Okay guys maybe u can help me out here. Bolted on a set AS stage 2.5 5.3 heads and dyno'd the next day 447/406, previous best was(cam only) 423/399. The dyno speed sensor died so I didn't get to play too much more after the 447 pull. Anyway went to the track and was only trapping 119.9, cam only I was trapping 122. All subsequent passes the car kept slowing down. Anyway went back to the dyno and the car pulled 430 first pull, 420 next pull and 410 the final pull with torque dropping to only 360-WTF? Anyway I pulled off the valvecover and decided to check my valvesprings-surprise surprise the valve spring installed height was only 1.78 I and 1.8 E-Jay told me he would he set them up at 1.75? So I checked the spring and at 1.78 installed height pressure was only 100lbs at the seat. So anyway threw in the new Cranes(striped) ones and shimed them up to get 145lbs on the seat. Took it to the dyno and pulled only 431/401-WTF? Now this is the strange thing-the car made 430 at 6000 and carries it to 6800-the curve just goes flat! Torques is also the same-it hits 400 at 4000 and stays at 400 until 5000! Now I'm thinking valvefloat. I know TR recomends these springs with their T-rex combos but on stock heads. I know Crane has revised these things and came out with note about how they need to be shimmed etc, etc..I'm just thinking these springs work fine on stock heads but cannot handle the loads of an aftermarket valve(heavier). I know Fireball also has had a similar problem-I'm hoping he can chime in. If u look at his graph for his T-rex GTP combo, his graph looks like mine. Is there anyhting else i could be missing or am overlooking? Thanks.

 

Swell. I just ordered a box Friday to replace my old style Crane duals soon. What kind of spring did you take off? You used the Crane seat and retainers, yes?

 

Replaced the old Crane duals-no stripe and yes I used the Crane seats and retainers.