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Kaegi,
No balancer, but I've often wondered if they would be a good addition. Were they used on all of the passenger cars?

Andy

it shouldn't matter. it wont fix a problem. they were used on lots of the cars but not sure all had them they made these engines from the 30s to as late as 80 so you see all different combos of pulleys. do you have a dwell meter? maybe points are closing up on you.

I have a pertronix in the truck.

If this thing does have a miss it's a sneaky one, there's no power loss and the AFR is normal.

ashyers wrote:I have a pertronix in the truck.

If this thing does have a miss it's a sneaky one, there's no power loss and the AFR is normal.

whats AFR? I never converted to electronic. heard of too many failures of pertornix. especially in hot conditions. points don't care how hot it gets. And I know how to use a dwell meter. ;/)

AFR is short of Air Fuel Ratio. We have an O2 sensor on the dyno so I can keep an eye on the mixture. Its response is quick and will usually show a miss.

As far as the points vs. pertronix, I have not had any issues with the pertronix and it is kind of nice not to have to set the dwell . It is more tolerant of any shaft wear and is easier on the dizzy bearings, plus it won't bounce when I'm winding things up to 3000 RPM!

I sure hope this issue is not something in the bottom end.

ya this is a strange one. let us know what you find. points don't bounce..... ;/)

Points WILL bounce, or rather float. But not at the paltry rpm these engines can muster.
Did you change the clutch and cover? If so, maybe the cover is not in balance. (Pressure plate)
Is the exhaust solid or compliance mounted?

just me wrote:Points WILL bounce, or rather float. But not at the paltry rpm these engines can muster.
Did you change the clutch and cover? If so, maybe the cover is not in balance. (Pressure plate)
Is the exhaust solid or compliance mounted?

I knew you were kidding about hte flathead. ;/). cheap or worn out points may float but I used to shift my big block at 7K and never had any float. would still be making power a spin the tire shifting into high gear at 95. I used accell hi perf points in that one. they have a bit higher tension spring than average.

I won't have time to play with the truck over the next few days, but here's what I'm thinking:
*remove the belt and run briefly at the vibe's RPM
*loosen the engine mounts & steering shaft and allow things to "float" then torque 'em back down
*run the engine at the vibe's RPM and short out one plug at a time and see if there's an effect
*drink egg nog and contemplate next steps

What bugs me is that this came on quickly.

Thanks again for the help and Happy Holidays!

Andy

Was there a bang before the vibration started? Like throwing a poorly welded balance weight?

any chance the belt got saturated with antifreeze? that can result in sounds and vibrations that seem like catastrophic bearing failure. if antifreeze got on belt pour some black coffee on belt when running or spray with brake clean when running and see if it goes away temporarily

just me,
No bang. I'm wondering if something shifted and is now transferring the vibes to the left front frame rail.

Kaegi,
The belt's fine, but I'm curious about the black coffee. Why black coffee?!

Andy

black coffee because that's what I have in my hand a lot and it is acidic (cleans the belt) and will stop a squeaking belt for a minute or 2. sometimes will stop it for good. and it wont hurt anything. less expensive than brake clean!

Clutch linkage is about the only thing connecting the engine to the laft rail.

bad rubber mounts ?