Help Diagnose Starter Problem

[adis]

I've got a starter problem on my sbc400. it's a rebuilt starter that I just bought. when i turn the key the solenoid engages the pinion, the starter motor turns and the fllexplate (FP) turns about one rotation (sometimes a bit more, sometimes a bit less) then abruptly the the FP stops rotating, as does the pinion, but the starter motor keeps spinning. The pinion continues to be engaged in the FP until I turn the key, at which time it snaps back.

Video here: https://youtu.be/A1fHLSCI_hc

If I keep trying, after about 25 bumps, I can get the engine to finally turn, and it idles fine. It's a new HEI dizzy, I set initial at 12*, mechanical at 34*@2800, and vacuum at 46*@3000. I took apart the starter, and the bendix/pinion seems to be OK - one-way clutch works, the threads on the shaft appear fine. teeth on the pinion are neat. I volt checked the batter terminals, ~11.5V, ~10V under load. I checked the battery terminal on the starter (the big one) ~10V under load. It's a new flexplate, Scat brand supposed to be slightly thicker steel, stiffer than stock.

I;m inclined to think that it's "starter drag" that I've read about on other sites. Doesn't seem to be electrical - seems to be mechanical. After about one rotation the engine just won't let the starter turn. It doesn't kick back, but it did when I first installed the dizzy, and hadn't set the timing yet.

Any thoughts, opinions are appreciated - this is driving me crazy. Thanks - mark

[adis]

Another video of my flexplate turning

https://youtu.be/QAIBgE6RoOc

<iframe width="560" height="315" src="https://www.youtube.com/embed/QAIBgE6RoOc" frameborder="0" allowfullscreen></iframe>

[starterman99]

The drive cluch is slipping in the starter. If you just bought the starter you should exchange it for another. If it is not under warranty buy a new drive and install it in the starter.

[adis]

Thanks for the reply, Starterman. looking at the cost of drive clutches, i'll just go with a new starter. i'm curious if you think the DC failure was the root problem or the result of something else? Do DCs fail all that much, especially in a new unit?

ill put in the new starter, but i think ill also retard my timing some. my engine is stock, and factory tune up specs say 4* initial timing. right now, mine's closer to 13* i did this because, running, the engine doesnt seem to mind, and everyone seems to say that SBC perform better at about 12* initial. thanks again! - mark

[VetteVet]

Looking at your video I thought about too much timing as well. 10 degrees seems to be the factory recommended setting if I recall. I would try retarding the timing before I invested in a new starter.

[adis]

well, i tried adjusting the timing and no improvement. so i installed a new starter and voila - turns perfectly. starterman, you were spot on. once the new starter was in i could hear the problem. originally, i thought the sound coming from the pinion was simply the sound of the gears engaging each other, but the buzz of the new starter sounds noticeably tighter than the ringing/scraping sound of the old one. thanks for everyone's help! - mark