The build sheet says they were installed at 1.800. I will calla nd ask how that pertains to shimming them.

 

We had 1.8 rockers with the Lingenfelter GT2-3. Changed back to stock rockers 6500 next pull.

 

Could be lifter pump up.

 

I see this point, but why would ehat affect this? I.e. car runs fine when cold.

 

I would assume you checked obvious things like the spark plugs?

I'd tend to also think it's the preload.
How far does a 1/4-turn go when you have shaft-mount rockers?
What ratio are these rockers?

 

I have put two sets of brand new ngk's in it, and ohm tested wires, and replaced coil packs. Therefore, I believe ruling out spark.

1/4 turn is a 1/4 turn regardless of them being shaft mount or regular. So long as thread pitch on bolts are same, and bolt stretch is equal.

Rockers are 1.7 ratio.

 

I've never run shaft-mount rockers before so that's why I asked. You don't see any clearance issues around the rockers, retainers or pushrods that could be a problem when hot do you?

How about the AFR?

I think I would use a CTS-tricker or resistor in place of the CTS when the engine is hot and test it to rule out the engine management system. If the engine is hot, but you tell it that it's cold and the problem goes away, that would be telling.

I'd also put a pressure tester on in place of the radiator cap and watch the pressure when you're testing it to see if the combustion is blowing by the gaskets when hot. It's not likely but would rule out another possible.

The problem being heat-based would seem to be due to thermal expansion of parts or a viscosity change in the oil. Both of those things sort of point to the lifter.

It could be springs, but I haven't seen a 918 change pressure with a temp change before. I could go in the garage and test the pressure hot to make sure though. Unless they weaken with heat then I don't see how they would float when hot and not float when cold, although I suppose the harmonics could change with temp, but the conicals are not supposed to have a big problem with harmonics.

I'll think on it some more.

 

FYI I did heat test some springs tonight and they showed no change in pressure. I went cold, 200*F and 300*F.

If some guides were too tight, or even one for that matter you might get enough bind to hold or slow down the valve from closing on time.
If you pull the valves you should see galling on the valvestem if this has happened.

If the motor is still together and running then hook a vacuum gauge to your plenum and watch what happens when the problem emerges.

 

PROBLEM RESOLVED.

Comp beehive springs were to blame. Ditched the 918 springs in place of 921 springs, readjusted valvetrain, and full rpm is there.

 

good deal! I'm glad you found the problem in reasonable time.
If you don't mind me asking, what valves are you running? Could something in your valvetrain have added a lot of mass? rockers? valves?

I ask because I have a friend running .630" lift with comp 918 springs installed at only 1.85" height. He's running heavy comp steel 1.85:1 ratio roller rockers, but the lightweight Z06 valves.

 

good deal! I'm glad you found the problem in reasonable time.
If you don't mind me asking, what valves are you running? Could something in your valvetrain have added a lot of mass? rockers? valves?

I ask because I have a friend running .630" lift with comp 918 springs installed at only 1.85" height. He's running heavy comp steel 1.85:1 ratio roller rockers, but the lightweight Z06 valves. He doesn't get any float.

 

i dont see the springs being the problem unless they were installed at the wrong height to begin with. you mention readjusting the valve train. did you do this correctly with the 918's?
i dont see those 918's being the problem, but whatever it was is gone.
have fun with it.

 

I'm running the ferrera stainless intake valves. And ferrera inconel exhaust valves. Comp shaft mount rockers. Yes we did readjust the valve train numerous times with the beehives, and in fact replaced the springs once as well. The entire reason I changed springs is that 3 different times the guys ont he comp tech line said that it was most likely the springs causing my problems.

 

Why was it different hot to cold?

 

That is the one thing we are lost on. The collective thought is that the setup was right on the edge, and the added ehat/expansion pushed it over. It seems like the theory is the springs were going into harmonics.