Camaro RS V8-305 5.0L VIN E TBI (1990)
Piston: Technical Service Bulletins
Engine Piston - New Engine Lightweight Design
Number:
90-111-6A
Section:
6A
Date:
December 1989
Corporate Bulletin No.: 936408
Subject:
ENGINE LIGHTWEIGHT PISTON DESIGN
Model and Year:
1990 B, F, Y CARS
TO:
ALL CHEVROLET DEALERS
The new piston is a low-friction, lightweight design for improved fuel economy. It is not interchangeable with the 1989 (or previous) piston. This piston
is a flat top design that gives a compression ratio of 10.25 : 1 in the 5.7L PFI (VIN 8) for the Y-car ONLY and 9.75 : 1 in the 5.7L TBI (VIN 7) and PFI
(VIN 8) for the F-car ONLY. Piston weight is 540 grams. The ring pack is also a new design and not interchangeable with the 1989 (or previous) piston.
The top ring is 2 mm thick but has a narrower radial width and shallower ring groove depth than 1989 (or previous).
The second ring is 1.5 mm thick and also has a narrower radial width and shallower ring groove depth than 1989 (or previous).
The oil ring assembly width is 4 mm, also new for 1990.
This piston is fit to the same clearance as the 1989 piston however, the new shape of the skirt requires the piston to be size measured differently. It is
measured at a point 11.5 mm (.45") above the bottom of the skirt. The skirt has a "barrel-shaped" profile so the piston skirt taper "cannot" be measured.
