The other possibility of course is that the previous
dyno result was "corrected" higher than realistic,
so any subsequent pull would read lower, and just an
exhaust change might not make up the difference....

Might be interesting to compare your original result
to similarly-set-up examples and see if your original
wasn't a bit "optimistic". You could be chasing a ghost.

There's too much after-the-fact fudgery applied to
make me trust anything besides relative readings on
the same strap-down.

 

I agree, the Macs would hurt you at that power level. But you may have made 720 or 730 with a set of AR or Kooks. I highly doubt SE has invested much money into the R&D of their headers. Unlike the two brands I mentioned, who I'm sure have passed some of that R&D cost on to their customers to provide them with a high quality piece that has proven performance gains.
Where is the evidence that SE headers perform as well as a more expensive name brand header, that has the proof to back thier performance claims.

 

Interesting header test results...this might be a case of the engine not moving enough air for the longer header.

http://www.superchevy.com/how-to/148...ders-shootout/

 

Jimmy...id trust new era. They have been in the game a while. This isnt their first rodeo.

 

I've seen a small drop once just because of a new U-joint, LOL
We broke one on a pull, and swapped in a stronger one of the same size and lost about 4 HP .. We put the a lighter duty one in that matched the broken one and it came back, then broke the U-joint again. Don't believe it was weight, our theory at the time was the newer stronger one was not as straight as the original? Heck I could see losing 5 HP on a different tank of fuel..

 

I've seen that test that wannafbody posted. The engines could be in the same power range. Although the differences between SBC & LS cylinder heads is substantial.

It's pretty much LS gospel to get long tubes for the best power. Although every once in awhile we see something odd happen.

One other thing I may ask is how does the car feel to perform? Same, little better or worse. A 20lb/ft loss may be quiet noticeable.

Maybe time to take it back to the track & see what she can do. Although switching the headers back will be interesting.

 

I could flip that same argument around on the MAC's. Where is their data proving they perform as well as more expensive name brand headers? You re-dyno on the MAC's will be super interesting to see what happens given the timeframe will be closer.

 

Exactly why I'm going back!

 

Can't wait. AndrewSS from your dyno section threads response was more along the lines of what I expected.

 

Me too, thats why I made the switch to LTs. Believe me, my jaw hit the floor when those numbers popped up!

 

Very interesting. In for the results on this one. It is a lot of work changing over back and forth between two complete systems.

 

Well I left the TSP cat back on because I cut up the flowmaster to get it off. The sound and quality of the TSP is soooo much better than the flowmaster. Yea, it only took me 3 hrs. start to turn key to swap back the headers.

 

I would also suspect the Y pipe. I only use the Flowmaster 250300 Y pipe on the last few vehicles I've owned, it is an excellent pipe with a beautiful merge.

 

Without reading this thread, no you didnt! End of story. If you were right, the fastest LS1 cars on this sight would be running mid length headers. See how dumb that sounds.

 

There are some long tube 1 7/8 headers for 4th gen LS cars that have a bit more equal in length primary pipes than the SE headers are. If this makes any difference to HP/torque or not on these engines I have no idea. It is just something I've noticed between the header brands.

 

Yea, the SE headers have no where near equal length primarys. Right or left side.

 

Not an ls engine, different heads, intake manfiold etc. ON an ls1 its been shown time and time again bigger headers make more power.

If I was the op I'd start looking for the headers contacting something. Check KR at WOT and ask the tuner if they had to pull any timing for KR. If not swap the other headers back on and retest.

 

No timing had to be pulled, I installed poly mounts at the same time as the SE headers and there was no banging on anything. The SE headers do fit great. With no interference on anything. The old headers were back on the next day, and a retune is scheduled for this Thursday.

 

I would really love to see what a set of American Racing headers would do on my car. I have a feeling they would be a big improvement. I may have to start shopping for a used set.

 

Btw the dyno graph for the long tubes only goes to 6k rpms and was still showing horepower gains. Have them rev it up to 6500 like they did on the dyno for the mid's