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Olds FAQ -- Blocks

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Nov 25, 2002, 3:02:10 PM11/25/02

Olds FAQ -- Blocks

Blocks

1949 - 1964 1965 - 1976 Big Blocks 1964 - 1990 Small Blocks 1995 -
Present

Blocks 1949 - 1964
Identification
On 1959-1963 engines, the 371 has gold valve covers, and the 394 has green
valve covers. This could easily be changed though.

The casting number is located at the rear of the bell housing. The number
are
about ¾" high, and oriented to the right (passenger) side.
Casting
Year(s) CID Number Color
'49 - '53 303 555614 Green
'54 - '56 324 568922 Green
'57 - '58 371
'59 - '60 371 Gold
394 Green
'61 - '63 371 Gold
394 Lo comp: Green, Hi Comp: Red
'64 394 585786 " This specific casting number seen on " an
"Ultra-High Compression" engine.
The number "4 1/8" follows casting number.
Please refer to the Engines section as well!

If you want to build these first generation Olds Rocket engines, consider
getting in touch with some of the oldtimer nostalgia racers who have raced
these Olds V-8's. The famous "Woods, Stone, and Cook" 1941 Willys was
powered
by a blown Olds. A lot of Willys-Overland gasers used the Rocket block for
power. Don "Big Daddy" Garlits knows some of these people - he might be a
person to contact. Southern California might be a place to start looking!
Try 1-800-FAST-88S. They carry a lot of parts for the mid 50's cars.
[ Thanks to Scott R. Clark, Clayton Pierce, Ray Woodward for this
information
]

Functional Differences
Parts might exchange from 1949-53 303, 1954-56 324, 1957-58 371 engines.
371
and 394 cranks might interchange (same stroke), as might 303 and 324
cranks
(same stroke). Cams should be interchangeable. In general, the 324 and 371
can
interchange a lot but not to the 394. Parts will not exchange with
post-1964
engines (260, 307, 330, 350, 403, 400, 425 and 455). These 1949 to 1964
blocks
are physically very different from the 1964 to 1990 blocks, at least in
appearance.
303 and 324 use the same deck height. The 371 and 394 have a taller deck
height than the 303 and 324 engines.
The 394 might have a weakness in the cylinder heads, and they have a
tendency
to crack.
You could call some for the cam grinders that were doing cams back in the
50's, like Isky and Crane (check Engle also), to see if they may still
have
some lying around. You'll probably need to have a stock cam reground. Cams
for
the 1964 to 1990 Olds blocks wont interchange with the 303, 324, 37 or
394.
There will be some trouble finding a few things, but generally, you can
find
any stock parts you need. Price is the problem. Parts for these beasts
generally run more than the more common motors (like a $100 gasket set).
Rod
bearing and timing chains should be fairly easy to find locally for a good
price. Kanter Products offers a complete line of parts to rebuild a stock
394.

Exhaust manifolds also differ greatly. For headers try a custom header
shop.
The J-2 Tri-Power setup will NOT fit the 394. There were differences
between
the 371 and 394, I believe in the port sizes. The 394 intake passages are
much
larger. Also available is a dual-quad intake for a pair of 625 CFM
Carters.
You can save the carbs and linkage. As far as performance intakes, Offy
used
to make intakes, like dual quads, 4 2bbls' and things like that.
Offenhauser
did make a nice 3x2 intake manifold. The problem now is finding one at a
reasonable price, to make yours a rare Tri-Power Oldsmobile. Your best bet
for
high performance, is a stock 4GC intake with a 625 CFM Carter AFB.
Besides,
the Offy manifold is aluminum and looks better.
Hilborn had a fuel injection setup of these things, at least I think it
was
Hilborn. I remember seeing a trick dragster with a late 50's old, port
fuel
injection, and stock velocity stacks for each intake. There were blower
intakes for these guys as well.
There is an old junkyard in NE Georgia that has about 5-10 1960 to 1964
394's,
if you need spare parts/engines.
[ Thanks to Doug Ahern, Bob Handren, Isagil, Scott for this information ]

Unit Numbers

Big Block Blocks 1965 - 1976

Big Block Identification
A big block measures 14" between the heads at the manifold base.
Facing the front of the engine, at the top surface of the timing chain
area,
to the left of the oil fill tube, there is a code about 1.5" high followed
by
the casting number. A letter indicates a big block, a number indicates a
small
block.
Big blocks have a little hump in that area, whereas the small blocks are
flat
the whole way across.

ID/ Casting
Code Year(s) CID Number Notes
A '65 425 381917?? 1st year, big cars.
386525
B '65 400 389298 442 only, one year only.
D '66 - '67 425 389244 Big-car engine. Toro is different
internally.
E '66 - '67 400 390925 442 engine [VERY rare].
F '68 - '72 455 396021 Most common big block. Two types of "F"
letters: stick type, and one with two
vertical
hangers and a base.
Fa '72 - '76 455 396021 Very common big block.
G '68 - '69 400 396026 442/Vista/etc. engine.
L '76 455 231788 Motorhome, maybe marine also. GM made
motorhomes
from '73-8, maybe in all?
Please refer to the Engines section as well!

