GM BODY PLATFORM DESIGNATIONS

Passenger cars:

A = Cutlass Ciera, Cutlass Cruiser Wagon, Century
B = Caprice/Impala SS, Custom Cruiser Wagon, Roadmaster
C = Ninety Eight, Park Avenue
D = Fleetwood
E = Toronado, Riviera ('93-'94), Eldorado
F = Camaro, Firebird
G = Aurora, Riviera ('95+)
H = Bonneville, Eighty Eight, LeSabre
J = Cavalier, Sunbird/Sunfire
K = Seville, Deville
L = Corsica, Beretta
M = Metro
N = Grand Am, Achieva, Skylark
R = Storm
S = Prizm
U = Lumina APV, Trans Sport, Silhouette
W = Lumina/Monte Carlo, Grand Prix, Cutlass Supreme, Regal
Y = Corvette
Z = Saturn

Truck platforms:

S/T = small pickup/utility
C/K = fullsize/utility
M = medium van
G = large van/medium-duty truck

Previous Platforms:

P = Fiero
V = Allante
X = Nova/Citation, Apollo/Skylark, Ventura, Phoenix

Here are some generic equations using 1/4 mile times/speeds and curb weight (lbs.) including the driver (note: ^3 is cubed and ^1/3 is cubed-root):

• HP = (.00426*MPH)^3 * Weight
• HP = (Weight/ET^3) * 200
• HP = (5.825/ET)^3 * Weight
• HP = (MPH/234)^3 * Weight
• MPH = (235) * (HP/Weight)^1/3
• ET = (5.5) * (Weight/HP)^1/3 (if MPH less than 100)
• ET = (5.5) * (235/MPH) * ((MPH-100/400)+1)^1/3 (if MPH grt than 100)

Use the following equation:

MPH = (RPM x Tire Diameter) / (Tranny Gear Ratio * Rear Ratio * 336.13524)

The constant at the end is for converting minutes to hours and inches to miles.

It's best to put this into a spreadsheet where the leftcolumn contains the ratios for each tranny gear and the top row contains the RPM in increments of 500 RPM.

It is uneconomical to manufacture parts for some precision assemblies to their final fit and surface finish. Instead manufacturers get them close, and get the final fit and finish by rubbing mating parts together to abrade them in a controlled fashion. This is true of many assemblies in a vehicle, particularly piston rings and cylinder walls, final drive gears, and brake pads/disks.

The purpose of break-in is tp perform some final machine work on an engine by running it. It bears a lot of similarities to machining parts with tools on a lathe. The proper lubricant is important. It is important not to bear down too strongly with the tool and to smoothly move the tool across the entire surface many times, rather than keeping the tool at one place and trying to take all the metal there off at once.

One major one is overheating the metal locally. The parts in question are usually sophisticated alloys which may have been subjected to precision heat treating. Ad hoc heat treating by localized overheating due to use too hard too early will weaken the alloy. The other major problem is not loading the parts enough. This can cause their finish to become too smooth (glazed) before the fit has been adjusted. The smooth parts then don't fit quite properly, leading to excess friction.

Break-in is accomplished by moderate, varying loading of the parts. RPM limits and varying speeds are approximations which work well. There are some ways to move beyond these approximations. It is a good idea to maintain higher RPMs under high loads (such as two up on a motorcycle uphill). Low RPMs and heavy throttle in these situations is likely to produce high local loads. Downshift a gear, even if it means exceeding the RPM limits, and use light throttle. In addition to varying speeds, getting somewhat on and off the throttle (accelerating and engine braking) will load different areas of the parts, particularly for gears. Sustained full throttle is something to avoid, regardless of RPM.

As for the "If you want it to be fast, break it in fast" theory, this legend probably arises from the fact that being too gentle during break in will glaze surfaces while maintaining a tight fit, causing friction. It is equally bad for vehicle reliability, to gouge away metal and overheat parts. The time required for break-in is dependent on the qualities of the metals involved, the machined fit and finish, the desired final fit and finish, and the loading and lubrication of the parts during break in. Race engines are engineered and manufactured for rapid break in, although some (10-100 miles) is still required. Porsche 911s and BMW motorcycles have very hard rings/ cylinder walls and take a long time, perhaps as much as 20,000 miles. The only good way of determining the end of break in, other than subjective judgments of performance, is to monitor oil consumption. If it starts out as noticeable, and falls to a constant low level (which may be approximately zero), you're there.

