GM Big Block 455 engine families--A primer

By Published by
GM Big Block 455 engine families--A primer
. Views . Comments Comment . 610 Votes
This guide is intended to familiarize you with the three different GM 455 V-8 engines, and provide some background history of those engines.  In addition, I've added some information on Cadillac.  Oldsmobile, Buick, and Pontiac each made a V-8 engine marketed as a "455".  Although there are some similarities, they really are distinct engine families.  In this day of "corporate engines" it's refreshing to remember a time when each GM division had it's own engine family or families.  In addition, you may care to look at a similar guide to small-block GM enginesFord V-8 engine families since 1932Mopar V-8 engine families , or a guide to  Chevrolet big block engines .  You may want to check out the guide to HEI distributors , too.

My thanks to GM Powertrain, who is now traveling the country with a display of GM "heritage" engines.  My photos were taken at the 2007 Car Craft Summer Cruise in the GM Powertrain display tent.  I am sorry for the very small photos, but I have NO CONTROL over picture size--eBay shrinks the photos to suit their space limitations.

Please remember that you may--or may not--have an engine that is the same "make" as your car.  GM was sued by Oldsmobile owners who were angry that GM installed "inferior" Chevrolet engines in Oldsmobile-branded cars.  GM settled the suit and then claimed that all engine designs were "Corporate" property, so they could install any engine in any car without buyer recourse.   Any number of Pontiac Trans-Ams have an Oldsmobile engine; as did Cadillac Sevilles.  Just because the fender says "Buick" doesn't mean there's a Buick-designed engine under the hood.  Therefore I have included engine identification hints in this Guide.

Oldsmobile brought out it's first Overhead Valve "Rocket" engine for the 1949 model year.  It was introduced as a 303 cubic inch engine; later expanded to 324; and then with an increase in deck height it expanded to a 371 and then a 394.  The last year of production was as a 394 in 1964.  Olds then introduced a new engine family in '64, as a 330 cubic inch, "small block" unit using similar but not identical cylinder heads and identical bore spacing as the 394.  In '65, a big-block version was introduced: the stroke was lengthened and the block decks were taller.  Crankshaft main and rod bearings were of larger diameter than the small-block version of this engine.  Big blocks used 3" diameter main bearings, while small blocks use 2 1/2" diameter mains.  The small-block and the big-block Olds are therefore very similar in most respects, aside from the necessary changes required by the taller deck height of the big block.  For example, you can bolt big-block heads onto a small-block, aside from compression ratio difficulties caused by the larger combustion chambers, minor issues due to pushrod hole location, and a change in later production engines to use 1/2" head bolts instead of the previous 7/16", they will fit just fine.  Edelbrock makes an intake manifold that allows this swap, there is enough metal cast above the runners to cover the taller ports of the big-block heads.  All pre-'68 model year engines use forged steel crankshafts.  Oldsmobile used two different lifter bank angles.  Everything produced for the '68 model year and newer has the 39 degree lifter banks, most but not all of the '67 and older engines use a 45 degree bank.  Be sure of what you have before you buy a camshaft!

The larger "big block" version of the Olds engine could be had as a 400 or as a 425 cid engine.  The "early" 400 and 425 shared the same stroke length, at about 3.980, while the 400 used a 4" bore to the 4.126" bore of the 425.

The 425 and the "early" 400 engines were both phased out for the '68 model year.  Oldsmobile lengthened the stroke to 4.25", and the 455 was introduced.  Along with the longer-stroke 455, there was a "new" version of the 400, using the longer 455 stroke and a very small bore of 3.870.  The newer 400 is a poor choice for performance use because of the small bore's interference with large valves and airflow around the valves.  For about the first month of production, the Olds 455 received a forged steel crankshaft.  After the first month, only cast iron cranks were used.  No production-line Oldsmobile engines have 4-bolt main caps, although some were produced for NASCAR racing.

Oldsmobile big blocks have rather poor combustion chambers and are prone to "ping" and detonation.  In addition, the 455-stroke (4.25") engines in particular tend to have bottom-end problems if used at high (5,500+) rpm for any length of time, in part because oil drainback from the cylinder heads is poor--so the oil pan is pumped dry while the valve covers are full of oil.  The oil drainback issues are common to all these Olds engines.  Fixing some oil system problems and careful attention to parts selection and machining techniques can result in excellent power production.

