Anyone give a techy definition of, what is "big block engine", as opposed to a "small block" [sm=feedback.gif]
Is the Hemi a big or small block [sm=confused06.gif]
Al

 

I don't know as far as a exact definition but I do know that the 5.7 Hemi is a small block while the original Hemi and possibly the 6.1 Hemi are big blocks.

 

External dimensions....the 5.7 and 6.1 have identical (pretty much) external dimensions. Look at a 340, then a 440 (or a 302 and 460, 350 and 454, etc..). The block, head size differences are huge. Almost doesn't matter anymore because you can make 400+ cubic inch small blocks making in excess of 500 hp. The LS7 in the Z06 Corvette is a 427" pushrod small block making north of 500 hp. Hopefully the proposed 392 hemi crate motor makes it to production (supposed to be 500+ hp). Adding to the confusion are engines like the original A 318 (before the modern LA version). That was a poly engine, but it was quite bigger size wise, even for its displacement. That's where you might hear about a big block 318.

 

small blocks have a shorter stroke then big blocks. the longer stroke gives the big block more HP and torque the old dodge 400 and 440 were big blocks.

 

Back in the day (60's) Chevy was the only company to produce a real "big block" and "small Block" (lets put aside the Hemi for a second.) Most of the other manufacturerers, regardless of displacment, the blocks sizes were the same. There was no way to tell the difference cosmetically between the 340 and 383, the 327 and 350, 348 and 409, etc. A chevy, you could tell if it was a BB or SB by looking at the size of the heads and block.

Now the Hemi was definately bigger in size then the rest of teh Mopar line. Alot of companies classified the Big blocks and small blocks, but most were actually the same size.

 

well he may be getting confused because they used to call the hemi's "elephants engines" and still are a decent size today

 

Hey, I know its a Dodge forum, but you forgot small block and big block fords, 265, 289 302 351(small) and 352, 360, 390 427, 428,429, 460 Boat anchor big blocks.

 

Pontiac is the same way... there is no such thing as a big block pontiac.... but there is such thing as long stroke short strok pontiacs...

The Pontiac 326-455 are the SAME EXACT external dimensions. Heck they all share the same exact 6.625" Rods... All engine parts are interchangable and the 350-400 share the same stroke/crank.

But the Pontiac blocks are HUGE... so you could technicaly call them big blocks as a Pontiac 326 will dwarf a chevy 400. And all the cam shafts fit 326-455... A cam froma 455 may not perform well in a 326 but it will bolt right in.... the heads are also ALL interchangable and a head off a 326ci will bolt right onto a 455ci.


SPEED SAFE, AIR RAM

 

I thought that the big block and small block motors were seperated by a ratio of bore size to stroke.

 

How wrong you are...340 was obviously physically smaller than a 383, not to mention the distributor on a 340 is in the back, 383 (350 & 361, actually) and up are in the front. All of the structures (block, heads) of 350-361-383-400-413-426W-426H-440 are more than obviously bigger than 273-318('67 and up)-340-360. With a little experience you can actually detect the width/deck height difference between the 350-361-383-400 (B engine) and the 413-426W-426H-440 (RB engine, including a one year only 383 RB...) Not to mention the difference between a Ford 302 and a 460....