Technical Data

GTO technical references from a variety if sources. The information about Pontiac Block Identification and V8 Displacements is courtesy of Boyle Works' Pontiac Street Performance website. The Cylinder Head information is provided courtesy of Geeb's web site.

Block Identification

Today more and more Pontiac enthusiasts are considering engine swaps as an easy and economical way to improve power in their Pontiacs. Here's some information that may be helpful in your quest to identify that block you're thinking about.

Make sure it's a Pontiac block

All Pontiac blocks have a hydraulic lifter valley pan. The distributor hole is located on the rear deck of the block which allows for the easy intake removal without disturbing the distributor. (I've always liked that feature). While most Pontiac motors were painted blue, metallic blue or what I call "robin's egg" blue, color is only a telltale sign and not one that can be relied upon to determine the Pontiac line. You have to do more looking and verifying to be certain.

Freeze plugs provide more clues

Some Pontiac blocks have 2 large freeze plugs and some have 3 on each side of the block. Early blocks, those from inception through 1966 had 2. Pontiac engine blocks cast in 1967 through the last casting in 1978 have 3 freeze plugs on each side.

Motor mount holes

Ok, I didn't say this was easy, but check out the number of drilled motor mount holes on the block. Go ahead get down there and look. Pontiac blocks with only 2 bolts holes per side were cast before 1970. Based on my observations,1964 to1969 Pontiacs engines were all "2-holers." Blocks cast in 1970 to the last of the run (1978) had 5 holes per side, at least in theory. Will Baker's block

Some blocks, like my 400 that's in my 79 TA 6.6, is different (see photo). It is a 3-holer with two blank pads (no holes). These pads can be drilled and tapped if necessary to accommodate a different engine mount. The other block is a "5-holer." These are all drilled and tapped. [Block belongs to enthusiast Will Baker.]

 

Block displacement

Here's more help to find the engine displacement.

  350/400/455 Displacement numbers cast into block on driver's side near the front freeze plug. [You should also look on the opposite side too--check photo.]
428
"428" located on driver's side near the center between the freeze plugs.
421
No "421" numbers located anywhere; look for a square machined area on front passenger side deck where the block meets the head.
 389
No "389" numbers cast any where on the block; look for notch on passenger side deck where the block meets the head.

 

Year of the block

What year is the block? At the rear of the engine at the top near the distributor hole can be found the important casting numbers that reveal the year of manufacture--the birth year. The fourth digit indicates the year of the casting. So, if you have examined the rest of the block, you can easily ascertain the year the block was manufactured. The other info in the string may be helpful, but is not usually to relevant. The first letter, could be A through L, signifies the month. A=Jan, B=Feb, and so on. After the letter are two digits; 01=1, 25=25. Remember the last digit is the year (0-9).

Where's the engine code

Sorry, but you really can't accurately determine the year of the engine by merely knowing the engine code. You have to put all the information together to be certain. Pontiac used two-letter engine codes in different years in various cars. In later years, Pontiac added a corresponding VIN number to the block. Whatever the case, you need to examine the front passenger side of the motor. If the VINs match, that determines the engine option from the factory. Look to see what's there. Based on my observations Pontiac engines started to include VINs on the block in 1972. [This paragraph was updated 2-25-00.]

Putting it all together

For example, you come across an engine that looks pretty clean. So you start to check it out. You look at the engine code and see it has the letters WF. So you take a peek under the distributor and see several casting numbers but the last one in the string is a 9. This could be a '59, '69, or '79. You need to keep going. Look at the freeze plugs next. You look and see three (3). The equation narrows it to a '69 block. You look further, scrape away the grease and low and behold you spot the casting numbers 428 between the two freeze plugs on the driver's side. A big smile erupts on your face, your respiration and heart beat pick up, you hear "Born to be Wild" in the background and your reach for your wallet... Hello--come back. Checking a Chiltons manual that covers 1969 tells you that the motor was rated at 370, and powered a 4 speed Grand Prix.

