bad vibrations

[hurricane]

Hey there everyone, I just installed a 383 in my 87 MC SS and after the install I set the timing as best as I could, then drove her home with no vibrations, Now I just got her back from the mechanic, they set the timing, they said I was way out, but now when I get the rpm's up she has a bad shake, I have a high lift cam 540 lift, I noticed that I didn't have enough vacuum for my brakes and now I am thinking this shake might be caused by a lack of vacuum, am I right and a vacuum canister will fix this or is my problem somewhere else?

 

[jociha]

First, before you drive again check the driveshaft, make sure it is centered, and both straps are on the back u-joint straight and centered, then when it is safe drive it at vibration speed then put it in neutral let the rpm's drop and see if the problem stays or goes, then you will have a good idea if it is the motor or trans back.

 

[All Motor Boys]

Whats your rear gear ratio. Have you been doing burn outs the drive shaft might be tweaked

 

[pontiacgp]

I wouldn't touch anything, I'd take it back to the mechanic and tell him/her exactly what you posted

 

[Kwik_Cutty88]

Check the motor mounts as well. Mine are in bad shape and I get bad vibrations at high rpm too.

 

[84GP455]

Check the transmission bolts on the housing to the motor, I always forget to tighten them up all the way and it will make your car shudder if loose.

 

[hurricane]

Well I do have vibration in idle, and they tore my transmission mount all to sh*t.
It wasn't doing this before I dropped it off at the mechanic so I don't think it's the motor , damn thing is new

 

[hurricane]

Well I do have vibration in idle, and they tore my transmission mount all to sh*t.
It wasn't doing this before I dropped it off at the mechanic so I don't think it's the motor , damn thing is new

Another rthing that I just cam across is this crate engine, the valves are not set, took a valve cover off to see and the first valve, tight,#2 lose,#3 lose, that's just on the one side so I think this could be my vibration problem , will update when valves are adjusted

 

[565bbchevy]

Another rthing that I just cam across is this crate engine, the valves are not set, took a valve cover off to see and the first valve, tight,#2 lose,#3 lose, that's just on the one side so I think this could be my vibration problem , will update when valves are adjusted

I'm not sure how you are checking your valves but there will always be some loose and tight ones on each side depending if they are on the lobe or the base circle of the cam.
What exactly did you have the mechanic do for you besides set timing?
Also who did you get this crate engine from and where did you get the 600 horse figure(as in your signature)? I would say closer to 450 with that parts list.

 

[pontiacgp]

If that isn't a roller cam who broke in the engine?