Hey guys, what is the difference between an internally balanced engine and an externally balanced engine besides the "hatchet" weight on the crank snout? The reason I ask is that I am building a 460 that was originally a pre-79 internal balance, but I want to use an externally balanced flywheel because they are so much cheaper. So, I guess the question is can I put the hatchet shaped counter weight on the crank on an "internally balanced" motor and use an externally balanced flywheel? If not, what are the differences between the two? Thanks.

 

the reason for the external balanced crank is that for 79 Ford extended the cylinder sleeves on the blocks by 1/2" or so (not sure of exact lenght) and they had to cut down the counterweights on the crank to fit the crank into the block. this required the hatchet weight on the crank to keep the correct balance.

therefore you cannot fit a internal balanced crank into a D9TE block (the block with the longer cylinder walls) without grinding on the block. but you can fit an externally balanced crank into the earlier blocks.

so you have a few options to go with. use the complete rotating assembly (including hatchet and flywheel) from an externally balanced engine in the earlier block or get the flywheel rebalanced to zero to use with the earlier cranks. you cannot use a externally balanced flywheel and hatchet on the internally balanced crank without causing a lot of damage.

rgds
Mike

 

Well that clears up a lot of things. Thank you. The crank I will be using is an externally balanced crank and the block is a '68, so that will be fine as long as I use the hatchet counter weight and an externally balanced flywheel, right? Also, could I use a flywheel for like an '87 460? Thanks again.

 

Yes your set up will work. As far as the flywheel goes, yes it will bolt on but need more imfo on what bell housing, size of clutch & style of psi plate you want to use ?

 

Well the motor is going in a '79 F-250 4x4. I was planning on using a 351/400 bellhousing and probably a stock or mild performance clutch set.

 

back to this yes, you can use an external flywheel and conterweight on an internaly ballanced motor .but in reality it wont be any cheaper. those flywheels you see in jeg's and sumitt wont fit in anytrucks and thats why there so cheap.

 

do NOT listen to this. you can NOT use an externally balanced flywheel and counterweight on an internally balanced engine without destroying the engine in short order. It will shake itself apart in minutes.

You can put them on the interanally balanced crank and have them rebalanced as a unit but do NOT just bolt them on and go. Yes they will physically bolt on but you won't have a motor for long.

 

explain why please?