Pontiac V8 Displacements

Year Displacement Bore in inches Stroke in inches Mains in inches
1955 287 3.75 3.25 2.50
1956 317 3.9375 3.25 2.50
1957 347 3.9375 3.5625 2.623
1958 370 4.0625 3.5625 2.623
1959-'66 389 4.0625 3.75 3.00
1963-'66 421 4.09375 4.00 3.25
1963-'67 326 3.720 3.75 3.00
1967-'69 428 4.120 4.00 3.25
1967-'79 400 4.120 3.75 3.00
1968-'77 350 3.880 3.75 3.00
1970-'76 455 4.150 4.21 3.25
1977-'81 301 4.00 3.00 3.00

Cylinder Head Reference

While extensive efforts and the compilation of a number of print & internet published sources have been made to ensure this chart is correct, LOEGTO's makes no guarantees of 100% accuracy.

Year Engine (ci.) Cast Code Casting # Part # Stud Type Intake (in.) Exhaust (in.) Volume (cc)
                 
59 389 531395     Press 1.88 1.60 68
60 389SD 535461 535461 535460 Pinned 1.92 1.60 68
60 389 536109     Press      
61 195/389 538177     Press 1.92 1.66  
61 389/421 SD 540306 540306 540304 Pinned 1.92 1.66 68
62 195/389 538177     Press 1.92 1.66  
62 389/421 SD 540306 540306 540304 Pinned 1.92 1.66 68
62 389/421 SD 544127 544127 544124 Pinned 2.02 1.76 68
63 389 543796     Press 1.88 1.60 92
63 389/421 543797     Press 1.88 1.60 72
63 389/421 SD 544127 544127 544124 Pinned 2.02 1.76 68
63 326 548232     Press 1.88 1.60  
63 389GTO/421HO 9770716 9770716 9770981 Press 1.92 1.66 68 (72)
63 421SD 9771980 9771980 9771983 Press 2.02 1.76 65
63 326 9772652     Press 1.88 1.60  
64 389 543796     Press 1.88 1.60 92
64 389GTO/421HO 9770716 9770716 9770981 Press 1.92 1.66 68 (72)
64 326/389 9773345     Press 1.92 1.66 70
65 326 22     Press 1.88 1.60 60
65 326 62     Press 1.88 1.60 70
65 389 75 9778775 9781078 Press 1.92 1.66 92
65 389GTO/421 76 9778776 9781079 Press 1.92 1.66 70
65 389/421HO 77 9778777 9781081 Press 1.92 1.66 (1.60) 68
66 389 091 9782091   Press 1.92 1.66 92
66 389/421 092 9782092 9784209 Screw 1.92 1.66 70
66 389GTO/421HO 093 9782093 9784212 Screw 1.92 1.66 68
66 326 094 9782094   Press 1.92(1.88) 1.66(1.60) 68
66 326 095 9782095   Press 1.88 1.60  
67 400 061       2.11 1.77 72
67 326 140 9786140     1.92 1.66  
67 326 141 9786141     1.92 1.66  
67 400 142 9786142     1.92 1.66 90
67 400 143 9786143   Press 1.92 1.66 75
67 400/428 670 9787670 9788067 Screw 2.11 1.77 72
67 400 RA 997 9787997 9787997 Screw 2.11 1.77 72
68 400 14 9791214 9792266 Press 1.96 1.66 90
68 400 15 9791215   Press 1.96 1.66 75
68 400/428 16 9791216 9790118 Screw 2.11 1.77 72
68 350 17 9791217   Press 1.96 1.66 72
68 350 HO 18 9791218   Press 1.96 1.66 64
68 400 RA I 31 9792731 9792700 Screw 2.11 1.77 72
68 400/428 62 9790062 9791559 Screw 2.11 1.77 75 (72)
68 400 RA II 96 9793596 9794040 Screw 2.11 1.77 71
69 400/428 16 9791216 9790118 Screw 2.11 1.77 72
