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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Silver_Bullet85 on May 27, 2014, 04:20:35 am

Title: Starter, flywheel, torque converter matching problem
Post by: Silver_Bullet85 on May 27, 2014, 04:20:35 am

Ok so I think I made a rookie mistake, I ordered a torque converter, flexplate and starter from summit for my 85 c10 with a 383 and TH350 and for some reason they're not matching up. Here's links to the pieces I have:

Torque converter:
http://www.summitracing.com/parts/bmm-20400

Flexplate:
http://www.summitracing.com/parts/pio-871002

Starter:
http://www.summitracing.com/parts/pro-66256

I guess I overlooked something, but I thought it should've all matched up. Is the flexplate wrong? I'm lost at this point, any help would be fantastic.


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Title: Re: Starter, flywheel, torque converter matching problem
Post by: bd on May 27, 2014, 09:43:42 am

Let me guess, the bolt holes on the flexplate don't match the flange spacing on the converter.  Am I right?  The notes for that B&M converter state, "This torque converter requires a small 10.75 in. bolt pattern flexplate."

GM flexplates were produced in two diameters: 12.75" and 14".  The 12.75" diameter flexplate had a 153-tooth ring gear.  The 14" flexplate had a 168-tooth ring gear.  GM also used three different bolt circles for converter mounting: 9.75", 10.75" and 11.5".  Some 12.75" flexplates were drilled with either 9.75" or 10.75" converter patterns, while some were drilled with both.  Similarly, some 14" flexplates were drilled with either 10.75" or 11.5" converter patterns, and some were drilled with both.

Edit:
On close inspection the flexplate you purchased is drilled with two bolt patterns - three of the mounting pads are drilled on a 10.75" circle - three of the mounting pads are drilled on a 11.5" circle.  The smaller circle is the one to use; spinning the converter 60° in either direction should allow the holes to line up.  The starter you selected can be used with both the 12.75" (153-tooth) and 14" (168-tooth) flexplates.

Title: Re: Starter, flywheel, torque converter matching problem
Post by: Silver_Bullet85 on May 27, 2014, 10:11:52 am

Well this is embarrassing, I must've been on something last night bc I'm walk out this morning and try to fit everything again and guess what, it all matches up perfectly, I'll blame the whiskey on that one I guess, thanks bd for the info tho!!


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