Definition of big block vs. small block

I believe I have something to add to this thread from a historical perspective. I am also a big car enthusiast (I own a 1974 Buick Estate, a 1959 Lincoln Continental coupe and a 1966 Imperial convertible) and so believe I know a big block when I see one. Big cars need big blocks because of the torque potential they offer.

The distinction between big and small block is perhaps most important to Chevrolet enthusiasts. Chevrolet of course added a second block size in 1958 with the introduction of the W-series.

Perhaps a metric for block size is in order. May I suggest bore spacing? It is the one dimension that is never changed in an engine series no matter what the other modifications are. It is a good indicator of CID potential. For example both the W and Mark series Chevrolet big blocks have a bore spacing of 4.84" and the Chevrolet small block has a bore spacing of 4.4".

Chevrolet was not the first manufacturer to introduce multiple block sizes however. In 1952 Ford added the Lincoln Y-Block (4.63") to the Flathead (3.8") and Chrysler added a Desoto Hemi (4.3125") to its Chrysler Hemi (4.5625"). Chrysler added a separate Dodge (4.1875") and Plymouth (4.46") V-8 engine series in 1953 and 1956 respectively. Thus from 1956-57 Chrysler had four different block sizes. By 1959 they pared this down to two different block sizes: the A/LA series (4.46") and the B/RB series (4.8"). They would continue to offer two different block sizes through 1979. When Mopar fans refer to big versus small block this is what they are usually talking about.

Ford replaced the venerable Flathead with a Ford Y-Block (4.38") in 1954. In 1958 they replaced the Lincoln Y-Block with the much larger MEL (4.9") and the Ford FE-series (4.63") was also introduced. Ford would continue to offer three basic block sizes through 1976 with the Ford 335-series taking the place of the Y-Block after a three year overlap (1962-64) and with the MEL replaced by the 385-series (4.9") in 1968. Thus talking about a big versus small block Ford is something of a misnomer as there were actually three different block sizes from 1958 through 1976.

Buick had only one block size, the Nailhead (4.75"), until the introduction of its small block in 1961 (4.24"). This engine was used on other makes, in particular Oldsmobile and Pontiac. Buick would continue to make two different block sizes through 1976 with the Nailhead being replaced by the "Big-Block" (4.75") in 1968.

Cadillac, Oldsmobile and Pontiac only ever offered one V-8 block size during this period. Cadillac increased its bore spacing from 4.5625" to 5.0" in 1968. Oldsmobile replaced its original Rocket V-8 with a new series in 1965 but both have the same 4.625" bore spacing. Pontiac's V-8 has a bore spacing of 4.62". As previously noted in this thread Pontiac enthusiasts are quite anal about the fact that there is only one Pontiac block size. On the other hand Oldsmobile fans are notoriously inconsistent and on this score and perhaps 67RocketPower is evidence of this.

And last but not least there are the independents. AMC's V-8 has a respectable bore spacing of 4.75" and Packard has a monumental bore spacing of 5.15". The Packard V-8 was supposedly going to be bored out to a 440 CID in 1959 but Packard went under before that could happen. The engine obviously had a lot of CID potential that was never realized.

This is clearly a matter of semantics but if one were to consider a universal standard for all V-8s may I suggest the following? Among manufacturers that had an extended period of offering two basic block sizes (Buick, Chevrolet and Chrysler) the largest small block was the Chrysler A/LA (4.46") and the smallest big block was the Buick Nailhead/Big-Block (4.75"). If one were to establish an arbitrary cutoff it should lie somewhere between these two values, perhaps at 4.6" bore spacing.

On the other hand, Ford had an extended period of offering three different block sizes. Perhaps it would be better to classify blocks with bore spacings from 4.47" through 4.74" as midsize blocks. Under this rubric the Lincoln Y-Block, the Ford FE-series, both of Oldsmobile’s V-8s, the Pontiac V-8, the early Cadillac OHV V-8 and the early Chrysler Hemi would be classified as midsize blocks.

I’ve researched this a little further and I’ve decided that this deserves a slight elaboration based on deck height. But first a correction is in order.

The Packard V-8 actually had a bore spacing of 5.00” not 5.15”. I’ve verified this by reading some Packard engineering bulletins from the period.

Deck height is also a relevant measure when talking about block size, particularly when considering Oldsmobile V-8s. Hence 67RocketPower may have a point although he didn’t know why.

The later series Oldsmobile V-8 came in two distinct deck heights: 9.33” and 10.625”. The former of these came in displacements ranging from 260 CID to 403 CID. The latter vary in displacement from 400 CID to 455 CID. Thus Olds enthusiasts can legitimately claim there are two block sizes, but the difference is deck height, not bore spacing. However, the difference between these engines is of course much less than that between the small and large block Chevys (for example).

