I just bought a truck that has a fresh rebuild with only a few thousand miles on it. It has the vortec top end on it with Speed pro hypereutectic pistons, and I believe the Lunati 4x4 cam. Is it possible for me to disassemble the motor and drop in a new 383 crank, clearance the typical spots, and reassemble? Do I need to do anything to the bores? Can I reuse the current rings or should I just get a new set? I know I would probably need rod bearings because the current crank was turned down. I guess I am asking how much can I re-use. Everything is practically brand new. I would like to get the rotating assembly balanced too, so does that mean I have to pull all the rods and pistons or can I just pull one set?

Thanks!


Don

 

You would also need new pistons, unless you use sbc 400 rods. You would need a 400 balancer and to balance the engine you would most likely need to have the crank, rods and pistons out of the block. You would also need a 400 flexplate. I say drive it until it blows and than build a 383. Someone else chime in here if I'm missing anything.

 

Thanks, that is the info I was looking for. What has to be different about the pistons? Shorter ? What length is the 400 rod ? Is it difficult to have the rotating assembly internally balanced for a stroker?

 

The 400 rod is 5.565" and the 350 rod is 5.7". The deckheight of a 400 block and a 350 block are the same. The cylinder bore is different. So what I'm gettin at is if you use the 400 crank with a 5.7" rod with the stock 350 piston than most likely the piston will be comin out of the block at tdc. If you use the 400 crank with the 400 rod with a 350 piston you're good since the only difference in the 400 and 350 pistons is diameter. A piston built for the 400 crank and 350 rod is a 383 piston and the wrist pin is moved higher up the piston to keep it from raising above the deck surface at tdc. Did I clear anything up for you or just confuse you more. A 400 crank is externally balanced so when you take it to have the rotating assembly balanced you would actually need the crank, pistons, rods, balancer, and flexplate/flywheel. You could buy a rorating assembly already balanced if you wanted. That's why I say just run it util it blows because to make the change to 383 is almost like building a whole new engine.

 

I completely understand. I did not think of the piston height differences. I guess there is quite a bit more than the crankshaft change. Maybe I will throw on a something like a Whipple or a gear change to make up some torque . Thank you explaining everything in detail for me.