folks i need some serious help. last year me and a few friends put a new motor in my 97z i finally got it running fairly well, but here is my problem around 4000 rpms and up i get a severe vibration throughout the entire car, (it feels like the worlds fastest massager) i have already rotated the drive shaft because i thought that might be the problem, it didn't help.
what do ya'll think it could be?

here is a list of mods:
bored 30 over, srp 10.1 pistons, lt4 hotcam kit, p&p heads w/2.02 1.60 valves, 30lb injectors,long tubes, ory, flowmaster american thunder catback.
it still has stock crank and rods

I would greatly appreciate any suggestions

 

i have a simaler problem is your like a hermonic vib or a shack everything apart vib also mine kinda does it sitting still but real noticable moving wish i could help but have same prob if you figure it out let me know

shane

 

Make sure the harmonic balancer isn't wobbling.

 

Was the engine rebalanced before assembly?

 

ooops i think you may be on to something

 

ya i had it balance before i put it to together no mile or anything before balance and back into car

 

could this quite possibly be the motor mounts? they are the factory originals

 

Dought it,unless one is broken.

Does this do it in the driveway @4000 or driving @4000 and what gear?

 

it does it while driving and in any gear

 

Ya got a poly tranny mount?

 

long checklist. does it vibrate while sitting still as well? you could eliminate drivetrain issues if so.

 

I just helped a friend build his motor up, and he tried saving money by not having anyof the internals balanced, which I busted his ***** for... but he had the same problem around 3500rpm and hes got the poly motor mounts, now he's out of money and stuck with "the worlds fastest vibrator" haha

 

my car has the same problem but mine does it setting still but i had the engine balance before assemably so i dont know what my problem is it had the vib wen it bought the car and it only had 30000 on the whole thing stock moter never touched so i dont have a clue

Shane

 

My car shakes at around 3500rpm's as well but then stops around 4500. Strange.

 

it must just be the 97 because it seems that most of us that have this problem have 97's