Other engines also came in varying deck heights and this naturally creates a plethora of block sizes. So how can one quantify all of this? Well one possibility is to compute engine block volume. In other words if one takes the square of block spacing by deck height and then multiply this result by eight to account for the number of cylinders. Doing this one gets the following results:

Rank Engine CID Bore Sp. Deck Hgt. Block Vol.
1. 68+ Cadillac 472-500 5.00” 10.8125” 2162.5 CI
2. Packard 320-374 5.00” 10.625” 2125.0 CI
3. 68+ Cadillac 368-425 5.00” 10.56” 2112.0 CI
4. Ford MEL 383-462 4.90” 10.482” 2013.4 CI
5. Ford 385 460 4.90” 10.322” 1982.6 CI
6. Chrysler RB 383-440 4.80” 10.725” 1976.8 CI
7. Ford 385 429 4.90” 10.29” 1976.5 CI
8. Buick BB 400-455 4.75” 10.57” 1907.9 CI
9. Lincoln Y-Block 317-368 4.63” 10.94” 1876.2 CI
10. Chrysler B 350-400 4.80” 9.98” 1839.5 CI
11. Chevrolet W 348-427 4.84” 9.80” 1836.6 CI
12. Chevrolet Mark 396-454 4.84” 9.80” 1836.6 CI
13. Oldsmobile BB 400-455 4.625” 10.625” 1818.2 CI
14. 49-63 Olds 260-403 4.625” 10.625” 1818.2 CI
15. Chrysler Hemi 392 4.5625” 10.87” 1810.2 CI
16. Buick Nailhead 401-425 4.75” 10.00” 1805.0 CI
17. Buick Nailhead 364 4.75” 9.75” 1759.9 CI
18. Pontiac 287-455 4.62” 10.25” 1750.2 CI
19. Ford FE 332-428 4.63” 10.17” 1744.1 CI
20. Chrysler Hemi 301-354 4.5625” 10.32” 1718.6 CI
21. 64-67 Cadillac 429 4.5625” 10.105” 1682.8 CI
22. Buick Nailhead 264-322 4.75” 9.25” 1669.6 CI
23. AMC 304-401 4.75” 9.208” 1662.0 CI
24. AMC 290-390 4.75” 9.175” 1656.1 CI
25. Oldsmobile SB 260-403 4.625” 9.33” 1596.6 CI
26. Ford 335 351-400 4.38” 10.297” 1580.3 CI
27. Desoto Hemi 330-345 4.3125” 10.37” 1542.9 CI
28. Chrysler A/LA 277-360 4.46” 9.60” 1527.7 CI
29. Ford Y-Block 239-312 4.38” 9.77” 1499.5 CI
30. Hemi-Magnum 392 4.46” 9.252” 1472.3 CI
31. Buick SB 215-350 4.24” 10.187” 1465.1 CI
32. Ford 90-Degree 351 4.38” 9.50” 1458.0 CI
33. Dodge Hemi 315-326 4.1875” 10.38” 1456.1 CI
34. Desoto Hemi 276-291 4.3125” 9.54” 1419.4 CI
35. Chevrolet SB 262-400 4.40” 9.025” 1397.8 CI
36. Dodge Hemi 241-270 4.1875” 9.29” 1303.2 CI
37. Ford 90-Degree 221-302 4.38” 8.206” 1259.4 CI
38. Ford Flathead 221-255 3.80” 10.4375” 1205.7 CI

This is hardly comprehensive and it may have some inaccuracies but it’s a good starting point for a volumetric discussion of block size.

I think this if anything makes it clear that talking about deciding what constitutes a small versus a big block is a somewhat arbitrary matter as there is in fact a continuum of block sizes. But given the popular terminology and the engines which were available at those times it would seem a cutoff between a two classification system should be somewhere between 1597 CI and 1759 CI, a range which includes seven engine blocks on this list.

Some corrections, elaborations and additions.


