340 vibration

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dust-u

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seems I have a vibration in my motor I am trying to locate.. its there either idling or under power.. thought it was power steering.. now manual.. clutch.. brand new.. trans rebuilt.. new cam, and heads.is it possible the damper slipped? any suggestions?
 
What year? What is the history of the car? Vibration can be caused by numerous things, it's just a process of elimination, starting with the most info possible
 
Early 340 or 318 or 273; a slipped damper ring would not cause this, unless the ring was getting ready to fly off. Late 340 or 360 could cause this.

So what engine? Is the manual trans new and did this replace an auto trans setup? Engine rebuilt?
 
There is no "balancer" on a 273/318/340 when you think of weights as they are all neutral balanced. The cast 340/360 had weight added on their dampers to offset the lighter weight of the cast crank and the heavier rods. I would suspect the flywheel as that has the most mass, then the clutch if its a balance issue. Have you indexed the crank to the bellhousing? Even the slightest off center will cause the clutch to seek its center every revolution, like a warped driveshaft. 4sp guys could chime in and tell you what the tolerance is. It would manifest itself under "in gear" condition only as a freewheeling clutch would just spin in there.
 
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And FYI the cast crank 340 does not use the same balancer as the 360.

What cam? What engine mounts? Engine build and flywheel used? Vacuum reading at idle?
 
Not enough information. Are you sure all the plug wires are where they are supposed to be?
 
dano said:
And FYI the cast crank 340 does not use the same balancer as the 360.

What cam? What engine mounts? Engine build and flywheel used? Vacuum reading at idle?
Click to expand...
yeah, I should have said "their dampers" ...corrected.
 
lets see... 72 340..original motor to the car. converted to manual trans many ys ago.30 over. balanced and blueprinted 12 to 1 slugs. ported x heads , 4 sp 391s. using the same flywheel it had when motor was built.. as is the balancer. has 68 cast iron bell.new centerforce clutch. motor mounts new, trans rebuilt.comp cams 491 lift cam(forgot #) new pilot bushing.runs 10 in vacuum . 770 holley street avenger on ld340 manifold. accel dist, Mallory ign box . new blue streak wires. firing order is correct?have not replaced trans mount, but it looks ok...
 
IIRC the later '72 340 had the imbalanced damper, so if it slipped, it would cause a vibration like you suggest. If you look at the damper, the imbalance is obvious.
 
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