68 302 shakes badly at idle.

Ok I have a 68 302 in a 80 Mustang did a T5 swap from a auto. After finally getting everything I need and finishing it when I start it it shake something horrible at idle (between 800-1100rpms) After that it runs smooth as can be all the way through each gear.

My first thought was balance since I changed out the flywheel. I need a 28oz fly for a 68 so I picked up a fly from a 63 fairlane 289. THAT'S ALSO 28OZ RIGHT? To double check I took a look at the flex plate casting #'s got a C5AE which I believe is a 65 generic full size ford. ALSO A 28oz RIGHT?

What can it be? after 1100rpm its smooth all the way to 5500rpm haven't gone any higher don't see the need to.


Help! Having problem after problem.
Tyler

Chrome_Rust said:

did a previous owner change the rotating assy. in the engine to a newer 50oz balance? if you have another flywheel, I would swap it in and check to see if it is better. I know that you can only put the flywheel on one way, but maybe there is a flaw in the one you have. Just an idea.

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IDK but the flexplate that was in there had the C5AE code so I'm like 99% sure it a 28oz. But the flexplate has 2 other weights welded on for a total of 3 it could have been rebalanced.

Is there a way to look at the damper (harmonic balancer) to see what balance it is? Like a casting code or stamped 50oz or 28oz.

Vacuum leak. Fixed. Thanks