Look for the casting number and letter on the horizontal shelf right
behind
the water pump, just to the [driver's] right of the oil pressure sensor.
The
casting numbers are usually about ¾" - 1" tall, and the ID/Code is usually
a
bit larger, a little over an inch, and covered with schmutz. The most
common
block will be the standard 455: "396021 F" or "396021 Fa". The "a", as in
Fa,
is actually an upper case A, but about ¼ as big as the F, and subscript to
the
F [set lower]. Also, on the 231788L block, the "L" is the same size as
most of
the rest of the digits, whereas the center "7" is noticeably smaller.
400's were bronze in color, most 425's and early 455's (1968, 1969) were
red,
while Toronado 425's and later 455's were blue. However, since engine
color
may have been changed, use this as supporting evidence only.
[ Thanks to Chris Witt, Ed Ekstrom, Daren for this information ]

Big Block Functional Differences
For those seeking to build a really heavy-duty engine, rumor has it that
the
blocks with an "F5" or "F6" cast on the rear face, under the flexplate
area,
are higher in nickel, and stronger. These are commonly 1967 to 1970 or so
425
or 455 blocks.
Year CID Nickel Content Code
'68 - '70 350 F4
'68 455 F4
'68 455 F2
'70 455 F1
350 Diesel F6

You can use either a 455 or a 425 block to make an engine of either
displacement; the bores are the same. What's different is the crank
[stroke],
rods (length), and pistons (compression height). So get the crank, rods
and
pistons! Also, different combinations of lifter diameter and that cam bank
angle were used. The 425 "D" blocks come in two configurations: Toronado
units
have larger lifters, set on a more modern bank angle, whereas more mundane
[non-Toro] 425 blocks have the common smaller lifters set on the early cam
bank angle. The Toronado block is generally preferred because of the more
common lifter bank angle, and the other perks that a Toronado engine
brings:
big valves, etc.
All engines 1968 and up, (all 455's, 400's, 403's, 350's, 307's, 260's),
use
the same lifter bank angle of 39°. All 455's and most small blocks [all
but
late 307's?] use 0.842" diameter lifters. Most pre 1968 engines use the
same
lifter, but set on a 45° bank angle. Some pre 1968 engines used larger
0.921"
lifters, notably 442 and Toronado engines.
KEY: The cam must be ground to match the block's cam bank angle. That cam
will
then work in any Olds engine with the same bank angle, but will NOT work
in
blocks with the other bank angle. Either lifter diameter can be used with
either cam, just get lifters to match the block. Which brings up two
important
differences: the 0.921" lifters are rather more costly, at about $100 a
set
vs. $30 a set for the more common units, and the larger lifters require
shorter pushrods. Also, some cam manufacturers no longer offer cams in the
45°
form. Contact Engle for custom cams, as they grind all Mondello's cams.
[ Thanks to Chris Witt for this information ]

Big Block Unit Numbers
Pre 1968 engines also had an engine unit number stamped on to the machined
pad
at the front of the RH head. I believe that the Toronado 425's started
with a
T rather than a V.
V 001001 1965 400 442's
V 100001 1966 400 442's
V 200001 G 1967 400 4V 442's, including W-30
V 200002 1967 400 2V 442's, [etc.?] Turnpike Cruiser
1968 and up engines had an engine unit number stamped into the oil fill
tube,
the first digit of which will match the last digit of the car's year:
9012345
would be a 1969 engine [or 1979 small block]. Since this part is easily
removed or replaced, use it for an indication, not a standard. No point in
mentioning the oil fill tube decal with a 2-letter engine ID code, which
is
99.99% of the time long gone, and easily replaced or faked anyway.
Also starting in 1968, the VIN derivative of the engine's original car was
stamped onto the vertical machined pad on the left side of the block, at
the
front, just under the head- block interface. It might look like
"38M203456",
where:
3= Oldsmobile, GM's 3rd division [1=Chevy, 2=Pontiac, 4=Buick, etc.]
8= year of issue last digit, like on oil fill tube [8=1968, 0=1970...]
M= build plant [1, E, G, M, R, or Z; see below], and 203456= the last 6
digits
of the original car's VIN.
Build plant info was also used in the car's VIN plate [1 character] and
body
tag [up to 3 letters]. Some build plants were: 1 or OS= Oshawa, Canada,
eh?; B
or BA= Baltimore, MD; E or BL= Linden, NJ; G or FRA= Framingham, MA; K or
KC=
Kansas City, MO; LA, LAN, or M= Lansing, MI; R= Arlington, TX; BF or Z=
Fremont, CA;
That'll help ID the block year in case the heads are not original.
For the purists: on the back of the block, near the distributor, is a 1 to
3
digit cast number, digits about 3/8", which is the Julian day of the year
on
which the block was cast [1 to 365]. It will generally match the Julian
Day
code cast into the heads, crankshaft, water pump, thermostat outlet, etc.
within a few [up to 20-30] days, and precede the car's date of build by up
to
30-40 days.
[ Thanks to Chris Witt for this information ]

