View Full Version : Anyone have a 406 here

12-04-02, 11:46 AM
If so I am wondering how you had it balanced? Internal or external?

12-04-02, 02:07 PM
I have a 417 ci small block (400 block), balanced internally.

12-04-02, 02:11 PM
forgive my stupid question but how do you do this, do you need a balance plate?

12-04-02, 02:24 PM
Machine shop. :D

_ken :w

12-04-02, 03:07 PM
Are all 400 small block's simeased cylinder wall's?

12-04-02, 06:25 PM
Dunno for sure but I assume that they are because they are just a larger bore. 4.125 350 block really but I could be wrong. Ia m no expert just learnin on the fly!

Also I may have access to 509 casting 2-bolt 400 blocks so I may be able to scrounge one or two up.

12-04-02, 08:45 PM
Originally posted by hotrodd
Are all 400 small block's simeased cylinder wall's?

All production SBC 400s are

12-11-02, 11:59 PM
I have a 406 in my 82. Machine shop did my balancing as well.


01-01-03, 05:14 AM
Anyone one have dyno info on the 406's?

I was wondering about the miniram combos that have been built here and how they performed. Any ET's or dyno info?

My 406 build will begin in a@ 1 1/2 months so I am beginning to salivate!

01-16-03, 11:48 AM
Originally posted by LD85
forgive my stupid question but how do you do this, do you need a balance plate?

Most sbc are internal balance from factory ... 400 is the exception being externally balanced. To further confuse things ... the 400 (like other sbc) is internally balanced BUT IN ADDITION IT IS ALSO externally balanced because it uses a unique harmonic balancer (damper) and flywheel/flexplate ... both are counterweighted. A balancer plate is used when an external balance assembly needs to use an internal balance flywheel/flexplate. An example would be a typical 400 cast crank w/ less than 6" rods running a 400 type damper ... BUT ... running a 350 type flywheel/flexplate. The 350 flywheel/flexplate has NO counterweight ... so the balance plate is bolted to the rear of crank (along w/ 350 flywheel/flexplate) to compensate.

Regardless, ALL custom-built rotating assemblies should be balanced by a machine shop. Ask your machinist if he can internal balance it ... about how much mallory metal it'll take ... about how much $ ? Ask same if he does it external? It seems you haven't chosen a cam or type of cam (roller vs flat). It's quite likely the rods will need clearancing to keep from hitting cam ... if so ... this MUST be done BEFORE you have the assembly balanced. As I mentioned elsewhere, if the block need align boring ... this will also move the rods closer to the cam.

Dunno, but you may end up needing the cam-to-rod clearance that is often provided by a roller cam (they often have a relatively smaller base circle).

From one of your other threads I see you already have now:
Block: 509 Casting GM std. to be bored to 406, no work done yet
Crank: Stock 509 400 std.
Rods: 6.0 Eagle 5140