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Rebuilding the New Chevy 262
Back in the late 1970s when everyone was worried about the "gas crunch," Chevy needed some smaller engines in a hurry, so it created a new family of junior-sized V6s by chopping two cylinders off its existing V8s.
By Doug Anderson
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This enabled GM to shorten the development process dramatically because it was able to adapt a proven design. But it also allowed it to share a lot of the existing tooling from the V8 production lines so the engines could be on the road sooner.
The original 200 V6 that came out in 1978 was based on the 262 V8, and the 229 V6 that came out in ’80 that was based on the 305. By 1985, both were replaced by the 262 V6 that was based on the 350. It was originally installed in both cars and trucks; since ’87 it has been used primarily as a truck engine. It also has been updated several times to make it one of the best in the industry. The engine combines performance and economy in a reliable package for most of GM’s pickups, vans and sport utility vehicles.
Although the basic architecture has remained the same, GM has made a lot of changes to the 262 as it has continually upgraded and improved the original design. In the process, it has changed the block to accommodate a one-piece rear seal, added a roller cam and a balance shaft, modified the crank and rods, upgraded the pistons and revised the heads for better performance and emissions.
There are some subtle differences between the engines built in the two different plants, too. For example, the cranks and rods used in a Tonawanda engine are not the same as the ones used in a Romulus engine. There can be problems if they are intermixed. So, let’s take a look at how it all began in 1985 and see how the 262 has evolved over the past 13 years, remembering that most of these changes were made to improve power; reduce emissions; increase mileage; and reduce noise, vibration and harshness (NVH).
1985: The original block in ’85 was a 14071177 casting. It had a two-piece rear seal, a flat tappet cam and a fuel pump hole because all of the trucks still had carburetors. Just for the record, there were some ’86 blocks shipped with pans for ’85 service replacements, so it is possible for a customer to have an ’85 car or truck with a one-piece rear seal.
1986: In 1986, the block (c/n 14088553) was modified to accommodate the new one-piece rear main seal. The fuel pump hole was still open, even though it wasn’t always needed, because all of the cars and some of the trucks came with throttle body injection.
1987- ’94 WITHOUT BALANCE SHAFT: In 1987, a roller lifter cam was installed, so the block was changed again. Two bolt bosses were added in the middle of the valley for the lifter retainer that kept the rollers properly located on the cam and perpendicular to it. This same basic block was used through ’91 for everything, and in ’92 through ’94 for all of the engines without balance shafts except for one small difference some of the blocks came with four bolt holes for the tunnel style retainer beginning in ’92. There were several different castings used, including the 10105867, 10172756, 14099073, 14093683 and 10066011 with the two-bolt retainer, and the 10172756, 14099073 and 10066061 blocks with the four-bolt retainer.
1992 WITH BALANCE SHAFT: The L35 balance shaft engine was introduced in ’92, so the block was modified to make room for it above the camshaft. The lifter retainer was changed to the tunnel design because of the balance shaft; it had two bolts on each side instead of the two in the middle.
There were two versions of the balance shaft blocks in ’92. The "first design" block had a needle bearing on the back of the balance shaft that was lubricated by the oil mist from the valley. The "second design" had a sleeve bearing that was pressure fed through an additional drilled passage in the back of the block.
All of the 1992 "first design" (c/n 10105903) and "second design" (c/n 10224834) blocks were missing the two bolt bosses, one on each side, that were used with the reinforcing struts for the automatic transmission on some of the ’93 and later applications, so they can only be used in ’92. Be sure to double-check the 10224834 "second design" blocks, though, because some of them came with the strut bosses in the later years so they can be used for the ’93s and ’94s.
1993-’94 WITH BALANCE SHAFT: Things got more confusing with the balance shaft blocks in ’93-’94. All of these engines have to have the two extra bolt holes for the strut bosses and 10 bolt holes for the tin front cover. See photo. There are five castings that may or may not be right:
All of the 10224534 and 10224535 blocks have the two strut bosses and 10 holes for the front cover, so they will fit everything in ’93 and ’94;
The 10227196 castings have the strut bosses, but they came with either six or 10 holes;
The 10224834 blocks have 10 bolt holes, but they came with or without the strut bosses;
The 10235359 blocks were the most confusing because they came with or without the two strut bosses and with either six or 10 holes for the front cover!
Consequently, all of these castings must be checked and sorted by both casting number and features in order to be sure that they will work in everything in ’93 and ’94.
1995 WITH BALANCE SHAFT: 1995 isn’t a whole lot better. All of the ’95 engines had a balance shaft and the strut bosses, but the flange around the timing gear was changed to accommodate the new plastic front cover. The overall shape stayed the same, but the flange was noticeably wider with big bulges around six of the bolt holes. See photo.
There was a mid-year change that can cause problems, too. The early engines used a "first design" tin front cover with 10 bolt holes. The later ones had the "second design" plastic cover that had only six bolts, so the flange can have either six or 10 holes drilled in it. See photo. That means that the tin cover won’t work on a block that was drilled for a plastic cover, so the blocks aren’t always interchangeable.
Things can get confusing in ’95, because the 10227196 and 10235359 castings that were used in ’95 came with the narrow flange in ’94 and were converted to the wide flange in ’95. All of the 10227196 castings had the strut bosses, but some of the earlier 10235359 castings didn’t.
You can use either one of these blocks in ’95 as long as it has the strut bosses and the wide flange with either six or 10 holes drilled for the front cover. But, you must be sure that the corresponding first or second design front cover is installed on the block.
Given the possible confusion over which cover the customer has and which block he really needs, it’s probably better to make sure all the blocks have 10 bolt holes so they will work with either front cover. Do not use an earlier block with the narrow flange with a plastic front cover under any circumstances because it will leak oil.
