Thats pretty cool, I monitor knock using mefi efi software on this but need something when we tune carbed motors, Thanks, Smitty

I still have to digest the data and do some over lays but here are basic AVERAGE numbers Ive seen:
2 1/4 race car converted dedicated dyno headers:
695 to 698 hp at 6300 , 635 to 637 ft lbs tq at 5300
same headers but with mufflers:
678-680 hp at 5900 628-632 ft lbs tq at 5200-5300
EMIS w 36" dry to tip tails, injecting water into exhaust stream at tip, going into 6" pvc pipes w 4 x6 couplers:
655 to 657 hp at 5900 , 619 to 623 ft lbs tq at 4800 (-40 hp/-15 ft lbs tq)
Now i made some fuel changes in the tune w the manifolds, my 2500 to 3800 AFRS dropped over 1.5 points and tq there was down 40+ ft lbs (I still haven't completely digested that data yet, did overlays etc, I often find weird things while doing so, cleaning the water up, putting pumps away, all the stuff I dragged out to do this wa more important at dark last night!)
I got some of that tq back by cleaning up the tune , I added and subtracted fuel and timing on top, it pretty much made same hp at 12.5 afr on top as it did at 13.2
At risk of damaging these exhaust manifolds on last pull I made sweep rate fairly fast and had my wife yank the power cords to both pumps sending water to exhaust at about 3800 rpms and pulled it to top,
IT MADE ZERO difference in hp , if anything it LOST a little torque, could not repeat it multiple times with these new out of the box tails and manifolds for obvious reasons but did not see anywhere in the dta where it did much except lean out .5 afr points and bsfcs went down slightly.
Now lets all think about this, you got the latest and greatest cncd heads, killer cam, making very impressive hp numbers (likes this) and you bolt on a set of even ****tier exhaust manifolds and a set of tails that mix in water in exhaust stream much earlier, losses would be even more , I would dare to say another 10 or 20 hp!

Were the Eickerts close to the dyno headers?

video of pull

In the "famous" published test Eickerts outperformed Imcos by about the same amount as Ive seen on my dyno between imcos and EMIS last fall. I'm going to say with your 710 hp 540 you'll still lose 20 or 30 hp at least. Muffled dyno pulls vs open header dyno pulls, gives cute numbers that are exciting but if a guys got carbs and they spend alot of time tuning with open headers then bolt manifolds on its going to end up rich. Wish I would have had a set of Eickerts to try, Im going to bolt a set of junky 1 7/8 headers I bought and made fit dyno and see what happens with them on this, I'd really like to find a set of headers that give results as close as possible to manifolds for dynoing and tuning, Smitty

I wish I had a set laying around, I'd send them you for testing. Right now, I'm running the factory 525 headers; however, they do not have equal length runners. The Eickerts do have equal length runners (or very close to it), as well as longer runners. Either way, great test with the EMI's.

That's an old test done on an HP 500, I have all the charts to this test. It would be great to see the results on a higher performance engine, one like being tested here. Bill, why don't you send Smitty a set to test out so we can see the real improvement over a typical manifold?