[ADMIN NOTE: Thomas tried to send this to GMCnet several times, but it
exceeds the 7,000 character limit. Since it contains much good info, I've
"approved" it and sent it to the list. It's obvious that this sort of info
needs to be in the FAQ. Patrick]
Looks like I have added to the confusion with my post. sunday I was
driving through Canton NY and stopped to look at a 1978 GMC transmode. The
engine had just been replaced and the old engine was sitting on the ground next
to it. I had already looked at it several months ago when it was in the
coach. I was told by the owner that it was a 403 (am not aware that the 455 was
offered in 1978). The distributer was in the front of the engine and the
air conditioning compressor was mounted to the intake manifold. The engine
was blue which narrows it down to either a 403 or a 455. Still confused.
Now I am to. Here is some of the other data that I have and can't remember
where I got it from now. hope this does not add to the confusion.
Olds Rocket V8s By Marlan Davis
For those of you who may not think "Oldsmobile" and "performance" are
synonymous terms, Oldsmobile's performance heritage dates all the way back
to 1903, when an Olds-built "Flyer" established the world's lightweight
speed record of 54 mph. In conjunction with Cadillac, Olds later introduced
the first modern overhead V8 engines in 1949. NASCAR's 160-mile Grand
National stock car race at Daytona was won in 1953 by a Bill Blair-driven
Olds at a new record average speed of 89.5 mph. Later in the decade, buyers
of 1957 and 1958 Olds models could opt for a 371-inch, triple deuce "J-2
Rocket" rated at 300 hp. The early '60s saw the introduction of an
all-aluminum 215 cubic-inch V8, some of which came with factory
turbochargers.
In 1964 the first modern Olds V8 debuted as a 330-inch small-block. The 400
and 425 big-blocks followed in 1965. In 1966 the hot 4-4-2 L69 400 inch
option came with 3x2 carburetion, fresh-air induction, and a hot hydraulic
cam. Underrated at 360 hp (just 10 hp, more than a 4-barrel stocker), the
option went for only $264.54!
GM's corporate edict soon eliminated multiple carbs, but Olds wasn't through
yet. In January 1968 the 325-hp/350 inch W31 Ram Rod Cutlass option produced
a conservative 325 hp. Meanwhile, the giant 455-inch motor was waiting in
the wings, first appearing in full-size passenger cars and Toronados, then
Hurst-Olds specialty cars, and finally in the legendary W30 4-4-2
intermediates.
Big Brother put a stop to the horsepower wars starting in 71, with the
big-block finally dying out for good after 1976. The 350 soldiered on, being
joined by the 403 in 1976. Both were superseded in 1980 by the 307. Olds
converted the 350 into a diesel engine from our point of view, the best that
can be said for it is that the beefy diesel blocks provide a strong
foundation for an all-out racing gasoline small-block
Among knowledgeable engine builders there's an old (Olds?) saying:
"Horsepower sells engines, but torque wins races." It's also a fact that the
loads on an engine's reciprocating parts increase geometrically with each
incremental rpm increase. With this in mind, it stands to reason that the
plan for consistent engine power and longevity on the street is ample low
and mid-range torque; not excessively high rpm. With many of the "most
popular" engines, this approach isn't possible, since they seem to really
work well only with high compression ratios and high rpm. But it is possible
to make mountains of torque without spending mountains of dollars by using a
commonly overlooked engine-the Oldsmobile V8. Available in both small-block
and big-block versions with displacements ranging from 260 to 455 cubic
inches, Olds engines abound in junkyards all across the nation.
BASIC INTERCHANGE
Modern Olds V8 engines displacing 260, 307, 330, 350, and 403 inches are
considered to be small-blocks. Big-blocks displace 400, 425, or 455 cubic
inches. The small-block motors are 1-inch shorter in height and 1-1/2 inches
narrower than the big-blocks. If the engine's original factory paint is
still intact a small-block will be gold or blue, while the big-blocks can be
red, green, blue or bronze. Late-model 307's are flat black. You can also
identify engines by casting letters and numbers.
While exceptions will be noted below, as a general rule the following parts
are physically interchangeable among all "modern" Olds V8 engines:
flexplate and flywheel, engine mounts, oil pan, front cover, water pump,
bellhousing (also interchanges with modern Buick,and Pontiac), oil pump, oil
pump driveshaft, rocker arms and fulcrum (except early 330), camshaft and
lifters (except for different lifter bank angles and lifter diameters; see
below), harmonic balancer, cam bearings, timing chains and timing gears. Heads
will basically interchange, except manifold ports may not align.
WEAK POINTS
Before taking a closer look at small and big-block specifics, we will
examine several weaknesses common to all Olds engines: oil system,
bottom-end strength, and valvetrain.
