I have no high Hope's it will help with noise to degree i need it to.

That's why I went with the bus muffler. Still need to do headers though, hoping that uncorks it and makes it pull to 5k. I feel like it has enough cam that it should want to. I'm not sure the stock cats are all that restrictive, I mean they're 3" in and 2.75" out.

Supercharged111 said:

That's why I went with the bus muffler. Still need to do headers though, hoping that uncorks it and makes it pull to 5k. I feel like it has enough cam that it should want to. I'm not sure the stock cats are all that restrictive, I mean they're 3" in and 2.75" out.

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Yeah as long as they're not plugged up somehow, I really don't think stock cats are going to hurt anything.

Supercharged111 said:

That's why I went with the bus muffler. Still need to do headers though, hoping that uncorks it and makes it pull to 5k. I feel like it has enough cam that it should want to. I'm not sure the stock cats are all that restrictive, I mean they're 3" in and 2.75" out.

Click to expand...

The stock 3" in/3" out cats on my Express van were actually quite restrictive. When I put the Tri-Ys on the Express I swapped out the cats for Thunderbolt 200 cell count metallic core cats and swapped the magnaflow for a bus muffler. ZERO drone from my 350. Almost all of my engine note is intake growl.