Rise of the Phoenix

iTrader: (27)

KCS, the only time it was a little rich was on the initial hit. After that, AFR was right at 12.7.

slow trap

iTrader: (22)

kinda like my results from switching over from 1 3/4 headers,fast 90/90 and 85 mm maf over to 1 7/8 headers, ported 102/102 and 100 maf/and tried speed density. gained around 12-15 tq but lost 12-15 rwhp. it is frustrating. mine didn't carry up top as well like yours. my cam in my motor (408) is a 244/248 on a 110 +1 so we both have tight lsa cams.

SoFla01SSLookinstok

What brand of headers were they?

slow trap

iTrader: (22)

went from qtp 1 3/4" with the merge to tsp 1 7/8" without a merge. even if the merge collector picks up that unicorn 5-10 rw i would still be down on hp.

Rise of the Phoenix

iTrader: (27)

See, my Stainless Works 1 3/4" headers did not have a merge collector, while the Speed Engineering 1 7/8" headers do.

Slow Trap, thanks for posting in here. So do you attribute the loss up top solely due to the cam and the tight LSA? KCS made a great point about retarding the cam a few degrees. I'd love to do that, but Kent does all my motor work for me, and he does a great job, but that would just be more money out of my pocket, and I'd hate to have Kent do that and it not yield any better results.

scotty2000ss

iTrader: (2)

Good info here for sure. Following for sure.

I don't think the intake is the issue here. Somethings up...

Rise of the Phoenix

iTrader: (27)

The million dollar questions is "what"? These pulls were made within days of each other. The valvetrain is good, fuel pressure is good, timing is right, AFR is spot on, the car sounds and feels the same, so what is it if it's not the intake? I can see the tight LSA of the cam being an issue, but since it carried so far with the smaller headers, why does it fall off so fast with the bigger headers?

blk00ss

iTrader: (66)

I would quit worrying about it until I got it to the same dyno where it was originally dyno'd at.

scotty2000ss

iTrader: (2)

What header gasket did you use? Before and after?

Rise of the Phoenix

iTrader: (27)

But the "A" and "B" pulls were made on the same dyno. "A" being with the 1 3/4" headers and "B" being with 1 7/8" headers. This is within a couple days of each other, on the same dyno.

Rise of the Phoenix

iTrader: (27)

Not sure what gaskets were on it before, but I got new graphite gaskets with the Speed Engineering headers. I'm not sure if Kent used those, or used the gaskets that were on there before.

blk00ss

iTrader: (66)

I understand that... Just saying I wouldn't put much faith in either dyno number from that dyno. Sounds like he's still having some growing pains with it. A lot of changing around it sounds like.

Rise of the Phoenix

iTrader: (27)

Yeah, I get that, but what's most concerning is the drastic drop off in power around 6,000 RPM's. It didn't do that on the first pull, but did after the bigger headers were put on. Could it be the tight LSA of the cam, combined with the stock intake and TB?

blk00ss

iTrader: (66)

Not sure about the cam. But I know that ls6 intakes have made over 500 on some bigger cube motors.

Rise of the Phoenix

iTrader: (27)

My worry is a FAST 92/92 won't help that much if it's truly the cam and the tight LSA causing it to fall on its face past 6,000 RPM's.

Darth_V8r

iTrader: (4)

Any chance that somehow you picked up an exhaust blockage? Like debris getting in the pipe during the header swap and blocking flow? Plugged cats, if you're running cats?

Rise of the Phoenix

iTrader: (27)

Only exhaust change was putting SLP loudmouth 1's on in place of the Texas Speed bullets. The SLP 1's are literally straight thru with no obstructions at all. I don't think there is a blockage, but I guess there could be. I'd think if there were a blockage, you'd see a loss throughout the RPM range. Also, no cats. Car has never had them.

scotty2000ss

iTrader: (2)

If it were me I would put the old tune back in and dyno it again. No disrespect just speaking out loud.

Darth_V8r

iTrader: (4)

ten four.

ddnspider

iTrader: (26)

Was spark advance played with given the better flowing headers? If everything is truly identical, I think your exhaust is too good compared to your intake and your overlap is causing you to suck intake charge out the exhaust at high rpm like the venturi affect. You don't see it at lower rpm cause the air isn't moving as fast. If you have a chamber with a super efficient exhaust and suck through a straw, some of the intake charge is going out the exhaust cause its lower pressure. I'd bet money you pickup power with a smaller cam with less overlap.