The '65-newer Olds big block engine family is identified by:
1.  An oil fill tube at the front of the engine, just over the timing chain enclosure.  It is offset to the right (passenger side) of the engine, and on most cars, it stands straight up 'n' down.  A few engines use a fill tube with a slight bend in it, but the base of the tube will be vertical.

2.  Distributor in the rear, but offset slightly to the left (driver's) side.  It rotates counter-clockwise as seen from above.  Distributor does not enter the intake manifold.

3.  Valve covers are held on with 10 bolts (early engines) or 5 bolts (later engines.)  The pattern is the same, but every other hole is unused (and perhaps undrilled) on the 5-bolt covers.  10 bolt covers use five bolts on the bottom row, and five bolts on the top row.  5 bolt covers use three bolts on the bottom row, and two bolts on top row.

4.  The timing chain cover is a flat, stamped sheetmetal cover with provision for the front main seal and water pump outlet openings.  Fuel pump is mounted to the right (passenger side) of the timing chain housing.

5.  There are identifying numbers and letters cast into the top of the timing chain housing at the front of the engine, just in front of the intake manifold.  If the large figure at the end is a number, you're looking at a small block.  If the large figure at the end is a letter, you're looking at a big block.  Most 455s use the letter F or Fa to identify them, a very few use L.  The 455s with the L use a different casting number; it looks like 231 L 788 where the other blocks will be 396021 F or 396021 Fa

Sorry--I have NO CONTROL over the size of the photos!

Olds W30 455 with special cold-air air cleaner

Buick made do with the "nailhead" 322, 364, 264, 401, and 425 engine family from 1953 through the '66 model year.  The new-for-'67 Big Block engine was produced in 400 (to replace the 401) and 430 (to replace the 425) cubic inch versions, sharing the same stroke of 3.9" which although short for big-block engines in general, was longer than what was used in the older engines.  The engines have a large bore-to-stroke ratio, with the bore of the 400 measuring  4.040", and 4.1875 for the 430.

Buick expanded the 430 by opening up the bore to 4.312 for the 1970 model year.  The 400 and the 430 were then discontinued.  The 455 uses a different scheme to supply oil to the rocker arms than the previous big block engines.  Starting in '72, blocks were slightly re-designed in the head gasket area.   In short, you must be very careful when swapping heads from one engine to another, to assure that the oiling system, coolant passages, and head gasket are compatable with one another.

Buick big-blocks have forged steel connecting rods, although small-blocks use cast iron rods.  Even fans of the Buick engine note that oiling system problems are the first thing that needs to be addressed in a performance application.  Poor oiling system performance is hard on the front cam bearing, and on most all of the crank bearings.  Aftermarket fixes are readily available, but in general high-volume oil pumps are not recommended due to excessive loading and therefore wear on the distributor/cam gear interface.  Fixing the oil system troubles added to "normal" high-performance modifications and expert machine work can result in surprising power--Buick enthusiasts think of a 455 as a "Chrysler Hemi"-killer, and with some justification.

The Buick big-block engine family is identified by:
1.  Distributor in the front, offset to the left (driver's side) and tilted to the left about 30 degrees.  Distributor rotates clockwise.  Distributor does not enter the intake manifold, it enters an aluminum front cover assembly that is bolted onto the front of the block.

2.  Valve covers have 5 bolts, two on the lower edge, and three on the upper edge.  (Small block Buick 350s have 6 bolts, three in the upper row, three in the lower row.  Buick 300 and 340 engines use four bolts.)

3.  Timing chain cover is aluminum, and also has the oil pump housing cast-in.  Fuel pump is on the left (driver's side.)

