[Razgrizs]

I have a 66 289. Today i hooked up a vacuum gauge to check my timing(I set it to proper timing ) and noticed the needle shaking at 20 Hg. I know a steady needle at 20Hg is a normal engine. But i dont know what a shaking needle means. Any ideas/ suggestions ?

[camloher]

could be its cold or maybe its distributor cap or a plug has gone or it could be somthing in its muffler orits just a fussy carb did you know that a holey truck avenger carb works great on the 60s models and no need to get a diff. intake manifold ttyl bye

[Razgrizs]

The car was at running teemapture, im postivie noting is stuck in the muffler, and cap and rotar have recently been replaced. Fussy carb is a possibily; are autolites 2100 fussy ? cuz thats what i have.

[kenton_90]

my 2100 works great no fussiness to it. I rebuilt it 6 months ago and thats about it.

[TheBarberShop]

Some "shaking" of the gauge needle is perfectly normal. If the sweep is more than 2-3"hg at 2000 RPM then I'd recommend a valve adjustment/inspection and top end decarbon with Seafoam. Make sure when checking running vacuum with a gauge that the PCV is plugged off. If you're not experiencing drivability issues (poor idle, bad MPG) I wouldn't worry about a slight variation in running vacuum.

[Razgrizs]

ohk, i thought the needle had to be perfectly steady. Thank you very much !

[TheBarberShop]

Perfectly steady is the ideal, but that requires a perfect carb, perfect ignition settings, and perfectly dialled-in valvetrain, all of which at once are difficult to achieve. Throw in leakdown due to wear on rings etc. and it's normal to see a small bit of shake. Vacuum should drop when you snap throttle open, rise when you snap it shut.