Is a 87-88 Chevrolet 305 internally or externally balanced? I really need to find this one out. Thanks.

 

i'm almost positive internally.

 

oddly enough, externally balanced on the flywheel/flexplate end and internally balanced on the dampner end.

 

this confusses a lot of people, but all SBCs except the 400 are internally balanced. the one piece rear seal blocks have a bat wing weight on the flex palte and that makes people, and parts makers call them external balance. an internally balance engine has a crank with counter weights equall to the weight, or mass, of the rods. on a 400 for example the rods are short so the piston would crash into the counterweight if the weight was equall to the rod so GM made the counterweights smaller and added mass to the flexplates and dampners. the bat wing weight on the one piece seal flex paltes is to replace mass from the flywheel flange when it was redesigned for the one piece seal.

 

it's not confusing ede, when the one piece rear seal crank is balanced, the flywheel/flexplate weight is where the rear balancing takes place when needed. this is why they changed the bolt pattern, if you could put a standard internally balanced flexplate on it, it would have been done by people accidentally and vibrated the engine to an early death.

 

Actually I think they changed the bolt pattern to keep the rear main seal from being hugem although I'm sure they thought of people putting older flexplates and flywheels on them (yeah, right, like they REALLY worry about what we do to the cars later in their life!)

 

gm will still change stuff like that even now to keep the tech's from screwing it up while it's under warranty. there are service vme's on stuff like that even now.

 

Here I thought the only reason they ever changed anything other than to save money was on Cadillac's, so that cheaper parts wouldn't work on Cadillac's! LOL