In stock form, the production oil system can't do the job above 5000 rpm. To
begin with, you'll suck the oil pan dry. The old '66-'78 Toronado pan (part
No. 398438) will hold an extra quart (six with filter), compared to other
stock pans. Naturally, an extended oil pump pickup is required with deepened
pans, preferably a fabricated tube of at least 5/8-inch diameter. Increased
oil pressure is also required; it can be achieved by installing a stiffer
relief spring, or ultimately, via the installation of a special aftermarket
high-volume oil pump. On serious engines, oil restrictor kits are used to
limit the amount of oil reaching the top end, retaining the vital lube
downstairs where it's needed to keep the main and rod bearings alive.
Also needed on an all-out high-rpm engine are main studs and better rod
bolts. Four-bolt caps may be added to diesel and big-block engines. On this
type of engine, special ultra-lightweight pistons and rods are used to
reduce strain on the bottom end.
While the above problems only become critical on race motors, valvetrain
deficiencies manifest themselves practically every time a cam is changed,
the block and heads are milled, or a simple valve job is performed. In stock
form, the Olds valvetrain is non-adjustable, so no tolerance exists for
changes anywhere in the system. For example, since the common everyday valve
job moves the valve seat higher up into the pocket, the valve stem height is
effectively increased, often upsetting the valvetrain geometry
(knowledgeable Olds head shops can compensate by slightly reducing valve
stem length). To permanently correct these problems, there are several
solutions. They are (from cheapest to most expensive): shimming or milling
the rocker arm pedestals, installing adjustable pushrods, or converting to
adjustable rocker arms by the use of a bolt-on aftermarket kit. The latter
solution is really the most practical.
There are also valvetrain component interchange problems you should be aware
of. Early engines used both 39-degree and 45-degree lifter bank angles (see
chart), as well as two different tappet diameters. When ordering an
aftermarket cam you must specify which engine you have. The 1964-'65
330/400's also used a different rocker arm design, for which parts these
days are extremely hard to come by. Except for these early motors, rocker
arms and fulcrums will interchange on all engines through 1979. Pushrod
length is the same for all small-blocks. Big-block pushrods are longer, and
may vary between different displacement motors by as much as .042-inch
(although aftermarket sources say they'll effectively interchange). In 1980
pushrod tip diameters were increased from 5/16-inch to 3/8-inch, with
corresponding changes made to the rocker arms and lifters. The two different
diameter pushrod designs must be used with the correct corresponding rockers
and lifters. Both systems interchange as assemblies. Since aftermarket
lifters are designed for 5/16-inch pushrods, you must either use early
pushrods and rockers or a special Mondello pushrod that has dissimilar ends
(one 5/16 and one 3/8). Finally, the '81-up diesel (block stamped "350-DX")
and '85-up 307's use hydraulic roller camshafts, with a .921-inch tappet
diameter. The roller lifter design is too heavy for high-rpm performance
use. However, you could use an early .921-inch diameter hydraulic tappet
mated to a conventional hydraulic cam ground for a 39 degree lifter bank
angle.
Forged cranks are distinguished by wide forging mark compared to narrow
casting seam. Big block forgings have forging No. located on rear throw
while cast cranks have No. on second throw from front. The 425 forging has
no hole on No.1 throw unlike 455 cranks.
BUILDING THE SMALL-BLOCK
All small-blocks feature a 3.385-inch stroke, with displacement varied by
increasing the bore diameter. Main and rod journal diameters are all the
same, except for the 350 diesel which uses 455-type mains with standard
small-block rod journals. All gas small-block cranks are completely
interchangeable, except for any rebalancing required when changing pistons
and rods. The 1964-67 330 engines were the only small-blocks to use a forged
steel crank; it is preferred for all-out, 7000 plus-rpm competition. These
early 330 forged cranks (as well as some big-block cranks) have slightly
different flywheel bolt patterns, requiring a unique flywheel or
flexplate that's currently available new only from Dave Smith Oldsmobile and
Mondello Performance.
For application under 7000 rpm, the '68-'70 nodular iron 350 crank is
adequate. Since many '71-up 350 cranks and most 260, 307, and 403 cranks are
only cast iron, and also have cut-down counterweights, they should never be
revved beyond 5500 to 6000 rpm. Non-forged crank longevity can be improved
by reducing piston and rod weight.
The diesel blocks are preferred for all-out racing because of their 3/8-inch
thick main webs and .400-inch-thick cylinder walls. A 425 crank with
cut-down counterweights will fit in the diesel block. Since, with sonic
testing, the diesel block will accept a 4.25-inch bore, up to 451 inches is
available with custom pistons and rods (what a sleeper!) 455 cranks won't
clear no matter what you do).
Even without a sonic test, diesel blocks can easily be bored 1/8-inch over
which still leaves greater wall thickness than a late-model casting, which
can safely be bored only .030-over. These late thin-wall gas blocks were
produced in 1976 and later, and may be identified by their weak "windowed"
main webs. The 403's have relatively thick siamesed cylinder walls, but most
have the late weak main webs. "Normal" '68-'76 gas 350's will go 1/8 over
after sonic testing, yielding about 370 cubic inches. The 330 blocks will
also accept 1/8-inch overbores. The '68-70 350's (cast "558") or early 330
blocks (cast "917") are preferred due to their higher nickel content.
