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Author Topic: Stripped Flexplate Bolt  (Read 6269 times)

Offline Jon87V20

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Stripped Flexplate Bolt
« on: February 11, 2017, 08:01:27 pm »
I've been able to get five of the six bolts out of my flexplate. However, the sixth one is somewhat stripped (I can get the socket/end wrench to bite on it but when I apply force it it rolls off.

Does anyone have any experience with those Irwin bolt extractors? I wouldn't mind paying the $20 for an extractor kit since I know I would probably get a lot of use out of it over the years, but I only want it if it works well.

My other thought was to try pounding a socket that's one size smaller on there (13mm instead of the usual 14mm) with a hammer and then try to break it loose with the torque wrench since it's not completely rounded off. I might be able to borrow my buddy's little electric impact wrench too.

Any other ideas besides drilling it out? I'd rather not drill it if possible. I'm pretty sure an easy out type set won't work because it's probably too tight for that too.

'87 Chevy Suburban V20
350ci TH400 NP208

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1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline LTZ C20

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Re: Stripped Flexplate Bolt
« Reply #1 on: February 11, 2017, 08:21:48 pm »
Have you tried a 9/16th. I don't believe they started using metric bolts on the engines until a little later, in 87, they might still be standard. That could be why it's slipping, those metric sizes that are interchangeable with standard sizes are always exactly the same, especially when the the quality of the tool being used is low. Just a thought.
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Offline bd

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Re: Stripped Flexplate Bolt
« Reply #2 on: February 11, 2017, 09:08:20 pm »
Can you post a clear pic of the bolt head?  Were you using a 6-point or 12-point socket? 

Apply some PB Blaster and heat the bolt head with a propane torch.  Let it sit for a few hours and repeat.  Repeat this cycle of dousing with penetrant and heating half-a-dozen or more times over a 24-hour, plus, timeframe.  Then after applying penetrant and heat, use a new 6-point impact socket if the bolt head hasn't been completely obliterated (or one of the more aggressive stripped bolt head removers) in combination with a 1/2"-drive impact driver and large hammer to try and break it loose.
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Offline VileZambonie

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Re: Stripped Flexplate Bolt
« Reply #3 on: February 12, 2017, 08:00:26 am »
Are you talking about the bolts in the crankshaft?
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Offline Jon87V20

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Re: Stripped Flexplate Bolt
« Reply #4 on: February 12, 2017, 07:08:10 pm »
9/16 felt a bit more sloppy on them so I tried the 14mm and it seemed to fit a lot better. I'll get a picture up asap.

I was using a six-point.

Vile, yeah I'm talking about the bolts that attach the flexplate to the crankshaft.


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350ci TBI TH400 NP208

Offline Dr_Snooz

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Re: Stripped Flexplate Bolt
« Reply #5 on: February 12, 2017, 11:03:40 pm »
I had good luck with the bolt extractor sockets from Harbor Freight. I was dealing with basically the same situation you are, half-rounded off bolt that slipped off when I got on it. Only difference is that mine was a bell-housing bolt tucked down between the engine block and firewall. I needed the extractors on a Saturday and HF was open, so I got them. They took the bolt out on the first try like it was no problem. I don't know what I would have done if they hadn't worked.
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Offline Jon87V20

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Re: Stripped Flexplate Bolt
« Reply #6 on: February 13, 2017, 04:12:25 pm »
Thanks, Dr. Do you remember what brand they were by any chance? About how much they were?


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Offline gunrac

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Re: Stripped Flexplate Bolt
« Reply #7 on: February 13, 2017, 06:41:31 pm »
Pittsburgh tools, I think is all they sale. They will replace if broken.
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Offline Jon87V20

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Re: Stripped Flexplate Bolt
« Reply #8 on: February 13, 2017, 07:50:21 pm »
Ok. I think I'll have to go the extractor route. I've been trying and trying today to get that thing out and it refuses to budge. Now I just have to hope the bolt head doesn't snap off.

If this thing does snap on me and I can't get the bolt out, how bad is it to only run 5 out of the 6 bolts in there? Will that cause balance issues that could affect anything?
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Offline Dr_Snooz

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Re: Stripped Flexplate Bolt
« Reply #9 on: February 13, 2017, 08:19:36 pm »
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Offline VileZambonie

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Re: Stripped Flexplate Bolt
« Reply #10 on: February 14, 2017, 07:18:54 am »
Weld a nut on there and draw it out. If you don't have a welder Use the grip sockets. Do not run it with a missing bolt
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Offline Jon87V20

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Re: Stripped Flexplate Bolt
« Reply #11 on: February 18, 2017, 10:57:06 am »
Is it bad practice to re-use old bolts (not the damaged ones of course)? Or is it okay to reuse the old ones?
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Offline VileZambonie

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Re: Stripped Flexplate Bolt
« Reply #12 on: February 18, 2017, 12:18:13 pm »
You can purchase a whole set at the auto parts store. Replace them

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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline Jon87V20

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Re: Stripped Flexplate Bolt
« Reply #13 on: February 20, 2017, 01:36:39 pm »
Update: I was able to get that bad bolt out using a cheap set of extractors I got at Harbor Freight. I bought some new ones at the auto parts store. Got the main seal in there and so far no leaking!
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Offline LTZ C20

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Re: Stripped Flexplate Bolt
« Reply #14 on: February 20, 2017, 01:37:40 pm »
Quote from: Jon87V20 on February 20, 2017, 01:36:39 pm
Update: I was able to get that bad bolt out using a cheap set of extractors I got at Harbor Freight. I bought some new ones at the auto parts store. Got the main seal in there and so far no leaking!
Very good!
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