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428 pontiac engine

Posted by Daniel Stancik 
Pontiac GTO Masthead

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428 pontiac engine
February 05, 2005 01:06AM
Have a 64 with 428cu.in. engine installed by dealer in 1967, what are the spec on this engine if in stock form? Or where can I find more info about this
motor so modifications can be done. Dan S
Re: 428 pontiac engine
February 21, 2005 04:15AM
There were two 428's. In 67, one had 10.5:1 compression ratio and had 360hp. The 428 HO had 376 hp. They had forged steel cranks. In 68 and 69, the one with 10.5:1 compression ratio ran 375 hp at 4800 rpm and the one with 10.75:1 ran 390 hp at 5200rpm. The were only options for the full size ponchos; Catalina, Executive, Bonneville and Grand Prix.

No expert here. Just quoting STANDARD CATALOG OF AMERICAN CARS. All I know is that my firebird loves its 428 and so do I.
Re: 428 pontiac engine
February 24, 2005 05:47PM
I can fax you the engine specifications as published in motors circa 1968 thru 1974.

1968 375 hp V8-428 4 bbl 4.120x4.00 10.50 375 @ 4800 445 @3600 (torque)

1968 390 hp V8-428 4 bbl 4.120x4.00 10.75 390 @ 5200 465 @3400

1969 360 hp V8-428 4 bbl 4.120x4.00 10.50 360 @ 4600 472 @3200
1969- 370 hp V8-428 4 bbl 4.120x4.00 10.50 370 @ 4800 472 @3200
1969- 390 hp V8-428 4 bbl 4.120x4.00 10.75 390 @ 5200 465 @3400

cranks were cast Steel Armalite. There were 4 bolt blocks 370 & 390 hp
hard to document exactly which vehicles were available with which eng. specs. (4 -speed & turbos).

Hope this helps you out.



Charles gracey
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