All small-block rods interchange, except for the slightly shorter diesel
rods. All are forged, except for some late 260/307 pieces. The best rod
(part No. 555142) is found in 403 engines; made from a better alloy, it is
also 10-percent larger across the beam.
When it comes to pistons, all factory slugs are cast flat-tops with
compression ratios varied by changing dish size. This design offers
efficient flame propagation, superior detonation resistance, and
high-compression ratios without excessive dome heights. On the small-block,
compression ratios were decreased starting in 1971 from the previous nominal
10.25:1 to around 8.5:1 by increasing the combustion chamber volume and
dishing the pistons. Assuming the head was cc'ed to minimum NHRA specs, a
modern 9.5: 1 street engine compatible with presently available pump gas can
be built by using early heads with the late short-block. Unfortunately, the
heads in stock form cc nowhere near the "blueprint" specs, and milling them
or the block upsets the stock non-adjustable valvetrain geometry. Mondello
offers a line of forged pistons designed to produce 9.5:1 or 11.5:1
compression with "out of the box" heads.
What are the best "out of the box" heads? If you could find them, the
1967-'70 350 W31 design least 405585), which has a good short-turn radius on
the intake ports and larger 2.005 intake/1.625 exhaust valves (compared to
the standard 350 1.875 intake/1.5 exhaust), is the best bet among production
heads. Since you probably wont find them, the "147" or "742" heads off a
'68-'70 350 work fine, too. They have the smaller valves,but retain the good
intake port. Naturally, larger valves can be added, even up to a 455's 2.072
intake.
After 1971, head quality declines. Not only are the chamber volumes high,
but the intake ports have a sharp shelf. While all Olds production heads
have siamesed center exhaust ports with a recessed divider, the recess is
much greater on late smog heads. Late 1976 and up heads are drilled for
1/2-inch head bolts. To use earlier heads on the late blocks, their
7/16-inch bolt holes must be opened up. Late heads may be installed on
earlier blocks. Due to water jacket differences, use the head gasket
designed for the model year of the block not the head.
For all-out race applications, CJ Batten has designed a state-of-the-art
Olds head that's cast in both iron (part No.22505143) and aluminum (part No.
22505805). They're available either from him or Olds dealers. Intake ports
are enlarged and raised up. This requires a special Edelbrock Victor intake
manifold (Edelbrock No. 2979). The best aftermarket intake for production
heads is the dual-plane Edelbrock Performer (No. 3711), which "makes torque
everywhere." Holley's Dominator is a tad stronger on the top end. Factory
intakes work well through 5000 rpm. Pre-'72 versions are preferred, since
they lack restrictive EGR passages. Original aluminum W31 intakes are
identical to the cast-iron versions, but save 25 pounds. The only available
small-block tunnel-rams are hand-fabricated by Dave Smith or CFE
Enterprises. Right now, 260's must use the stock intake, since other
aftermarket intakes won't match the 260's small ports. Manifold match-up
also makes it difficult to run big-block heads on a small-block. While the
tall deck castings physically bolt on, the intake port is taller than
small-block manifold mating flanges. A bigblock head's larger combustion
chambers will also lower compression by about one full point.
When it comes to camshafts, today's engines should use today's camshaft
profiles that feature less overlap, decreased duration, and increased lift.
While good in their day, the old factory W30 and W31 grinds are designed
with lots of duration and mild lift. Not only can this cause problems with
vacuum-actuated accessories, but they also won't work well in today's
low-compression, weak-geared smog motors. Olds specialty houses now offer
modern, computer-designed profiles tailor-made for Olds engines.
All Olds timing gears will interchange. Big-block chains are beefier than
the small-blocks. An aftermarket roller is better yet. The water pump used
in late air-conditioned cars (part No. 556283) features a superior low-drag
impeller.
BUILDING THE BIG-BLOCK
Big-blocks have been built with two different stroke lengths, connecting rod
lengths, and piston compression heights (see chart). Main and rod journal
diameters are the same for all big-blocks.
Since the 425 and 455-inch engines share the same bore size, but use
different stroke cranks, the question arises, "Can a 425 be made into a 455
by swapping cranks?" Yes, but the different-length 455 pistons and rods are
also required.
Both the short and long-stroke cranks have been produced in forged steel,
nodular iron, and cast iron. Short-stroke forged cranks are relatively
plentiful, but the long-stroke "943" 455 forgings are relatively rare.
The thickest blocks are early 455's stamped "FO" or (in the bellhousing
area) "68 F". F1 or F2 blocks are a good second choice. Any of these can be
bored to 4.25-inch without sonic testing. The '68-'70 455's used two
different con rods, with the rare extra-heavy-duty version having more meat
around the rod cheek and bolt head area. Other than this rare rod, all other
big-block rods are identical from a metallurgical standpoint.
