I have a stock 1974 2 bolt 350. What do I have to do to make it a 383? I know I have to get the crank, and bore it 30 over, but do I have to have any work done to the block for the 400 crank to fit.
Thank You
Mike

 

Typically you can just buy a 383 crank, which is a 400 crank with the mains ground down to the size of 350 mains. I also have seen people using 400 cranks and having them ground down, but I believe it is just cheaper to buy the 383 crank.

As for the rods and pistons, rods are not specific to 383's but the pistons are, you'll have to get 383 pistons.

You could bore it over more, or less, I have seen pistons for a 3.75 stroke in standard (4.00 bore) all the way up, .020,.030,.040, etc.

 

Check for oil pan rail to rod clearance. I know for my 383 i had to have some grinding done so that the rods would clear. Also, you may want to check for cam-to-rod clearance. Just be sure that the rods dont hit the lobes. Ive heard of it happening, never seen it personally. I agree with the Wizard that it would probably be best to use a 383-designated crank if you have to buy one anyway.

On a side note, be cautious if buying parts individually. ive seen it split right down the center; either internal or external balance for aftermarket 383 crankshafts. Just make sure your balancer and flexplate match up. If you have to buy all the parts, a good alternative (and one i suggest looking into) is buying a pre-matched kit. These kits usually come with the crank, rods (either 5.7" or 6"), rod bolts, pistons, rings, rod and main bearings, sometimes the balancer, and flexplate. Often times the kit is pre-balanced. This way you know everything is good to go for the bottom end.

 

When you build a 383 using a factory block you have to clearance the very bottom of the cylinder walls or the connecting rods will make contact. You need a minimum of .050" clearance between the rods and cylinder walls. The same .050" rule goes for the clearance between the rods and camshaft. You wont usually have clearance issues on more then 2 of the cylinders(I believe it no.1 and no.4 cylinders).

As for purchasing the parts I agree that its better to purchase them as complete matched and balanced assemblies. If your on a budget Summit racing equipment has an Eagle 383 balanced rotating assembly with hypereutectic flat top pistons for 895.95. There are also companies on ebay that sell 383 rotating assemblies with hypereutectic or forged piston combinations at very reasonable prices.

One word of warning though, when building a 383 using a stock GM block you should resist the urge to buy a kit with H-beam connecting rod like the Eagle ESP 3-D rods that come with some of the kits. Stick to the I-beam style rods. The reason is that it requires alot more grinding to get the big H-beam rod to clear the cylinders on a stock block. You run the risk of cutting into the water jacket and destroying the block trying to get them to clear. The odds are like 1 in 4 that it will but I dont recommmend that anyone take the risk. If your building an engine that requires the strength of an H-beam rod you should spring for an aftermarket block anyway.