I'm very new to the engine building scene, I just purchased a 84 trans am with a 305 in need of repair, and a 89 camaro iroc 350 engine with .0040 over pistons a comp cam, edlebrook (*sp) performer series Intake and same brand carb. The engine is already apart waiting for new gaskets. What I am wanting to do is make a 383 stroker out of it, I understand I need a 383 or 400 crank. And depending on the crank possibly 6" rods. What I am wondering is if I do need to go to 6" rods because of my crank selection do I need to buy a new set of pistons to accommodate the longer rods, also I've seen cranks that say they will work with either 5.7" or 6.0" rods, how is that possible? I would also eventually like to purchase a set of aluminum heads, to increase my horse power and torque. Am I on the right track to some decent power?

 

Nate-so as to not infringe on this O/P,I suggest you start your own thread so we can work with you.OK??.

 

I apologize I'm not quite sure how to do that I'm having some difficulties navigating this site.

 

Yes you would have to have new pistons.

Since that's a 1-pc rear main seal block, the way to go is an aftermarket 383 crank. A 400 crank would require some extra contortions as well as being overall generally inferior.

The longer rods primarily allow for internal balance, as the shorter ones don't allow enough space under the piston at BDC, for large enough counterweights. Other than the counterweights, the crank doesn't particularly care what the rod length is.

 

Thank you very much, that was very helpful. Is there specific pistons that I should look for to accommodate the longer rods and bigger crank, or am I better off just buying a kit? I'm trying to keep it low budget, not bad quality just not top of the line. Thanks for your really.

 

Think about the relationship among the block, stroke, rod length, and pistons...

The block is always the same "height", from crank CL to deck.

You want the pistons to come up even with the top of the deck. They don't usually, but that's the goal.

Therefore half of the stroke, plus the rod length, plus the compression height of the piston, must equal the "height" of the block.

"Compression height" of the piston is the distance from the center of the wrist pin, to the top surface.

Not hard to see that if you increase the stroke, something's got to give.

The stock 400 piston is the same "height" as the stock 350 piston. Stock 400 rods are therefore shorter than stock all other SBC rods, by half the difference between the 400 stroke and the 350 stroke.

The short rod doesn't allow for the counterweights to be large enough on the 400 crank. That's what it's "externally" balanced. It's THE ONLY SBC that's built like that. Later model motors, with the 1-pc rear main seal, have a little bit of the rearmost counterweight on the flywheel, but that DOES NOT make them externally balanced. But the term is often confused, so it's best to avoid it altogether except when talking about the 400 itself.

To make a crank with the 400 stroke but have it the same balance as all other SBCs, the rods must be AT LEAST as long as the other SBCs; 5.700". However this requires that the wrist pin be moved up A BUNCH toward the top of the piston; so much in fact, that the rings must be narrower, closer together, and/or over the wrist pin hole. None of these things are good for robustness of the ring package. Therefore a minimum of rod length should be used, to accomplish the "standard" balance condition.

If you don't know what you're doing, best to buy a kit. But it's not that hard to figure out either, so you can buy the individual parts you want.