Big-block piston design is similar to the small-blocks-variations on a
flat-top theme. With two basic combustion chamber sizes and two piston dish
sizes, stock compression ratios range from 8.5:1 to 10.25:1. Early heads
displaced either 70 or 85cc, with smog heads all having the big chambers.
Use of a 70cc head on a late smog motor will raise compression about one
full point. The 1970-'7l W30-type "F" heads had the small chamber, along
with a good intake port. Unfortunately, they're scarce. Other early castings
make a good alternative: Type "C" castings have an excellent intake port
high nickel content, and the most material around the ports for hogging out.
However, they do have 80 to 83cc chambers, and some 2-barrel versions have
only 2-inch intake valves instead of the preferred 2.06 intakes. All
big-blocks have 1.63-inch exhausts, except for Type J heads that had
1.690-inch exhausts. But the J heads have a poor "shelf intake port," as do
the G and K castings. A, B, and D heads are acceptable subs for C or F
castings, however. The larger valves can be installed in the small-valve
heads.
Finally, there's the C J. Batten heads previously mentioned for the
small-blocks. They'll bolt onto a big-block and really work great on the
street or in race applications; but there's no off-the-shelf intake manifold
available. Dave Smith can modify a small-block Edelbrock Victor to fit, or
less expensive C.J. Batten spacers will adapt conventional big-block
intakes, if some port misalignment is acceptable. For production heads, the
old Edelbrock 04B dual-plane works best, but it's no longer available.
Edelbrock plans to introduce a Performer eventually, until they do, if you
can't find an 04B, stick with the stock cast-iron piece or its aluminum W30
duplicate. Any of these work better than the old 442 tri-power units, which
should be considered only for restorations. Race-oriented packages usually
use the Edelbrock Torker. Offenhauser offers the only off-the-shelf tunnel
ram but its passages at the carb end are way too small for all-out engines.
Dave Smith offers his own custom tops for this intake, or complete ground-up
tunnel rams.
Nothing more needs be said on cams-the same rules apply as on a small-block.
Modern profiles cream the old '60s stuff. When properly cammed and built
according to the Olds experts guidelines, the big-block Olds will produce an
ungodly amount of torque, yet still runs well on available pump gas while
delivering exceptional mileage for its displacement. Even better, they'll
bolt right in place of existing Olds small-blocks. Cores are plentiful and
cheap. Cutlasses and Omegas are cheaper than Chevelles and Novas. Olds
blocks are cast from better material than the competition's, resulting in
better long-term bore wear. Olds specialty parts houses have solutions for
the oiling and valvetrain problems. Still don't think Oldsmobiles make
serious performance cars? Check out who is the NHRA manufacturer's champion.
(It isn't the Bow-Tie boys!) Maybe it's time you built yourself an Olds
Rocket-ship!
Oldsmobile Engine Specifications:
CID YEARS BORE STR. Jrnl. Mains Conn. Piston
Rods Dia. Rod Comp. Ht
SMALL- 260 1976-82 3.5 3.385 2.12 2.5 6.0 1.615
BLOCK 260D 1979-80 3.5 3.385 2.12 3.0 5.886 1.770
307 1980-86 3.8 3.385 2.12 2.5 6.0 1.615
330 1964-67 3.938 3.385 2.12 2.5 6.0 1.615
350 1968-80 4.057 3.385 2.12 2.5 6.0 1.615
350D 1978-85 4.057 3.385 2.12 3.0 5.886 1.770
403 1976-85 4.350 3.385 2.12 2.5 6.0 1.615
BIG- 400 1965-67 4.0 3.975 2.5 3.0 6.998 1.615
BLOCK 400 1968-69 3.870 4.250 2.5 3.0 6.735 1.74
425 1965-67 4.125 3.975 2.5 3.0 6.998 1.615
455 1968-76 4.125 4.250 2.5 3.0 6.735 1.74
Cam Bank Angle And Tappet Diameters:
YEAR CID MODEL LIFTER DIA. CAM BANK ANGLE
1964-67 330 ALL .842 39deg
1965 400 ALL .842 45deg
1965 425 ALL .842 45deg
1966-67 400 ALL .921 39deg
1966 425 exc.Toronado .842 45deg
1966-67 425 Toronado .921 39deg
1967 425 exc.Toronado .842 39deg
1968-69 400 ALL .842 39deg
1968-80 350 ALL (gas) .842 39deg
1968-76 455 ALL .842 39deg
1975-82 260 ALL (gas/dsl).842 39deg
1977-79 403 ALL .842 39deg
1978-80 350 ALL (diesel) .842 39deg
1980-84 307 ALL .842 39deg
1981-85 350 ALL (diesel) .921 39deg
1985-86 307 ALL .921 39deg
exceeds the 7,000 character limit. Since it contains much good info, I've
"approved" it and sent it to the list. It's obvious that this sort of info
needs to be in the FAQ. Patrick]
Looks like I have added to the confusion with my post. sunday I was
driving through Canton NY and stopped to look at a 1978 GMC transmode. The
engine had just been replaced and the old engine was sitting on the ground next
to it. I had already looked at it several months ago when it was in the
coach. I was told by the owner that it was a 403 (am not aware that the 455 was
offered in 1978). The distributer was in the front of the engine and the
air conditioning compressor was mounted to the intake manifold. The engine
was blue which narrows it down to either a 403 or a 455. Still confused.
