| Editor's Note: The following block identification information is reprinted with permission of Pete McCarthy, author of Pontiac Muscle Car "Performance 1955-79" (part # FP16) and "Pontiac Racer's and High Performance Handbook" (part # FP10). Both of these books can be found in our Literature section, and are highly recommended for those researching and/or modifying Pontiac V8 engines. |
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| BLOCK IDENTIFICATION |
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Pontiac blocks are easy to identify if you know what to look for. It is simple, for example, to visually categorize all 1959-and-later blocks into 389/400 or non-389/400. All displacements other than 389/400 possess a "transfer lug" (found at the rear of the block shaped like a "mountian" or "pyramid"). There are only two exceptions: the 1961-62 421 SD (the same blank casting as the 389) and the 1973 SD-455. All V8 blocks cast prior to 1959 (287, 316, 347, and 370) were "standard" displacement and did not have a transfer lug. In addition, these 1955-58 blocks did not use side-mounted motor mounts as did all blocks from 1959 forward. All blocks through model year 1963 have a production number cast into the passenger side of the block. The casting number for these blocks are as follows:
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1955 (287 c.i.d.) #518037
1956 (316 c.i.d.) #521560
1957 (347 c.i.d.) #523293
1958 (370 c.i.d.) #528456
1959 (389 c.i.d.) #532000
1960 (389 c.i.d.) #536387
1961 (389 c.i.d.) #538181
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1961 (421 SD) #538181
1962 (389 c.i.d.) #538181
1962 (421 SD) #538181
1963 (326 c.i.d.) #548211
1963 (389 c.i.d.) #543680
1963 (421 c.i.d.) #544988
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Beginning with the 1959 389 c.i.d. blocks, side motor mounts were utilized for the first time. Two motor mount holes appear on each side of the block, a feature that would continue through 1969. Beginning in 1964, all blocks were cast with provisions for block-mounted starters, even though most of the large cars still used the bellhousing-mounted starters. The block casting number location moved from the side to the distributor pad (except for the 421s). All the blocks cast through model year 1964 included cylinder head stud oiling passages. No engines after 1964 utilized the stud-oiled heads, so these passages were eliminated in 1965. All blocks from 1955-66 used two freeze plugs per side. Block casting numbers for the 1964-66 engines are as follows:
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1964 (326 c.i.d.) #9773153
1964 (389 c.i.d.) #9773155
1964 (421 c.i.d.) #9773157
1965 (326 c.i.d.) #9778840
1965 (389 c.i.d.) #9778789
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1965 (421 c.i.d.) #9778791
1966 (326 c.i.d.) #9778840
1966 (389 c.i.d.) #9778789
1966 (421 c.i.d.) #9778791 early
1966 (421 c.i.d.) #9782611 late
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All blocks are cast with a date of production code. This code appears on the distributor pad. The code consists of a letter, followed by two or three digits. The letter signifies the month (A = January, etc.). The letter "L" signifies December for all years but calendar 1966 (1967 model) when the letter "M" was used for December. Since "I" was used in all years, it is possible that both "I" and "J" were used to designate September. The reason is not known. The 2nd character in sequence (or 2nd and 3rd if three digits appear) is the day of the month. The last digit designates the year of production (not necessarily the model year). For example:
A #9773155 block with a date code of J23 = October 2, 1963.
A #9782611 block with a date code of F126 = June 12, 1966.
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All blocks produced for model year 1967 were recast for three freeze plugs per side. Beginning in mid-1967, the block casting number changed location from the distributor pad to the rear of the block, just behind the #8 cylinder. The foundry line casting can be found in two places, on the front side of the block (GM1, GM2, GM3, etc.) and at the extreme rear end of the block on the distributor pad (1, 2, 3, etc.). In addition, 1968-69 428s received two additional displacement identifiers, a cast "428" on the side, and a "28" cast into the center lifter valley rib. Similar identifiers would be used to identify other displacements (455, 350 in 1970, and 400 in 1971). Casting numbers for the 1967-69 blocks are as follows:
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1967 (326 c.i.d.) #9786339
1967 (400 c.i.d.) #9786133
1967 (428 c.i.d.) #9786135
1968 (350 c.i.d.) #9790079
1968 (400 c.i.d.) #9790071
1968 (400 RA) #9792506
1968 (428 c.i.d.) #9792968
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1969 (350 c.i.d.) #9790079
1969 (400 c.i.d.) #9790071
1969(400 RA IV) #9792506
1969 (428 c.i.d.) #9792968
1969 (303 c.i.d.) #546313
1969 (400 RA V) #9792968
1969 (400 RA V) #545887
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NOTE: All 1967-68 428s are 4-bolt. All 1969 428s have 4-bolt holes, but low-performance engines with #46 heads have 2-bolt caps. All 1968-69 #9792506 Ram Air 400 blocks have 4-bolt caps.
