406 Internal vs External balance??
Thread Starter
Melting Slicks
Joined: Sep 1999
Posts: 3,155
Likes: 8
From: Hendersonville TN
406 Internal vs External balance??
I am about to buy a 406 from a friend that does not have the crank in yet(on order), the motor will go in an 89. Should this motor be balanced in or out?? I need to find out so I can have a different crank installed before hand.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The 406 is a 400 engine that has been bored .030" over, and was originally externally balanced. Most engines that get a simple bore job, don't get the crankshaft replaced. If you want an internally balanced engine you can have heavy metal added to your crank or buy one with it installed.
RACE ON!!!
RACE ON!!!
Last edited by CFI-EFI; Jun 18, 2006 at 11:07 AM.
Melting Slicks
Joined: Jan 2003
Posts: 2,804
Likes: 1
From: OKC Oklahoma
I always internal balance. Your engine will run smoother and it will rev higher. It should also take care of your engine parts better, because the balance is on the inside near the rotating parts and not at the end of the crank where it is being stressed.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Do yourself a huge favor, and have it internally balanced now, or buy an internally balanced crank
I just went thru 3 years of screwing around with this stupid external balance crap,
you have a limited choice of flywheels, dimensional stack up tolerance crap when using a balance plate, I beg you to have it internally balanced,
I just went thru 3 years of screwing around with this stupid external balance crap,
you have a limited choice of flywheels, dimensional stack up tolerance crap when using a balance plate, I beg you to have it internally balanced,
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Originally Posted by LD85
Do yourself a huge favor, and have it internally balanced now, or buy an internally balanced crank:
Do yourself a favor and purchase an internally ballanced crank, and have the entire rotating assembly (pistons/rods/crank) ballanced at the same time. Not expensive and WELL worth the $$$Eddie
Team Owner
Joined: Jun 2002
Posts: 21,510
Likes: 0
From: On a Wisconsin Death Trip
Originally Posted by LD85
Do yourself a huge favor, and have it internally balanced now, or buy an internally balanced crank
I just went thru 3 years of screwing around with this stupid external balance crap,
you have a limited choice of flywheels, dimensional stack up tolerance crap when using a balance plate, I beg you to have it internally balanced,
I just went thru 3 years of screwing around with this stupid external balance crap,
you have a limited choice of flywheels, dimensional stack up tolerance crap when using a balance plate, I beg you to have it internally balanced,
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Mine is externally balanced and revs smooth as a babies azz to 6500 RPM. Scat now sell a internally balanced nodular iron 9000 series crank for a 406ci 
Last edited by MotorHead; Jul 29, 2006 at 04:42 PM.
Melting Slicks
Joined: Oct 2003
Posts: 2,951
Likes: 3
From: Mount Vernon OH
Internally balanced is certainly better especially if you have plans of spinning your engine down the road. Also, internally balanced utilizes a smaller harmonic balancer. Take a look at the BH&J balancer if you internally balance. They look a little like a stock unit but they work awesome. My 406 in my pro street truck runs 8300 rpm over and over for years without an issue and it's internally balanced.
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Large Impressive Member
Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
There's no reason on earth to not internally balance when building from scratch. My 388 uses all lightweight stuff, the small ATI damper, neutral flexplate, etc. and is one smooth SOB. 
