BIG block or small ? RIVIERA 1966 - engine 425

[cquisuila]

hELLO

I have a question on my engine 425 on my riviera 1966

 

confirm you that it is a big block ?

[NTX5467]

264-322-364-401-425 would be "NailHead" V-8 engine family members.  As evidenced by their valve cover design, and other design items.

 

NTX5467

Edited May 10, 2023 by NTX5467 (see edit history)

[cquisuila]

9 minutes ago, NTX5467 said:

264-322-364-401-425 would be "NailHead" V-8 engine family members.  As evidenced by their valve cover design, and other design items.

 

NTX5467

so big block ? 😊

Edited May 10, 2023 by cquisuila (see edit history)

[RivNut]

53 minutes ago, cquisuila said:

hELLO

I have a question on my engine 425 on my riviera 1966

 

confirm you that it is a big block ?

In 1966, Buick had a 225 cubic inch aluminum V8, a 300 cubic inch cast iron V8,  and the 401 and 425 cubic inch “nailheads.”  From 1953 - 1966, the nailhead came in 264, 322, 364, 401, and 425 cubic inches but the same exterior dimensions.  Up until 1961, Buick only had the one engine, the “nailhead.”

Edited May 10, 2023 by RivNut (see edit history)

[60FlatTop]

 

I usually go by the valve size. Some are big, others not so big.

 

[RivDad]

1 hour ago, cquisuila said:

hELLO

I have a question on my engine 425 on my riviera 1966

 

confirm you that it is a big block ?

To answer your question... no the 425 is not considered a "big block". It is physically the same size as the 401, but with larger displacement. The true Buick "big blocks" began in 1967 and ran through 1976. They were the 400, 430, and 455.

[telriv]

Most piston manufacturers denote big block as 4.251" bore or more.

4.250" or less is denoted as a small block.

 

Tom T.

[joelj]

Typically big/small block is a Chevrolet nomenclature used to distinguish the mark IV family of engines from the original small block V8 and its successors. Buick Olds and Pontiac engines are each of a different design and different from Chevrolet regardless of displacement. I am not sure if the big/small block nomenclature applies to BOP engines as well as it does to Chevrolet. I think I would refer to your engine as a Buick 425 or 425 Nailhead to avoid confusion.

 

[The 55er]

Source book is only calling the Buick 400, 430 and 455 engines big blocks.

[RivNut]

Oldsmobile refers to its 403 as a small block. It has a 4.351” bore.  But its 400 with a bore of 4.000” is referred to as a big block. Go figure? 

[Pat Curran]

There are some misconceptions out there about what constitutes a big block.  Some think that once you get into the 400’s, it is a big block automatically.  Not correct.

As an example, Pontiac never manufactured a “big block” engine.  Big bore yes, but they were technically not big blocks.  

 

[cquisuila]

 

 

so big or small block it is difficult to choice but certainly a small block for my engine

my engine 425 :  4.3125 * 3.640

intake valve 1.87

exhaust valve 1.50

340 HP for 4400 RPM

Edited May 11, 2023 by cquisuila (see edit history)

[EmTee]

The 425 cubic inch nailhead was the largest displacement Buick engine available in 1966.

[60FlatTop]

I have never used the term "Big block" to describe a Buick engine and don't recall anyone I associated using it either. It was just a Chevy term all my life and that's a pretty long time.

[NTX5467]

The whole "big block" or "small block" issue IS more related to later model engines than those built by BOP starting in the earlier 1950s.  Back then, there was only ONE block architecture for each of the carlines.  Just as GMC had ONE engine architecture which went from 228cid to 302cid (the same oil pan and valve cover fit all of those engine sizes). 

 

By observation, the Chevy 265-400 V-8 engine family did not get to be a "small block" until mid-year 1965 when the Mark IV engine family was introduced.  Before that, it was the 265/283/327 engine family and the W-block 348s and 409s  -- NO big block or small block designations!  Back then, everybody talked about engine displacement (as that was more important!) and engine manufacturer.  As each OEM had their distinctive engine sizes, if you mentioned that you had a 327 in your Chevy, everybody knew what it was.  Same for a Buick NailHead.  Or an Olds Rocket V-8.

 

Respectfully, I have NEVER heard that piston diameter was a determining factor in this discussion!  More of a generality than actuality, it seems to me.

 

If you want to talk about engine weight, there is only ONE "big block", which is the Chevy Mark IV family, as most of the other GM brands' V-8s have usually been very close to the weight of the original Chevy 265-283 engine family, but with much more displacement, in many cases.

 

Enjoy!

