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#1 |
Senior Member
Join Date: Jun 2003
Location: Westminster, CO
Posts: 3,071
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Need some help with Flex Plate questions...Please.
Ok...converting from 3 on the Tree....Not that TREE.....kidding... Let me rephrase....So I'm changing from a 3 speed trans to a 700r4 trans. Engine had a flywheel of course...the question is: How do I determine if I need a 168 tooth flex plate or a 153 tooth flex plate??? Those two seem to be the popular ones for a 350... which I have in this truck. Thanks guys!
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Alex 1971 Lil' Red 350 SBC 700R4 |
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#2 |
Registered User
Join Date: Feb 2002
Location: Vacaville, CA
Posts: 2,746
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Which starter bolt pattern do you have? The staggered bolt pattern goes with the 168 toothed plate and the 153 toothed unit has the straight bolt pattern.
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#3 |
Senior Member
Join Date: Jun 2003
Location: Westminster, CO
Posts: 3,071
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Don't really know the starter bolt pattern....looks like there is 3 bolt holes for the starter forming a squished triangle....Block stamp # 3970010 oil dip stick on the driver's side
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Alex 1971 Lil' Red 350 SBC 700R4 |
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#4 |
Registered User
Join Date: Oct 2004
Posts: 393
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If you had the motor behind the 3 speed, why not count the teeth on the old flywheel, then get the same tooth count on the flexplate.
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#5 |
Registered User
Join Date: Feb 2002
Location: Vacaville, CA
Posts: 2,746
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I think all blocks have three holes but the starters have two, straight across or diagonal (staggard). Do you not have the starter? If you have to get a new one take your pick just get the flex plate that matches.
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#6 |
Senior Member
Join Date: Jun 2003
Location: Westminster, CO
Posts: 3,071
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Does that work???? and ahhhh had no motor behind the 3 speed...but did have a 350 in FRONT of it. LOL!!!
Starter is long gone...soooo now what?
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Alex 1971 Lil' Red 350 SBC 700R4 |
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#7 | |
Registered User
Join Date: Oct 2004
Posts: 393
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Quote:
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#8 |
"Ochre Ogre"
Join Date: Apr 2000
Location: Springfield, MN
Posts: 3,558
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If I am understanding what you have asked you would need a 168 tooth flex plate. The starter that was on your 3spd manual wouldn't be the one to use after the swap. Manual transmission starters have a different nose cone.
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#9 |
Senior Member
Join Date: Jun 2003
Location: Westminster, CO
Posts: 3,071
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So what I'm hearing ..is just get a starter and flexplate that match that are for a SBC and I will be good to go. In that case...don't I have to get a smaller starter for the 700r4 anyway?
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Alex 1971 Lil' Red 350 SBC 700R4 |
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#10 |
97' Tahoe 2dr/2wd
Join Date: Jul 2002
Location: Huffman,TX
Posts: 1,168
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if your going to buy an starter and flywheel, just get the ones that match. i usually go to the auto parts and tell them different years of vehicles that i want my parts off of.
just get the starter and fexplate for the same vehicle. make sure you get the right flexplate, some have a weight on them (externally balanced?) like for newer model 350s (i think the first one i tried was a 91 chevy truck, it had this weight on the flexplate, and wont work with an internally balanced engine) i think i ended up getting a flexplate and starter for a 76' 1/2 ton 2wd thats what i used for my 350, and 700r4 combo. the bolt pattern for a th350 and 700r4 torque converters are the same (correct me if i'm wrong). also be sure to take the old pilot bearing/bushing out of the end of the crankshaft, sometimes the torque converter wants to hit it if its left in there. time for another beer. |
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#11 |
Registered User
Join Date: May 2003
Location: Shreveport LA
Posts: 3,170
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A 168-tooth flywheel is 14" in diameter. Counting teeth will drive you nuts.
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#12 |
Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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If you need a starter also the only issue's would be what size torque converter and what 350 you are using. Most flexplates are drilled for 2 most common sizes 9.75" and 10.75" torque converter and is the 350 a 2 piece rear seal '85 and earlier or a 1 piece rear seal '86 and later, The crank is a different size. Then buy the flexplate for your application and a starter to match. I think the 153 tooth flexplates are 12.75" and the 168 tooth are 14" in size.
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#13 |
Watch out for your cornhole !
![]() Join Date: Jun 2003
Location: Azle, Texas
Posts: 14,162
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If it's a pre 86 engine, that is 2 piece rear main seal engine, the most common flexplate is the bigger one. Pioneer part number FRA-100, available at most any parts store.
It's common enough that most parts stores will carry 5 or 10 in stock at all times.
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#14 |
Senior Member
Join Date: Jun 2003
Location: Westminster, CO
Posts: 3,071
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Thank you all very much for your help. Engine is pre 86, so it must have a 2 piece rear main seal so 168 tooth it is. Thanks again guys!!
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Alex 1971 Lil' Red 350 SBC 700R4 |
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#15 |
Registered User
Join Date: Feb 2000
Location: Center City, MN, USA
Posts: 3,254
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Don't forget to get shorter flywheel to crank shaft bolts. The ones you got now will be too long with your new flex plate.
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#16 |
Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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Measure your torque converter. The 14" flexplates were drilled for the 10.75" and 11.5" converters from trucks with big TC in th400's. The 1 piece seal engines have a 3" crank mount and the 2 piece seal engine cranks are 3.58". So the TH700r4 might be 9.75 or 10.5 depending what it came out of. Just a note powerglides used the 9.75" holes.
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72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
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