Help find the missing RWHP : 408ci, M6, Moser 9"
Thread Starter
Joined: Apr 2003
Posts: 853
Likes: 0
From: Tallahassee, Florida
Help find the missing RWHP : 408ci, M6, Moser 9" here is the graph....each time hp went up. a few things to note. the car is a full bolt on car, Fast 90/90, 30# Fast injectors, 257/266, .622/.642, 113 lsa cam, PRC stage 3 heads, ASP pulley. Headers are Grotyohan 1-3/4" Long tubes, 3" into a Hooker Aerochamber. he dual cutouts are in the y pipe.
Motor has about 1000 miles on it, also with a new 9" installed at the same time. Fuel pressure is fine as the AFR is pretty dead on, and last run i believe had 28* of timing. I am throwing a code or 2, 1 being a misfire that i believe to be my drivers side o2(awaiting my extension to install new o2), and egr code, and maybe a TPS code(p0121).
im thinking theres more there with more of a break in and some more tuning(something broke so we had to quit for the night), my tire pressure was pretty damn low, weather was about 88*, ~56% humidity, and ~30.07 barometric pressure(i think)
help....
Motor has about 1000 miles on it, also with a new 9" installed at the same time. Fuel pressure is fine as the AFR is pretty dead on, and last run i believe had 28* of timing. I am throwing a code or 2, 1 being a misfire that i believe to be my drivers side o2(awaiting my extension to install new o2), and egr code, and maybe a TPS code(p0121).
im thinking theres more there with more of a break in and some more tuning(something broke so we had to quit for the night), my tire pressure was pretty damn low, weather was about 88*, ~56% humidity, and ~30.07 barometric pressure(i think)
help....
first of all, if your throwing a code from your oxygen sensors being fucked up, that will be a big dip in power right there cause your probably misfiring... at least it did on my car and the power loss was noticable.
next, your gonna wanna get 1 7/8 headers to maximize your flow, something like kooks or qtp, and possibly with a set of true duals.
also is it 6 speed or auto? auto then it wouldnt be so bad, but if its 6 speed theres something missing for sure...
next, your gonna wanna get 1 7/8 headers to maximize your flow, something like kooks or qtp, and possibly with a set of true duals.
also is it 6 speed or auto? auto then it wouldnt be so bad, but if its 6 speed theres something missing for sure...
Thread Starter
Joined: Apr 2003
Posts: 853
Likes: 0
From: Tallahassee, Florida
would a code or two rob about 40-50rwhp though? it is throwing the p0300 random misfire code, most likely til i replace that o2, but at WOT does that matter?
i cant afford $1000 headers at the moment, i figured i'd sacrifice 10 or 15hp with what i got for now, since i couldnt afford them after doing a new motor and 9" at the same time.
this is a six speed car(textralia clutch). imo im missing at least 40-50rwhp, i would expect at least 500-510rwhp, even through the exhaust, if people are seeing 530's-550's with bigger headers.
i cant afford $1000 headers at the moment, i figured i'd sacrifice 10 or 15hp with what i got for now, since i couldnt afford them after doing a new motor and 9" at the same time.
this is a six speed car(textralia clutch). imo im missing at least 40-50rwhp, i would expect at least 500-510rwhp, even through the exhaust, if people are seeing 530's-550's with bigger headers.
the power isnt all that bad but the tq is what more draws my attention. double check your wires and make sure all cylinders are actully firing . reasoni say that is ive had a plug go bad before and it was about 35-45hp that i was down and the car still ran great 
. has it been tuned? the codes dont help as they put it into a "safe" mode but i think theres more to it than just tuning
. has it been tuned? the codes dont help as they put it into a "safe" mode but i think theres more to it than just tuning Thread Starter
Joined: Apr 2003
Posts: 853
Likes: 0
From: Tallahassee, Florida
Originally Posted by badpewter-z
the power isnt all that bad but the tq is what more draws my attention. double check your wires and make sure all cylinders are actully firing . has it been tuned? the codes dont help as they put it into a "safe" mode but i think theres more to it than just tuning
when i saw that code, i checked all the plugs(new tr-55's) and all 8 wires (stock) to be sure they're plugged in, and they werent arcing on anything...everything checked out good. it has been partially tuned(using SCT software) with some of the specs above, but we had to quit before finishing due to an equiptment failure(the xcal got fried somehow)
the A/F is 12.70-12.90 pretty much across the board.
