Flex Plate change
Thread Starter
Intermediate
Joined: Jan 2004
Posts: 26
Likes: 0
From: Houston Texas
Flex Plate change
Ok, the last time I talked with Forum members I was about to change engines on my 71/350/auto. I now have the old engine out and have a 383 stroker ready for install. Before I put it in, it occurred to me that the flex plate might need updating. Can I use the original 168 tooth plate or should I spring for the new $75 one? Scroggins/Dickey has one for a S/B 400 but don't know if it will work with my new 350/383 stroker. Jegs also has one that might work but don't know for sure.
Is it better to be safe than sorry with the flex plate?
Is it better to be safe than sorry with the flex plate?
Le Mans Master
Joined: Oct 2005
Posts: 9,429
Likes: 44
From: Macon, GA
I could be wrong, but I'll chime in on it. As far as I know, 168 tooth flex plates are for externally balanced 350, 383 and 400 engines and 153 tooth are for internally balanced 350 engines and requires a balancing plate for use on 383, 400 and 454.
Anyone agree?
Anyone agree?
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
Most 383 stroker kits are external balanced needing the correct flexplate and damper. The one from jegs is SFI approved (stronger) and can be had with weights for the external balanced engines (555-60152 for 168 tooth 400 plate) but you may need one for the newer 350 one piece seal crank (555-60153/55560154 for 153/168 teeth) and a flud damper street damper is (388-790100) the best way to go but kinda pricey.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Originally Posted by sperkins
I could be wrong, but I'll chime in on it. As far as I know, 168 tooth flex plates are for externally balanced 350, 383 and 400 engines and 153 tooth are for internally balanced 350 engines and requires a balancing plate for use on 383, 400 and 454.
Anyone agree?
Anyone agree?
Disagree ...153 available as either Int or Ext ... 168 available as either Int or Ext.
b-line:
71 350 was internal aka neutral balance with two-piece rear main seal.
Most 383 (not all) are external balance. Most 383 (not all) have cast crank. Most (not all) cast 383 cranks are external. Most (not all) forged 383 cranks are internal.
You MUST determine whether YOUR 383 is internal or external ... only then can you install correct flexplate/flywheel ... with confidence.
Whoever built YOUR 383 should be able to tell you what type crank was installed & what type flexplate/flywheel is required. If you built it ... then you should go back to your parts list & P/Ns and crank mfg ... AND to whatever shop balanced the rotating assembly.
IF ... IF YOUR 383 was built internal balance AND it has a two-piece rear main seal ... your old 71 350 flexplate will work ... otherwise NO. BTW ... a new OE-type flexplate can be had at local parts store for under $20. Not likely I'd ever put a 35 year old stock flexplate on a fresh 383 ... not on anything I planned to play with.
Instructor
Joined: Jun 2005
Posts: 248
Likes: 1
From: Apopka Florida
Originally Posted by b-line
Ok, the last time I talked with Forum members I was about to change engines on my 71/350/auto. I now have the old engine out and have a 383 stroker ready for install. Before I put it in, it occurred to me that the flex plate might need updating. Can I use the original 168 tooth plate or should I spring for the new $75 one? Scroggins/Dickey has one for a S/B 400 but don't know if it will work with my new 350/383 stroker. Jegs also has one that might work but don't know for sure.
Is it better to be safe than sorry with the flex plate?
Is it better to be safe than sorry with the flex plate?
Replace the flexplate. Ask me how I know?
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
Originally Posted by sperkins
I could be wrong, but I'll chime in on it. As far as I know, 168 tooth flex plates are for externally balanced 350, 383 and 400 engines and 153 tooth are for internally balanced 350 engines and requires a balancing plate for use on 383, 400 and 454.
Anyone agree?
Anyone agree?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Since you had 168 you need to stay 168 because that is what your starter was set up for.
If your 383 was sold as externally balanced it would have arrived with a balanced damper and flex plate. That is how the motor is balanced. as a package.
Internally balanced motors you slap on the damper and flex of your choice. If your old flex has nice teeth and no cracks near the crank bolts don't worry about.
If your into racing, go with SFI stuff.
If your 383 was sold as externally balanced it would have arrived with a balanced damper and flex plate. That is how the motor is balanced. as a package.
Internally balanced motors you slap on the damper and flex of your choice. If your old flex has nice teeth and no cracks near the crank bolts don't worry about.
If your into racing, go with SFI stuff.
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