Buick 455 Stage 1 with special cold-air air cleaner

Pontiac introduced it's engine family 'way back in '55.  Although there were many updates over the years, all the engines except for the 301 and the 265 use the same deck height, and since the smaller 301 and 265 blocks are terrible for performance usage, most enthusiasts will say that Pontiac does not have a "big block" or "small-block" engine division, rather, the division is in the size of the crankshaft main bearings:  All engines 400 cid and smaller use 3" diameter main bearings except the very early motors which have even smaller bearings.  All engines larger than 400 cid (that is, 421, 428, and 455) use 3 1/4" main bearings.  The Pontiac engine is considered by many to be the most performance-oriented of the 455s.  This would be disputed by fans of the Buick and Olds engines, who rightfully point out the cast iron (not forged steel) connecting rods used in almost all Pontiac V-8s since the early '60's as being a limiting factor for over-5,500 rpm operation in a 455-stroke application, or 5,800 in a 400-stroke engine.  Still, it was Pontiac, not Buick or Olds that won so many NASCAR victories in the early '60's.  455 and other Pontiac engines often have a oil pan windage tray as standard equipment, and many (most) 455 blocks are drilled for four-bolt main bearing caps, even when the block actually has two-bolt caps installed.

Pontiac introduced it's 455 for the '70 model year, replacing the 428.  '70 and newer blocks have the displacement cast into the side.  The 455 has a bore of 4.15" and a stroke of 4.21".

The Pontiac engine family is identified by:
1.  Distributor in the rear, spins counter-clockwise as seen from the top.  Distributor does not enter the intake manifold.

2.  Intake manifold does not seal the lifter valley as on the other engines.  Air gap between bottom of manifold and top of the sheetmetal lifter valley sealing cover.

3.  Large aluminum water pump housing bolted to the block and with one bolt attaching it to the intake manifold to the left of, and lower than, the thermostat housing.  The back part of the water pump housing also makes up the timing chain cover, and it seals to the oil pan at a 45 degree angle.

4.  Fuel pump on the left (driver's side) of the timing chain housing.

Pontiac 287.  Note water pump discharges into cylinder head via short section of rubber hose and 90 degree metal elbow.

Pontiac 428.  455 similar.  Water pump discharges into block. (front of head now covered by power steering pump.)

Cadillac, like Oldsmobile, first released an Overhead Valve V-8 in 1949 model year cars.  That engine family, with displacement and a deck height increase continued through 1962  A very major revision in the block for the 1963 model year left many people confused:  Although the new engine was shorter, stiffer, and lighter, it was still the same displacement as the '62 engine it replaced:  390 cubic inches.  The "new" '63 390 used the same cylinder heads as the previous engine family.  This design was expanded to 429 cubic inches the next year, 1964.  The 429 lasted through the 1967 model year.  In 1968, Cadillac released an all-new engine displacing 472 cubic inches.  This family expanded to 500 cubes, and then because of fuel economy and emissions concerns, was reduced first to 425 cubes, and then to 368 cubes.

Cadillac First Series--331, 365, 390, with the 390 being a taller-deck-height version of the smaller engines.
1.  Distributor in the rear.

2.  Valve covers held on with 4 bolts

Cadillac Second Series--390, 429
1.  Distributor in front

2.  Valve covers held on with 4 bolts

Cadillac Third series--472, 500, 425, 368
1.  Distributor in front

2.  Valve covers held on with 9 bolts.

Although Buick also uses a front-mounted distributor, the distributor on a Buick enters an aluminum front cover assembly that bolts to the block.  The Cadillac iron block extends further forward, eliminating the Buick-style removable housing.  Therefore the Cadillac distributor enters the front of the iron block itself.

Parts Interchangeability among the 455s:
1.  Olds 455 and Pontiac 455 hydraulic lifters interchange.

2.  Some sources claim that Buick 455 and Cadillac 472/500 hydraulic lifters interchange.

3.  Rear wheel drive Cadillac 472/500 (not Eldorado FWD) and Buick 455 use the same starter motor.

4.  That's about it:  They really are different engines!

If this guide has been helpful, please give me a "Yes" vote by clicking the button below.  If you have suggestions for improvement, you can contact me through the "My Messages" feature of eBay by clicking on my user name, above, then click on "Contact Member". 

Entire contents copyright (C) 2007, 2008 Camino3X2    Feel free to LINK to this Guide in your auctions.
Explore More
Choose a template