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My Poncho And MeI have a '69 Pontiac Grand Prix with what I believe is a 428ci engine. The VIN identifies this car as having the 428, but I want to make sure the engine it has now is still a 428. How do I know? The heads have casting numbers over the center exhaust ports of No. 62, but I can't find the block casting number.Jim DietzLincoln, NE
We've found conflicting information regarding the 428 engines used in the '69 Grand Prix. Part of the confusion may stem from the fact that there were actually two versions of the 428 offered: 370 hp and 390 hp. According to the Pontiac specs, the 370hp version had 10.5:1 compression while the 390hp engine had 10.75:1, though some sources show both engines as having the same combustion-chamber volume in the cylinder heads. Some sources show No. 62 heads on the 428 in the '69 Grand Prix (no specifics on power rating), and others claim the No. 48 was used, which Pontiac fans may recognize as the same head used on the '69 400ci Ram Air III engines. Both the No. 48 and the No. 62 are listed as having 72cc chambers.
To narrow your focus, check the numbers stamped in your engine. Look at the front of the engine block on the passenger side on the machined surface adjacent to the timing cover to find the VIN. If the number matches your car, it's the original engine. Also check the area on the front of the block just under the passenger-side cylinder head for the block code. This will be a pair of letters, and can be found under another stamped number (the engine serial number, which is of no real use to you). The 428 engine codes for the '69 Grand Prix are as follows:
WF:428/370 hp, manual transXF:428/370 hp, auto transWL:428/390 hp, manual transXG:428/390 hp, auto trans
Note that if the engine in your car is not the original, these block codes can't be considered an absolute identifier, because the same codes were used for different engines in different applications. You should, however, be able to look at the sides of the block, below the cylinder heads, to see the engine size cast into the block. The easiest to spot with the engine in the car is the driver side-look up from the bottom, past the fuel pump, and you'll hopefully see the "428" cast in the block, though it isn't very big and could be covered with crud.
When Is A Big Cam Small?I'm working on an Olds 350 that I would like to build to the ol' magical 1 hp/ci. This engine will be going into my weekend cruiser, and I need over 15 inches of vacuum to run the power brakes, A/C, cruise control, and so on. I plan to run either heavily ported stock heads (i.e., No. 5s) or aluminum aftermarket units (Bulldog's maybe). Compression should be around 9.5:1. I'm looking at a hydraulic-roller cam that has 214/222 intake/exhaust duration at 0.050 and 112-degree lobe separation angle. The manufacturer notes that this cam produces a good idle and fuel efficiency. They also note that it fits a 260 to a 455. My question: Wouldn't a cam that idles good in a 455 be way too big for a 260 or even my 350? Is there a rule of thumb or formula that can be used to estimate vacuum levels at idle based on duration, displacement, and head flow?Greg SmithBritish Columbia