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In 1970, all blocks received three additional motor mount holes for possible mounting in the new Firebird chassis. In some cases, only three holes were tapped, but five pads were machined. Blank block castings for 1970-76 are as follows:
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1970 (350 c.i.d.) #9799916
1970 (400 c.i.d.) #9799914
1970 (400 RA III) #9799914
1970 (400 RA IV) #979991(5)
1970 (400 RA V) #481708
1970 (455 c.i.d.) #9799140
1971 (350 c.i.d.) #481990
1971 (400 c.i.d.) #481988
1971 (455 H.O.) #483677
1971 (455 c.i.d./late H.O.) #485428
1972 (350 c.i.d.) #481990
1972 (366 c.i.d.) #(485)212
1972 (400 c.i.d.) #481988
1972 (455 c.i.d.) #485428
1973 (350 c.i.d.) #488986
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1973 (400 c.i.d.) #481988
1973 (455 c.i.d.) #485428
1973 (455-SD) #(490)132
1974 (350 c.i.d.) #488986
1974 (400 c.i.d.) #481988
1974 (455 c.i.d.) #485428
1974 (455-SD) #(490)132
1975 (350 c.i.d.) #488986
1975 (400 c.i.d.) #488986 early
1975 (400 c.i.d.) #500557 late
1975 (455 c.i.d.) #500813
1976 (350 c.i.d.) #488986
1976 (400 c.i.d.) #500557
1976 (455 c.i.d.) #500813
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The block date code is found just to the left of the distributor hole at the back of the block. This can make it difficult to read if the engine is installed in the car. This code (B059) breaks down as February 5, 1969.
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The block casting number on mid ‘67-and-later blocks is found just behind the #8 cylinder on the passenger side of the block. This number, 9792968, denotes a 1969 428. The number is located next to the distributor hole on earlier engines.
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Non-389/400 engines featured an identification or transfer lug on the rear passenger side of the block. The exceptions to this were the 1961-62 421 Super Duty, and the 1973 455 Super Duty engines.
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Many of Pontiac’s 2-bolt main engines, most notably the lower-performance 428s (1969) and 455s (1970-and-later), were drilled and tapped for 4-bolt caps from the factory.
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Along with the displacements cast into the side of the block, additional identifiers were added to the lifter valley ribs as well. “28” denotes this as a 428, while “55” would reflect a 455 and “00” a 400.
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Displacement identifiers for the 350 began in 1970, while all 1971-and-later 400s received the treatment.
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| Pontiac began casting displacements in the sides of the block (among other places) in the late ‘60s. This practice started with the 428s in 1968. 455s received the identifiers in 1970 when they replaced the 428s. |
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FYI: In 1977, only the 350 and 400 c.i.d. engines remained. A new 301 Pontiac short deck engine joined the line-up along with some other "corporate engines", such as the Olds 403 and the Chevy 305. The Pontiac 400 block was cast with revised motor mount bosses, and will only mount in late Firebirds or Grand Prixs. The blank casting number for the 1977-79 400 is #568557. The 301 can easily be recognized by the lateral oil filter location. In other words, the 301 oil filter sticks straight out, unlike other Pontiac blocks which are attached to a housing that aims the oil filter downward.
A wide variety of specific engine/trans codes are stamped into the front of production blocks. Trans codes may appear to conflict. Prior to 1965 (the start of the "two letter" system) the two digit engine code, which was the last two digits of the full six or seven digit part number, was stamped followed by the standard trans code. An optional trans code, if installed in the vehicle, appears nearby, often on top of the other characters. Most production blocks, except 1964-66 and most 1967s, received a vehicle identification (V.I.N.) stamp. Prior to 1964, the block V.I.N. was identical to the actual vehicle code. Beginning in late 1967, block V.I.N.s appeared with the digit "2" designating a "Pontiac" engine, followed by the year, a letter identifying the assembly plant, and the vehicle serial number.
