Dynoed today at Heffners (BIG Viper shop) in Glen Burnie, MD this afternoon. Finally got a chance to tune the car in.

I am fairly pleased for the numbers I got with my setup but I have a technical issue that I need to resolve (with your alls help if possible) to pick up the lost HP. More of a problem diagnosis of sorts.

Results (SAE Corrected) - 406 RWHP/38x LB/FT which is a 36 HP and about 30 LB/FT improvement over my cam only XER 224 setup.

98TAauto will be sending me a link for the graph and certain values - not 100% certain of the torque #. (To be posted SOON)

LINK: http://www.easternfbody.com/easternfbody/willdyno.JPG

Here is the thing that stumped everyone there:

The car would pull hard all the way to 5900-6000 rpms and then just die - loose ALL power. You will see in the dyno graph that the RWHP/TQ completely fall off as if you lost all throttle. The car would still spin RPM's and tach up - but the power would not be there. It showed on the graph and it is noticeable when WOT on the street. I thought the noticed drop was possibly due to the new cam and its peak power (see setup below) but that would show more of a gradual drop and leveling off I would think. This was almost like I had a govenor that kicked in exactly at 5900-6000 rpms EVERY time we did a pull.

So basically we were all dumbfounded and threw around a bunch of options and eliminated as many as possible.

What we know:
- Car was showing 100% throttle
- Injectors all were working fine
- No knock was detected at all
- Wires/plugs are all new.
- No signs of broken spring, etc
- Car would consistanly loose power at 5900-6000 rpms EACH pull (5x's)
- There were no indications AT ALL of any problem until 5900 rpms

Possible causes and reasons we ruled out (we think):
- Valve float was mentioned but quickly ruled out due to the curve being consistant all the way through (no zig-zagging of the curve consistant with high RPM valve float) and due to the problem hitting right at about the same point each time.
- Plugs/wires - again, wouldnt happen EACH time at 5900-6000 rpms and they are very new (1000 miles at most).
- Heads stalling at a certan lift = but again, wouldnt see the drastic drop in HP over a certain RPM

Idea the stuck (with me atleast):
My buddy (who has worked on cars for god knows how long) called me and asked me how I did. I told him what all happend and the FIRST thing out of his mouth was "rockers" and he was insistant on it.

This struck me as funny because I just installed the YT's on my car about 3 weeks ago after after seeing my stock rockers beating up my retainers. He is almost possitive this is the culprit but unfortunately I didnt get a chance to talk to him then and havent since. I am wondering if maybe something was done incorrectly when I installed the YT's. Maybe I used shims when I shouldnt of? Would something like that make SUCH a difference? Limit the travel of a valvetrain component to that point?

I cant recall if the car fell over like this before I did the YT install or not. Unfortunately my shift lift wasnt hooked up and I avoided venturing above 6K rpms trying to avoid my rev limiter (4.30's rev QUICK) and to also take it "somewhat" easy on her before she was tuned/checked out (in terms of A/F ratio).

Could using the shims if I really didnt need them cause this? I "thought" I needed them by checking out my preload but I am fairly green to this and could easily have misunderstood my determinations.

Any other possible causes for this?

EVERYTHING ELSE runs perfectly fine and feels perfectly good - no codes, etc. Car under 6K rpms pulls hard as hell and as the graph shows - she is still picking up HP when it hits the wall of 6K rpms so it was the guess of the people around that I ought to see 420+ if allowed to run to 6800 rpms.

Setup (2001 Camaro SS):

- Full bolt-on car (headers, lid, cutout, pulleys, etc, etc)
- Patriot Stage 2 (5.3L) heads (milled .005 to clean)
- Futral 228/230 .578/.596 113 LSA
- Comp Lifters
- Strange 12-bolt w/ 4.30 gear
- McLeod Iron Disc clutch
- Shaner S2 ported TB
- Yella Terra rockers
*** I know I am missing some stuff - but this is the important stuff I would think.

Any ideas would be kindly appreciated - gotta shootout to hit on the 4th but more importantly I want to solve this.

 

I had the exact same problem with Comp 915 springs.. The exact same thing. We changed the springs and the problem went away.. The car was fine below 6krpm, but just fell past that.. The funny thing is on the first dyno it went up too 6500rpm b4 falling.. I got the car tuned and on the first pull it went to 6400rpm and fell. Then 6100rpm on the 2nd pull and fell. Then 6krpm on the next pull and fell.. Richie and Tim told me to get some new springs and I did. They installed CC941's and the problem went away.. This happened with the little T1 cam..

