Problematic Starting - rotate crank before starter engages?

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AZ Highlander

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My 16 year old son is having a tough time getting the 78 K25’s 350 5.7L to crank and fire. He’s messed with every combo of starter shim, counted the teeth on the flex plate to ensure it is the correct starter, and all he can do is this process of turning the engine by hand, then trying to crank it. Most times it wants to grind and not turn over, sometimes it doesn’t engage, and sometimes it actually fires and starts. Any ideas for him?

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PrairieDrifter

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You need to get in there and get an eyeball on the actual gap between the bendix and ring gear. Should be about an 1/8 inch. You can use a drill bit. Wouldn't hurt to watch what it's doing while someone tries starting it. Get a visual if it's way too far away or too close.

Make sure you have the proper starter bolts with no washers. I have seen a couple instances where the gap was way too big, I wouldn't recommend but you could take enough material off the starter pad. The only other thing I can say is try another starter, what brand did you get? You said you checked tooth count already
 

75gmck25

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Also make sure it’s installed with real Chevy starter bolts. They have a knurled section that helps everything to align properly. Similar length bolts might fit, but don’t keep the right alignment.
 

fast 99

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Bad starter drive gear plus starter engagement is rough and noisy. Have been through this countless times on customer cars. Only way it will ever work and sound right is a new ring gear and starter. New starter will not engage properly when the ring is messed up. Shims should not be necessary. Use correct starter bolts.
 

AuroraGirl

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Sounds like the starter is engaging but the bendix is slipping. Have you tried another starter?
I hear the starter spinning and based on the speed it sounds like your are correct. on a small motor where its visible this is even more distinct. Bad battery connections(Id like to see or get a visual/view of all your battery cables, your setup looks like stock+ which may not cut the cheese depending on how it looks at the battery!)

Is the replacement starter a direct-drive 10mt (the kind that came with them) or a smaller PMGR starter (needs new bolts) which is superior?

Aand that of course brings us back, make sure its starter bolts and shims not any old bolts. Also some gm blocks were metric thread, is this engine a 1978 engine?
 

AuroraGirl

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AZ Highlander

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Thanks everyone. We also talked to a couple guys at the hot rod shop in town. They said to hit the flex plate with an hammer and see if it rings like a gong or not. If it doesn’t ring out, it’s broken and needs to be replaced. They also said to try a 88-98 starter instead, which I think is what Aurora Girl also recommended above. Will let you know how it goes. Thanks so much for taking a look and adding your thoughts.
 

DoubleDingo

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Hope you figure it out. Definitely report back.
 

AuroraGirl

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Thanks everyone. We also talked to a couple guys at the hot rod shop in town. They said to hit the flex plate with an hammer and see if it rings like a gong or not. If it doesn’t ring out, it’s broken and needs to be replaced. They also said to try a 88-98 starter instead, which I think is what Aurora Girl also recommended above. Will let you know how it goes. Thanks so much for taking a look and adding your thoughts.
 

staco

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The only time I have had to turn the engine by hand to get the starter to engage is when the ring gear had bad teeth in 3 or 4 spots
 

Broken85

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Check your timing. If it is to far out the starter will bind and not turn over. It will actually lock up the motor until you spin it by hand to let the starter work. Makes the starter sound like a train wreck too
 

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