How many RPM's is too much, think I hurt the motor.

[streetknight]

OK guys sorry if this gets long.

Took the GN in my sig to the 1/8 track Friday night. I've been noticing that when it shifts the boost drops 3-5 psi and comes back up. I put 980 comp valve springs on it a while back since the others were tired and the car wouldn't turn passed 4500. Well, while at the track I noticed on the PL files the RPM's are going to almost 5500 now. The AFR was getting to 11.5 on the shifts and I was getting a little knock, which I thought was false on the shifts.

I have a TT Alky chip and it says 23-25psi. I'm only running 20psi and the car's leaning out, fuel pressure @ 43 line off.

My first pass was as stated above, then I added 3% WOT fuel via the chip since it was leaning out on the shifts. When I let out after that pass, the motor is rattling now. Sounds like it's in the top end, but I haven't had time to tear into it.

SO, my big question is how Many RPM's should this motor be able to take. It's .020" over TRW forged piston, 200/200 cam and ported irons. I'm hoping I have a minor problem and just need to do some adjusting on the detent cable to get the RPM's down.

What do you guys think?

TIA

 

[TurboBuRick]

The cam and valve train determines the rpm range. When it stops making power, you at the end of the line. The rest of the motor does/should not care unless your running the oil system dry.

I just had a car that's sounds similar to what you describe. Rattles only when motor decelerates. Oil pressure is good. Everything checks out. The car will run and drive but the decell rattle is something that can't be ignored.

Sounds to me like a wrist pin. They take allot of abuse. Specially the factory press fit ones.

Race motor pins should be full float with c clips.

 

[streetknight]

To clarify, mine is rattling all the time. A steady tick that goes up and down with the RPM's. Oil Pressure is fine.

 

[TurboBuRick]

Then check out the valve train.

 

[Just a Six??]

If it does it when you rev it in Park unplug 1 injector at a time & see if it goes away. I pancaked a rod bearing once & when we unplugged the injector the noise went way down. Altho, it only rattled between 2200 & 2500 rpm.

 

[TR87386]

Cracked/broken rocker shaft?

 

[Alaskabuick]

Cracked/broken rocker shaft?

+2, I stuffed a pushrod thru a rocker once and also broke a rocker shaft another time. This was on a BBB but could do the same on our v6's.

 

[streetknight]

Cracked/broken rocker shaft?

We have a winner. Finally had time to take it apart today. Shaft cracked pretty badly where it hangs off the pedestal on the #1 cylinder.

 

[threerail]

and i was just about to tell u how to check to see if it was a wrist pin, and which one, damn

 

[TR87386]

Yep, been there done that. At least it's not a wrist pin