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Engine sizes?


Murphy

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I see on various posts where people list their engines size in cubic inches........Some show a 355 or a 383 or 385. Are the dimensions (CI) after a 350 block has been bored to say .030 or .050?

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A 350 with the 3.75 stroke (400 crank) is a 377 with a .030 overbore, or a 383 with .060 overbore.

 

The 400 crank in a 350 became so popular among hot rodders that Chevy finally made their own 383 crate motor a few years ago.

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Chances are you have a regular 350 crank - 3.48" stroke.

 

If somebody put a stroker crank in your 350, chances are that it would have to be externally balanced (like the 400s were from the factory). When you use the 400 crank, you need the 400 balancer and flexplate. The balancer is weighted more on one side (of the inside by the hub) and the flexplate has a weight about the size of a pack of gum near the teeth. There are some exceptions such as when somebody has the crank itself balanced with some heavy metal so they can run a regular balancer and flexplate, but that's expensive and not too common.

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Chances are you have a regular 350 crank - 3.48" stroke.

 

If somebody put a stroker crank in your 350, chances are that it would have to be externally balanced (like the 400s were from the factory). When you use the 400 crank, you need the 400 balancer and flexplate. The balancer is weighted more on one side (of the inside by the hub) and the flexplate has a weight about the size of a pack of gum near the teeth. There are some exceptions such as when somebody has the crank itself balanced with some heavy metal so they can run a regular balancer and flexplate, but that's expensive and not too common.

 

I wouldn't say that is true. In fact you'd be hard pressed to find an externally balanced 383 or non stock 400 now-a-days. Summit lists qty 53 3.75" stroke 2 pc main crankshafts, of those, 47 are internally balanced. The 6 they have are all cheapy cast ones from 160 bucks to 250 bucks. When doing a 383, you started with a 350 and wouldn't want to buy a 400 balancer and flywheel, since you can use the 350 stuff with the correct crank.

 

Just don't want to send somebody down the wrong path.

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A 350 with the 3.75 stroke (400 crank) is a 377 with a .030 overbore, or a 383 with .060 overbore.

 

 

 

huh? a 383 is a 350 block bored .030 with a 3.75" stroke

 

388CID with a .060 overbore

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400 oil pans are pushed out at the rails for rod clearance. Most aftermarket pans are clearanced for longer stroke.

 

Small Block bore/Stroke

262 3.67/3.10

265 3.75/3.00

267 3.5/3.48

283 3.875/3.00

302 4.00/3.00

307 3.875/3.25

327 4.00/3.25

350 4.00/3.48

400 4.125/3.75

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Originally Posted By: 72 LS5
Chances are you have a regular 350 crank - 3.48" stroke.

 

If somebody put a stroker crank in your 350, chances are that it would have to be externally balanced (like the 400s were from the factory). When you use the 400 crank, you need the 400 balancer and flexplate. The balancer is weighted more on one side (of the inside by the hub) and the flexplate has a weight about the size of a pack of gum near the teeth. There are some exceptions such as when somebody has the crank itself balanced with some heavy metal so they can run a regular balancer and flexplate, but that's expensive and not too common.

 

I wouldn't say that is true. In fact you'd be hard pressed to find an externally balanced 383 or non stock 400 now-a-days. Summit lists qty 53 3.75" stroke 2 pc main crankshafts, of those, 47 are internally balanced. The 6 they have are all cheapy cast ones from 160 bucks to 250 bucks. When doing a 383, you started with a 350 and wouldn't want to buy a 400 balancer and flywheel, since you can use the 350 stuff with the correct crank.

 

Just don't want to send somebody down the wrong path.

 

Sorry to steer ya down the wrong path! I haven't had a small block in a while and was just going by what I remembered - things have changed a lot. Please scratch that info about the externally balanced stuff. That's the way they USED to do it!

 

And the 377 is the standard bore stroker, 383 is .030 over - I need a cup of coffee.....

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  • 3 weeks later...

That is correct.

And you can build a real screamer with a .030 over 400 and a 327 crank that is a 352

 

Or a .030 over 400 and a 302 crank is a 325 both of these engines will need to be turned hard and will need lots of valve spring. $$$$

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I like that listing showing all the various bore/stroke combos-I notice most of them have a relatively short stroke relative to the bore-I remember hearing when the stroke is shorter than the bore dia the engine is referred to as 'undersquare' was this just a local talkin after too many Michelobs? But does that configuration make for a more mechanically sound engine? I would think it would less inertia with a smaller stroke-just thinking out loud-engine gurus please comment/set me straight thanks Brian

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Actually a engine with a bore larger than stroke is "over square". Shorter stroke engines are said to rev better. Bigger bores unshroud the intake valve next to the cylinder wall helping flow. and it is easier to get big valves in a large bore engine.

Piston speed is slower in a short stroke engine. It is also said that long stroke engines create more torque because the piston is exerting the same force on a longer lever. There are lots of theories out there and a bunch or talented guys making them work, or going different directions and making big power.

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Thanks Mike-I vauguely remembered 'under over and square' were in there somewhere-but I had it reversed after all those years-makes sense-the higher rev vs higher torque on the 2 combos- I do find all the theories of operation and the way air fuel and fire react in different mechanical combinations to give such diverse power curves quite interesting-these engine threads always provide great info-so I will step off and let the discussion continue ... brian

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400 oil pans are pushed out at the rails for rod clearance. Most aftermarket pans are clearanced for longer stroke.

Small Block bore/Stroke

262 3.67/3.10

265 3.75/3.00

267 3.5/3.48

283 3.875/3.00

302 4.00/3.00

307 3.875/3.25

327 4.00/3.25

350 4.00/3.48

400 4.125/3.75

 

Oo you forgot one Mike:

305 3.735/3.48

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