NTX5467

 

 

[drhach]

I understood "big block" "small block" as having more to do with bearing journal size and specifically as it relates to Chevy. I suppose Ford fell into that camp too. The FE's were often referred to as big blocks. But those started as "352's". So, it really isn't displacement. 

[telriv]

In reality the 1st. FE Ford block was a 332CID in very early 1958 & very closely followed by the 352.

 

Tom T.

[60FlatTop]

6 hours ago, NTX5467 said:

and the W-block 348s and 409s 

We just called those "The truck" block.

 

I should also note that I kind of wrote off those Ford FE engines, (which we called by a really derogatory name related the the shape of the carburetor). When half the head was part of the intake manifold we knew we were dealing with a tainted design. It just wasn't right.

Edited May 11, 2023 by 60FlatTop (see edit history)

[cquisuila]

 

Edited May 12, 2023 by cquisuila (see edit history)

[cquisuila]

i have to mesurate now !!! 🤣

Edited May 12, 2023 by cquisuila (see edit history)

[EmTee]

The figures above are specific to Chevrolet engines.  The only time I hear the term 'big/small block' associated with Buick is with the '70 and up 350 (small) and 455 (big) engines.  I agree, however, that this is really a Chevrolet term that is partially necessary because Chevy had both small and big block versions of its '400' cubic inch engine.  (The Chevy '400' big block was also known by its actual displacement as a 402...)

[cquisuila]

6 minutes ago, EmTee said:

The figures above are specific to Chevrolet engines.  The only time I hear the term 'big/small block' associated with Buick is with the '70 and up 350 (small) and 455 (big) engines.  I agree, however, that this is really a Chevrolet term that is partially necessary because Chevy had both small and big block versions of its '400' cubic inch engine.  (The Chevy '400' big block was also known by its actual displacement as a 402...)

ok 🙂

[drhach]

I think if you can't lift it without a hoist, it's a "big" block. 

[cquisuila]

In France it will be a big block ! lol

 

and engine 425 nailheads is neither big nor small !!😅

Edited May 12, 2023 by cquisuila (see edit history)

[RivNut]

It’s all about the design of the block, not the cubic inches.  

[NTX5467]

Perhaps the "New Normal" orientation might be at play here.  For those of us who were around in the 1950s and 1960s, being old enough to pay attention to "things" related to cars, IN THE BEGINNING . . . there was only ONE Chevrolet V-8 family (starting with the 1955 265), only ONE Pontiac V-8 family (starting in 1955 also), only ONE Oldsmobile V-8 family (the Rocket family), only ONE Buick V-8 family (the "Nail Head" family), and only ONE Cadillac V-8 family.  Chrysler had their HEMI family (with displacements related to carlines they were in) and their POLYSPHERE family (starting with Plymouth in 1955).  NO 'big block" or otherwise, just the car brands and maybe displacement sizes.  The Chevy 348-409 was NEITHER "big block" or "small block", just the car brand and engine size!

 

In those earlier times, the key words were "Power Pack" or "Power Pak".  Which meant a 4bbl carb and dual exhausts, for another 25 or so more horsepower output.  Maybe a bit lower rear axle ratio, too?  But these higher-output motors were not avaialble with 3-speed + Overdrive, usually.

 

The ABOVE things were "normal" for me as I "hit ground" when the new 1952 cars had been in the showrooms a month or so, after showdate.  "Showdate" was a really big deal back then, unlike now.  There was a massive amount of excitement to see what was new and exciting about the new cars . . . unlike now.  New colors and combinations, new interiors, new or freshened styling and chrome trim.  Upgraded engines and transmissions were some KEY things, back then, when 300 horsepower was a magic number of sorts for any engine which had any claim to "performance" and 0-60mph in about 7 seconds wss very fast.  In 1968, a new benchmark became 0-100mph in 20 seconds (which was what the then-new Plymouth Road Runner 383 4bbl could do it in, stock).

 

For anybody who started paying attention to "cars" in about 1965, their "normal" started to include "small block" and "big block" related to physical engine size families.  Chrysler had introduced their new LA engine family, with the 273 V-8, Ford had introduced their 221/260/289 small V-8 engine family.  Buick and Olds had their 215 V-8, as Pontiac V-8s just got bigger displacements from their existing engine family.  The Chevrolet V-8 engines evolved from 283s to 327s and the 348-409 engines were replaced by the then-new Mark IV V-8 engine family (396/427, with later 402 and 454 variations). 

