CYLINDER HEADS 4 rg The 1970 and l97l LT l and Z 28 cylinder heads Special Performance feature screw in replaceable rocker arm st Also any castings fabricated after December 1970 will he the beefed up area around the valve seats The sta ess steel beaded gasket used with these heads are 0 ck d should be sealed with aluminum paint Q Improved performance of either V 8 or M 4 type heads attained by reworking the seats and valves Valve V be increased in circumference so the seat portion of h ds mates with valve faces at the highest and largest di or tions of the valve faces This is accomplished b 4 IV 50 I stone cutter to develop the exhaust seat l develop the inlet seat This a surface for fw X T J V S 3 H JZ Q 49 x O30 Intake Seat u Y O50 Exhaust Seat a 4 gi r P Q2 Qzv J Valves are modified by removi e on of the alve face and underhead This is plished with narrowing the valve face to mate with the LsE seat M Y V head Remove all ridges fro the c V e Q out exhaust ports to maximum T eaml e th ex valve guide bosses Do not Q V 6 Repeat the above operations for V YVV take ports in the V B heads only On the M 4 aluminum heads the intake ports are not enlarged Fillets should be blended and sharp edges removed only g i i Refer to chart on Page 8 for related parts and specifications V I Cylinder head porting and preparation is extremely important in extracting the maximum power from the small block engine Aluminum Zndldesign M 4 heads should have the holes in the I underside of the two intake ports plugged when E used in E conjunction with the aluminum blocks g I L I Y imp q ty 18 ll 16 70 L