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#1
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CR question for 1960 389's
Was the hi vs low CR in the 60 389's achieved by the machining of the heads or the pistons. I'm assuming it was head machining. Am I wrong?
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#2
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I know in 61-62 they had a LCR piston,in 63 I believe they made the diff in the head.No clue about 60.Tom
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#3
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In 1960 they had a slew of CRs, and the lowest compression with the tiny Rochester 2 bbl, it had dished pistons, besides the head modifications. Pontiac used the same 2bbl that the early tri-powers used for the center carb. I believe it's designation was 420 E, meaning economy. The 420 E was only rated at 215 HP with an 8.6 CR. I had a friend that I attended Vo tech with, that had one of these 420 E cars that pulled the heads to do a valve job, and I saw the dished pistons on his car. Pontiac used 3 different compression ratios and 9 different HP ratings in 1960. I owned a 318 HP tri power 1960 Pontiac with 10.75 CR so I saw the highest offered CR, and also saw the lowest CR in the same year.
The table below shows only 2 different head CCs, and the only way to arrive at lower CR was dished pistons. 1960 Pontiac HP Disp C.R. Ind. Carb Model Head cc Valves Trans 215 389 8.6 1-2 Roch 2GC 71.3 1.88/1.60 Std 215 389 8.6 1-2 Roch 2GC 71.3 1.88/1.60 Std 230 389 8.6 1-2 Roch 2GC 71.3 1.88/1.60 Auto 235 389 8.6 1-4 Cart AFB 71.3 1.88/1.60 Std 281 389 8.6 1-4 Cart AFB 71.3 1.88/1.60 Auto 283 389 10.251-2 Roch 2GC 71.3 1.88/1.60 Auto 303 389 10.251-4 Cart AFB 71.3 1.88/1.60 Auto 318 389 10.753-2 Roch 2GC 66.8 1.88/1.60 All 333 389 10.751-4 Cart AFB 66.8 1.88/1.60 All 348 389 10.753-2 Roch 2GC 66.8 1.88/1.60 All |
#4
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Thx for the great replies/info. Much appreciated. Did the low CR heads have any external identity features different than the high CR ones. Anyone know?
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#5
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Quote:
Quote:
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#6
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The 1960 Pontiac Master Parts Catalog lists 2 part numbers for heads (could easily be the same casting numbers). 536794 for "All 3/2 B.C. & T425A" engines and 536794 for all other engines. There are no heads listed in the "Special Engine and Chassis Parts" section.
Same catalog has a good chart of what parts were used in which engines in 1960.
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My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
#7
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Forgot to translate the "Model Application" info from the Engine Identification Chart into readable English:
Model 21 is Catalina, 23 is Ventura, 24 is Star Chief, 27 is Bonneville Wagon and 28 is all other Bonneville models.
__________________
My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
#8
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See http://www.pontiacsafari.com/L1Garag...dex.html#Heads.
That should explain it. See http://www.pontiacsafari.com/L1Early...nes/index.html and scroll down to 1960 for options -- and other information. |
#9
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After Larry's comment about the 1960 options and my comment
Quote:
Cylinder head and valve train pkg. Use w/535480 camshaft ....... 989670 I'm guessing this 989670 head and valve train package would include the casting number X 535461 O "Super Duty" head Larry refers to. Here are the cams listed in the "Special Engine and Chassis Parts" section.
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My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
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