Now I am to. Here is some of the other data that I have and can't remember
where I got it from now. hope this does not add to the confusion.
Olds Rocket V8s By Marlan Davis
For those of you who may not think "Oldsmobile" and "performance" are
synonymous terms, Oldsmobile's performance heritage dates all the way back
to 1903, when an Olds-built "Flyer" established the world's lightweight
speed record of 54 mph. In conjunction with Cadillac, Olds later introduced
the first modern overhead V8 engines in 1949. NASCAR's 160-mile Grand
National stock car race at Daytona was won in 1953 by a Bill Blair-driven
Olds at a new record average speed of 89.5 mph. Later in the decade, buyers
of 1957 and 1958 Olds models could opt for a 371-inch, triple deuce "J-2
Rocket" rated at 300 hp. The early '60s saw the introduction of an
all-aluminum 215 cubic-inch V8, some of which came with factory
turbochargers.
In 1964 the first modern Olds V8 debuted as a 330-inch small-block. The 400
and 425 big-blocks followed in 1965. In 1966 the hot 4-4-2 L69 400 inch
option came with 3x2 carburetion, fresh-air induction, and a hot hydraulic
cam. Underrated at 360 hp (just 10 hp, more than a 4-barrel stocker), the
option went for only $264.54!
GM's corporate edict soon eliminated multiple carbs, but Olds wasn't through
yet. In January 1968 the 325-hp/350 inch W31 Ram Rod Cutlass option produced
a conservative 325 hp. Meanwhile, the giant 455-inch motor was waiting in
the wings, first appearing in full-size passenger cars and Toronados, then
Hurst-Olds specialty cars, and finally in the legendary W30 4-4-2
intermediates.
Big Brother put a stop to the horsepower wars starting in 71, with the
big-block finally dying out for good after 1976. The 350 soldiered on, being
joined by the 403 in 1976. Both were superseded in 1980 by the 307. Olds
converted the 350 into a diesel engine from our point of view, the best that
can be said for it is that the beefy diesel blocks provide a strong
foundation for an all-out racing gasoline small-block
Among knowledgeable engine builders there's an old (Olds?) saying:
"Horsepower sells engines, but torque wins races." It's also a fact that the
loads on an engine's reciprocating parts increase geometrically with each
incremental rpm increase. With this in mind, it stands to reason that the
plan for consistent engine power and longevity on the street is ample low
and mid-range torque; not excessively high rpm. With many of the "most
popular" engines, this approach isn't possible, since they seem to really
work well only with high compression ratios and high rpm. But it is possible
to make mountains of torque without spending mountains of dollars by using a
commonly overlooked engine-the Oldsmobile V8. Available in both small-block
and big-block versions with displacements ranging from 260 to 455 cubic
inches, Olds engines abound in junkyards all across the nation.
BASIC INTERCHANGE
Modern Olds V8 engines displacing 260, 307, 330, 350, and 403 inches are
considered to be small-blocks. Big-blocks displace 400, 425, or 455 cubic
inches. The small-block motors are 1-inch shorter in height and 1-1/2 inches
narrower than the big-blocks. If the engine's original factory paint is
still intact a small-block will be gold or blue, while the big-blocks can be
red, green, blue or bronze. Late-model 307's are flat black. You can also
identify engines by casting letters and numbers.
While exceptions will be noted below, as a general rule the following parts
are physically interchangeable among all "modern" Olds V8 engines:
flexplate and flywheel, engine mounts, oil pan, front cover, water pump,
bellhousing (also interchanges with modern Buick,and Pontiac), oil pump, oil
pump driveshaft, rocker arms and fulcrum (except early 330), camshaft and
lifters (except for different lifter bank angles and lifter diameters; see
below), harmonic balancer, cam bearings, timing chains and timing gears. Heads
will basically interchange, except manifold ports may not align.
WEAK POINTS
Before taking a closer look at small and big-block specifics, we will
examine several weaknesses common to all Olds engines: oil system,
bottom-end strength, and valvetrain.
