85F-body

you know how a 387 is just a 350 with a longer stroke basicly. well is a 400 something like that or is it just a 400

Chris 84TA

a 383 is a .30 overbored 350 block with a 400 crank...

i have seen kits to bore and stroke a 350 to as much as 396... but a 400 block is a different block... while still a small block chevy it has siamesed cylinders and the heads have steam holes drilled in them...

so in short... yes and no... yes it is similar to a 350, but no it is a different block...

later,
Chris

RB83L69

A 400 is a 400. Period. (actually 401.6)

A 383 is what you get when you put a 400 crank in a .030" overbored 350 block (4.030" after boring). When you put a 400 crank into a stock 400 bore (4.125") block you get.... a 400.

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"So many Mustangs, so little time..."
ICON Motorsports

Grand Prix

They are all right, I'll just see if I can clear it up a little. The 400 block is a different block than the 350. It has different cylinder sleeves (not changeable) that are larger to make the extra displacement from a 383 to a 400. The sleeves are so large in fact that they run continuously without break from the first cylinder to the last cylidner. A 350 would have paper thin cylinder walls by the time it was overbored enough to reach the stock 400 bore. A 383/387/396 are all aftermarket creations by using a longer stroke crank in a 350 block. A 400 is a factory configuration using the same stroke as the 383 but the larger block. From the outside though the 305/327/350/400 block are almost identical, making the engines easy to interchange.

Apeiron

Don't forget the 283, 302, 307, etc.

JoelOl75

The 400 is a 3.75" stroke on a 4.125 bore.
The 350 is a 3.48" stroke on a 4.000 bore.
The 383 is a 3.75" stroke on a 4.030 bore.
The 388 is a 3.75" stroke on a 4.060 bore.

You would need to overbore a 350 to +.125 over and install a 400 crank with the journals cut to fit the 350 and shorter rods from the 400.. which isn't a very good idea if not impossable(on the bore). Also the 400's stock use a shorter rod and have larger main journals along with siamesed cylinder bores and steam holes to release any gas buildup as a result of 'barracading' the waterjacket.

Mark W. Winning

Lets take this one step further. We know you can stroke a 350 to 383/39? , but what kits are out there for the 400. I just picked up a virgin short block and it is being shipped out to be bored .30 over and have spayed caps added.

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1992 Pontiac Firebird 350/Six Speed
1987 Toyota Pickup 383/500+ HP

RB83L69

Yes! If you're like some of us and can never quite get enough, there are stroker cranks for the 400 available. I just built such a motor for a friend, it was a .030" over 400 with a 4" stroke and 6" rods, which works out to 434. Unfortunately the rings were the 1/16" width, tightly packed at the very top of the piston, and the oil ring still was over the pin. I don't know how long this is going to make it on the street.

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"So many Mustangs, so little time..."
ICON Motorsports

RyanSS

I've always wondered if you can put a 4" crank in a 350 block. Anybody know?
If you can it would take a hellofalotta machine work.

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89 RS 350 TBI auto Hooker SC/LT headers Open element 3in K&N CVT protorque mini-starter

Daily driver 91 RS auto LO3 63k

Grand Prix

You can, and people have. GM played with this idea when developing the 400. Yes it takes a fair bit of work and a reduced base circle cam is almost required. It comes up to something around 396CI. Some people swear by it, I swear at it. 4"X4" is not a good combination. It would be bad enough with a 4.185" bore (400 .060" over). Makes me start to feel like the 455 olds is born again. It can be done but the bore/rod/stroke combination is poor. Not to mention getting the ring package over the wrist pin is unavoidable. But before tomorrow someone will be jumping up and down that their 10 second nitrous fed 396 is the best engine ever made.

AlkyIROC

Trouble with the design of the small block is that GM forced the design out to 400 CID and kept the external demensions the same as all the other small block. This was the maximum they decided the block could go and keep the engine reliable for many miles as a street engine.

A 400 block can be safely bored .030 over and can go to .040 over if there's no core shift in the block.

A stock production block can be extended further with aftermarket stroker cranks out to 434 CID however long life of the engine is greatly reduced.

Aftermarket and bowtie blocks have been extended out to 454 CID.

If you want to go bigger that a 400, your best choice is a big block. The larger block allows for more CID without the internal clearance problems of a small block.

If you want to build a 383 then buy an aftermarket stroker crank. If you have to use a 400 to build a 383 then just build a 400/406 engine. Since they stopped producing 400 engines in 1979, there are fewer out there every year.

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87 IROC-Z SuperPro ET Bracket Race Car
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