[Iggy]

I have been led to believe forever that Pontiac engines were internally balanced, now that I am getting ready to balance and assemble my short block I researched parts and discovered there is more to this than I thought. I have not purchased a flexplate or balancer yet so my question leans on what flexplate to purchase - internal or external balance?

I know, in order to answer that you need more information on my short block - I have a .030 over early 75 (481988) 400 block with a stock early 1970's 400 crank. I L2262F30 Speed Pro forged pistons (heavy I know) and Eagle 6.625" 5140 I-Beam rods. My understanding from information I could find is the pistons are close in weight to the stock cast pistons and the rods are slightly lighter than stock cast rods.

When complete, this will be in my 1974 Grand Prix mainly for cruising and shows. The car will have a 200-4R overdrive and 3.73 gears (maybe 3.42 gears if I eliminate the torque converter lock-up. If I planned on running it hard, I would use a better forged piston but feel the L2262F's should be plenty strong for how I plan on using the car.

My gut says I should use the external balance flex plate, no matter what I do I will have it professionally balanced. I just want to avoid adding heavy metal to the counterweights if possible - it really add to the cost of the balance job! Thanks. for your responses up front. Tom