Help Chevy Flexplate question

Old 09-14-2009, 05:25 PM
  #1  
jjam
Member
CRAFTSMAN
Thread Starter
 
Join Date: Apr 2003
Posts: 56
Default Help Chevy Flexplate question

Just pulled an engine out, it was shaken (not stirred, LOL) The car had a bad vibration. After getting out the engine, noticed the block was a BBC 427 with a internal balance dampner, but the flexplate looked like it was for an external balanced engine. The flexplate had a counter weight, is this correct? or is there another way to tell? I guess my question is will an internal balanced engine flexplate be smooth (no counter weight welded to the flexplate)??
jjam is offline  
Old 09-14-2009, 07:37 PM
  #2  
Tod74
Senior Member
RACING JUNKIE
 
Join Date: Sep 2007
Posts: 4,140
Default

You have a 454 flexplate.An internal balance will NOT have a weight. Are you certain it isn't a 454? The block is the same. The old 512 casting block was used on both 454's and 427's...just a different crank and pistons.
Tod74 is offline  
Old 09-14-2009, 09:17 PM
  #3  
ashbros
Senior Member
RACING JUNKIE
 
Join Date: Nov 2004
Location: St. Louis, Missouri
Posts: 663
Default

You hit the nail on the head,

Who put on the flex plate?
ashbros is offline  
Old 09-15-2009, 03:22 AM
  #4  
chevyfireball
Senior Member
MASTER BUILDER
 
Join Date: Dec 2005
Location: Napier, New Zealand
Posts: 230
Default

My engines internal balanced. I buy internal balance flexplates (without weights), and I get them balanced too. You'd be surprised how unbalanced they are to begin with.
chevyfireball is offline  
Old 09-15-2009, 04:46 AM
  #5  
jjam
Member
CRAFTSMAN
Thread Starter
 
Join Date: Apr 2003
Posts: 56
Default

Tod74, how can I tell which it is 454 or 427 the cast # 3963512 by the location of the crank? I did not install the old flexplate, but I will get the right one and a new ATI dampner (to be safe) then take both the flexplate, dampner, along with the rest (the lightest rod, bearing, piston, rings, crank)
jjam is offline  
Old 09-16-2009, 08:39 AM
  #6  
Tod74
Senior Member
RACING JUNKIE
 
Join Date: Sep 2007
Posts: 4,140
Default

You Can't.....You can find out what it was from the facvtory by the suffix on the front pad, but you have no way of knowing(without pulling a head or pan) what crank someone has put in it since,other than the balancer and flexplate.... If that is a 512 block I WOULD NOT have it in a hotrod. Depending on the casting date they can bring big bucks. If it has a late 1969 cast date then it is a ls5 or ls6...chevelle and vette guys will pay big bucks for it if the dates are right ...I have 2 of them.One IS A Dec 68 cast 427 4 bolt main and one is a December 69 LS5 2 bolt main...It came in a chevelle with a manual trans.....It is damaged from a lifter failure because I didn't know it was worth anything and had it in my race car...
http://www.chevelles.com/forums/showthread.php?t=289174

I think they used the 512 block for several years after 70 so it may be just another 454 but I would look at the dates on the block and see.
Tod74 is offline  
Old 09-16-2009, 02:07 PM
  #7  
jjam
Member
CRAFTSMAN
Thread Starter
 
Join Date: Apr 2003
Posts: 56
Default

Well just my luck the stamp numbers are gone, block must have been decked... the heads are 3873858. Are there any other numbers I can find on the block, now I have the heads off and droped the pan
jjam is offline  
Old 09-16-2009, 03:31 PM
  #8  
Tod74
Senior Member
RACING JUNKIE
 
Join Date: Sep 2007
Posts: 4,140
Default

Originally Posted by jjam
Well just my luck the stamp numbers are gone, block must have been decked... the heads are 3873858. Are there any other numbers I can find on the block, now I have the heads off and droped the pan
The casting dates on the block is what you want to look at to see if it's a valuable one...if it is 1970 or newer they will be on the bell housing flange...the older ones are on the side of the block down close to the pan rail. It will be something like L 19 9 Which means December 19 of 1969. If the block has a tall boss around the distributor in the lifter valley, the block is 1969 or older...If there is no raised boss around the distributor hole in the lifter valley it is 1970 or newer...or at least late 69 . You can't mistake this area I'm talking about it is very obvious.
Tod74 is offline  
Old 09-16-2009, 04:36 PM
  #9  
BEAST477
Senior Member
RACING JUNKIE
 
BEAST477's Avatar
 
Join Date: Feb 2007
Location: Michigan
Posts: 1,908
Default

Well since you have the pan and heads off, Measure the bore and stroke. That will tell you what you got.
BEAST477 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service