D Stroked 400Chev

[LoBroWithGo]

Hi
Can someone tell me the pro's & cons off D Stroking a 400chev to a 383
always thought bigger was better.

[MagicRat]

The typical 383 is built using a 350 block (not the 400 block).
A 400 crankshaft is modified (the bearing journal diameter is reduced) and installed, along with 400 rods.

The result is an engine with the 350's bore and the 400's stroke. And, yes, people build this combo because 'bigger is better'.

400's usually are not de-stroked, because the block is not as good as a 350 block.

The 400 has siamesed (joined) cylinder bores, which sometimes causes overheating problems. A 350 block is stronger, more reliable and cheaper.

Building a de-stroked 400 is tough, because a suitable crankshaft would be hard to get. The 400 has larger bearing journals, so every other Chevy crankshaft will not fit.

[MrPbody]

When 383s became "popular" (in the late '70s), the "leftover" parts would be the 400 block and the 350 crank. Moroso began supplying bearing "spacers" to use the 350 main bearings in the 400 block, when bored .030" over, called "377". Now, several companies offer the spacers. Speed Pro offers "spacer bearings" (the shells are WAY "thick", eliminating the need for spacers). We (CVMS) prefer the spacers and "regular" 350 bearings.

There are a couple of real advantages to the combination. The bore/stroke and rod/stroke ratios are vastly improved over the 400 as "standard". The larger bore also helps the heads "work" better by unshrouding the intake valve a bit.

The end result is a high-revving hot rod. A VERY GOOD drag racing combo.

The downside is what MR says. The 400 block is a POS. Between the larger main journals taking away material in the block where it's needed for strength, and the "siamesed" cylinders (joined in the middle, no water passes through), the block is simply "stretched" too far for the original design. To lend credence to this, realize Chevrolet never produced a production "performance" 400. There's a "Bowtie" block, and Dart Little M, etc. Those aftermarket "race" blocks have much better designs to them.

If you DID decide to build a 377, , and plan to use the factory production block, ALWAYS use a 2-bolt main, NOT a 4-bolt. Unlike the 350 block, where Chevy installed the outboard bolts removes even MORE material where it's needed the most. "Splayed" caps can help, but again, you MUST start with a 2-bolt.

Jim

[MagicRat]

Wow, that takes me back. It's been years since I read about the 377 combo... I had forgotten about it.

Originally Posted by MrPbody

A VERY GOOD drag racing combo.

Well, yes, even a modded 400 block can't overheat if it only runs for a few minutes

[sub006]

The de-stroked 400 for my C2 Corvette came out to 388" with the forged crank out of a sprint car. It now lays rubber for a block in my son's '63 Chevy II.