What Chassis Parts Swap Into My '75 Gp?I have a dilemma, and I hope you can help me. I want to know what body designation a '75 Grand Prix Model J is. Mine has a 400 and a Turbo 400 trans. What other cars does it share brakes and suspension parts with? I want to restore it, but I haven't seen many good parts for this particular year and model. I'm trying to find information on the vehicle, so any help you can provide would be appreciated. Thanks in advance.Luis RodriguezVia Internet
Rocky Rotella Responds:
Beginning in 1969, Pontiac built its newly redesigned Grand Prix on the G-body platform, which is essentially an extended A-body (LeMans) with a wheelbase of 118 inches. When the new GP body was introduced in 1973, its wheelbase was shortened to 112 inches, but it still shared many suspension components with the redesigned A-body. As such, any similar vintage A- or G-body from any GM model should contain the components your Grand Prix might need.
If you're looking to improve your Grand Prix's ride and handling ability, you might consider the current offerings from Performance Suspension Technology. Glancing through the company's latest catalog, I found it offers a wide selection of stock-replacement and aftermarket components for your vehicle, including larger-diameter front and rear sway bars and urethane bushings. Visit the company's Web site (www.p-s-t.com) for further details. Another choice is Just Suspension (www.justsuspension.com), which also has many stock replacement and performance upgrades for your G-body GP.
Camming A 400
Thanks for an outstanding magazine! I am the original owner of a '78 T/A with a W72 400 code X7, auto trans, and a 3.23 rear. The engine is stock except for revised Q-jet metering rods from H-O Racing and an open hoodscoop. It has 100,000 miles on it and I just noticed a head gasket leak, so I am considering a full rebuild instead of just pulling the heads. A local Pontiac engine guy suggested replacing the stock W72 cam with a No. 068 cam, claiming it will really wake up the 400. I started looking into this idea and found conflicting opinions about using this cam in a W72 motor with 8.1:1 compression. What are your thoughts about just doing the head gas- kets versus a rebuild, and is the No. 068 cam the way to go if I do the rebuild?Ira KesslerVia Internet
Paul Spotts Responds:
Good question. The later Second-Gen T/As seem to be getting a good deal of attention recently. It's pretty understandable as there wasn't much else in the late '70s that was worth driving. The '78 has a special place in my heart, as my brother once owned a gold T-Top W72 model. I really enjoyed that car. It's awesome that you bought yours new. I think you're the fourth person I know of that is an original '78 owner.
Please do not "consider" the full rebuild-just do it. One hundred thousand miles usually requires a 0.030 overbore, remachined crank, rods, valve job, etc. You can simply keep the engine intact and build another one. I've suggested this before and prefer this choice for my customers. As I stated previously in HPP, I predict that your car (especially since it's an original-owner car) will increase in value. By leaving everything intact on the original engine, the super hard-to-find factory items will be in one place and in the stock locations, should you decide to restore the T/A in the future. As your power desire increases, the original parts are usually replaced and are not always kept with the car.
If your goal is to keep the car stock with all the emissions equipment, have the engine rebuilt to mostly stock specs. There are many new choices in pistons, so you can bump compression slightly with a domed hypereutectic piston. If you decide on flat-top pistons, do yourself a favor and use forged ones.