Hey guys. I just got my new 383 up and running saturday night. my problem is, it vibrates and it gets worse with rpm increase. When my engine was balanced at the machine shop they balanced it with a new flexplate that had he weights removed. Turns out, the new flexplate was too big (looked like an LS1 Flexplate). So we were stuck putting the stock flexplate back on. My buddy said that the stock weighted flexplate should make that much of a difference. Well needless to say, he was wrong! the car really vibrates at anything above 2500 rpm. At idle you cant feel it. earlier today I had to move the car in my drive to get my beater car out and I think I hear a very faint knock noise. Please tell me that the bearings arent trashed. The motor only has 35miles on it and I parked it until I get the right flexplate in there. Do you guys think that faint knock noise will go away once I put the right flexplate on?

 

anyOne?

 

post after you try it if you are going to do it anyway don't worry about it for now - also, wait more than 30 minutes before taking your thread back up to the top....

 

Do not force posts back to the top more frequently than once in a 24-hour period.

Why would you drive it 35 miles with it vibrating so badly? Why would you believe someone who old you that is wouldn't hurt to put an externally balanced flex-plate on an engine that had been internally balanced with a plate with no weight on it?

Did you assemble the engine, or did someone else? Given the track record so far, its hard to tell by looking at an Internet post whether the knock was due to faulty assembly, the incorrect flex plate or some other screwup.

 

The mojority of the mileage was on the high at low rmps which you couldnt feel it vibrate until you hit around 2500 rpm. But If the bearing are trashed, how loud would the knock be?