The Stovebolt Site Forums The Shop Area Engine Shop GMC 401 V6 Max Bore?

Does anyone know the spacing on these? I have the opportunity to pick one up and I thought about doing some interesting things to it. I have some 5.25 pistons that I have been saving for a project and this might be it.

Spartan

Does "interesting" include having a big basket handy to pick up the pieces when you scatter it all over the landscape? Hotrodding a 401 V6 makes about as much sense as painting racing stripes on a snail! Those engines are torque monsters, with factory-matched and balanced crankshafts and piston assemblies. Just swapping crankshafts was usually very risky, according to the machine shop where I worked that sort of specialized in keeping the big V6's running 30-something years ago for some of their oldtime customers who still had trucks equipped with them.
Jerry

What does the 401 share with the 478? Just swapping in a 478 might be the best “hotrodding” plan.
EDIT: they share a lot, likely one bolts in place of the other.

Stroke

Thanks guys. I'm not looking to hot rod it. just do something different and "interesting" as I said. I was just curious if it was even a possibility. I'm not a speed demon. I would probably put it in a tow rig. Or maybe not. I have a few weird motors that I rebuilt that are just on stands. I just like to do things.

Spartan

If you choose to do a big overbore, be absolutely sure to weight-match your replacement pistons with the originals. On the round track race engines I've built over the past 40-something years, I weight-match anything that moves down to 1/10 gram- - - - -a dollar bill weighs one gram. Then we do a dynamic (spin) balance after that.
Jerry

Thanks Hotrod Lincoln.

Do you have the equipment to do the balance yourself or do you send it to a shop? Or are you a shop?

Maybe thats a silly question but I don't know you at all.

Spartan

I have the static balance equipment- - - -it consists of a commercial-grade triple-beam balance scale and some ball bearing support fixtures to weight-match connecting rods. I sublet the dynamic balancing to one of three machine shops I trust to do that work, two of which are owned by former students of mine. I started building precision engines in the mid-1960's, mostly for dirt trackers. Now I'm an opinionated 73-year-old retired geezer who likes to stir the pot on internet forums.
Jerry