[Guest]

It's my understanding that 289/302s are completely externally balanced, with the flywheel weights & the harmonic dampener. If this is the case, what would cause this same engine to vibrate at 4000 rpms or so? I've got a 302 engine that, with no tranny connected to it, has a vibration that is progressively worse at higher rpm's. I'm sure that the correct flywheel is on the engine, and the harmonic balancer looks to be in good shape (other than cracks in the rubber or metal, I don't know how to tell if it's good). So, I'm puzzled as to what would make this engine vibrate. Is there an RPM threshold that is going to have vibration regardless - in other words, is it simply a limitation of the engine that anything over 4k is going to be a progressively worse vibration? Or is there something else going on here? For the record, the engine doesn't use any oil and has about 50k on a rebuild. There's no knocking sounds coming from inside.

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[390fastback]

These engines are not totally externally balanced, after '82 they were internally balanced, or vice-versa. Anyway, it could be the balancer is about to go and trust me you don't want that. When mine let go it broke the crank in two, pulled the front main bearing cap bolts out of the block (the bolts didn't break), split the block down both sides, etc.... The only salvagable parts were the intake and carb. You can get a diferent balancer from a wrecker fairly cheep just to check. Its better to spend a small amout instead of a large amount of money.

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68 fastback, 390 4V premium fuel
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[camachinist]

Stock balancing is....well....a less than exact science....

Add to that a complete new stack of imbalances from replacement oversize pistons, crank journal grinding, rod-resizing, etc....and you have a recipe for exactly what you describe...

Yeah, it could be the balancer is going....you can always get that done over at Damper Doctor....BTW, is the balancer the wide 302 one with the differing thicknesses on the outer ring? If so, how do the timing marks line up? Could be outer ring (and imbalance weight) slippage....

That's all I can come up with tonight....time for beddie bye...

Bye, Bye...*G*

Pat
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[mstngjoe]

Check FORDMUSCLE.COM archives for an article on vibrations.

65 FB "J" 302 lots of mods. 94 GT K&N only.
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[whisperer]

The fact that there is no torque converter bolted to the flexplate (I'm assuming?) means that there is effectively no flywheel on the engine. This will not make it unballanced, as the weights are on the flexplate, but it sure will vibrate. The torque converter is where most of the "flywheel" weight is in an automatic car. On a stick car, of course there is an actual flywheel, and the engine will run smooth on a stand, (or in the car with no trans). When I had my old test stand I had an assortment of stick flywheels that I could install for testing new engines. (all the old take-offs with bad clutch faces.....hehe).

It should not hurt the engine to run it with no torque converter as it is still in ballance. However, every time a cylinder fires it will shake.

Did this same engine "vibrate" when the trans was installed?

Hal
Love hard, drive fast, wear your seat belt.

PS, that's my 'bird...... My Mustang is too ugly to take pictures of yet........*G*.

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[Dean_T]

I believe the flywheel/flexplate balance changed from 28oz to 50oz in '82. I think the 302 is still "externally" balanced like the 289 - both are balance internal and external.


Dean T

Shikatta Ga Nai - "It cannot be helped"

 

[dickson]

Wish I could offer some advice. Good luck.

Glad I just got a new (if stock) aftermarket damper for my 289. Cheap insurance - Dickson

1965 GT fastback
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