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Discussion Starter #1 (Edited)
Ok, I have build numerous cars and never had this problem. I'm building a 1971 Nova with a Blueprint 383 stroker - 2 piece rear seal, factory powerglide with Hughes PG25 torque converter, Pioneer 2 piece seal weighted flexplate with weight towards motor. I rebuilt the trans and installed a Sonnax front pump gear set. It is install correct with recess towards the converter. (spoke to Sonnax tech today and its correct. ****Converter is installed into all splines and engaged into pump tabs***. I can only get 7/8 clearance not 1"1/8 from converter mount tabs to trans bell housing face. The converter is almost rubbing the inside bell housing. The torque converter is snug, not pushing against the flexplate. I know it should have some space/clearance from flexplate to conv but I have removed everything three times to check and I don't see any errors in the install. Any one else run into this??? Please help me. Frustrated X10 Is there any difference with SCAT cranks, is this my issue?
 

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I don't know anything about the trans parts you used, did you try measuring from the front seal to the pump to see if that dimension is less? I would start comparing everything. Converter snout length, pump depth, etc. I never had an issue with Scat cranks whether it be manual or automatic.
 

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Scat crank is not your issue. Either your pump or converter or off or it's not engaged all the way.
 

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Discussion Starter #5
When you say a different flexplate is required with this converter which one would I use? I used the external balanced 2 piece rear seal PIO-871002.
 

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When you say a different flexplate is required with this converter which one would I use? I used the external balanced 2 piece rear seal PIO-871002.
Looks like he runs an external like you.
 

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I sometimes mark my two pump tangs or at least one of them in relation to the bellhousing and also I mark the torque converter. Sometimes the new stuff(converter) and new pump gears can be tight and hard to find or click into. This way when I line them up and then work them back and forth I can see when it goes in that extra 1/4" which is about what you need/
 

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Scat crank is not your issue. Either your pump or converter or off or it's not engaged all the way.
I think you have correctly diagnosed the issue.

This is dangerous territory. You can destroy the front pump if the converter is not fully seated.
 

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Discussion Starter #9
Thanks all, So I placed two marks on the convertor flywheel face, I engage the convertor in the pump and 12 and 6, spin convertor to 9 and 3 and remove converter the pump moves exactly like it should. I'm so frustrated doing this I'm thinking of just selling the car.
 

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How are you engaging the converter on the pump? Can you post a pic of the distance between the trans output shaft and the back face of the converter?


From top trans builder -

The old “3 clicks” method is not an accurate way to determine if the converter is correctly installed. There MUST be clearance between the converter and flexplate when the trans is bolted to the engine. In a perfect world this would be 1/8″ or .125″ everytime, and you just bolt it up and go. In the real world, we have to check it and make adjustments as necessary.

On a typical GM engine, the flexplate mounting pads are 1″ away from the bellhousing flange area of the block. The converter pads when seated completely will be approximately 1 and 1/8th inch ( 1.125″)recessed into the bellhousing. Seat the converter, then measure the distance from the engine block bellhousing mating flange, to the mounting pad on the flexplate.

Then do the same from the transmission bellhousing mating face, to the converter mounting pads. You should have the converter sitting deeper than the flexplate protrudes from the engine. If so, you can now bolt the transmission to the engine. With the trans bolted to the engine, you should be able to turn the converter freely. Check the distance from the converter to the flexplate with the converter completely seated into the transmission. You should have 1/8″ to 3/16″ clearance. (.125″-.187″) If it is more than 3/16″, you should use flat ground washers to shim between the flexplate and converter.
 

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Discussion Starter #13
I called Hughes Transmission and they said it was correct PG25. I even sent photos of the pump and they said it was installed correctly. I'm at a loss.
 

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post pic from below showing space between pump and converter hub


this is odd

with the way that converter is fitting in there I could see it expanding some and making contact with the bellhousing under acceleration
 

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You talking about converter to flexplate distance? Did you measure that.
 

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that converter is clearly pretty much rubbing the bellhousing when seated... I would send it back at this point or show pics to hughes support

Freak Show Performance out of Texas makes some nice budget torque converters
 

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Got rushed out last night before being able to read more. It seems you have the converter seated all the way as it's almost touching the back of the trans housing. It can be tricky to get that last bit of engagement but if you've done a few you can tell when it's not quite seated. I asked about the distance between the flexplate and converter tabs cause I had an issue where I only had about .040" converter movement up to the flexplate. I ended up using a .090" mid-mount plate as a shim to get within the 1/8" - 3/16" spec I wanted. I see now where you say it's rubbing the flexplate when you turn the converter. I agree with above, that converter needs to be checked out. Maybe you just got a bad one that was machined incorrectly. I'm guessing you don't have another converter around you can try.
 

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Discussion Starter #20
Yes, Stock Bell housing on a stock Power Glide Trans. No machining to the back of the block per Blueprint and torque convertor has to be the correct one with 17 splines or it would not even engage. I'm so disappointed with the car and it is now just sitting and I have no drive to even finish it.
 
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