Correction:

Engine CID Bore Sp. Deck Hgt. Block Vol.
Ford 385 429 4.900” 10.30” 1978.4 CI


Elaborations:


The early Olds block came in three different sizes:


Engine CID Bore Sp. Deck Hgt. Block Vol.
Olds 371-394 4.625” 10.625” 1818.2 CI
57-58 Olds 371 4.625” 10.375” 1775.4 CI
Olds 303-324 4.625” 10.25” 1754.0 CI


The Buick Small block also came in three different sizes:


Engine CID Bore Sp. Deck Hgt. Block Vol.
Buick SB 340-350 4.240” 10.187” 1465.1 CI
Buick SB 300 4.240” 9.543” 1372.5 CI
Buick SB 215 4.240” 8.96” 1288.6 CI


The Ford 335 block came in two different sizes:



Engine CID Bore Sp. Deck Hgt. Block Vol.
Ford 335 351-400 4.380” 10.297” 1580.3 CI
Ford 335 351 4.380” 9.200” 1412.0 CI


Additions:


Engine CID Bore Sp. Deck Hgt. Block Vol.
Rambler 250-327 4.75” 9.994” 1803.9 CI
Studebaker 224-305 4.50” 10.065” 1630.5 CI


The list should now have 46 blocks and 10 fall in that grey middle area.

Ford has engine families and lends no credence to the BB/SB terminology .
They did however allow this series of tech books.

http://m69.photobucket.com/albumview/albums/mil1ion/67-79%20Ford%20Truck%20Information/Engine%20Related/Fordsmallblock.jpg.html

Here is a link to the best big block small block explanation I've ever seen check this out
https://www.youtube.com/watch?v=LPZuEWli4gQ&list=HL1389556570&feature=mh_lolz

The MFG's who designed the blocks are the ones who decided big block and small block or if there were no such animal in their engine line Pontiac for example has neither big or small block distinction it's just a Pontiac It's not bore spacing or any of that It's what the Factory's who designed the engine say it is Big, Small , or neither

All Pontiacs are short blocks period. Neither big nor small blocks are apt descriptors.

short block refers to a engine without the head(s) not the size

If you are saying that any engine minus it's heads is a short block, you are mistaken.

https://en.wikipedia.org/wiki/Short_block
argue with them

I spent an hour today correcting Wiki on various topics. If enough people on the net repeats something it apparently becomes fact. This is what has become of the world today. And by the way I was also correcting some of the corrections. I have various resource material from the 70's that says Wiki is wrong. The net is a vast universe of misinformed users on all topics who don't know the difference between two to and too or there their and they're. Yet you're asking me to challenge Wiki and the pool of users that supplies most of the content there. Isn't it ironic the dictionary keeps changing the spelling of words to appease those that can't or don't use it. I foresee in the future many years from now that yes you will be right, a big block chevy without it's heads is indeed a short block. LOL

You are incorrect. It sounds more like you are confused. It sounds like you are confusing deck height as being part of the "short block" definition.

The term short block refers to ANY engine. It usually refers to the bottom end with rotating assembly. Long block usually refers to the short block plus heads and sometimes include intake manifold.

You can buy a short block for a BB 396.

Hell look at Summit Racing. They sell short blocks for several engine sizes, both BB and SB.

EDIT: http://www.summitracing.com/parts/mll-bp4960/overview/

That link right there shows a 396 big block bottom end being called a short block by one of the largest racing parts companies in the world.

I foresee in the future many years from now that yes you will be right, a big block chevy without it's heads is indeed a short block. LOL
You are correct.
A rat motor with no heads and ancilleries is a short block.
See.......... you're learning.

The term small block or big block may not have much meaning now but For Ford it started way back in 1952! Ford built two new Engines known as the Y blocks! The first was the Lincoln Y Block it had a 10.7 inch deck high and a 4.63 bore spacing it Was a big blocki A Ford car
Y block made it had a 9.7 deck and a 4.38 bore spacing and was a small block
If you look at the specs the Lincoln y block has the same bore spacing as the all ford FE engines from 332 to 428 at 4.63! The Ford y block has the same bore spacing as all ford small blocks from the 221 to the 400 at 4.381 the reason for these dimensions were to fit these engines into the small cars built in the early 1960's the y block was down sized to 8.2 deck to make the engine small enough to fit into the 1962 Falcon! The small block ford dimensions were increased to 9.5 to build the 351 then shortened to 9.2 for the Cleveland then increased to 10.3 for the 4001
although the deck increased fords small block engines all had the 4.38 bore spacing as the original Y block engine!

A Chevy small block.has a 4.40 bore spacing a big block Chevy has a 4.84 bore spacing! A Pontiac engine has a bore spacing the ids the same as the Ford FE that makes it a big block! Dodge small block has a bore spacing
of 4.46 and there big block is 4.80! To get big power Big block engines were needed! To fit into the small tight chassis of the mid 1960's all the manufactures needed to have a small engine or be stuck with a 6 cylinder engine!

And your name implies you put a stroker crank into a 302 Windsor small block, and converted it into a -------big smallblock!
BTW, if you still have it, what is the buildup?

And your name implies you put a stroker crank into a 302 Windsor small block, and converted it into a -------big smallblock!
BTW, if you still have it, what is the buildup?