Pretty much all oil and vehicle manufacturers recommend against of use of synthetics during break in, because of too efficient lubrication. Some anecdotal information says that this does interfere with break in, while others view it as simply legend. It seems unlikely that waiting to use synthetic could be a bad idea. In the good old days, manufacturers relied a lot on break in, as opposed to manufacture, for final machining. They sent the vehicles out with special (generally light weight) break in oil. These days, manufacturing techniques are better and break in less important, so few do this now.

Many manufacturers now do not specifically recommend changing oil or filter during break in, although they used to. But, it can't be bad to get the machining residue out of there after a few hundred miles. The minimum standard should be the manufacturers recommendation, and changing more often during break in can't hurt except for (modest) damage to your wallet.

A manufacturer's new-vehicle warranty is not automatically voided once an aftermarket part (non-original equipment) is installed. Rarely does the use of aftermarket parts violate a new-vehicle warranty.

Federal law (the Clean Air Act) requires 2 emissions warranties: a "defect" warranty and a "performance" warranty. Defect warranties require the vehicle manufacturer to produce a vehicle which, at the time of sale, is free of defects that prevent it from meeting required emission levels for its useful life, as defined in the law. Performance warranties require the vehicle manufacturer to make repairs at NO COST to the owner-should the vehicle fail to meet certain levels of emissions performance during the warranty period. This period ranges from 2 years or 24,000 miles to 5 years or 50,000 miles for most parts, to 8 years or 80,000 miles for certain emission-control parts (specifically, the catalytic converter, the electronics emissions- control unit and the on-board diagnostic device) on most 1995 and later vehicles (check owner's manual for specifics on your vehicle).

Consumers are protected under a parts self certification program administered by the EPA. If a parts maker self-certifies its parts under this program, the vehicle manufacturer cannot void the emissions warranty even if the certified part fails and/or is directly responsible for the emissions warranty claim. In this situation, the vehicle manufacturer must arrange a settlement with the part manufacturer, but the new-vehicle warranty is NOT voided under the law. If a parts maker chooses not to self-certify its parts, the ONLY case where a vehicle manufacturer can void the emissions warranty is if a non-certified aftermarket part is proven to be RESPONSIBLE for an emissions warranty claim.

To aid consumers in identifying aftermarket parts which are not considered as tampering, SEMA-member manufacturers have instituted voluntary emissions- sensitive product identification. The following numeric/color symbols are intended to provide guidance on proper sale and use of emissions-sensitive products:

• Green diamond with a "1" in the middle means the product has been granted a CARB "EO" number, or is a direct or consolidated replacement part. It is 50-state legal, per the manufacturer's application guide.
• Blue diamond with a "2" in the middle means the manufacturer of the product represents that it has not been found, nor is believed to be, unlawful for use under the provisions of the Clean Air Act, per the manufacturer's application guide. This product is NOT legal for sale or use in the State of California or in states which have adopted CA emissions standards except on pre-emissions-controlled motor vehicles, motor-vehicle engines (pre-1966 vehicles certified to CA standards, pre-1968 vehicles certified to federal standards, and ALL pre-1968 foreign vehicles), per the manufacturer's application guide.
• Gold/Yellow diamond with a "3" in the middle means the product is legal ONLY for off-highway use (except in California or states that have adopted CA emissions standards), competition racing, marine or for use on pre-emissions-controlled motor vehicles, motor vehicle engines (pre-1966 vehicles certified to Cal. standards, pre-1968 vehicles certified to federal standards, and ALL pre-1968 foreign vehicles), per the manufacturer's application guide.

If you have a dispute with a vehicle dealer regarding a new-vehicle warranty claim or an emissions warranty claim, obtain a written explanation and letter of refusal from the dealer and consult the owner's manual for the appropriate steps you should take. If the vehicle manufacturer improperly denies the claim, call the EPA at (202)233-9040 or (202)233-9100, and also report it to the Federal Trade Commission (FTC), at (202)326-3128.