Small Block Blocks 1964 - 1990

Small Block Identification
A small block measures 12" between the heads at the manifold base.
Facing the front of the engine, at the top surface of the timing chain
area,
to the left of the oil fill tube, there is a code about 1.5" high followed
by
the casting number. A letter indicates a big block, a number indicates a
small
block.
Big blocks have a little hump in that area, whereas the small blocks have
a
completely flat shelf.
Small blocks from 1977 onward will have the CID or liters cast in large
numbers right above the center core plug. The engine VIN number will also
be
cast onto the side of the block.
From the outside they don't look different at all because the 260, 307,
330,
350, and 403 are all the same basic block. But externally the distributor,
valve covers, water pump, front cover, oil pan, carb, etc are the same.
[ Thanks to Chris Witt, Tony Waldner for this information ]

ID/ Casting
Code Year(s) CID Number Notes
1 '64 330 381917
2 '65 330 381917
2 '68-70 350 395558
3 330
4
5
'73,'74 350 395558
2A '76-81 260 Solid main webs for 2A's only? At least for
'76.
2B ??-'81 260 557751 Windowed main webs. Windowed main webs for
2B's only?
3A
4A '77 403 557265 Solid main webs possibly
553990 for these three
554990 casting numbers.
4B '77-'79 403 557265 Windowed main webs always.
?? '85 307 556607
5A '81- 307 3161
D3 350 7582 Diesel
Please refer to the Engines section as well!

Small Block Functional Differences
307 Block Quality
There was a problem in 1987. I don't know if it is due to poor nickel
quantity, but there was a cracking problem in the deck area. Engine
rebuilders
are aware of this and check the decks of 1987 307's very close.
Olds wasn't the only division to suffer in 1987. The small block Chevy
cracked
in the cam valley that year, and the 2.5 liter 4 cyl Pontiac suffered
block
and head cracking problems.
[ Thanks to Tony Waldner for this information ]
Solid / Windowed Main Bearing Webs
403's are usually the engine mentioned when windowed webs are discussed
because there are rumors and some sightings of solid main web 403's. Solid
main webs would mean a much stronger bottom end. As far as 403's go, some
people doubt that a solid web engine was ever made. According to Mondello,
2500 solid web 403's were produced in 1977 and they were used in big Buick
and
Olds wagons. You can determine if you have a solid web by looking at the
serial number.
All small block Olds engines produced after 1977 have windowed main webs,
with
exception of the diesel 350. Oldsmobile re-tooled the engine foundries in
early 1977. This is the reason that you see so many 350 Chevy engines in
1977
Delta 88's. There was a shortage of 350 Olds engines, and the Cutlass line
was
selling like crazy, so those engines were reserved for that line.
403 Olds Solid Main Web Production

2500 produced
Block Casting Numbers: 557265-4A, 553990-4A, 554990-4A
Blocks with these casting numbers were used in certain 1977 Buick Station
Wagons built in 1976, the Pontiac Bonneville with tow package, the 1979
Pontiac Trans Am with tow package (w/block casting #554990-4A), and in
1977
Olds 98's. Block casting number is found behind the timing cover between
the
oil fill tube and the oil sending unit. Might also be found in 1977
Toronados.

All "4A" blocks don't necessary have solid main webs. #554990 has been
found
to have open webs. 1977 models built early in the model year, fall of
1976,
are likely to have solid main webs.
Source: Mondello Olds V-8 Engine Technical Reference Manual
[ Thanks to Michael R. Hall, Chris B. Witt, Tony Waldner, Mark Prince for
this
information ]

Small Block Unit Numbers

Blocks 1995 - Present
Please refer to the Engines section as well!

General
4 Bolt Mains
Except for experimental and ultra-exotic [Mondello, Dave Smith
Engineering,
etc.] custom setups, there is no such thing as an Olds 4-bolt block or
main
caps [455 or 350, etc.]. There were never any made.

Oversize Lifter Bore
With any block, watch out for the 'O' stamp on the lifter bore boss,
indicating a 0.010" oversize lifter. Either Oldsmobile would only have
stock
0.010" over replacements or THERE ARE NONE AVAILABLE. Which means you
either
get to sleeve the lifter bore (difficult and expen$ive), or scrap the
block,
or, re-use that old lifter. Resleeving the lifter bore is not fun.

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