A researcher familiar with the various assembly plant code letters can sometimes ascertain whether a block was originally installed in a Firebird or a GTO. Lordstown (U), Norwood (N), and Van Nuys (L) built Firebirds, but not Tempests. A block V.I.N. of 29L123456 would indicate that the block was originally installed in a Firebird built at Van Nuys, CA. |
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CYLINDER HEAD IDENTIFICATION
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Identifying Pontiac cylinder heads is also a fairly straightforward procedure. This process is made easier since the majority of Pontiac cylinder heads have the casting number, or a portion of it, on the outside of the head (as opposed to under the valve cover like many other makes). Determining which head you're looking at is as simple as reading the casting number and the date code -- usually.
Some heads are missing either the casting number, (an example would be early production '68 Ram Air II heads or some '73 Super Duty heads), while others are missing date codes ('69 Ram Air IV and '70 Ram Air IV cast before November, 1970).
Most of the time, however, both date codes and casting numbers are found on the heads. Early heads often used the entire casting number which is typically seven digits. Later heads (from the mid-Sixties on) usually used only the last two or three digits of the casting number. These numbers are usually found on the exhaust side of the head, either just below the valve cover rail, on the center two exhaust ports or on the end exhaust ports. Some heads carried the casting number (or a portion thereof) below the spark plug holes between the center and end exhaust ports.
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1-Certain heads, like this 1970 Ram Air IV, had the casting identification number on the end exhaust port. Still others would feature the number on the area just below the valve cover rail.
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2-Most Pontiac cylinder heads feature an identification number cast into the external surface, which greatly simplifies identification. This number was usually the casting number, or a portion thereof. The area above the two center exhaust ports was a popular location for the casting numbers. “7F6” is the code for a 1972 455 H.O. head, while “13” is a 1970 330-horse (Firebird) or 350-horse (GTO) 400 head. |
3-The head casting date is usually found on the exhaust side of the head just below the valve cover rail. These dates are read just like the block codes. The first letter identifies the month, the next one or two digits represent the day, while the last digit denotes the year the head was cast. “C090” decodes as March 9, 1970 (this date code was taken from a 1970 #13 head). |
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Machined combustion chambers are a unique feature of Pontiac cylinder heads. When GM mandated a corporate-wide drop in compression ratios for the 1971 model year, Pontiac obliged by greatly increasing the size of the chambers. Compare the ‘72 455 H.O. (8.3:1 cr) chamber on the left to the ‘70 400 (10.5:1 cr) chamber on the right. Upping the compression on a Pontiac V8 is as simple as bolting on a ‘70-or-earlier head.
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Beginning in 1968, Pontiac fitted their highest-performing engines with heads featuring redesigned round exhaust ports (shown above). Engines so equipped were the ‘68 Ram Air II 400, 1969-70 Ram Air IV 400, 1971-72 455 H.O., and 1973-74 Super Duty 455. The more standard “D-port” exhaust arrangement, shown below, is still a capable performer in all but the most extreme applications.
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Correctly identifying Pontiac cylinder heads is a particularly useful skill when planning your engine combination. Putting large-chamber 455 heads on a 400 is certainly not the way to go (the compression ratio would be down in the sixes), while swapping ‘70-or-earlier 400 heads onto a 455 would result in an 11:1 engine that would be tough to feed on today’s gas. |
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FYI: Date codes can usually be found just below the valve cover rail on the exhaust side of the head. One exception is the previously mentioned Ram Air IV heads of '69 and early '70. These heads were actually cast with a date code, but the code was located under the valve cover between the two center cylinders. This area was then machined for the head bolt, which removed the casting date! This slight oversight was fixed on Ram Air IV heads cast after November, 1970.
One important point to keep in mind when identifying cylinder heads is that certain partial casting numbers can be found on more than one type of head. For example, casting # 16 is found on four different types of cylinder heads, although none of the same year. This is why it's important to find the date code along with the cylinder head cast number, otherwise mis-identifying is very likely.
The date code format used by Pontiac on cylinder heads is the same as that used on blocks; the month of production is coded as a letter (A=January, B=February, etc.), followed by one or two digits which are the day of the month, and ending with the last digit of the year in which it was produced.
