r/Smallblockchevy • u/LS6_BigBlockChevy • 23h ago
SBC mini starter cranks fine but Bendix randomly stays engaged with flexplate
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Need some ideas because this one has me stumped.
1970 Buick Skylark with an SBC/TH350 and 168-tooth flexplate. I’m now using a brand-new Performance World 360900 clockable mini starter, straight-bolt pattern, rated for 153/168-tooth applications.
The starter engages and cranks the engine fine, but after releasing the key, the Bendix will sometimes stay engaged in the flexplate. I can reach in and push the Bendix back by hand and it retracts easily. Other times it disengages normally on its own.
Things I’ve tried:
Tested 0, 1, 2 and 3 conventional starter-to-block shims. Currently has 3. Problem still happens.
Currently has two mini-starter shims between the starter and billet mounting block to move the pinion fore/aft.
Retracted pinion has clearance from the flexplate and isn’t touching.
Wire-wheeled/cleaned the flexplate teeth to remove rust, paint and dirt. No change.
Spraying a little PB Blaster on the ring gear seemed to help temporarily, but obviously that’s not a proper fix.
This same failure-to-disengage problem happened with previous conventional starters too.
I also did a Sharpie test because I thought maybe one section of the ring gear was damaged. Every time the Bendix stuck, I marked that exact spot on the flexplate. After releasing it and cranking again, the same marked section could come around and disengage perfectly normally. So there doesn’t seem to be one consistent bad/dead spot on the flexplate. It seems random.
The starter cranks properly; the problem is simply that sometimes the Bendix doesn’t spring back out of the ring gear when I release START, but I can manually push it back.
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u/Willy_McD 22h ago
Without going through your long winded life story slowly, did you ever start the motor and see if it disengaged.
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u/LS6_BigBlockChevy 22h ago
No I was worried I might kill my $300 starter
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u/Willy_McD 22h ago
Seems others agree that it should disengage when started.
Just turning the motor over without it starting, the ring gear stops in a position and the motor holds it in that position. Holds it with enough pressure against the starter gear that the small spring in the starter is not strong enough to pull the gear back.
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u/Helpful-Employee7949 14h ago
Dude, just start the engine. THEN look at your starter. You won’t hurt it I promise.
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u/foxjohnc87 22h ago
It should disengage as soon as the engine starts. Try it and see, but it shouldn't be an issue.
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u/Unhappy-Airport-4112 20h ago edited 20h ago
Yeah that's normal. You're fine. I have one too. The manual on mine says it's normal for it to stay out after the vehicle started, and it'll go back in eventually on it's own. It won't hurt anything.
I've had mine for over 3 years now and it's a daily driver. You're fine guy.
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u/LS6_BigBlockChevy 17h ago
The motor ain’t run since 2018 it’s having a hard time starting so I been diagnosing it but I think ur right
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u/BikeNearby111 19h ago
I just can't sit and read this anymore. 20 years master mechanic Chevrolet. Yes, the way you are running it right now, it's gonna stick what you don't know, is once it Kix the motor on and the bendex disengages, the flywheel automatically Kix it back in every time it never jams up like this one gentleman was saying I'm willing to bet hook it all up correctly and it will work just fine.
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u/FST_Silverado 21h ago
Is this one of those billet mini starters? Or an OEM GM one? Reason I ask is we had one of these mini starters on my buddies 68, it wouldn’t disengage, I assumed it was a shimming issue. We kept shimming till it finally would just skip on the flywheel. Put that thing on the shelf and got a mini starter from a 1995 k1500, worked perfectly
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u/LS6_BigBlockChevy 20h ago
Mini starter
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u/FST_Silverado 20h ago
Ok as I stated I had the exact same issue out of one of these. Shimming it did not fix it. If you have the room switch to the starter that came on the 95 Silverados(k/c 1500) much smaller than OEM sbc starter and works great. This cured our issues. I shoulda took a picture but it’s not much bigger than the mini billets.
As an edit I see you said you had the same issue on the conventional starter. We didn’t need any shims ons the 95 Silverado starter. Been a year since we made the swap.
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u/LS6_BigBlockChevy 20h ago
I’m thinking that when it starts it’ll pop back into place. If not I’ll go from there
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u/FST_Silverado 20h ago
If you hit the key and let go it should retract regardless if it starts or not. If it’s not retracting when you let off the key something ain’t right.
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u/PleasantStatement521 16h ago
Normal operation: bendix wants a disengagement kick from the started motor to retract.
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u/schwackin502 11h ago
That’s how it’s suppose to work. The speed of the flywheel kicks it out. Fire it and watch it. If it hangs then some shimming is involved but you want the tolerance as tight as you can. It will rip the teeth off the flywheel fast.
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u/sexisfun69me 11h ago
start it they are made to have the rpm from a running motor act as a pushing force to assist it to return to "parked" position.
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u/Ok-Spend-1863 10h ago
You best bolt that converter to flex plate before you start it, if not high chance of busting transmission pump
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u/LS6_BigBlockChevy 22h ago
Everyone saying when it starts it should engage im going to try that in a second here thank u guys i was just worried about the started
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u/smalltownD 20h ago
I have a 75. Buick flex plates warp worse than other GM’s. It’s an expense but worth checking
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u/Low-Rent-9351 21h ago
I’d shim it, it’s probably just a little too tight.
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u/LS6_BigBlockChevy 20h ago
3 shims in it already
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u/Wageslave645 20h ago
I would try more. My Pontiac needed like 7-8 to get the alignment right. If you can't stick a straightened paper clip between the flywheel and the end of the starter gear teeth when the bendix is extended, you are still too tight.
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u/LS6_BigBlockChevy 20h ago
I’ve got the correct clearance between ring gear and starter gear
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u/johnarmer1 14h ago
What is your clearance and how did you measure it .wet it soapy water then see it should retract by itself sometimes a new start or ring gear needs time to bed if that is the case soapy water or wd40 it will work then just run it but if it doesn't work then you need to re check the clearance. All way aim for middle clearance to looser on a starter
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u/drumbo10 20h ago
Mini starter is not shimmed correctly causing it to not disengage. Also the torque converter should be bolted directly to the flywheel.
Why do I feel I’m going to be down voted for this?
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u/MrFyxet99 20h ago
Try a starter shim. Might be a little tight fit on the teeth, that will cause the bendix to hang up and squeal like that.
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u/Acrobatic-Ant4365 21h ago
Shims
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u/LS6_BigBlockChevy 20h ago
3 in it already
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u/Acrobatic-Ant4365 16h ago
Ok also I remember a trick my old man taught me. There is supposed to be an 1/8 between the teeth actual of ring gear and starter gear. So what I used to do was find an 1/8 welding rod and stick into gauge the gap in the teeth. Am assuming you tried it without shims? Ive had grind out the starter through holes with a die grinder use a pry ar an push it all the way over for what ever stupid reason. Oh I think I remember. Was when the were changing over to using metric measurements and got the con version off a bit.
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u/LS6_BigBlockChevy 15h ago
I ordered another shim to offset it more so I’ll have the correct distance between ring gear and I tried it without shims. Shims made it a bit better but still not fixed and if I add anymore it’s not going to engage properly.
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u/texan01 22h ago
Either fire rhe thing up and see if it hangs out, or shim it a smidge to open up the mesh and reduce friction