In stock form, the production oil system can't do the job above 5000 rpm. To
begin with, you'll suck the oil pan dry. The old '66-'78 Toronado pan (part
No. 398438) will hold an extra quart (six with filter), compared to other
stock pans. Naturally, an extended oil pump pickup is required with deepened
pans, preferably a fabricated tube of at least 5/8-inch diameter. Increased
oil pressure is also required; it can be achieved by installing a stiffer
relief spring, or ultimately, via the installation of a special aftermarket
high-volume oil pump. On serious engines, oil restrictor kits are used to
limit the amount of oil reaching the top end, retaining the vital lube
downstairs where it's needed to keep the main and rod bearings alive.
Also needed on an all-out high-rpm engine are main studs and better rod
bolts. Four-bolt caps may be added to diesel and big-block engines. On this
type of engine, special ultra-lightweight pistons and rods are used to
reduce strain on the bottom end.
While the above problems only become critical on race motors, valvetrain
deficiencies manifest themselves practically every time a cam is changed,
the block and heads are milled, or a simple valve job is performed. In stock
form, the Olds valvetrain is non-adjustable, so no tolerance exists for
changes anywhere in the system. For example, since the common everyday valve
job moves the valve seat higher up into the pocket, the valve stem height is
effectively increased, often upsetting the valvetrain geometry
(knowledgeable Olds head shops can compensate by slightly reducing valve
stem length). To permanently correct these problems, there are several
solutions. They are (from cheapest to most expensive): shimming or milling
the rocker arm pedestals, installing adjustable pushrods, or converting to
adjustable rocker arms by the use of a bolt-on aftermarket kit. The latter
solution is really the most practical.
There are also valvetrain component interchange problems you should be aware
of. Early engines used both 39-degree and 45-degree lifter bank angles (see
chart), as well as two different tappet diameters. When ordering an
aftermarket cam you must specify which engine you have. The 1964-'65
330/400's also used a different rocker arm design, for which parts these
days are extremely hard to come by. Except for these early motors, rocker
arms and fulcrums will interchange on all engines through 1979. Pushrod
length is the same for all small-blocks. Big-block pushrods are longer, and
may vary between different displacement motors by as much as .042-inch
(although aftermarket sources say they'll effectively interchange). In 1980
pushrod tip diameters were increased from 5/16-inch to 3/8-inch, with
corresponding changes made to the rocker arms and lifters. The two different
diameter pushrod designs must be used with the correct corresponding rockers
and lifters. Both systems interchange as assemblies. Since aftermarket
lifters are designed for 5/16-inch pushrods, you must either use early
pushrods and rockers or a special Mondello pushrod that has dissimilar ends
(one 5/16 and one 3/8). Finally, the '81-up diesel (block stamped "350-DX")
and '85-up 307's use hydraulic roller camshafts, with a .921-inch tappet
diameter. The roller lifter design is too heavy for high-rpm performance
use. However, you could use an early .921-inch diameter hydraulic tappet
mated to a conventional hydraulic cam ground for a 39 degree lifter bank
angle.
Forged cranks are distinguished by wide forging mark compared to narrow
casting seam. Big block forgings have forging No. located on rear throw
while cast cranks have No. on second throw from front. The 425 forging has
no hole on No.1 throw unlike 455 cranks.
BUILDING THE SMALL-BLOCK
All small-blocks feature a 3.385-inch stroke, with displacement varied by
increasing the bore diameter. Main and rod journal diameters are all the
same, except for the 350 diesel which uses 455-type mains with standard
small-block rod journals. All gas small-block cranks are completely
interchangeable, except for any rebalancing required when changing pistons
and rods. The 1964-67 330 engines were the only small-blocks to use a forged
steel crank; it is preferred for all-out, 7000 plus-rpm competition. These
early 330 forged cranks (as well as some big-block cranks) have slightly
different flywheel bolt patterns, requiring a unique flywheel or
flexplate that's currently available new only from Dave Smith Oldsmobile and
Mondello Performance.
For application under 7000 rpm, the '68-'70 nodular iron 350 crank is
adequate. Since many '71-up 350 cranks and most 260, 307, and 403 cranks are
only cast iron, and also have cut-down counterweights, they should never be
revved beyond 5500 to 6000 rpm. Non-forged crank longevity can be improved
by reducing piston and rod weight.
The diesel blocks are preferred for all-out racing because of their 3/8-inch
thick main webs and .400-inch-thick cylinder walls. A 425 crank with
cut-down counterweights will fit in the diesel block. Since, with sonic
testing, the diesel block will accept a 4.25-inch bore, up to 451 inches is
available with custom pistons and rods (what a sleeper!) 455 cranks won't
clear no matter what you do).
Even without a sonic test, diesel blocks can easily be bored 1/8-inch over
which still leaves greater wall thickness than a late-model casting, which
can safely be bored only .030-over. These late thin-wall gas blocks were
produced in 1976 and later, and may be identified by their weak "windowed"
main webs. The 403's have relatively thick siamesed cylinder walls, but most
have the late weak main webs. "Normal" '68-'76 gas 350's will go 1/8 over
after sonic testing, yielding about 370 cubic inches. The 330 blocks will
also accept 1/8-inch overbores. The '68-70 350's (cast "558") or early 330
blocks (cast "917") are preferred due to their higher nickel content.
