Running out of steam up top?
05-10-2009, 07:36 PM
#1
11 Second Club
Thread Starter
Running out of steam up top? So I just recently had my 408 tuned at Khaotic Kreations.
First I want to say John did a GREAT job and found quite a bit my power thru out the entire curve.
Pre-tuned numbers
Post tuned numbers.
Now for the question. I know that this 408 has a big cam . It is being supported by AFR 225 heads, jet hot LT's and Racetronic fuel system w/ 42lbs injectors
What is puzzling me is peak power is being made at 6100 RPM and power drops hard after 6400.
I would have thought this set up would peak higher and pull hard t0 7000....
I am not dissappointed, I mean 500 at the wheels with a 4.11 geared 9" rear, running a stock WS6 cat back and LS6 intake aint bad at all. I am just confused as to why it runs out of steam so early?
possable valve float?
stock muffler choking it up?
intake/TB too restrictive?
I would think VF would make it choppy at the end of the graph.
I would have thought the other 2 would simply flatten the curve out not drop it on its face...
What do you guys think?
First I want to say John did a GREAT job and found quite a bit my power thru out the entire curve.
Pre-tuned numbers
Post tuned numbers.
Now for the question. I know that this 408 has a big cam . It is being supported by AFR 225 heads, jet hot LT's and Racetronic fuel system w/ 42lbs injectors
What is puzzling me is peak power is being made at 6100 RPM and power drops hard after 6400.
I would have thought this set up would peak higher and pull hard t0 7000....
I am not dissappointed, I mean 500 at the wheels with a 4.11 geared 9" rear, running a stock WS6 cat back and LS6 intake aint bad at all. I am just confused as to why it runs out of steam so early?
possable valve float?
stock muffler choking it up?
intake/TB too restrictive?
I would think VF would make it choppy at the end of the graph.
I would have thought the other 2 would simply flatten the curve out not drop it on its face...
What do you guys think?
05-10-2009, 08:15 PM
#3
11 Second Club
Thread Starter
No cutout, (I have one for the car just have not welded it up yet) I wanted to see what we could squeeze out of her while being reasonably quiet. (read sneaky)
Still how does peaking the exhasts ability to flow make the car fall on its face like that? I would have thought it would flatten out then taper off?
(thanks for the input)
Still how does peaking the exhasts ability to flow make the car fall on its face like that? I would have thought it would flatten out then taper off?
(thanks for the input)
05-10-2009, 08:35 PM
#5
11 Second Club
Thread Starter
Dont get me wrong I agree the ls6 is holding it back, but I would have thought that if this was the case then at what ever RPM it reached its peak flow, the hp curve would just flatten then taper....
Course I may have that completely wronge perhaps someone could explain why the nose dive? instead of taper?
Course I may have that completely wronge perhaps someone could explain why the nose dive? instead of taper?
05-10-2009, 09:15 PM
#6
Are you running the 8019 upgrade valve springs? (if the heads were purchased in the last 12 - 18 months or so they would have come standard equipment).
Obviously a properly ported FAST is worth big on this set-up (20 - 25 RWHP) and the LS6 will pose the largest restriction at the top of the curve due to it killing 50 CFM's of your cylinder heads potential airflow (thereby acting like you have a much weaker head which will always show you weaker peak numbers).
A weak exhaust will also hurt peak numbers more than lower/midrange figures for the same reason....when airflow is at a premium (and you have less time to fill and evacuate your cylinders) a weaker exhaust will usually take its bigger bite out of the power curve upstairs.
And I agree with some of the other sentiment that looking at your overall combination (and whats still left under the table), the numbers are very impressive and you should be pleased.
Get in touch with me when your ready for that induction swap....I bet a ported FAST and a cut-out would wake that car up noticably. You wont need a dyno to tell you your making a bunch more power after thise two additions.
Cheers,
Tony
Obviously a properly ported FAST is worth big on this set-up (20 - 25 RWHP) and the LS6 will pose the largest restriction at the top of the curve due to it killing 50 CFM's of your cylinder heads potential airflow (thereby acting like you have a much weaker head which will always show you weaker peak numbers).
A weak exhaust will also hurt peak numbers more than lower/midrange figures for the same reason....when airflow is at a premium (and you have less time to fill and evacuate your cylinders) a weaker exhaust will usually take its bigger bite out of the power curve upstairs.
And I agree with some of the other sentiment that looking at your overall combination (and whats still left under the table), the numbers are very impressive and you should be pleased.
Get in touch with me when your ready for that induction swap....I bet a ported FAST and a cut-out would wake that car up noticably. You wont need a dyno to tell you your making a bunch more power after thise two additions.
Cheers,
Tony
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05-10-2009, 11:45 PM
#8
But please clarify which valvespring you are running. I would like to rule out float assuming you definitely have the upgrade valve springs. And what rocker arms as well for that matter?
-Tony
05-11-2009, 11:01 PM
#9
11 Second Club
Thread Starter
I bought them about 2 years ago. (give or take)
05-13-2009, 12:07 AM
#10
The only way to tell is to pull one spring.
If your willing to do that let me know and I will tell you how to easily identify which springs you have.
-Tony
05-13-2009, 04:22 PM
#11
11 Second Club
Thread Starter
Yes I am willing to pull one.
I bought them from TSP and I THINK back then they sold them with with TSP dual springs, if they did, thats how I would have bought them.
I bought them from TSP and I THINK back then they sold them with with TSP dual springs, if they did, thats how I would have bought them.