AutomagicLS1

iTrader: (18)

I have been having this issue which I thought was valve springs/valve float. I was for sure it was valve springs when I had them replaced the other day some broken ones were found. I knew the car was down on power but the valve spring swap made night and day difference. I wouldn't hesitate to say the car picked up 5mph. Although they did have a hard 20K miles on them. Problem is still there. In 1st, 2nd, 3rd, 4th, park, neutral anytime the rpm's reach 6450 it will NOT turn anymore rpm's. The pull to 6450 feels great. Car pulls very hard, smooth then instantly quits turning rpm's. It's not a gradual start feeling a miss or cutting out then it gets worse type deal. It's just car pulling hard then wham car quits making rpm's. Also at 6450 when it starts the afr goes rich. It will go from 12.7-12.9 to anywhere from 10.9 to 11.5. My only guess is it's floating the valves on brand new springs OR an ignition issue and both are obviously messing with the burn of the air/fuel mixture.

Keep in mind I had no problem turning the car to high rpm's with the springs before they obviously got old, current pushrods and rockers. The car turned high rpm's months after I fessed up and finnaly bought hp tuners. I have patriot golds, 7.35 pushrods, and comp pro mag rockers also LS7 lifters. I find it really hard to believe I got a bad set of new patriot golds.

Could it be something electrical? Theres no voltage drop in the system, I have checked fuel pressure 60psi at wot, replaced the crank sensor and coil packs thinking maybe the ignition was cutting out up top.

I also questioned the transmission in the car but this not turning any rpm's is happening way before its supposed to shift (6900). It also does it in park and neutral if you bring the rpm's up that high....so I kinda ruled the trans out.

Basically I have to band aid the tune to let the car only turn about 6200 rpm's on a h/c/fast car so it can make a somewhat of a pass on the street....unacceptable. Any ideas? Thanks

LS1-450

iTrader: (33)

Did you change the rev limiter setting in HP tuners by accident? How 'bout timining starting @ 6450, any accidental changes made that have reduced it to a very low setting from 6450+?

AutomagicLS1

iTrader: (18)

Haven't changed my rev limited and this is happening 400-500 rpm before the car is supposed to shift. My timing stays at 28 deg during the pull and while it quits pulling

jmm98LS1

iTrader: (28)

Can you post your tune? Do you have any logs while this is occurring?

AutomagicLS1

iTrader: (18)

Tune and log are at the bottom of post
I have shot a couple videos actually of what my car is doing. One a couple months ago and one yesterday when I thought the valve springs took care of my problem. I just noticed something. In the video the voltage stays 13+ at wot untill upper rpm's and the voltage drops fast in the car. You can tell the voltage rapidly rises again after I get out of wot. This is interesting....

You may have to click on the actual youtube link to watch it full screen to see the voltage
Yesterdays video. I didn't stay in it long b/c if It was valve float I didn't want to hurt anything. You can definitely hear it start to lay over and watch the voltage before the pull, during, and after
http://www.youtube.com/watch?v=BJ2j-6D67Nk

Couple months ago before valve springs
http://www.youtube.com/watch?v=Aenvt-hK0wM

Log you can see around 6400 it goes pig fat

Droptopws6

iTrader: (13)

My friend had the exact same problem. He ended up having a dead coil. Not saying this is your problem but worth a look. By the way he ran a 12.80 on 7 cylinders, twice. Then he scattered his new motor.

ae13291

iTrader: (8)

humm voltage issues? it starts loosing spark at 6400 rpm?

jmm98LS1

iTrader: (28)

sent you a PM

XtraCajunSS

iTrader: (2)

Your problem is the Pro-Magnum rockers. Put stock rockers back on the car... problem solved. The reason why the car goes pig rich at that RPM is because the valves are bouncing on the seat causing incomplete combustion and raw gas out of the tailpipes. I've seen this problem many times.

Thanks,
Shane

livefast1

iTrader: (1)

what causes this, poor rocker design? i assume its lack of valvetrain stability due the the increased size/weight of the rockers? i don't doubt you would just like to know what causes this issue. if you were to recommend a good set o 1.8 rockers what would they be just for future reference, sorry for the hijacking.

ae13291

iTrader: (8)

wow very interesting Shane. now im subscribed

1BAD_LS1

iTrader: (36)

having a similar issue.... subscribing.

XtraCajunSS

iTrader: (2)

The rockers are actually a very good design and work well in other applications with lower ratios and much milder cam lobe families. I've used Comp Pro-Magnum rockers for years with great success in SBC, LT1, and SPF applications with no problems. Most of these engines only rev to 6K or so and are running a max of 1.6 ratio with .550" lift cams or less. I also use 7/16" studs for these apps.

The problem with the LSx version is two fold. First of all, the weight of the rocker tip over the valve. With most current LSx cam lobe designs and the extensive use of higher rocker ratios, you end up with excessive acceleration/deceleration of the valve which causes valve bounce or "float".

The second issue has to do with the 8mm rocker stud which is basically 5/16". This is not a very stable platform for the rocker to work off of and also contributes to instability in the valvetrain.

These are the 2 primary factors along with engine speeds commonly in excess of 6500 rpm which contribute to a power robbing, parts destroying situation. This is a primary cause of valve spring and lifter failure and can also cause piston to valve contact if the valve bounce is great enough.

IMHO, there are very few options better than a stock rocker with trunion upgrade. I know some folks are having success with the Yella Terra ultra lights but even in this case, you had better know what you are doing when setting them up. That's why my most common reccomendation is to run stock rockers. I've had hydraulic cam stock headed cars turn 8200 rpm with stock rockers. GM really did their homework with this design.

Thanks,
Shane

Shane

burntblkZ

iTrader: (5)

My car has the same problem since the new engine but only happens intermitly. Sometimes it will nose over at 6400 and othertimes it will pull to 7200 with no problems. Ive changed coils, wires,battery, alternator(has the same problem dropping voltage @high rpms),even threw an extra ground strap to the engine. Thought it could be valve float but wouldnt it happen everytime if it was? Hate to say it but im about to try a carb and see if it still happens. Somebody has had to come across this problem and found a cure for it.

AutomagicLS1

iTrader: (18)

Well I think I may know what the problem is. I suspected the tranny could have been bad. It honestly felt like to me if it was the trans 2 gears were trying to engage or something at the same time. Well I lost the tranny tonight. Heres a short video. It had no problem revving to 7000+ when the tranny let go tonight during a pull on the street. There was sure no hesitation in the motor when the trans slipped at 6400+ heres a video from limping it home tonight

http://www.youtube.com/watch?v=DXLb_OznQG4

Minshall

Damn Curtis what did you do to that tranny?

1BAD_LS1

iTrader: (36)

I think mine was the tranny also! with the 4l60E i would pull 45-100mph in 5.953 seconds now it pulls 45-100mph in 4.563 seconds!!!!!!!! thats a 1.39 seconds faster... lol

Hopefully you get yours figured out!!!! I will have to get mine back on the dyno to know for sure though....

AutomagicLS1

iTrader: (18)

Nothing out of the ordinary

Jeep09

got a set on the way, should I use them?

AutomagicLS1

iTrader: (18)

Problem still there going to put stock rockers on and see what happens