Engine vibration question

Ken B

Ken B

Senior Member
I am trying to get to the bottom of an engine vibration problem with my newly rebuilt engine. The rods, pistons, crankshaft, and flywheel have been balanced during the rebuild. The rods were balanced on the heavy end, the light end, and the total weight. The pistons are all less than one gram apart. The crankshaft and flywheel were balanced to less than one gram. There is still some very noticeable vibration at idle up to about 35mph in third gear. There are new motor mount rubbers on the sides. I am wondering what else might be causing the vibration. I vaguely remember a post awhile back with similar vibration issues and it ended up being something with the front engine mount. Does anyone remember the old post to Fordbarn about this? Thanks in advance. Ken B.
 
Inline four cylinders have an inherited vibration. They can't help themselves. Look at that throw and that crankshaft whip. And the space between the con rods. You'd vibrate too.

Probably the off-set cylinder bore of the block to the center line of the crankshaft. Could be why the rpm of the crank is limited to 2600 give or take.

skip
 
Ken,, After balancing who fitted flywheel? its posible to put on in two positions, I have known of owners here putting flywheel on after receiving engine back from balancer & because of weight left the flywheel off only fitting once unloaded & in the work shop , Engine vibrated more than usual, on removing found the correct marks, refitted ,no vibration. I run counter balanced & pull 5800 revs, smoth as a babys bottom, Another engine purchased rebuilt shook the headlights almost off. found crankshaft had 5thou bend in it. $3500 later fixed it with another crank. Derek in sunny NZ.
 
The flexable front motor mount setup is covered in the Service Bulletins page 296. The entire section is page 294 to 296.
 
Hi Ken, I have to confess that I'm very much with Derek (quickchange) on this. Excessive levels of vibration on an otherwise "balanced" engine will often be connected with flywheel mounting considerations. The slightest amount of X/Y, or Z axis runnout can cause a significant amount of vibration in your engine. While theoretically the flywheel can be mounted at any disposition on its index pins, in practice this will not always hold true. If I could get someone to do it for me, I would turn and face the flywheel ON the crankshaft, and then balance it as an assembly. That ought to set this forum humming! ... Good Luck!
 
You must log in or register to reply here.
Back
Top