Each of GM's divisions except Cadillac released "small-block" engines marketed as "350" cubic inches during the '60's and '70's.  This guide is intended to help you identify the differences between the Chevrolet, Pontiac, Oldsmobile, and Buick 350s, as well as to provide some background information on each engine family.  Cadillac of course sold cars with 350 engines, but those engine were sourced from Olds or Chevrolet.  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 wish to look at guides to Olds, Buick, and Pontiac big block engines , Chevrolet big block engines, Mopar V-8 engine families , and/or Ford V-8 engine families since 1932 .  In addition, you could look at a guide for HEI distributors. .

Chevrolet
Hey, everyone knows the Chevy Small-Block, and the 350 was the most-produced combination of bores and strokes offered.  The 350 was introduced in '67 in some Camaros, but not as a "performance" engine.  It took until the next model year before Chevrolet trusted it to have "real" power.  The Chevy design engine was installed in other division's cars, prompting a lawsuit by Oldsmobile owners in the '70's, who felt cheated that their new Olds had the "inferior" Chevy engine.  GM settled the lawsuit, then promptly declared that all GM engines were "Corporate" property, and therefore they could install any engine in any division's cars without buyer recourse.  Since that time, all the other division's 350 engines--and in fact almost all the other division's V-8 engines--were discontinued in favor of what were once the "Chevrolet" designs.  The continued production of small-block "Chevy" engines--along with a basically sound design to begin with--has made this engine the most-raced and one of the longest-produced engine families in the world.  A major change in '86 provided a revised crankshaft, block, and flexplate/flywheel all of which was done in order to implement a one-piece rear main seal.  At that time, the block was also given casting revisions to the lifter bore area to permit low-cost hydraulic roller lifters to be used.  Not all of these newer blocks were actually equipped with the roller lifters, however.  The '86 revision also included valve covers that have four bolts in-line across the top of the cover, not around the flange.  The change to the valve cover and gasket dramatically reduced oil leaks.  Also beginning in '86, Corvettes began to use aluminum cylinder heads on the one-piece seal block.  These aluminum heads are not up to the power production of aftermarket heads, but are a great entry-level aluminum head upgrade for "hot rods", and a version of them is installed on the ZZ4 crate engine.  In 1996, pickup truck engines got "Vortec" cylinder heads which, although made from cast iron, is an excellent piece for moderate performance use.  The '96 and newer Vortec head is nearly as good--maybe even better--than the '86 Corvette aluminum head in terms of making horsepower, although it weighs more of course.  The Vortec head requires a Vortec-specific intake manifold, as it uses only four bolts per side to hold the manifold to the head instead of the more usual six bolts per side.  Production of traditional Chevy small blocks continues as GM still sells lots of these as marine, replacement and crate performance engines, but none have been installed in a production-line GM vehicle for years.
 
Other 350 engines installed in Chevrolet vehicles
From 1990 to 1995, Chevrolet also sold a dual-overhead-cam, four valve per cylinder 350 in Corvettes as the LT-5.  This exotic engine was designed by Lotus, with manufacturing handled by Mercury Marine.  It is NOT a development of the familiar "Chevy small block", it is a totally different engine.

Starting in 1997 Corvettes, an LS-series 350 engine was introduced.  Various other cars and trucks also got a variation of the LS-series engines in different displacements in following years.  Please understand that despite propaganda from every automotive magazine on Earth, the newer "LS-series small block" engine is NOT RELATED to the familiar old Chevy small block.  GM loves and encourages the mis-perception that the LS is just an outgrowth of what came before, because what came before had a stellar reputation and customer loyalty, whereas the new engine is a clean-sheet design sharing NOTHING except bore center measurements (4.40") and most but not all of the bellhousing bolt pattern.  Even the firing order and head bolt pattern is new.  The LS-series really is a "Corporate" engine, as it was wholly designed by GM Powertrain Division, NOT Chevrolet.  The new engine is better than the old one in many regards--it's just not a descendant of the Chevrolet design that first entered production for the 1955 model year.

The familiar Chevrolet small block 350 engine uses a 4" bore and a 3.48" stroke.
Aftermarket parts are so plentiful that you'd have to be dead to have not seen some.  Everything including cylinder blocks in both iron or aluminum are available from multiple sources, GM and otherwise.  An eBay Guide to small block Chevy cross-ram manifolds and also Chevrolet-Small-block-Tri-Power-3X2-Manifolds is also available.