1996-’98: The block was changed again in 1996. Structural reinforcing ribs were added on both sides of the timing cover and both sides of the block were contoured to follow the shape of the cylinders more closely. See photo. This one is a 14099090 casting. This same block is used up through 1998.
MORE ABOUT BLOCKS
There is one other subtle difference in the blocks. The cam bearing sets are different, depending on whether the block was made in Romulus or Tonawanda. The Tonawanda blocks use two larger diameter cam bearings, one in front and one in back, instead of only one large one in the front. Both bearing sets are available in the aftermarket.
There are three characteristics of each block which will tell you where it was manufactured:
If it’s a Tonwanda engine, it will have a "T" stamped on the machined surface on the block just in front of the right cylinder head. The engine ID will be number stamped on the pad, and the chamfer on the cylinders will be quite shallow;
If it’s a Romulus engine, it will have an "R" stamped on the machined surface on the block. The ID number will be made up of a series of dots, and the cylinders will have a deep chamfer on them.
Some of the blocks are drilled for a knock sensor and some aren’t. It’s almost impossible to know which applications came with and without the sensor hole, so most rebuilders drill and tap every block so the hole is there when it’s needed.
The roller cam motors have used three different lifter retainers. All of the ’87 through ’91 non-balancer blocks and some of the ’92s used a flat retainer (p/n 10046165) with two bolt holes in the middle. As of ’92, all of the balancer motors and some of the non-balancer motors came with the tunnel-shaped retainer (p/n 10105916) with four bolt holes, two on the outer edge on each side.
Starting in ’94, Chevy used two plastic retainers (p/n 12551431) that are bolt-in replacements for the tunnel-shaped version. There are some later intakes that will hit on the reinforcing ribs on the tunnel-shaped retainer, so it’s best to use the plastic retainers in all of the blocks that have the four bolt holes.
There have been three front covers used on the 262. The first one came on the ’85 to ’94 non-balancer engines. It’s the same one that was used on the small block Chevy. The second one was a tall, metal cover with 10 bolt holes that was used from ’92 through the ’95 "first design" balancer motors. See photo.
The latest version is a unitized plastic cover that is held on with only six bolts. It came out mid-year in ’95 and was installed on the "second design" engines that had the wide flange with only six bolt holes drilled in it. The plastic cover fits on the earlier balance shaft blocks, but it shouldn’t be used on them because it leaks around the bolt holes. It comes with or without a large hole drilled in the bottom corner for the crank position sensor that was installed on the engines that came with OBD II.
Chevy has used several different cranks in the 262. They came with one- or two-piece rear seals and in both light and heavy versions that were specific to each engine plant. Here’s an overview:
1985: The 1174N casting came with a two-piece rear seal and a flange in the back. See photo.
1986-’87: The 14088640 and 10105865 Tonawanda castings with a one-piece seal were both used only for heavy applications during these years. See photo.
1988-’98: The Tonawanda cranks were all 10105865 castings that came in both light and heavy versions.
1988-’98: The Romulus cranks were all 10055480 castings that came in light or heavy versions.
All of the engines with the one-piece seal were externally balanced with specific flywheels and dampers, but the cranks were also balanced according to the weight of the pistons and rods that were installed in the engine; it’s important to use the right combination of parts. Unfortunately, there’s no sure way to tell a light crank from a heavy one short of knowing where it came from and marking it at teardown or spinning it on a balancer. There are a couple of clues that can help, though:
All of the 14088640 castings are heavy cranks that can be used in either the ’87 to ’94 non-balancer engines or in the ’93 to ’95 VIN "Z" balance shaft motors with the heavy pistons.
If a 10105865 Tonawanda casting came without a hole in the first rod pin, it’s definitely a heavy crank. If there’s a hole in the first rod pin, it’s probably a lightweight crank. However, there were a few early 10109865 cranks that had the hole drilled in the rod pin to correct the production process, so having the hole drilled doesn’t always guarantee a lightweight crank.
The 10055480 Romulus crank came both ways, too. If it has a hole in the first rod pin, it’s the lightweight version, and if it doesn’t, it’s always a heavy crank.
The heavy cranks were used in all of the engines without a balance shaft and in all the VIN "Z" balance shaft motors with the heavy pistons, including the ’95 "second design" versions. The lightweight cranks were used with the lightweight pistons in the ’92-’98 VIN "W," the ’95 VIN "Z," "first design" engines, and in the ’96-’98 VIN "X" engines. Using the right crank in the right engine will help prevent balance problems out in the field.
However, you should also be aware that all of these engines are externally balanced with various combinations of flywheels/flexplates and dampers for balance, and that they are "trimmed" at the factory after the hot-run test by pounding balance weights into the holes that are already drilled in the damper. So, if you build them right and still have a shaker, the customer will have to add or subtract weight from the damper and/or flywheel/flexplate in order to get it right.
There is one other subtle difference in the cranks, too. Any of the engines that were installed in ’96 or later and all of the ’95 "S" and "T" trucks with OBD II, including all of the Olds Bravadas, any Blazer with California emissions, and about 10% of the Blazers with federal emissions, had a reluctor wheel installed in front of the crank gear for a crank position sensor that was a part of OBD II. The raised, machined area on the snout is about .100" longer on these cranks than it was on the earlier ones so the reluctor wheel has a slight press fit. Be sure to sort out the 10105865 and 10055480 cranks with this longer, machined step and save them for the engines that have the crank position sensor.
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by: jessica smith 9/29/2010
I have a question for Doug. I have a a '92 Code "Z" engine and a '92 Code "W" engine. Can I mount the Throttle Body and Intake from The Code "Z" engine onto the Code "W" engine without any trouble?
Not sure if this is the right place to ask Doug this question but its the only place I could find.
by: stomperz71 9/6/2008