What lifters? Preload? Was geometry checked on install? Too much prelaod could hang the valves open bleeding off cylinder pressure and not make contact with the valve reliefs in the pistons.
Trending Topics
Thread Starter
Joined: Apr 2003
Posts: 853
Likes: 0
From: Tallahassee, Florida
Originally Posted by John02SS
What lifters? Preload? Was geometry checked on install? Too much prelaod could hang the valves open bleeding off cylinder pressure and not make contact with the valve reliefs in the pistons.
this was a assembled long block, and i dont have the spec sheet with me here at work to even tell you what kind of lifters are in it.
slowhawk, that response kind of makes me feel at ease about where some of that extra power is. my o2 extension should be here thursday, and maybe by next weekend(depending on xcal turnaround) ill be able to get it on the rollers with no SES codes and it being a little more broken in, will yield some better numbers. these 5 or 6 pulls on the dyno were its first time seeing over 4500 rpm. Something else i noticed on the street it pulls very hard, noticably stronger than my old 436rwhp combo, i know its another ~24rwhp, but it feels like a lot more.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
What's the compression? That cam likes a lot of compression ~12.5:1 or so, but the problem is it's an iron block. It doesn't like a lot of timing and a lot of compression. So, you'd probably be limited to 22 degrees or so in the Florida heat, even with 93 octane.
Also, those heads are costing you a solid 20rwhp, lower compression at least another 15rwhp. Ported FAST would probably pick up 10rwhp. 480+45 puts you in the 525 range, which is not bad at all for a 408 - and the torque would go up quite a bit also. But, I'd figure that'd be the lowest you'd be at if you were using ETP 240s or TFS 235s with at least 12:1 compression and a ported FAST. Run Cometic .040" or Felpro 1041 to improve quench and help against detonation at such a high compression ratio (though, the cam motion cam you're running will definitely lower the dynamic compression quite a bit).
Those headers are actually a good design, so I don't know that a 1-7/8" is actually going to do much. Maybe 5rwhp on the topend while loosing at least that much in the midrange and you are already soft in the torque department. It really depends more on the exhaust port of the heads as to what they want. Large valve and port works well with a smaller, higher velocity header, while the opposite holds true.
Otherwise, once you get the codes and things fixed, I don't see why 500rwhp couldn't be attainable with the current combo.
Also, those heads are costing you a solid 20rwhp, lower compression at least another 15rwhp. Ported FAST would probably pick up 10rwhp. 480+45 puts you in the 525 range, which is not bad at all for a 408 - and the torque would go up quite a bit also. But, I'd figure that'd be the lowest you'd be at if you were using ETP 240s or TFS 235s with at least 12:1 compression and a ported FAST. Run Cometic .040" or Felpro 1041 to improve quench and help against detonation at such a high compression ratio (though, the cam motion cam you're running will definitely lower the dynamic compression quite a bit).
Those headers are actually a good design, so I don't know that a 1-7/8" is actually going to do much. Maybe 5rwhp on the topend while loosing at least that much in the midrange and you are already soft in the torque department. It really depends more on the exhaust port of the heads as to what they want. Large valve and port works well with a smaller, higher velocity header, while the opposite holds true.
Otherwise, once you get the codes and things fixed, I don't see why 500rwhp couldn't be attainable with the current combo.
Teching In
Joined: Mar 2006
Posts: 7
Likes: 0
The 27hp and 25ft/lbs jump just from uncapping the cutouts should be a pretty good indicator that you should have gotten the longtubes everyone told you to get during the course of your nine month build. The number went up with each pull because Tony was tuning it and making changes.
