Big block, small block? Not what you think.....

[American Muscle]

I am doing research to buy a new engine for my '68. It's a 318 and I am looking at either a new 360 or a new 440. My question is not about power. It's about the cubic inches. I saw a few 440 engines online but they all say it's a 440 engine but it is built with a 340 block. What does that mean? I always thought numbers like 440 or 360 mean the blocks are supposed to be 440 and 360 but this 440 I see says it is made with a 340 block. Can someone please explain this to me? Thanks.

[mauve66]

indy cylinder head has 360 blocks with strokers for 408 and 440 cubes, less weight over the front end and more power............ and you can actually get to the spark plugs if you want....... but i still prefer big blocks

[American Muscle]

I'm sorry, I have no idea if you answered my question or not. All I want to know is why or how a 440 can be made with a 340 and still be called a 440 and if it can't be made why are they calling the 440 with a 340 block a 440?

[mikepmcs]

Disclaimer: I will be swiftly corrected if any of this information is in error.

The small block is "stroked" to make it that way

http://www.carcraft.com/howto/ccrp_0702_stroke_any_engine/index.html

As I see it, the bore and stroke has been increased on the 340 block to reach the bore and stroke of a 440 through a combination of the grocery list in the above article.(ie from 4.04" bore x 3.31" stroke to 4.250" bore x 3.875" stroke on this particular application)  It is now a stroked small block that has a cid of 440. 

Another advantage of using your existing small block engine and beefing it up is that you won't have any issues with fitment in your car because it came with a small block.  You will need to change a few things before dropping a big block(383, 440, etc....) in there.

FWIW worth I believe a factory 440RB motor has a bore and stroke of 4.32" x 3.75" respectively.

Another good article
http://www.hotrod.com/howto/69883_stroke_any_engine/index.html


Bigger hole, bigger boom, more power
http://en.wikipedia.org/wiki/stroke_(engine)
For whatever reason the above link will not work to get you to the stroke definition. I've tried everything I can think of to make it work.  Hit the hot link and then when it gets to the page, look up in the url and you'll see the other half of the prenthesis is missing ..")"  add it in there and hit enter and the definition will come up.

[Troy]

There are "families" of engine blocks which use (essentially) the same casting. The number describes the displacement of the engine in cubic inches (bore x stroke). The 318, 340, and 360 are "LA" small blocks with different bore/stroke combinations. Likewise, the 383 and 400 are 'B" blocks and the 413, 426 (wedge and Hemi), and 440 are "RB" blocks. These are the stock combinations that Chrysler produced. Any change cylinder dimension changes the overall displacement. For example, when rebuilding an engine it is often necessary to increase the bore to clean up the cylinder walls. Typically this will be .020, .030, .040, or .060 and new pistons with the correct size need to be purchased. Increasing the bore increases the displacement - although only a small amount (I think a .030 over 440 ends up at 446 cubic inches). Many times engine builders will also change the stroke of an engine to get a more ideal bore/stroke ratio. This makes a "stroker" motor and, depending on how it's done, can add a large amount of displacement. There are a multitude of combinations but popular kits are 318 to 392, 340 to 410, 360 to 408, 400 to 451, 440 to 496, and several that take a 440 beyond 500 inches. The fact that a "stroked" motor produces the same displacement as a different original motor is usually marketing but can be confusing.

Troy

[American Muscle]

Mike, thanks for the response. The sites you gave me more insight on what a stroked motor was and how they work.

Troy, I appreciate your answer as that was the exact explanation I was looking for. I understand the difference now and I definitely now have more of the knowledge and understanding I need to make the right purchase for my vehicle. Thanks.

If I have anymore questions I will definitely ask again. Thanks again.

[mauve66]

sorry, i should of said 360 blocks with stroker CRANKS

[American Muscle]

It's cool, man. I appreciate the response. I've learned so much about my Charger because of this site. Believe me, I learn something new everytime I come here. Trying to be like a sponge when it comes to my muscle cars.