Help Diagnose Starter Problem
 

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

Re: Help Diagnose Starter Problem
 

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>

Re: Help Diagnose Starter Problem
 

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.

Re: Help Diagnose Starter Problem
 

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

Re: Help Diagnose Starter Problem
 

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.

Re: Help Diagnose Starter Problem
 

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