Thread Starter
Joined: Apr 2003
Posts: 853
Likes: 0
From: Tallahassee, Florida
Originally Posted by JakeFusion™
What's the compression? That cam likes a lot of compression ~12.5:1 or so, but the problem is it's an iron block. It doesn't like a lot of timing and a lot of compression. So, you'd probably be limited to 22 degrees or so in the Florida heat, even with 93 octane.
Originally Posted by JakeFusion™
Also, those heads are costing you a solid 20rwhp, lower compression at least another 15rwhp. Ported FAST would probably pick up 10rwhp. 480+45 puts you in the 525 range, which is not bad at all for a 408 - and the torque would go up quite a bit also. But, I'd figure that'd be the lowest you'd be at if you were using ETP 240s or TFS 235s with at least 12:1 compression and a ported FAST. Run Cometic .040" or Felpro 1041 to improve quench and help against detonation at such a high compression ratio (though, the cam motion cam you're running will definitely lower the dynamic compression quite a bit).
Originally Posted by JakeFusion™
Those headers are actually a good design, so I don't know that a 1-7/8" is actually going to do much. Maybe 5rwhp on the topend while loosing at least that much in the midrange and you are already soft in the torque department. It really depends more on the exhaust port of the heads as to what they want. Large valve and port works well with a smaller, higher velocity header, while the opposite holds true.
Otherwise, once you get the codes and things fixed, I don't see why 500rwhp couldn't be attainable with the current combo.
Otherwise, once you get the codes and things fixed, I don't see why 500rwhp couldn't be attainable with the current combo.
the 1 3/4 tubes isn't the problem. many 408s have easily made over 500 rw with them.my single 3" hooker catback only lost 6 rwhp,10 rwtq to an open 3" cutout. even with 11:3x scr your dcr is probably on the low side but that combo should still clear 500 rw with that large of a stick. i agree with the code fixing and a retune.
Teching In
Joined: Oct 2005
Posts: 4
Likes: 0
Just a little more info about the car. The misfire code is being set at idle/part throttle due to the A/F being 16-16.5:1 @ idle. I was working on the idle when the Xcal2gm died. The timing is at 30.5 total, it fell off at 31.5. The computer is not seeing any knock or misfire codes at WOT.
Last edited by Gt-358; Jun 19, 2007 at 01:09 PM.
Originally Posted by slmdLS1
curious to know what area the heads are costing me...2.08"/1.60" valves and ports flowing around 320cfm @ .650 lift on the intake side...are they considered not enough?
Also, flow isn't everything, especially @ .600" - most of the heads I just quoted destroy those heads in the .300-.500" range, which is where power is made, regardless of what the lift on the cam is. There are bottlenecks in the car that help to emphasize that area of head flow. Having huge numbers there is worth more horsepower.
Originally Posted by JakeFusion™
I've just never seen great numbers out of the PRC stage 3s. They Stage 1 and 2s have done well, but compared to AFR 225s, ETP 225/240s, TFS 225/235 or even L92 heads, they are always down on power. But it might be that they are never paired up with the proper compression either.
Also, flow isn't everything, especially @ .600" - most of the heads I just quoted destroy those heads in the .300-.500" range, which is where power is made, regardless of what the lift on the cam is. There are bottlenecks in the car that help to emphasize that area of head flow. Having huge numbers there is worth more horsepower.
Also, flow isn't everything, especially @ .600" - most of the heads I just quoted destroy those heads in the .300-.500" range, which is where power is made, regardless of what the lift on the cam is. There are bottlenecks in the car that help to emphasize that area of head flow. Having huge numbers there is worth more horsepower.
If $1850 GM castings did anywhere near what $2500 aftermarket castings did, AFR, Trick Flow, ET, and a whole bunch of other companys would surely be out of business.Now, to the original poster...stock FAST 90 or ported? I'd say the two biggest bottle necks are your heads and headers, but get the car running totally correct first and then see where you are at.
Originally Posted by slmdLS1
the A/F is 12.70-12.90 pretty much across the board.
Fix codes, and retune. Personally, I'd go with a 1 7/8'' header as well, through true duals preferably.