Flexplate for 200R4 conversion question
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Flexplate for 200R4 conversion question
Hi, I have a rebuilt 200R4 sitting waiting to be lifted into place to replace the TH400 behind my SBC 350 but now find that the flexplate holes wont line up with the torque converter. My question is should I have bought a special torque converter for this swap or would it be easier to change the flexplate now? The torque converter came with the trans and is new.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
What is probably going on is that you have the wrong TC. TH200R4 trannies are from later model chevy and pontiac motors. The later generation motors of course had different flex plate bolt patterns.
You just need to buy a Gen I small block 200R4 TC
You just need to buy a Gen I small block 200R4 TC
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
That is my suspicion too but on this side of the world it might be easier to source a flex plate but did one exist that had the bolt pattern to go from Gen 1 engine to the later TC that I think I have? Not very impressed with the whole shebang now as I bought it through an intermediary for shipping purposes) from a company in Florida and they were supposed to know it was going behind a Gen 1 engine. What I thought was going to be a 2 day conversion has now had the car sitting on the hoist for 5 weeks:-( Every time there is a hold up like this the mechanic gets diverted to other work and my job goes to the back of the queue again.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I went to " chevy flex plates summit racing" and then on the summit site just called up B&M You can see in the pictures that Gen I two piece rear main seal flex plates are the same as the One piece rear main Gen II motors.
Then you have the liter class LS motors and the flex plate bolt holes are completely different.
I was working on a 2001 firebird with a 200R4 tranny and I noticed that the flex plate and TC were a different bolt pattern than the old school motors like ours.
Look up the site above and you see if that is what you have for a TC bolt pattern
this is an LS flex plate
http://www.summitracing.com/parts/bm...make/chevrolet
this is our 2 piece
http://www.summitracing.com/parts/bm...make/chevrolet
Then you have the liter class LS motors and the flex plate bolt holes are completely different.
I was working on a 2001 firebird with a 200R4 tranny and I noticed that the flex plate and TC were a different bolt pattern than the old school motors like ours.
Look up the site above and you see if that is what you have for a TC bolt pattern
this is an LS flex plate
http://www.summitracing.com/parts/bm...make/chevrolet
this is our 2 piece
http://www.summitracing.com/parts/bm...make/chevrolet
Last edited by gkull; Feb 13, 2014 at 02:41 PM.
Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
gkull is right, you need a dual bolt pattern flexplate. this is the one i used when i did my 200-4r conversion last year. Summit racing brand.
http://www.summitracing.com/parts/su...make/chevrolet
http://www.summitracing.com/parts/su...make/chevrolet
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Flexplates for SBCs have the following variations:
1. Crank bolt circle - pre 85 or 85 up for SBC.
2. Diameter/# of teeth (153 or 168) - and as you know they take different starters
3. Bolt circle diameter for bolting up the torque converter - your best bet is one that has two bolt patterns
4. Weights - only 400 small blocks have a weight, pre 85.
Aluminum Powerglide, TH350, TH400, 200-4R, and 700-R4 all have similar flexplates and all can have the above variations.
1. Crank bolt circle - pre 85 or 85 up for SBC.
2. Diameter/# of teeth (153 or 168) - and as you know they take different starters
3. Bolt circle diameter for bolting up the torque converter - your best bet is one that has two bolt patterns
4. Weights - only 400 small blocks have a weight, pre 85.
Aluminum Powerglide, TH350, TH400, 200-4R, and 700-R4 all have similar flexplates and all can have the above variations.
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Drifting
Joined: Dec 2004
Posts: 1,714
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From: Austin Texas
Here is a pic. This is like the one that was on the 74 / TH400 I have. This is a duel pattern and it is up against a D5 converter for a 200-4R. The TH400 used the other set of holes.
Notice how the other set of bolt holes is in the same triangular pattern but the bolt holes are just a tad bit closer to the outer ring.
Does that help any? If your flex plate is like this one and its in the car you may need to turn the motor by hand to test the other set of bolt holes.
What year is your car?
Notice how the other set of bolt holes is in the same triangular pattern but the bolt holes are just a tad bit closer to the outer ring.
Does that help any? If your flex plate is like this one and its in the car you may need to turn the motor by hand to test the other set of bolt holes.
What year is your car?
Last edited by johnt365; Feb 13, 2014 at 08:51 PM.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Thanks guys, yes the bolt pattern is the old one which I understand was also used in the trucks? We have located a suitable unit here with the two different hole configurations which will suit the 200R4 TC and not have to change the starter motor. Arrives next week so hopefully car will be off the hoist by next weekend
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Fantastic offer and I would have taken it up in a heartbeat but now committed to one found by mechanic which is already on route here.