CAMS, LIFTERS, TIMING GEARS
Several cams have been used in the 262. There are important differences in both the specifications and the base circle diameter.
1985-’86: The same flat tappet cam was used in ’85 and ’86.
1987- ’91 VIN “Z”: The original roller cam used for the throttle body motor was a 10088148 or a 14093686. It had a 1.380″ intake base circle, a 1.335˝ exhaust base circle, and a pretty mild grind.
1990-’91 VIN “B”: The H.O. motor had a much hotter cam that should not be interchanged with any other application. It’s a p/n 10055487.
1992-’94 VIN “Z” WITHOUT BALANCE SHAFT: The specs for this cam were comparable to the earlier VIN “Z” cams, but the base circle on both the intake and exhaust was reduced to 1.260˝. The OEM part numbers are 10144176, 10214713 and 10172776.
1993-’95 VIN “Z” WITH BALANCE SHAFT: The specs on this cam were similar to the ones used in the VIN “Z” without a balance shaft, but a snout was added for the balancer drive gear. It’s a p/n 10144065.
1992-’95 VIN “W” WITH BALANCE SHAFT: The premium high output engine came with central fuel injection, a balance shaft and a better cam starting in ’92. The original cam, p/n 10144047, was used from ’92 to ’94. It was replaced by p/n 10241693 in ’95. They are comparable grinds so most rebuilders are interchanging them.
1996-’98 VIN “X” WITH BALANCE SHAFT: The VIN “X” engine replaced the VIN “Z” in ’96. It is identical to the ’96 VIN “W” engine except for a milder cam and 10 less horsepower. The cam is a p/n 10241692.
1996-’98 VIN “W” WITH BALANCE SHAFT: The VIN “W” engine has a 10541691 camshaft and makes 10 more horsepower than the VIN “X” engine. There is also a special roller cam for the VIN “Z” turbocharged engines (p/n 10214714) along with a couple more with a fuel pump lobe for marine and industrial applications, but these are the common ones that were used in most of the cars and trucks. All of these cams can be identified by the last three digits of the part number that is stamped on the barrel of the cam, just behind the last lobe and in front of the distributor gear.
Matching the right cam with the right lifter and adjusting the valves correctly is important in order to avoid noisy lifters at startup, a problem that’s commonly known as “morning sickness.” Prior to ’92, the 262 had the traditional adjustable rockers that had been used on all of the small block Chevys for years. The cam had a 1.380″/1.335″ base circle and used a short-travel lifter. Turning the rocker nut one turn gave the lifter a .040″ preload and put the plunger in the middle of its travel.
In 1992, when Tonawanda switched to a “net lash,” non-adjustable valvetrain; the base circle was reduced to 1.260″ on all of the cams, and a lifter with more travel was used across the board, apparently to provide more latitude for manufacturing tolerances with the “net lash” rockers. (Note: The Romulus plant did not switch to “net lash” until ’95). Unfortunately, this combination can cause noise problems in the field because it takes longer for the lifter to refill at startup when it has bled down overnight, unless the preload is set at .080″.
This problem can be cured by turning the rocker nut two turns with the adjustable rockers, but that can’t be done with the “net lash” setup, and it’s contrary to everything everybody knows about setting the valves on a Chevy, too. The best approach requires the replacement of the “net lash” studs with a set of special conversion studs that have metric threads on the bottom, along with 3/8″ threads on the top, and using them along with the short lifters that are preloaded one turn.
If you prefer to rebuild the engines as they came and use the longer lifters with the adjustable rockers, increasing the preload to two turns will help avoid “morning sickness.” Carefully controlling the stem heights and clearances with the “net lash” rockers will help ensure that you have enough preload to avoid noisy lifters most of the time.
Just for the record, there’s one extra benefit to switching to the short lifters and the adjustable valvetrain on everything; you can disregard the base circle issues and consolidate more of the cams.
There are two cam thrust plates used for the roller cam engines. The one for the non-balancer engines that are smooth on both sides are available under either p/n 14093636 or p/n 10088128. The thrust plate for the balancer engines is smooth on one side and has four radial grooves on the other side. It’s a p/n 10144059.
Chevy has used three different timing gears for the 262 since ’85. The flat tappet engines used a p/n 340235, the non-balancer, roller cam engines had a p/n 12552128 and the balancer engines used a p/n 10144121. They are not interchangable.