All small-block rods interchange, except for the slightly shorter diesel
rods. All are forged, except for some late 260/307 pieces. The best rod
(part No. 555142) is found in 403 engines; made from a better alloy, it is
also 10-percent larger across the beam.
When it comes to pistons, all factory slugs are cast flat-tops with
compression ratios varied by changing dish size. This design offers
efficient flame propagation, superior detonation resistance, and
high-compression ratios without excessive dome heights. On the small-block,
compression ratios were decreased starting in 1971 from the previous nominal
10.25:1 to around 8.5:1 by increasing the combustion chamber volume and
dishing the pistons. Assuming the head was cc'ed to minimum NHRA specs, a
modern 9.5: 1 street engine compatible with presently available pump gas can
be built by using early heads with the late short-block. Unfortunately, the
heads in stock form cc nowhere near the "blueprint" specs, and milling them
or the block upsets the stock non-adjustable valvetrain geometry. Mondello
offers a line of forged pistons designed to produce 9.5:1 or 11.5:1
compression with "out of the box" heads.
What are the best "out of the box" heads? If you could find them, the
1967-'70 350 W31 design least 405585), which has a good short-turn radius on
the intake ports and larger 2.005 intake/1.625 exhaust valves (compared to
the standard 350 1.875 intake/1.5 exhaust), is the best bet among production
heads. Since you probably wont find them, the "147" or "742" heads off a
'68-'70 350 work fine, too. They have the smaller valves,but retain the good
intake port. Naturally, larger valves can be added, even up to a 455's 2.072
intake.
After 1971, head quality declines. Not only are the chamber volumes high,
but the intake ports have a sharp shelf. While all Olds production heads
have siamesed center exhaust ports with a recessed divider, the recess is
much greater on late smog heads. Late 1976 and up heads are drilled for
1/2-inch head bolts. To use earlier heads on the late blocks, their
7/16-inch bolt holes must be opened up. Late heads may be installed on
earlier blocks. Due to water jacket differences, use the head gasket
designed for the model year of the block not the head.
For all-out race applications, CJ Batten has designed a state-of-the-art
Olds head that's cast in both iron (part No.22505143) and aluminum (part No.
22505805). They're available either from him or Olds dealers. Intake ports
are enlarged and raised up. This requires a special Edelbrock Victor intake
manifold (Edelbrock No. 2979). The best aftermarket intake for production
heads is the dual-plane Edelbrock Performer (No. 3711), which "makes torque
everywhere." Holley's Dominator is a tad stronger on the top end. Factory
intakes work well through 5000 rpm. Pre-'72 versions are preferred, since
they lack restrictive EGR passages. Original aluminum W31 intakes are
identical to the cast-iron versions, but save 25 pounds. The only available
small-block tunnel-rams are hand-fabricated by Dave Smith or CFE
Enterprises. Right now, 260's must use the stock intake, since other
aftermarket intakes won't match the 260's small ports. Manifold match-up
also makes it difficult to run big-block heads on a small-block. While the
tall deck castings physically bolt on, the intake port is taller than
small-block manifold mating flanges. A bigblock head's larger combustion
chambers will also lower compression by about one full point.
When it comes to camshafts, today's engines should use today's camshaft
profiles that feature less overlap, decreased duration, and increased lift.
While good in their day, the old factory W30 and W31 grinds are designed
with lots of duration and mild lift. Not only can this cause problems with
vacuum-actuated accessories, but they also won't work well in today's
low-compression, weak-geared smog motors. Olds specialty houses now offer
modern, computer-designed profiles tailor-made for Olds engines.
All Olds timing gears will interchange. Big-block chains are beefier than
the small-blocks. An aftermarket roller is better yet. The water pump used
in late air-conditioned cars (part No. 556283) features a superior low-drag
impeller.
BUILDING THE BIG-BLOCK
Big-blocks have been built with two different stroke lengths, connecting rod
lengths, and piston compression heights (see chart). Main and rod journal
diameters are the same for all big-blocks.
Since the 425 and 455-inch engines share the same bore size, but use
different stroke cranks, the question arises, "Can a 425 be made into a 455
by swapping cranks?" Yes, but the different-length 455 pistons and rods are
also required.
Both the short and long-stroke cranks have been produced in forged steel,
nodular iron, and cast iron. Short-stroke forged cranks are relatively
plentiful, but the long-stroke "943" 455 forgings are relatively rare.
The thickest blocks are early 455's stamped "FO" or (in the bellhousing
area) "68 F". F1 or F2 blocks are a good second choice. Any of these can be
bored to 4.25-inch without sonic testing. The '68-'70 455's used two
different con rods, with the rare extra-heavy-duty version having more meat
around the rod cheek and bolt head area. Other than this rare rod, all other
big-block rods are identical from a metallurgical standpoint.
