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727 torque converter question

DrEamer

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When I got my Challenger project, it came with a big block 727 and torque converter. I'm going small block, so the trans is going up for sale, but I am wondering if I can keep the converter. If I understand correctly, as long as the converter is a 24 spline and I have the correct bolt circle flex plate, they are good for small and big block 727's. Please correct me if I am wrong.
 

704406

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The stall speed is quite different from a 340 to a 440
I think the 440 has the lowest stall speed because it has so much more torque that the small block.
I'm not able to look up the stall speeds right now, but when I get home I can if you need the info.
I think a big block converter behind a small block might not be such a good idea, the small needs to rev up a bit to get going, the big block doesn't.
 

DrEamer

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I was able to talk to a torque converter rebuilder today and confirm I can use the same converter on both big and small block. Since I have no idea what specs the current converter is built to, I am going to have them go through it and set it up to my engine. Also, if I want a smaller converter, they can use mine as a core if need be, and make whatever I may need.
 

aussiemark

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If it is from a big block with 6 pack rods it will be for externally balanced engine (counter weight welded to it) may be ok for a 360? but not the others. Check the transmission if it is trashed the converter could be full of crud waiting to destroy the next transmission. I'd sell it with the transmission and get a new one then you will know what you have, it will be clean and should have a warranty.
 

DrEamer

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If it is from a big block with 6 pack rods it will be for externally balanced engine (counter weight welded to it) may be ok for a 360? but not the others. Check the transmission if it is trashed the converter could be full of crud waiting to destroy the next transmission. I'd sell it with the transmission and get a new one then you will know what you have, it will be clean and should have a warranty.

The transmission and converter are both rebuilt and have never been ran. The problem is as you stated, I do not know who rebuilt it, or to what specs. So, I am starting over in a sense by getting the converter rebuilt to the specs of my engine when it gets done. Plus, going to sell the big block trans to fund the new small block one. That way I know what I have when I am finished.
 

transman

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I was able to talk to a torque converter rebuilder today and confirm I can use the same converter on both big and small block. Since I have no idea what specs the current converter is built to, I am going to have them go through it and set it up to my engine. Also, if I want a smaller converter, they can use mine as a core if need be, and make whatever I may need.
Yes, your converter builder is partly correct. Just make sure that when you have it built, you tell him what engine you've got as the small block is balanced differently than the big block. Stall wise, the 340 would stall around 2300-2400, and most 440's stalled between 1800-2100, depending on which engine option was in front of it.
 

DrEamer

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Yes, your converter builder is partly correct. Just make sure that when you have it built, you tell him what engine you've got as the small block is balanced differently than the big block. Stall wise, the 340 would stall around 2300-2400, and most 440's stalled between 1800-2100, depending on which engine option was in front of it.

Understood, my plans are to build a internal balanced 408 stroker. That will let me run a neutral balanced harmonic balancer, flex plate and converter. Fortually, the rebuilder does a fair amount of race converters to specs, so he should have no trouble dialing one in for me.
 
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