CAMSHAFT LIFT SPECS. MEASURING CAM LOBE LIFT

MODELS AFFECTED: 1982-1985 ELDORADO, SEVILLE, FLEETWOOD, DEVILLE AND BROUGHAM

Some Cadillacs equipped with an HT4100 engine may experience poor engine performance normally described as rough idle, lack of power, engine miss, backfire, valve train noise, or idle surge. This condition may be caused by camshaft wear on one or more lobes.

When camshaft wear is suspected, lobe lift can be measured. A dial indicator should be used at the lifter or top of the push rod while manually rotating the engine. The rocker arm should be removed prior to making the check to prevent inaccuracies in the measurement due to lifter bleed down.

A lobe lift measuring tool (J-8520) is available for use. However, appropriate adapters may be used to allow the check to be made using available dial indicators with sufficient travel.

The HT4100 camshaft lift specifications are:

Intake - 5.840-6.094mm (.2300 in.-.2400 in.) Exhaust - 6.031-6.285mm (.2375 in.-.2475 in.)

A camshaft which measures below these specifications should be replaced with a new camshaft and lifter kit, P/N 1628822.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.