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Flexplate problem

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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2021 at 6:47pm
Imo, its better to go with what was given, any M11 or m12 flexplate will work, since you are having it rebalanced. To limit it to a 390 and 69 of all things, is greatly limiting your options, if trying to get it done ASAP.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
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Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dgordner Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2021 at 7:40pm
Ok. Thank you
Safety is only what one makes of it!!! 1969 chevelle SS 1970 Elcamino SS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dgordner Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 8:11am
Can I have your phone number to talk to you. 
Safety is only what one makes of it!!! 1969 chevelle SS 1970 Elcamino SS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 8:34am
Originally posted by 304-dude 304-dude wrote:

Imo, its better to go with what was given, any M11 or m12 flexplate will work, since you are having it rebalanced. To limit it to a 390LOL and 69 of all things, is greatly limiting your options, if trying to get it done ASAP.

Tag, you're itLOL
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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 8:43am
Originally posted by Heavy 488 Heavy 488 wrote:

Originally posted by 304-dude 304-dude wrote:

Imo, its better to go with what was given, any M11 or m12 flexplate will work, since you are having it rebalanced. To limit it to a 390LOL and 69 of all things, is greatly limiting your options, if trying to get it done ASAP.

Tag, you're itLOL


Ha! I did not expect it. Just tried to simplify, the over thinking of what is going on. Down and Dirty should pop up with a link or two on what he has available.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dgordner Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 8:48am
May I call you to discuss?  Don
Safety is only what one makes of it!!! 1969 chevelle SS 1970 Elcamino SS
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SC397 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 9:23am
Originally posted by dgordner dgordner wrote:

I am putting an m12 from a 69 390 behind my 70 304. My flexplate from the 304 has 6 mounting bolts for the converter. I have a 390 torque converter that has only 4 mounting bolts. It is my understanding That I must use the 304 flexplate because of balance. What can I do to mount the 390 converter to the 304 flexplate?  Help would be great!!!!
  
You need a flex plate from a 343 and have it match balanced to the 304 flex plate that is original to the engine.  If you can't find a machine shop to do that locally, send it to me and I can get it done for you.
Any flex plate that bolts to the M11/M12 will work but the one from a 343 will be the easiest to find. 
I will sell you one for $50.00 if you can't find a cheaper one.
003 by Rick Jones, on Flickr


Edited by SC397 - Jul/25/2021 at 2:56pm
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sweatlock View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 9:37am
As 304-Dude points out, Down & Dirty Dan’s has a ‘small hole’ flexplate available for a 343/360 V8 (Dan is not sure which) which would would work with an M11/M11B/M12 Borg Warner transmission. Get it match-balanced to your original(?) 304 flexplate and you should be good to go. 

Basically, you’re trying to do something that’s not impossible but was not done by the factory - the 290 V8 was mated to an iron-case M11 only in the ‘68 & ‘69 AMX; for all other applications it was attached to an aluminum case BW M40. The 304 debuted in ‘70 and was not an option in the AMX; the only engine options fof the ‘70 AMX were a 360 or a 390. If you bought a ‘70 Javelin with a 304 it got an aluminum case BW M44. So a 304 mated to an iron-case Borg Warner M12, the strongest automatic transmission offered by AMC/Borg Warner from ‘68 to ‘71, designed to go behind torque-monster 390 & 401 V8’s, is a bit unusual. Just be aware that there will be more drivetrain power loss with the M12 than with a smaller trans. 

Oh, and I’m rubber you’re glue, everything bounces off me and sticks to you. 


Edited by sweatlock - Jul/25/2021 at 9:39am
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SC397 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 9:45am
Yes, I know this.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dgordner Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2021 at 12:37pm
May I call you or you call me. 570-515-0379 evenings after 5 or anytime on weekends 
Safety is only what one makes of it!!! 1969 chevelle SS 1970 Elcamino SS
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