I recently put a new engine in my 2008 GMC Sierra 2wd truck. I used a new gen4 GM block, K1 58tooth 3.622” crank, 6.125 K1 rods and BTR/Wiseco pistons with valve reliefs that roughly calculated to a 10.4 compression I also used a summit under drive dampner.

The heads are stock 243/799 with comp bee hive springs and trunion upgrade on the rockers. I have a set of TSP 1 3/4” long tubes and y going to 3” tubing, a vibrant resonator beside the trans to a huge magnaflow after the rear end exiting behind the wheel in the stock location all 3” also.

im using the nnbs throttle body and intake to a MIT tune to a Airaid filter n the stock box. The cam is a BTR truck 2. While tuning John Weeks told me the stock injectors were flowing 105% so I’m going to get the flex fuel injectors, they were fine on the original LY5 5.3.

I’m wondering if the single 3” is a little small for the engine now. I’m guessing around 470 crank HP due to injector flow and Holdner dyno videos.

thanks!

 

3" will be plenty for your hp level.

 

The 6.2 Sierras run a 3.5" exhaust. Make some passes down the quarter mile at your nearest track and weigh the truck to determine how much horsepower is actually making it to the pavement. 470 seems optimistic to me for a 5.3.

 

it’s a 6.0 should have mentioned that in the original post

 

Did Weeks not tune it on a dyno? Shouldn't have to guess based on fuel consumption.

For a 6.0 with slight compression bump, untouched heads and 212.218 cam, (assuming mandrel bent pipe and a good transition at the Y) the exhaust described in the op would be fine unless you were wanting to ring every last hp out of it on the top end. If that were the case, headers would need to be upsized as well.

 

street tune is all we did, it’s has a ton of torque compared to the 5.3 it replaced, just wanted to see if any gains would be realized by more exhaust mods

thanks everyone

 

I do suggest bumping up to something larger than the FF injectors so as to future proof.

 

No back-to-back testing, but i switched to a single 3.5” after my heads/cam 6.0 started blowing apart the single 3” at one of the band clamp connections.

 

I’m going to try a 3.5” after a visit to the track and bigger injectors

 

[QUOTE=Beatdown Z;5504640]No back-to-back testing, but i switched to a single 3.5” after my heads/cam 6.0 started blowing apart the single 3” at one of the band clamp connections.[/QUOTE/]

Were you running mufflers?