*NOTE: Some books show #16 used in 69, but this may be totally incorrect.  Concours guys - dont risk it!
69 400 45     Press 1.96 1.66 94
69 400/428 46       1.96 1.66 68
69 350 47     Press 1.96 1.66 72
69 400 RA III 48 9795048 9795043 Screw 2.11 1.77 72
69 350 HO 48 9795048   Screw 2.11 1.77 64
69 400 62 9791562 9791559 Screw 2.11 1.77 72
69 400 RA IV 722 9796721 9796722 Screw 2.11 1.77 71
70 350/400 11 9799611     1.96 1.77 (1.66) 80
70 400 RA III 12 9799612 9799496 Screw 2.11 1.77 72
70 400 13 9799613 9799497 Screw 2.11 1.77 75
70 455 15 9799615     1.96 1.66 87
70 400 16 9799616 478102 Press 1.96 1.66 78
70 400 RA IV 614 9799614 9799498 Screw 2.11 1.77 71
70 455 64 9799364 9799362 Screw 2.11 1.77 87
71 455 HO 197 481197 481758 Screw 2.11 1.77 111
71 455 66 481766 483714 Screw 2.11 1.77 114
71 350 94       1.96 1.66 90 (96)
71 400 96 481196 481760 Screw 2.11 1.77 96
71 455 98       1.96 1.66 114
71 400 99       1.96 1.66 96
72 455 HO 7F6 486076 485319   2.11 1.77 111
72 350 7H1       1.96 1.77 (1.66) 80
72 400 7J2       1.96 1.77 (1.66) 96
72 400 7K3 486073 486316 Screw 2.11 1.77 96
72 455 7L4       2.11 1.77 114
72 455 7M5 486075 494498   2.11 1.77 114
73 455SD 16 485216 485214 Screw 2.11 1.77 111
73 350 46     Press 1.96 1.66 89
73 350 4C 494442   Press 1.96 1.66 89
73 400 4C 494449   Press 1.96 1.66 98
73 455 4X (1H) 488541 494331 Press 2.11 1.66 114
73 400 4X (3H) 488543 494333 Press 2.11 1.66 98
73 400 4X (4H) 488544   Press 1.96 1.66 98
73 400 4X (7H) 491347   Screw 2.11 1.66 98
*NOTE: All 73 heads went to Screw-In Studs beginning with castings dated around May 7, 1973.
74 455SD 16 485216 485214 Screw 2.11 1.77 111
74 350 GTO ?? 46 494346   Screw 2.11 1.66 89
74 350 46 494346 494336 Screw 1.96 1.66 98
74 350 4C 494442   Screw 1.96 1.66 89
74 400 4C 494449   Screw 1.96 1.66 98
74 455 4X (1H) 488541 494331 Screw 2.11 1.66 114
74 400 4X (3H) 488543 494333 Screw 2.11 1.66 98
74 400 4X (4H) 488544   Screw 1.96 1.66 98
74 400 4X (7H) 491347   Screw 2.11 1.66 98
75 400 5C 495354 495345 Screw 2.11 1.66 101
75 455 5I     Screw 2.11 1.66 124
75 455 6H     Screw 2.11 1.66 124
75 455 6S     Screw 2.11 1.66 115
76 455 6H     Screw 2.11 1.66 124
76 400 6S     Screw 2.11 1.66 101
76 455 6S     Screw 2.11 1.66 115
76 350 6X (4)     Screw 2.11 1.66 94
76 400 6X (8) 500762 500801 Screw 2.11 1.66 101
77 301 01     Screw      
77 400 W72 6X (4)     Screw 2.11 1.66 94
77 350 6X (4)     Screw 2.11 1.66 94
77 400 6X (8) 500762 500801 Screw 2.11 1.66 101
78 301 01     Screw      
78 400 W72 6X (4)     Screw 2.11 1.66 94
78 400 6X (8) 500762 500801 Screw 2.11 1.66 101
79 301 01     Screw      
79 400 W72 6X (4)     Screw 2.11 1.66 94
79 400 6X (8) 500762 500801 Screw 2.11 1.66 101
80 301 01     Screw      
81 301 01     Screw