Prc ls6 stage 2.5 results
 

Alright, i know i personally hate when i find a thread where someone does a before and after but its not a apples to apples comparison.

this is a true comparison. No other changes beside the prc 2.5 ls6 heads.

I picked up 26whp and 24ftlb torque throughout the whole rpm band. The car before had STOCK 243 heads already.

this is a 140k mile LS1 with a tick stage 2 cam, home ported fast 92, pacesetter longtubes and y pipe, slp lm1, 4l60e yank ss3600, 10bolt 3.23, 26 tire. Speed density, ftp lid, chrs1313 nonac

https://cimg3.ibsrv.net/gimg/ls1tech...65b44b9c31.jpg

Nice. I love seeing legit comparisons like this back to back on the same dyno. Did timing and afr stay the same basically?

That I don't know as I wasn't there. But another thing to note is this was done on br8 plugs and not a typical tr5.

I wonder if the plugs really make any difference in the numbers though. When i went to the br7's my car felt exactly the same in every aspect. How much are you spraying?

.084 nitrous jet.

timing stayed the same. So power was all from heads.

Good deal. Nice numbers too. Will be interesting to see how much it picks up at the track

There is a lot of Hp/Tq left on the table with your engine.

I keep harping on my reason for saying the above. You have an "A Typical' TQ curve, where TQ starts up nicely, then "Flatlines" and starts dying to soon.

First time Tq peaked at 4750 RPM.

Replaced heads that flow more air and Tq peaked even earlier at around 4600 RPM.

Simple reason your haven't tapped the power potential of either build. That "Y" pipe can't meet the flow needed to support either build.

Look at any Dyno sheet where "Y" pipe is listed as exhaust and you'll see Tq dying off an start to fall off rapidly in the same RPM range as your build, instead of slowly and carrying HP higher than it's around 6300 RPM peak now.

Swap out that "Y' pipe for a 3.0" TD system with good flowing mufflers. If that's not practical for your car or pocket book, then at least install 3.0" dump valve on each header, and let your engine/air pump breathe.

Loved to see how either of those effects the engine TQ curve and how that effects your HP Peak.

I personally like to keep the torque down low so the exhaust setup is staying the same same reason why I will not swap to 1 7/8 headers. I experienced with a 4in bullet-style muffler for the axle and felt a super noticeable decrease and download Torque and no increase in horsepower. I went back to the exhaust shop one week later 2 redo the SLP exhaust. And the second I left the car felt extremely better again

Was it spraying during those dyno pulls?

Great to see back to back results. My set up will be something pretty similar to yours. Thanks for sharing!

How much were the heads?

Poor house is correct, exhaust is your bottleneck. This engine should have 1 7/8 primaries and true duals. With a retune, you will pick up hp and tq everywhere - I would bet another 25-30 across the curve, maybe more. Don't buy into the backpressure argument, these need to breathe especially yours. Nice before and after, you are absolutely right on apples:apples.