Combine all of this with a 2.25-inch dual exhaust system and a 3.23 rear-axle ratio, and you should notice a healthy performance boost from your Grand Prix. And if you remember to keep the revs under about 4,500 rpm, your 301 should provide many more miles of reliable performance.
'70 GTO Axle-Bearing WoesI'm trying to replace the rear axle bearings on my '70 GTO and have hit a dead end. I tried GM dealers, bearing warehouses, auto-parts stores, and none have listings for my bearing size. The rear is a 10-bolt and I'm sure it's original.
I bought the car in 1976 with 52,000 miles on it. The bearing measures 1.378-inches id, 2.558-inches od and 0.670-inch-wide od, 0.765-inch-wide id. The outer race is narrower than the inner race. This is a single-piece, nontappered roller bearing. The bearing isn't RW-507-CR or set No. 9, which is what everyone tries to sell me. I hope you can help me on this.John T.Spokane, WA
Quint Stires responds:In 1970, Pontiac was transitioning over to other designs of rear bearings and guts. The great thing is that you know what you're looking for and you have the dimensions. I'm impressed. So often, I speak with GTO owners who don't know what they have and think everything is in a book or manual as if it's a dictionary and part numbers are as easy to find as windshield wipers.
To find your bearings, I called Shannon LaFave from Ames Performance (www.amesperf.com), and he knew exactly what you needed and explained in length about the mid-year change. Feel free to call him at the number in the company's ad or any one of the Pontiac specialists advertising in this issue. For whatever it's worth, often parts stores have great information but don't always have the most up-to-date or change-over information. It's the companies who specialize in your car or its issues that know the best way to solve the problem at hand.
Oil-Pressure GaugeWhere is the best place to hook a mechanical gauge for oil pressure? I have a '74 455. Bret SnyderVia Internet
Rocky Rotella responds:Bret, it seems the most common location to plumb a mechanical oil-pressure gauge into a Pontiac V-8 is near the distributor hole on the driver side of the block. There you will find a 31/48-inch-diameter pipe plug with a recessed 51/416-inch square opening. The plug covers a direct path used during initial machining to bore an internal oil passageway that was subsequently tapped and sealed off during production. Because of this and its close proximity to the instrument panel, it makes an ideal location for accurately retrieving an oil-pressure reading.
The pipe plug is commonly removed during engine rebuilds to access the internal oil passageways for cleaning and is typically replaced with a new unit. If your 455ci has been rebuilt in the past, the plug may come out easily. If the engine hasn't, you might find the original plug very tough to break free, possibly rounding out during the attempt. To prevent this, I suggest heating the plug for a short time before hand, it typically makes removal much easier. This assumes, however, that your engine isn't in a vehicle and you can fully access the plug.
If your engine is installed and you don't have plans on removing it, an alternative source for an accurate reading may be the oil-filter adapter. Simply remove the existing electric oil-pressure sending unit, and connect the mechanical gauge's hardware. A drawback to this location, however, is the lengthy distance required to plumb the gauge into the passenger compartment. If going this route, be sure to securely route the gauge's oil line away from the entire exhaust system to prevent burning the line and causing an oil leak.