crank difference

[BlackBandit]

I need to find out how GM balanced their cranks. I mean, I know they didn't really "balance" everything like you would get from a machine shop, but did they remove a static amount of material from the cranks and then use a generic balancer? Do the 3.8 NA and the 3.8 Turbo cranks have the same static balance with the only difference being the flexplate/balancer? Is the only difference between a 3.8 turbo and a 4.1 crank external or did they get different amounts of material removed AND use different wieghts on the flexplate/balancer? Please help me figure this out. I've wasted countless hours reading post after post and other tech stuff and haven't found an answer. (It doesn't help that I'm easily sidetracked by anything Buick:biggrin: ) TIA james

 

[getchasum]

James, Here's a litlte info I can share. When I had a 4.1 crank balanced for a 3.8 109 block the crank was 15 grams heavier on at the lopes (that had to be removed) than my prior crank. The 4.1 motors also used a different balancer & flex plate. All you realy need to do when using a 4.1 crank is take the balancing shop a good 3.8 turbo balancer, flex plate, rods, pistons & rings. The rest is no problem for them.

Also post up what you are tring to do so other may share some advise.

 

[BlackBandit]

I need to put a new crank in my car and don't want to pull the pistons out. I know, it's half assed, but I don't have much of a choice. It has a turbo crank now and I was thinking about just pulling a junkyard crank, having it cut and dropping it in. james