302-347 engine vibration

cmciver4

New Member
Nov 1, 2018
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Edmond, OK
Hi all! This is my first post on this forum and I am hoping for some help. I recently took the 302 out of my 69 mustang and stroked it to a 347. It is bored .030 over and I used an eagle kit to stroke it to 347. I took the entire assembly to the machine shop with my flywheel and harmonic balancer (fluidampr) to get balanced. I assembled the block and also installed an Edelbrock Pro flo 4 efi system. I want to be able to drive it all the time but have some bad vibration and I think its coming from the motor. The motor mounts are not new but they are adjustable so I can move the motor forward or back to line everything up. The mounts were not rotted or cracked in any way. I do have the alternator, power steering and ac hooked up with under drive pulleys. At this point I am so frustrated I keep second guessing everything that needs to be done and really don't want to rip the motor out again. If you need any other info please let me know and PLEASE HELP!
 
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Bad vibes when its idling or when its driving? When I did my 5.0 swap I put an aod on the motor that had a 5 speed before, and had to get a 58oz flywheel to make it not vibrate. Do you have the right flywheel for your tranny?

shem
 
Bad vibes while idling. I have revved it and tried to do the break in period but the vibration shakes the car and I can feel it in the gear shift and steering wheel. I haven't even taken it on the road yet. I have a t-5 transmission on it and its a 28oz flywheel. It was the same transmission that I had on the motor before I stroked it and never had that kind of vibration.
 
Def worth a shot, machine shop shoulda checked all that. Can you see the motor mounts letting the engine shake? Maybe a dead cylinder/do a compression test. No knocking sounds? A stuck valve will make an engine shake bad

shem
 
I called eagle and they said it is a 28oz external flywheel that's needed. That is the flywheel I have. No knocking sounds at all. I did have some exhaust leaks that after retightening the headers went away. All the valves opened when I adjusted the rocker arms too. It is pretty hard starting though. I will check the compression and see if I have a bad cylinder. I would hope not after just rebuilding.
 
OK, before you go nuts, take all the belts off and see if the vibration goes away. That will eliminate everything except the trans and the engine. If that doesn't do it, pull the trans and try again.
 
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