The chart at the end of this article shows cylinder head casting numbers and their original applications. Swapping cylinder heads between applications is a good way to juggle compression ratios and change the performance characteristics of an engine. Don't forget, though, that heads used up to 1964 oiled the valvetrain through the rocker arm studs, and that Pontiac changed the valve angle in 1967. To be safe, head swaps should take place only among those of the same generation (Pre-1964, 1964-66, 1967-and-later except 301 and 267). |
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ENGINE BLOCK CODES
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Original Build Information
Ever wondered how your Pontiac was originally equipped? A service has been established to research original build information for 1989-and-earlier Pontiacs. For information on your car, send $35.00 and a note with your serial number to: Pontiac Historic Services, P.O. Box 884, Sterling Heights, MI, 48311-0884. See them on the web at www.phs-online.com.
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1964-74 ENGINE BLOCK CODES
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The following table shows block codes for Pontiac V8 engines installed in A-bodies from 1964 to 1974. Engine codes for manual transmission cars are in bold type. Automatic transmission engine codes are in plain type.
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1964
326/250 hp
326/280 hp
389/325 hp
389/348 hp
1965
326/250 hp
326/285 hp
389/335 hp
389/360 hp
1966
326/250 hp
326/285 hp
389/335 hp
389/360 hp
1967
326/250 hp
326/285 hp
400/255 hp
400/335 hp
400/360 hp H.O.
400/360 hp
(Ram Air)
1968
350/265
350/320
400/265
400/350
400/360 H.O.
400/360
(Ram Air)
400/366
(Ram Air II)
1969
350/265 hp
350/330 hp
400/265 hp
400/350 hp
400/366 hp
(Ram Air III)
400/370 hp
(Ram Air IV)
400/375 hp
(Ram Air V)
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92X,92W,92J
94X,94W,94J
78X,78W,789,79J
76X,76W, 769, 77J
WP, ZN
WR, YP
WT, YS
WS, YR
WX, WP, XF, YN
WR, XG, YP
WT, WW, YS, XE
WS, WV, XS, YR
WP,WX,WC, WH,
YO,YN, XF,
YJ, XI
WR, XR,WK, WD, YP, XG, YM, XO
XL, XM
WT, WW, YS
WS, WV, YZ
XS, YR, XP
WD, WC, YN, YJ
WR, WK, YP, YM
XM, YA
WT, XZ, YS, XH
WS, YZ
XS, XP
WY, XW
WC, WP, WM, WU, XL, YJ, XR, YN, XB, YE, UY, XS
WR, WV, XT, XU, YP
XM, YZ, XX, YB, YF
WT, WX, YS, XH
WS, YZ
WW, XP
WI, WY, XY, XW
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1970
350/255 hp
400/265 hp
400/330 hp
400/350 hp
400/366 hp
(Ram Air III)
400/370 hp
(Ram Air IV)
455/360 hp
1971
350/250 hp
400/265 hp
400/300 hp
455/325 hp
455/335 hp H.O.
1972
350/160,175 hp
400/200 hp
400/250 hp
455/220 hp
455/250 hp
455/300 hp H.O.
1973
350/150, 175 hp
400/170, 185 hp
400/200, 230 hp
455/215, 250 hp
1974
350/155, 170 hp
350/170, 185,
200 hp
400/175, 190 hp
400/200, 225 hp
455/215, 250 hp
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W7, WU, X7, YU
XX, YB
XZ, XV
WX,WT, XH, YS
WS, YZ
WW, XP
WA, YC, YH
WR, WU, WN, WP, XR, YU, YN, YP
XX, YX
WK, WT, YS
YC
WL, WC, YE
WR,YU,YV,YR
ZV, ZX
WK,WS,YS,YT, ZS
YA, YC, Y4
YD,YK
WD, WM,YB,YE
XR,WV, ZB, ZD,
Y2, Y7, YR, YV, ZR,
ZV, WA, WC, WD,
WF, WL, WN, XZ
YI, YP, YX, YZ, Y4, ZK, ZX, XH, XI, X3, X4
WK, WS, WP, YF,
Y6, YG, YN, YX, YT,
Y3, ZN, ZS, XK, XN,
XX, XZ, X5
YA, YC, YD, YK, ZA, AC, XA, XE, XJ, XL, XY, XT, X7, XO, YE
WA, WB, AA, YA,
YB, YC, ZB, YN, YP,
YS, ZA
WN, WP, YN, YP, YS,
ZP
AH, YH, YJ, ZH, ZJ,
AD, YF, YK, ZD, ZK
WT, WR, Y3, AD,
YL, YM, ZS, AT, YT,
YZ, ZT
AU, YR, YU, YW,
YX, YY, ZU, ZW, ZX,
A4, Y4, Y6, Y9, Z4, Z6
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1964-74 PONTIAC V8 CYLINDER HEAD CASTING NUMBERS
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1964
326/250 hp
326/280 hp
389/215, 230, 235 hp
389/267, 283, 303, 306 hp
389/325, 330, 348 hp
421/320 hp
421/350, 370 hp
1965
326/250 hp
326/285 hp
389/256 hp
389/290, 325, 333 hp
389/335, 338, 360 hp
421/338 hp
421/356, 376 hp
NOTE: All casting #s are on end port.