Big-block piston design is similar to the small-blocks-variations on a
flat-top theme. With two basic combustion chamber sizes and two piston dish
sizes, stock compression ratios range from 8.5:1 to 10.25:1. Early heads
displaced either 70 or 85cc, with smog heads all having the big chambers.
Use of a 70cc head on a late smog motor will raise compression about one
full point. The 1970-'7l W30-type "F" heads had the small chamber, along
with a good intake port. Unfortunately, they're scarce. Other early castings
make a good alternative: Type "C" castings have an excellent intake port
high nickel content, and the most material around the ports for hogging out.
However, they do have 80 to 83cc chambers, and some 2-barrel versions have
only 2-inch intake valves instead of the preferred 2.06 intakes. All
big-blocks have 1.63-inch exhausts, except for Type J heads that had
1.690-inch exhausts. But the J heads have a poor "shelf intake port," as do
the G and K castings. A, B, and D heads are acceptable subs for C or F
castings, however. The larger valves can be installed in the small-valve
heads.
Finally, there's the C J. Batten heads previously mentioned for the
small-blocks. They'll bolt onto a big-block and really work great on the
street or in race applications; but there's no off-the-shelf intake manifold
available. Dave Smith can modify a small-block Edelbrock Victor to fit, or
less expensive C.J. Batten spacers will adapt conventional big-block
intakes, if some port misalignment is acceptable. For production heads, the
old Edelbrock 04B dual-plane works best, but it's no longer available.
Edelbrock plans to introduce a Performer eventually, until they do, if you
can't find an 04B, stick with the stock cast-iron piece or its aluminum W30
duplicate. Any of these work better than the old 442 tri-power units, which
should be considered only for restorations. Race-oriented packages usually
use the Edelbrock Torker. Offenhauser offers the only off-the-shelf tunnel
ram but its passages at the carb end are way too small for all-out engines.
Dave Smith offers his own custom tops for this intake, or complete ground-up
tunnel rams.
Nothing more needs be said on cams-the same rules apply as on a small-block.
Modern profiles cream the old '60s stuff. When properly cammed and built
according to the Olds experts guidelines, the big-block Olds will produce an
ungodly amount of torque, yet still runs well on available pump gas while
delivering exceptional mileage for its displacement. Even better, they'll
bolt right in place of existing Olds small-blocks. Cores are plentiful and
cheap. Cutlasses and Omegas are cheaper than Chevelles and Novas. Olds
blocks are cast from better material than the competition's, resulting in
better long-term bore wear. Olds specialty parts houses have solutions for
the oiling and valvetrain problems. Still don't think Oldsmobiles make
serious performance cars? Check out who is the NHRA manufacturer's champion.
(It isn't the Bow-Tie boys!) Maybe it's time you built yourself an Olds
Rocket-ship!
Oldsmobile Engine Specifications:
CID YEARS BORE STR. Jrnl. Mains Conn. Piston
Rods Dia. Rod Comp. Ht
SMALL- 260 1976-82 3.5 3.385 2.12 2.5 6.0 1.615
BLOCK 260D 1979-80 3.5 3.385 2.12 3.0 5.886 1.770
307 1980-86 3.8 3.385 2.12 2.5 6.0 1.615
330 1964-67 3.938 3.385 2.12 2.5 6.0 1.615
350 1968-80 4.057 3.385 2.12 2.5 6.0 1.615
350D 1978-85 4.057 3.385 2.12 3.0 5.886 1.770
403 1976-85 4.350 3.385 2.12 2.5 6.0 1.615
BIG- 400 1965-67 4.0 3.975 2.5 3.0 6.998 1.615
BLOCK 400 1968-69 3.870 4.250 2.5 3.0 6.735 1.74
425 1965-67 4.125 3.975 2.5 3.0 6.998 1.615
455 1968-76 4.125 4.250 2.5 3.0 6.735 1.74
Cam Bank Angle And Tappet Diameters:
YEAR CID MODEL LIFTER DIA. CAM BANK ANGLE
1964-67 330 ALL .842 39deg
1965 400 ALL .842 45deg
1965 425 ALL .842 45deg
1966-67 400 ALL .921 39deg
1966 425 exc.Toronado .842 45deg
1966-67 425 Toronado .921 39deg
1967 425 exc.Toronado .842 39deg
1968-69 400 ALL .842 39deg
1968-80 350 ALL (gas) .842 39deg
1968-76 455 ALL .842 39deg
1975-82 260 ALL (gas/dsl).842 39deg
1977-79 403 ALL .842 39deg
1978-80 350 ALL (diesel) .842 39deg
1980-84 307 ALL .842 39deg
1981-85 350 ALL (diesel) .921 39deg
1985-86 307 ALL .921 39deg
