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Home/Technical Info/Oldsmobile/01. Engines/1964-1988
260-455 V8
/ General Information /
1964-1988 Olds Gen 2 Engines - Cylinder Head ID and Casting Number Decoding
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Cylinder Head Casting Codes
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Identifying Oldsmobile 330-455 CID Rocket Cylinder Heads

In 1964 Oldsmobile introduced its newly designed 330 C.I. engine. The 330 was much lighter than the 394 and more powerful than the 215 F-85 V-6 power plant it replaced.
For over 25 years we witnessed the 330 evolve into many other cubic inch engines. The 400 and 425 big blocks were introduced in 1965 to power the 442 and full size Oldsmobiles respectively. In 1968 the 330 grew to 350 cubic inches and the 425 became the 455 when Olds changed the crankshaft stroke. The 400 changed bore and stroke also that year to share the 455's crank.

In 1975, the 260 V8 joined the Olds lineup as the new small block, and a year later the 455 was dropped forever. The 403 small block was to replace the 455 in its duty of powering the bigger bodied Olds and Cutlass series cars so optioned in 1977. It was not a Cutlass option in '78 and lived only through 1979. The long lived 350 was also dropped when the 307 arrived which became the sole surviving Oldsmobile designed V8 engine.

As the 330 grew, so did the list of cylinder heads used on its upgraded cousins. Although the basic design stayed pretty much the same, valve size, port shapes and combustion chamber volumes changed to meet the demands for more horsepower at first and cleaner air as smog restrictions tightened.

In the late '60s Toronado, marine and 442 heads were given larger intake valves (2.077 vs. 2.00) than the other big block cars of that period. In 1970 this trend continued on the G.T. version of the Toronado, the 442s and marine engines. In '72 the only big valve heads were found only on 442s with manual transmissions and all W-30 and marine motors. An interesting twist developed in 1972. Some 455s were fitted with 1.688 diameter exhaust valves instead of the 1.625 diameter valves that were normally used. These oversize exhaust valves were not used after '72 but can be used in other big intake valve heads.

The last big valve head was the KA which was listed as a marine, W-30 replacement and standard manual transmission head up to 1975 in the '83 Olds parts book.

When the W-30 first arrived in 1966 it had its own special heads, part No. 387174. The '67 W-30 also had a special head (pt# 389213 or 230369). I believe these heads were also used on big block cars destined for California. These heads had the exhaust port "bumps" drilled and tapped for air pump fittings. Non-California cars had plugs installed in these tapped holes. The '68-'69 W-30s, non-air '68 Hursts and all '69 Hursts utilized special heads, too. These heads, commonly called "D" heads, carried the casting #400-370. The 1968-'69 D, the '70 F and the '71 H heads received two slight but important modifications.

Due to the firing order of Olds V8s, number 3 and 6 spark plugs fire in succession. This caused interference at the intake manifold crossover passage, disturbing the exhaust pulses for these cylinders. So Olds engineers had a small horizontal wall cast between the center exhaust port divider and the #3 or #6 port wall (depending on what side of the engine you face),closing off the passage to the intake manifold. Number 5 & 4 ports still fed heat to the passage for fast warm ups and these heads showed improved horsepower ratings; especially when exhaust headers were used. The second modification was the port shape just below the intake valves. Olds actually decreased the diameter of the opening just below the valve head. This created a venturi effect increasing flow with these heads.

The small block Ram Rod and W-31 s ('68-'70) utilized special head castings featuring 2" intake and 1.625" exhaust valves. Even though they were small port heads, Olds engineers found these heads to work better on the 350s than the big block heads. Quarter mile test results from magazines of the era show ETs to be very close to the W-30s. These #5 heads carried the casting # 397-742 for '68-'69, and the #6 heads had the 403-859 casting number for '70.

When looking for big valve #5 and #6 heads, be careful. The '68-'69 #5 small valve heads have the same 397-742 casting number and the '70 small valve #6 heads carry the 403- 859 number just like the bigger valve heads.

How can you tell which heads you have on your Rocket? Two ways. All big block heads have a large (5/8" tall) letter cast next to #1 spark plug hole, A, B, C, etc. All small blocks have a large number in the same location, 1, 2, 3, etc. Olds heads also have a six digit casting number cast in one of two locations. Early heads had this number cast near the rocker arm assemblies which would require you to remove the valve cover to see it. Heads produced after 1969, including A, B, C and D heads, have the casting number on either side of the center bolt just below where the valve cover sits. This casting number location is visible with the valve cover in place. When buying D, F, or H heads look for the cast wall I described earlier and the second half of the casting number is also found on the combustion chamber side of the head. So be careful when purchasing these high priced heads by looking them over thoroughly.

Based on what I have learned, I've listed all the '64 -'90 heads. This�may not be�a complete list, so I need your help to finish it. If you have or see any other heads you can call or write me so I can add this information to the list and share it with all of you.

Contact me at:�

PS - The only casting numbers I believe I am missing are for the 1965 Irrigation heads.

Donated by: Karl Sarpolis, Homer Glen, IL  January 2011

(This list began about three years ago by  attending Olds shows, hunting around junk yards and bothering Dave Pastrick, both Bob Clines, Ken & Joe at Flames Olds in Palos Heights, IL, and my friends Tony and Scott. Thanks guys).

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Here is 1970 thru 1988 - Click to View - NOT for DOWNLOAD




















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