The traditional Chevrolet small block design engine is identified by:

Pontiac
Pontiac like Chevrolet also 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, instead, the division between "big" and "small" is not the block size, it is in the size of the crankshaft main bearings:  All engines 400 cid and under use 3" (early engines have even smaller) main 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 non-Chevy designs.  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.  Still, it was Pontiac, not Buick or Olds that won many NASCAR victories in the early '60's.  An interesting variation of the Pontiac V-8 is the slant-four "half-of-a-389" used in Tempests.

The early Pontiac block featured reverse-flow cooling, in that the heads were cooled before the block.  Pontiac discontinued this for unknown reasons in the late '50's or early '60's, but GM Powertrain picked it up when building the revised '92 LT1 Chevy small-block, only to discard it again when designing the LS-series engines a few years later.

The 350 has a bore just larger than the stroke, at 3.875 X 3.75.  The Pontiac 350 was introduced in '68, and discontinued in '77.  '70 and newer blocks have the displacement cast into the side.

The Pontiac engine family is identified by:

Oldsmobile
(For information on the all-aluminum 215 Olds engine, please see the Buick section.)
Oldsmobile introduced a new engine family in '64, as a 330 cubic inch, "small block" unit.  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 necessiary 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, a change to later engines to alter the angle of the lifters and therefore the pushrods, and a change in later production engines to use 1/2" headbolts 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.

The 350 Olds has the biggest bore, and the shortest stroke of all the GM 350s.  Bore is 4.057 and stroke is 3.385".

All Olds small blocks use the same stroke as the 350.  The 403 uses a "siamese" bore, in that the bores are internally joined to each other just like the 400 Chevy small block.  Many small changes were made over the years--early engines used a 45 degree lifter bank angle, this was changed to a 39 degree bank angle in '68.  (well, it's more complicated than that, but this Guide isn't the place to list every detail--you better be sure of what you have before you order a camshaft!) Because the lifters moved slightly, the pushrods also moved just a touch, and therefore the pushrod holes in the head also had to move just a bit.  Later engines use 1/2" head bolts instead of 7/16.  Starting in '77,  350s and 403s use lightweight "windowed" blocks.  The support structure for the main bearings has weight-saving holes cast into the block, which makes the block weaker.  Despite printed claims from Someone Who Should Know Better, and a "Million Dollar Reward" no one has been able to prove the existence of a Solid Main Web (not windowed) 403.

Oldsmobile engines have rather poor combustion chambers and are prone to "ping" and detonation.  In addition, 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 Olds engine family is identified by:

Buick
Buick produced an aluminum-block and head V-8 engine of 215 cubic inches, introduced in '61.  There was an Oldsmobile version of the aluminum engine, using Oldsmobile-designed cylinder heads on top of the Buick-style block.  The Buick version uses 5 head bolts around each cylinder, while the Olds uses 6 bolts around each cylinder.  The Olds version may have had the extra head bolt because Oldsmobile offered an optional turbocharger, and they were concerned the added cylinder pressure would lift the head off the block.  Pontiac also installed the Buick version of the 215 aluminum small block. These aluminum V-8s stayed in the GM lineup only until '63.  A cast-iron version of the Buick engine, with two fewer cylinders was introduced--the famed Buick V-6.  The V-6 was considered to be both cheaper to make and cheaper to run, and the tooling and the rights to produce the aluminum V-8 were eventually sold to Rover of England. (Many owners of Buick/Olds aluminum V-8 engines use the Rover parts--longer strokes and heavy-duty blocks are available!)  The V-6 also lasted for only a few years as a Buick engine, and then the tooling and the rights to produce it were sold off to Jeep, which became part of American Motors Corporation (AMC).  GM bought the tooling and the rights from AMC and began making the Buick V-6 again in '76.  The other offshoot from the aluminum 215 V-8 was a cast-iron V-8 derivative, first made as an iron block 300 with aluminum heads ('64) then as a 300 with iron heads ('65.)  The engine was subsequently expanded to a 340, (1966-'67) and finally to a 350 in 1968.   The aluminum V-8 had the lowest deck height, (8.99) the 300 had a taller deck height (9.543), and the deck height was raised again (10.18) for the 340 and 350.
Note that the Buick 350 deck height is taller than a Big Block Chevy passenger car block!  Buick uses full-skirt pistons instead of the more common slipper-skirts, long connecting rods and extra room is needed to clear the crankshaft counterweights.

 The 350's bore is 3.8", the stroke is 3.850".

Buick small-blocks use cast iron connecting rods.  The 72-up "capscrew" rods are preferred for heavy-duty use.  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 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

The Buick small block engine family is identified by:
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 content copyright (C) 2007, 2008 Camino3X2    Feel free to LINK to this Guide in your auctions.