Flexplate Question
Thread Starter
Instructor
Joined: Feb 2001
Posts: 224
Likes: 41
From: Catawba, N.C. USA
Flexplate Question
1973 350 stroked to 383. I have a rebuilt TH400 out of a 72 going into the 73. Can I use the 72 flexplate? Made the mistake of going down the internally balanced vs. externally balanced rabbit hole. My harmonic dampener is internally balanced and presumed I could use the 72 flexplate but just want to make sure. Thanks for the help.
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
If your 383 is internally balanced, and the flexplate is out of a Corvette, then yes, you can use the flexplate. The 400 is the only externally balanced small block, and the General never put a 400 in a Corvette.
You only mentioned that the harmonic balancer is for an internally balanced engine. The internal/external balance is a function of the crankshaft. If you have an externally balanced engine, you need the external balance damper and flexplate. If you have an internally balanced engine, you go with neutral balance damper and flexplate. It's not quite that simple, but the point is you need to know how your engine is balanced.
You only mentioned that the harmonic balancer is for an internally balanced engine. The internal/external balance is a function of the crankshaft. If you have an externally balanced engine, you need the external balance damper and flexplate. If you have an internally balanced engine, you go with neutral balance damper and flexplate. It's not quite that simple, but the point is you need to know how your engine is balanced.
Thread Starter
Instructor
Joined: Feb 2001
Posts: 224
Likes: 41
From: Catawba, N.C. USA
Thanks for the replies. I'm restoring a 72 and 73 (oringinally bought as a donor). I got a Muncie for the 72 so decided to take the 72 th400 and had it rebuilt to use in the 73. Took the small block out of the 73 and am doing a budget rebuild stroking to 383 using dart heads, performer intake and Summit top and bottom ends. About to mate the trans to the engine but got nervous on the flexplate issue.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Thanks for the replies. I'm restoring a 72 and 73 (oringinally bought as a donor). I got a Muncie for the 72 so decided to take the 72 th400 and had it rebuilt to use in the 73. Took the small block out of the 73 and am doing a budget rebuild stroking to 383 using dart heads, performer intake and Summit top and bottom ends. About to mate the trans to the engine but got nervous on the flexplate issue.
Jebby