1966
230/165 hp
230/207 hp
326/250 hp
326/285 hp
389/256 hp
389/290, 325, 333 hp
389/335, 360 (GTO) hp
421/338, 350 hp
421/356, 376 hp
1967
230/165 hp
230/215 hp
326/250 hp
326/285 hp
400/255,
260, 265 hp
400/290 hp
400/325, 333 hp
400/350 hp
(Grand Prix)
400/325, 335, 360 hp
400/325, 360 hp,
Ram Air
428/360, 376 hp
1968
250/175 hp
250/215 hp
350/265 hp
350/320 hp
400/265 hp
400/290, 340 hp
400/350 hp
(Grand Prix)
400/330 hp
(Firebird)
400/335, 350, 360 hp
400/335, 360 hp
Ram Air
400/340, 366
hp Ram Air
428/375 hp
428/390 hp
1969
250/175 hp
250/215, 230 hp
350/265 hp
350/325 hp
400/265 hp
400/290 hp
400/340 hp
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9773345, (845)
9773395
543796
9773345,(845)
9770716
9773345,(845)
9770716
62
22
75
76
77
76
77
9782005
9782229
094
095
091
092
093
092
093
9778692
9778693
140
141
142
143, 061
143, 061
670,9787671,187
670
670,97, 997
670, 9787671
9791194
9791195
17
18
14
15, 215
16, 216, 62
16, 216, 62
16, 62
31 (37)
R, 96, A
16, 216, 62
16, 216, 62
9795456
9795457
47
48
45
46
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1969
400/330, 335,
350, 366 hp
400/345, 370 hp
Ram Air IV*
428/360 hp
428/370 hp
428/390 hp
400/375 hp (Ram Air V)
*NOTE: Cast # on end port.
1970
350/255 hp
400/265 hp
400/290 hp
400/330 hp
400/330 hp
400/330 hp
400/335,366 hp
(Ram Air III)
400/350 hp
(Grand Prix)
400/350 hp (GTO)
400/350 hp (GTO)
400/345,370 hp
Ram Air IV*
455/360 hp
(B-body)
455/360, 370 hp
*NOTE: Cast # is on
the end port.
1971
350/250 hp
400/265 hp
400/300 hp
455/280 hp
455/325 hp
455 H.O./335 hp*
*NOTE: Cast # is on
the end port.
1972
350/175 hp
400/200 hp
400/250 hp
455/200 hp
455/250 hp
455 H.O./300 hp
1973
350/150, 175 hp
400/170, 185 hp
400/200 hp
400/230 hp
455/215, 250hp
455-SD/290 hp
** NOTE: Screw-in studs.
1974
350/155, 170 hp
350/200 hp
400/175, 190 hp
400/200 hp
400/225 hp
400/225 hp
** NOTE: Screw-in studs.
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16, 62, 48
722, 9796722
16(Sm.valve)
62
16, 62
44
11, 47
11, 47
16 Sm. valve
16 Sm. valve
12 (M/T)
13 (A/T)
12
13
12 (M/T)
13 (A/T)
614
15
(GTO, GP,
and B-body)
94
99
96
98
66
197
7H1
7J2
7K3
7L4
7M5
7F6
46, 4C
46, 4C
4X, 4C
4X**
4X**
16, 485216**
46, 4C
46** (GTO)
46, 4C
4X, 4C
4X**4C (A/T)
4X**4C (M/T)
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