determining whether the flexplate has a round or oval center - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-08-2010, 03:46 PM
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determining whether the flexplate has a round or oval center

I'm going to replace the flexplate on Thursday (thanks to all the Vets out there we deserve a holiday!) and am wondering if there is a way to tell which shape the center is. I'm told it could be either depending on the year but would like to figure it out so I've got the part on hand. Again we think the 350 is a CE originally built in 68 but the car is a 78. It looks like the transmission is a THM350, from the ID guide I downloaded, if that helps.

Thanks

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Old 11-08-2010, 06:28 PM
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Round or oval center??? All 350 Chevrolet flex plates that I've seen are round..
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Old 11-08-2010, 06:33 PM
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Yea, never heard or seen an oval center flexplate.
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Old 11-08-2010, 06:55 PM
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X3 I read this earlier and thought.


Cole
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Old 11-08-2010, 07:56 PM
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If you have an oval hole in the flexplate then I agree it needs to be replaced.
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Old 11-08-2010, 09:29 PM
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ummmm....an oval is like a circle that has been squished on two sides lol, did someone have issues in pre-school? just kiddin lol
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Old 11-08-2010, 09:55 PM
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Hmm, it's not the center hole of the flex plate...

I gotta thank you all. This is the most responses i've gotten on a question. http://www.hotrodders.com/forum/newr...e=1&p=1335657#

I went out to the napa website and determined that what the guy actually told me was that the converter holes could be round or oval. For a 68 they have two and each has a comment. I copied the stuff below from their site. So, maybe what i really need to know is what are the converter holes, and can I check them before taking the plate off?

Engines : 5.7 L 350 CID V8
Transmission Types : General Motors TH350 (M38), 3 Speed, Automatic Transmission
Comments: w/ Round Converter Holes

Engines : 5.7 L 350 CID V8
Transmission Types : General Motors TH350 (M38), 3 Speed, Automatic Transmission
Comments: w/ Oval Converter Holes;Standard Duty
Per Car Qty: 1

Thanks
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Old 11-09-2010, 08:30 AM
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Are you perhaps talking about the holes used to attach the flexplate to the torque converter? The ones on the perimeter of the flexplate? Some flexplates have an 'elongated' hole on 1 or 2 of the three holes, to help with centering / alignment of the torque converter to the flexplate.
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Old 11-09-2010, 04:01 PM
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Quote:
Originally Posted by Benscamaro
I gotta thank you all. This is the most responses i've gotten on a question. http://www.hotrodders.com/forum/newr...e=1&p=1335657#

I went out to the napa website and determined that what the guy actually told me was that the converter holes could be round or oval. For a 68 they have two and each has a comment. I copied the stuff below from their site. So, maybe what i really need to know is what are the converter holes, and can I check them before taking the plate off?

Engines : 5.7 L 350 CID V8
Transmission Types : General Motors TH350 (M38), 3 Speed, Automatic Transmission
Comments: w/ Round Converter Holes

Engines : 5.7 L 350 CID V8
Transmission Types : General Motors TH350 (M38), 3 Speed, Automatic Transmission
Comments: w/ Oval Converter Holes;Standard Duty
Per Car Qty: 1

Thanks
What's the link to hotrodders for? It's a reply link


Cole
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Old 11-10-2010, 06:18 AM
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Flex plate holes

Cucumber1949,

Thank you, it was the converter holes. I just went ahead and picked one up that doesn't have the elongated holes and am told it should be fine. I'll find out for sure tomorrow.

ELOC431962,
I thought I was putting a 'smiley' in.

Thanks again for the feedback.
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Old 11-10-2010, 08:31 AM
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Either will work. I've only seen the oval holes on 153T flexplates- one hole is oval towards the crank, the other two are oval in line w/the ring gear, if you follow.

This is simply an installation aid that allows the bolts to be started easily, yet maintains the correct centering of the TC to the flexplate.

You will be fine, in any event.
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Old 11-10-2010, 08:44 AM
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Flex plate converter holes

COBALT327,

Thanks, I feel better about what I bought. It's good to know that it really wouldn't have mattered.
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Old 11-10-2010, 08:50 AM
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In case it wasn't mentioned- tighten the TC bolts up after all of them have been started. I'm thinking you already knew this, but in case someone comes across this thread, they will know, too.

And now would be a good time to check the torque on the starter bolts, the battery cable (disconnect the "+" cable from the battery first) and solenoid connections, the trans to the block bolts, trans mount, etc. Make the most of it while you're up under there!

Good luck.
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Old 11-10-2010, 09:04 AM
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Flex plate converter holes

Thanks, I read about the bolts but a reminder definitely doesn't hurt. Good point on looking at the rest of the bolts and connections. The last time I was under there, I decide to just check the oil pan and the transmission pan. All the bolts were loose on both. I shouldn't have been surprised, when we got the car there was oil all over under the hood and in the cover that goes over the flex plate and converter. The result of not tightening the valve covers after changing the gaskets. I could turn a couple with my fingers...
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