Alright guys, here it is as promised.
My intentions for going from a 1-3/4" header to a stepped (1-3/4" - 1-7/8")header was because of my future plans for heads and intake. I didnt really expect much if any gain. I just figured that since i was swapping headers, I'd do a dyno comparison for you guys that have wondered about the hp difference between the 2. Thats why I posted up my dyno results with the old headers awhile back just for this reason. https://ls1tech.com/forums/dynamometer-results-comparisons/821772-asa-cam-s-updated.html
Old headers: 1-3/4" Jet-Hots
New headers: 1-3/4" -1-7/8" Edelbrocks
Everything else: same (same mods, exhaust, dyno)
Results: almost 4rwtq peak. It was almost a direct overlay of the old graph. It did seem to pick up some on the bottom end (which surprised me). It dipped a little @ 4000-4400 for some reason, but overall its a little better through the entire rpm range.
Overall, I'm happy with the results. Like I said, I did this with heads and intake mind, not because I thought I was gonna gain a lot of hp over the other headers.

 

That is within the margin of error so the conclusion I personally would come to would be "no change." Thanks for posting the results though. This site needs more tests like this. Over the winter I will change headers and post my before and after results. I'm going from FLP 1-3/4" to ARH 1-7/8". I'm hoping for 5 to 10 rwhp gain across the entire curve. (My "entire curve" is from 5200 to 6800) LOL

 

At least this isn't the typical "I picked up 15rwhp going from brand X to brand X" thread. The good news is you didn't really lose any. My jethots on my last Z picked up awesome power, so this says good things for Edelbrock.

 

Yeah, I'm just taking it fwiw. I've dynoed here before and all my runs were within +/- 1-2hp/tq so I'm not really worried about claiming the 4rwtq, just glad to see the #'s on the high side since I was a little worried I might lose a little by going to a bigger header. Glad you got something out of the comparison! Good luck with your header swap. Looking forward to the results!

 

LOL! Yeah, I wish I picked up 15rwhp!
I'm happy with the results. I was actually expecting to lose a little on the bottom end and I didnt, so thats good! Btw, my friend picked up 17rwhp over his Mac mids & Flowmaster catback with my old Jethots & TD's!

 

I agree, especially since you did your second run on a cooler, less humid day which should increase power a little to begin with.

I'd be curious to see what happened to your numbers from idle. Maybe the stepped headers hurt your low end? That could signify that stepped headers are bad for a stock cubed motor. I guess we'll never know.

 

Interesting. I would of expected you to gain atleast 5rwhp on the top end. Maybe if you had a bigger cam you would of seen more gains. It seems that the FLP's weren't holding you back at all.

 

i think the most impressive thing about the whole swap was the difference in sound

 

Were these dynoed on the same day? That would be the truest test you could run.

 

Hummidity is quite different between runs and pressure is a tad also.

 

I wouldn't expect to see a gain with the mild setup.We've done back/back before and seen real good gains but the cars are more built to use the headers.

 

With my set-up I gained 25rwhp and 14rwtq going from kooks 1 3/4 to kooks 1 7/8 headers. But this is with a 408, ET 245`s and a huge cam!

 

Good post, at least people can see how it works in the real work vs on paper. I have a bud switching to 2" primaries on a 402 high comp motor from 1-3/4" primaires, i cant wait for that comparision.

 

Awesome...thank you for doing the test. That is definitely good data.

 

Yeah, I was hoping for a few hp, but not expecting any. I think these headers will help with the new heads and intake. Otherwise, the 1-3/4" were plenty.

Yeah, I was surprised at the sound difference too. Its a little deeper, and a little quieter.

Exactly, I agree. The heads I'm getting should bump the comp to 11:1, so I did the swap with that and a 90mm intake in mind.

 

Thanks!! I'm sure he should have some good results!

Thanks! It was no problem!
I see its not as conclusive as many would like, but I figured since I was doing a swap, why not dyno both headers fwiw?

 

Sorry to Hi-jack

Slowhawk, do you think a stepped 1 3/4-1 7/8 would help on a high comp 11.5:1 384 stroker with a good amount of overlap (24 degree's @ 0.50)? Or would I be wasting my time and stick with my QTP 1 3/4's?

I'm in the same boat as PewterZ28 as far as wanting to test a little larger header on my stroker.

OP, thanks for the comparison Maybe this will humble some that always say you will lose all low end with a larger primary (on an LSX anyways)

 

To me, what it tells me is that the original headers weren't the flow restriction in your current setup and that the new headers didn't hurt scaveging either. The step can only help when you go with a larger cam and headers in the future.

 

My thoughts exactly. Like I said, I made the swap with a 90mm intake and a set of heads in mind.

 

me too, mine was right around 30rwhp, but i went with the 1-7/8's stepped to 2" and td's.