 

Wouldnt the dual springs that come with the PP2 (I want to say 978's) be adequate?

 

http://www.easternfbody.com/easternfbody/willdyno.JPG


there is the graph from today... im puzzled as to wtf happened. I mean it sounded like the car was just cutting off right ar 6000-6200. Almost like you would lift off the throttle??

Its funny though, one pass you could hear it, and the rest she sounded fine, but look at the drop at 6200!!!

 

Just because they are double doesnt mean they have enugh spring pressure to control the valve motion, make sure they do have compareable pressure to what we are runnign with other springs.

I didnt think about rockers (doesnt occur to me with LS1 pedastool torque to 22 ft lb LS1 bs) sounds an awful lot like it could be too much preload

 

Looks like a valve spring problem.

 

are those the springs that Patriot was having problems with and arent using anymore? im not sure

 

Springs for sure. If they are not setup correctly that could happen.. You car has more in it by looking at that graph..

 

Firat of all:
The 22ft/lbs of torque on the rocker bolts does not determine the preload of the lifters. The preload is determined by setting zero lash, then checking the number of turns on the rocker arm bolt before 22ft/lbs is reached. If you get less than 1 turn you're preload is fine. If you get more than 1 turn, install a shim and check it again. THEN you do a final torque to 22ft/lbs.

Now to help Hannibal with his HP dropoff problem, just a few suggestions:
#1 What is your fuel pressure?
#2 Your injectors might me maxed out?
#2 The PCM might be pulling timing at that point for some reason.

 

yes ive doen about 20 ls1 cams, and often have to go to different length pushrods. I was saying assuming proper pushrod length given an adjustable vlvetrain, too tight can cause a power loss when everythign binds up. Being an LS1, it woudl be an adjustment issue, but one of proper valvetrain geometry altogether

 

You mentioned XE-R lobes. If this is the case, a 230 XE-R lobe would see .595" lift. This is not safe for 918 springs. I wouldn't use a 918 on a XE-R lobe period, no matter what lift. Only other thing I can think of would be a loss of fuel. This is where your "governor" statment would make the most sense. I would put a fuel pressure gauge with a hose to outside of the hood. Run it up and see if the pressure drops when the wall comes in.

 

[quote]
he doest have a fp gauge so we dont know that, but the a/f didnt move.

the injectors were in the 80-90 percent duty cycle and only went to 100 percent for a few frames on efi live. so i dont think it was that.

there was no kr, and the timing stayed right where i set it thru all of the pulls.


i think its either valvetrain or some electrial gremlen somewhere.

 

Beast, he has dual springs though

still im beting its either the RR's or bad springs... Will, did you email Terry the issue? I dont think its anything wrong with the heads, just something simple that can be fixed easy. She's damn sure making plenty of power

 

The XER lobe I mentioned was with a 224 cam from LS1 Speed unless Futral uses an XER as well - but I didnt think that to be the case.

I emailed both Terry at Patriot and Alan at Futral to pick their brains a little bit for any possible info.

I really dont want to have to go through swapping dual springs but if I must ...... I guess I will.

But so I am clear - the whole rocker statement doesnt seem to make sense in this case? Fixing that I could do myself - springs on the other hand are a little beyond me.

 

Assuming it was LS1 Edit tuned, check your top speed limiter settings. You may find something interesting...

 

nope, already thought of that and it was fine.

 

Its very easy to check for proper pushrod length especially since he has already run the car. Just remove one of the rockers and look at the tip of the valve stem. There should be a small wear pattern directly in the center. If its to either side of center the pushrods are the wrong length. I doubt its a pushrod issue, especially since the heads weren't milled and stock pushrods should be fine with his cam.

 

I would hook a vacuum guage up to the intake and see what happens over 6k. My car did the EXACT same thing, the vacuum guage would show 0 until 6k than it would flutter. If it flutters than your valve springs are bouncing on the seats or floating.
Phillip

 

map rreading shoudl show the same as vacuum hauge right? barometer minus map equals vacuum

 

The same thing happened to my car once.. it ended up being that I had gapped my TR6 plugs at .055 and they wouldn't ignite the mixture at hight rpms until I closed them back up to .040. It would run fine until about 5,900 and then just die. it even set a misfire code one time.