luke4907

iTrader: (5)

I was racing some friends this past weekend and I noticed that at about 4200rpm and above (until the auto shifts) it vibrates pretty badly. I'm just curious if this would more likely be caused by the stock ignition being stock and not being able to handle the high rpm or if maybe my balancer needs to be replaced (doubt it's ever been). I'm pretty sure I need some new motor mounts additionally, but I'm just wondering what is causing the extra vibration at high rpm. Engine is basically a stock tpi350 with pulleys and air foil. Anyone have an idea?

BTW 1st run I chalked up a win on my friend's brand new 2001 GT 5sp w/ exhaust and Steeda pulley He got me on the 2nd one though (tranny was in 2nd from a roll and didn't shift properly for me)

Vader

There are multiple possibilities. It could be due to an actual mechanical imbalance, or misfire at that RPM.

Mechanical imbalance could be due to a failing harmonic balancer or hub, damaged torque converter, bent driveshaft, incorrect flexplate, damaged crankshaft, and several other remote possibilities. If the vibration occurs while sitting still and running at 4,200 RPM, you can obviously concentrate on the engine and torque converter.

The other possibility is misfire due to weak ignition, floating valves, or lean mixture.

luke4907

iTrader: (5)

thanks for the advice.. as soon as I get the chance I have a rebuilt 700r4 and torque converter waiting to go in so we'll see if that does anything... but considering what you are telling me and that my engine runs rich, idles roughtly sometimes, take a long time to crank, and smokes a little at startup, sounds like a tune-up might resolve the issue... makes me wonder what kinda top-end power I'm losing if it's misfiring... thanks again