 

The Chevrolet 348/409 was NEITHER big block or small block!  But the W-motor did lead the evolution into the NASCAR "Mystery Motor" which Smokey Yunick ran in his NASCAR Chevrolets.  Perhaps the original Chevy 265/283 would be "Mark I", the Chevy 348/409 would have been "Mark II", the NASCAR Mystery Motor would be "Mark III", with the later 396 V-8 being "Mark IV"?

 

BUT before the "small block" and "big block" terminology for Chevy V-8s, there was "Mouse" for the 350s and "Rat" for the 396s.  As the Chrysler 426 HEMI was termed "elephant".

 

The smaller V-8s which started to arrive in the early 1960s were usually designed to power smaller "intermediate" cars introduced back then.  With the Ford 221 OHV V-8 for the new 1962 Ford Fairlane, the Chrysler LA 273 for the Plymouth Valiants and Dodge Darts of 1964, and the Buick/Olds 215s for the Buick Specials and Olds Cutlass compact models.  All were physically smaller and lighter while still producing good power for their size.  With a more-efficient casting methods to build them, too.

 

So by the time the later 1960s came to be, as those who were just old enough to be paying attention to "cars", the terms "small block" and "big block", relating to V-8 engines, were much more operative for the engines being produced back then.  By that time, too, the various engine families had flowered into larger displacements and higher horsepower outputs.  Enough so that the smaller engines had their "base 2bbl", "optional 4bbl" and "HP or HO 4bbl versions" by that time, not unlike their "big block" family relatives.

 

NOW . . . contrary to some of the images presented above, there are NO physical size specs for what constitutes a "small block" or "big block" motor!  Never has been, no matter what, period!!!  Regardless of which version of "normal" one might use.

 

By observation, the most reliable information can come from the CAMSHAFT and ENGINE GASKET catalogs!  Where they list all of the various engine sizes and model years for their products.  Forget about bore diameters or stroke lengths.  DO consider "bore spacing" (the dimension between the cylinder bore centers, which will be greater for larger bores, unless they might be siamesed (as the Chevy TurboFire 400 V-8).  The Chevy TurboJet V-8 family is the 396 Mark IV engine family.  A Chevy TurboJet 400 is really a Chevy TurboJet 396 factory-bored +.030", but still marketed as a "400" V-8, for various reasons.

 

The Chevy TurboJet V-8 family also includes some TRUCK motors, too.  Not just installed in truck-chassis vehicles, but designed as "truck" motors with taller decks and 4-ring pistons.  Which will include a 366cid V-8 and a 427cid V-8.  With their tall deck height, they are perfect for an approx 500cid stroker motor (with a shorter 3-ring piston)!  But also necessitating several related items due to their taller deck height.

 

Sorry if I might have upset some peoples' apple carts in my explanations, BUT if you were around and paying attention back then, THEN you knew what was what as things evolved into the 1970s engine families.  EACH of the particular engine families had their own neat cubbyholes back then, just that NONE of them were labeled "Small Block" or "Big Block" NOR should they have been.

 

In modern terms, for the Chevy V-8s, the Chevy 265-400 TurboFire V-8s came to be "Gen I", with the LT1 (LT no-dash 1) being the ones in the 1990s Buick Roadmasters, with their EFI systems, reverse-flow cooling system, and Opti-Spark ignition systems (but still the original architecture, so a 4bbl and HEI could still be installed, if desired).  Gen III would be the "Vortec" variations on the original architecture, with their improved cyl heads and such.  Gen IV would be the "LS" family, which is still termed "small block", although more recent versions can be had with over 500cid displacements.  As the current Corvettes have an "LT variation.

 

The original LT-1 was the 370 horsepower 350 used only in Corvettes, with a 360 horsepower version used in Camaro Z/28s.  The 1990s LT1 was the reverse-flow cooling system 350 engine variation.  With the current LT1 being on the basic LS architecture.  All different decades, so allegedly NO possibility of getting them mixed up?

 

Sorry for the length.  Not a "sound byte"-capable subject.  There's still MORE to this story, when Chrysler and Ford are considered!

NTX5467

 

 

Edited May 12, 2023 by NTX5467 (see edit history)

[60FlatTop]

57 minutes ago, NTX5467 said:

MORE to this story, when Chrysler and Ford are considered!

It is a story alright. With all the accuracy of a real estate agent pointing out property lines.

[gungeey]

Small block in a  rivvie 😆

[60FlatTop]

!/4-20 bolts threaded into aluminum.

A water manifold with an O-ring 90 degrees to the attaching bolts.

And an incandescent light bulb.

 

Eh.

[NTX5467]

Looks like it was born pre-mature laying in there.