My ranger is a 1983 ranger it was a first year Ranger 4x4 that came with a 2.8 v6 and a C-5 automatic transmission! The stock 2.8 engine was never much to talk about so when my dad give the truck to me I decided to build a real engine! The engine is a scat 347 stroker kit with Wiseco pistons! the heads are a set of world Windsor heads with 194 intake valves and 1.60 exhausts headman ranger headers! The cam is a Comp 284 extreme energy!
Edelbrock torque intake and a 670 street avenger Carb!
I run 3.73 gears in and 8.8rear! the engine is mild 355 hp at 5500 rpm!

Glad to see you ditched the stock heads. They don't flow well.
Maybe next spring I'll install a Trick Flow upper end kit on my 93 Cougar with a 5.0 H.O.
Leave out the hot(ter) roller cam but install the heads, intake, some headers, roller rockers, etc.
Should be fun. Put some life in the car, and it only has 53K miles on it.
Already have the stuff, just need to put it on..
... waiting for the Washington State smog testing to expire--just in case it gets cranky.

Glad to see you ditched the stock heads. They don't flow well.
Maybe next spring I'll install a Trick Flow upper end kit on my 93 Cougar with a 5.0 H.O.
Leave out the hot(ter) roller cam but install the heads, intake, some headers, roller rockers, etc.
Should be fun. Put some life in the car, and it only has 53K miles on it.
Already have the stuff, just need to put it on..
... waiting for the Washington State smog testing to expire--just in case it gets cranky.

When my dad give me the ranger The first thing I seen was the tranny was a C5 This made the swap easy! I rebuilt the tranny with 5 red clutch discs in both front and rear pack and used a 147 tooth flex plate! and by spacing the Mustang II Bell housing to proper depth I use a pinto Converter for a factory high stall!

the 302,351W,351C,351M, the always forgotten Ford 400(the missing link).

A 302 and 351W are small blocks. But also note that a 302 and a 351W are different blocks due to the 351W's taller deck height.
Now the 351C,351M, and Ford 400 are all actually the same block except that the 351M/400 have larger crank journals, also they are all big blocks.
The cleveland came first, then Ford wanted to use the block in trucks and passengers cars so the stroked it to 400 and changed the mains and ditched 4V heads. All this to make more torque at lower rpm's more suitable for a car/van/truck. Once the gas crunch hit they destroked the 400 back to 351. It was a modified 400 hence the name 351M.

I don't know about Chevy/Mopar etc.. but I know why Ford has such a messed up line is purely cause of History. Once you know the chronological order you understand.

if a Cleveland and a 400 are big blocks then how come the head off a 400 will bolt directly onto a 221! The Cleveland engine block is not the same as a 400! The 351 block has the same engine mounts and bell housing as a 302! the deck height of a 351 is 9.2 inches! The 400 has engine mounts that were compatible with the full size cars and the and the deck height is 10.3 inches!
400 bell housing bolt pattern is the same as 429 - 460! If you can take the head off a 400 and bolt it on to the 221 these engines are from the same family! The 400 is not a big block the only part that will fit a 400 from a big block is the bell housing!

I just go with what people call them; I'm not going to re-invent the world. With Fords, there were both a small block 351W and a Cleveland-based 351M. Same displacement, 2 very different engines with almost zero parts interchangeability. And there was an entirely different 352 as well. Most Ford aficionados will refer to the 351 as either a Windsor (W) or a Modified (M) or sometimes calling that last one a "big block 351" even though it was never referred to as such by Ford. As long as everyone knows which engine you're talking about the point is rather moot about what you call it. BTW, a Ford 400 is the same basic block casting (but not interchangeable with) the 351M, and although they were based on the 351 Cleveland block design, there's almost no interchangeability there either.

The C6 trans you can find behind both of these comes with different bolt patterns for each and it comes in both a car and truck version with different gearing. It's a can of worms with Ford small-blocks with even cylinder heads which are from the same engine but different years fitting but not working correctly, and cylinder heads from different engines having the same issues when swapped out. Heck, most Ford V8's were like this- consider the several different 429's they made! Mid-year changes were common and even the crank, balancer, and flywheel/flexplate can be different with the exact same engine/drivetrain in the same model year. On old Chevys, if it bolts up it will probably work. With old Fords you have to know the details and what it takes to make things work right even if it bolts right up because it might work and it might not.

Just an old Ford nut here, I don't know a lot about the newer ones but I've got a 5.0 Mustnag roller-cam block running a near-stock 302 everything else because it works and that's what I was building with. Crappy heads have about 400K miles on them now with only new seals, springs, and retainers and they're still like new. Go figure, it's a Ford!

Phil