406 SBC starter problems

[J_Garry]

So here’s a little background before I get to the meat and potatoes. I have a 1988 Monte Carlo SS with a 406 with the 200 4-R transmission. Some of you may look at that and be surprised with that combo, yeah so am I haha. I bought the car a year ago and they guy had given me a TH350 to go along with the car. So it wasn’t a bad deal. Just need to find some time to get it all together.

Now here’s my problem. A few months down the road I noticed there was an issue. I go to start up the car and I heard this loud grinding noise. I assumed it was a bad starter. It was a Proform OEM style starter with the staggered mounts. So I bought a Powermaster XS Torque starter. So I thought great I can get the ball rolling here. Starter arrived and we shimmed the nosecone and we clocked it so it would pass the header. Installed back into the car and I go to fire her up and she sounded great, no grinding. Next day I fire her up and I hear the grinding. I couldn’t understand it. So at this point we decided to shim the bolts as well. We did, fired her up and she sounded great. A couple months down the road I fired her up again and I hear the grinding. So at this point we take the shins out from the bolts, along with the shins from the nosecone. We did that, installed the starter back into the car and she once again, sounded great. Literally the next day I decide to fire her up and I again hear the grinding.

At this point I don’t know what to do. I’ve been searching around forums online for months and I haven’t found an answer to my problem which brings me here today. Has anyone ever had this problem with their 400/406 SBC? I’ve heard that this is perhaps a common issue with the 400’s? I’m not too sure how true that is. But please, if anyone has a solution please come forward haha. Any input would be greatly appreciated. I hope someone can help me out. Thanks,
Jordan

 

[pontiacgp]

have you inspected the flex plate teeth?

 

[J_Garry]

have you inspected the flex plate teeth?

Thanks for the reply man. On the starter bolted into the car, I slid the drive and it would engage into the flywheel at a pretty good depth. Now this is after we took the shims out from the nosecone and the shims from the bolts. Now regarding the flex plate, the teeth now are certainly getting torn up. And there’s also a chip on the stater drive. So yeah I mean we could replace the flex plate, but who says I won’t have the same problem? This is pickle I’m in haha

 

[79 USA 1]

The starter attachment bolts were tight each time you removed them to adjust the shims correct? I have a 406 in my 79 Monte Carlo with the factory high torque starter and have never had any issues.

 

[pontiacgp]

Thanks for the reply man. On the starter bolted into the car, I slid the drive and it would engage into the flywheel at a pretty good depth. Now this is after we took the shims out from the nosecone and the shims from the bolts. Now regarding the flex plate, the teeth now are certainly getting torn up. And there’s also a chip on the stater drive. So yeah I mean we could replace the flex plate, but who says I won’t have the same problem? This is pickle I’m in haha

you had 2 starters develop the same problem so the only common part is the flex plate. If some teeth on the flex plate are chewed up that would cause the teeth on the starter to chip and after a few starts you'll get the grinding.

 

[J_Garry]

The starter attachment bolts were tight each time you removed them to adjust the shims correct? I have a 406 in my 79 Monte Carlo with the factory high torque starter and have never had any issues.

By eye it doesn’t look like the starter has moved out of position. Never loctited the bolts but made sure they were tight every time

 

[pontiacgp]

If you end up changing the flex plate I used to use two long bolts on the second bolt from the top for the bell housing so I could slide the transmission back enough to get to the bolts for the flex plate. It saves a bit of work putting the transmission back in

 

[lilbowtie]

Check the flex for cracks - could be moving.

 

[J_Garry]

you had 2 starters develop the same problem so the only common part is the flex plate. If some teeth on the flex plate are chewed up that would cause the teeth on the starter to chip and after a few starts you'll get the grinding.

The original I had, the Proform, when it had stopped, the flexplate looked fine when we had taken that out. We even rotated the flexplate and it looked fine

 

[J_Garry]

What about a thrust bearing on the crank? My dad had some experience with a Ford 302 and it was badly worn. The crank would walk and it would tear the rear main seal. But oddly enough it did start....quietly haha