Posted: Tue Aug 24, 2004, 4:08 am Post subject: the holy grail of 4.3 info!!
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Ok, I've had this book in my safe for almost a year, and now ill share it with all of you. Try not to drool on your computer (they don't respond too well to that) :rock: :bang: (p.s. the picks didn't make the transition, I think. The website is www.engine-builder.com, then look at back issues. Then search for rebuilding the new 262. There are a lot of informative picks. Enjoy!!
Rebuilding the New Chevy 262, Doug Anderson, Automotive Rebuilder, April 2000
Thanks to all who have contributed information to this article, including the people at GM Powertrain - Lansing Engine.
In the late 1970s, when everyone was worried about the "gas crunch," Chevy needed smaller engines in a hurry, so it created a new family of junior-sized V6s by chopping two cylinders off its existing V8s. This enabled GM to shorten the development process dramatically because it could adapt a proven design. But it also allowed it to share much 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 was based on the 305. By 1985, both were replaced by the 262 V6, based on the 350. It was initially installed in 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 machine 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 many 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 subtle differences between the engines built in the two different plants. 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).
BLOCKS
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 the trucks still had carburetors. Just for the record, there were some '86 blocks shipped with pans for '85 service replacements so that a customer can 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 the cars and some 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 adequately 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 a tiny difference – some of the blocks came with four bolt holes for the tunnel-style retainer beginning in '92. Several different castings were 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 two extra bolt holes for the strut bosses and ten bolt holes for the tin front cover. See photo. Five castings may or may not be suitable:
•All of the 10224534 and 10224535 blocks have the two strut bosses and ten holes for the front cover so that they will fit everything in '93 and '94;
•The 10227196 castings have the strut bosses, but they came with either six or ten holes;
•The 10224834 blocks have ten 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 six or ten holes for the front cover!
Consequently, all of these castings must be checked and sorted by casting number and features 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 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 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 ten bolt holes. The later ones had the "second design" plastic cover with only six bolts so that the flange could have either six or ten holes drilled. See photo. That means that the tin cover won't work on a block that was prepared for a plastic cover, so the blocks aren't always interchangeable.
Things can get confusing in '95 because the 10227196 and 10235359 castings used in '95 came with the narrow flange in '94 and were converted to the broad flange in '95. All 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 ten 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 needs, it's probably better to make sure all the blocks have ten bolt holes so they will work with either front cover. Please do not use a previous partnership with a 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 union 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 differ depending on whether the union was made in Romulus or Tonawanda. The Tonawanda blocks use two more oversized diameter cam bearings, one in front and one in back, instead of only one large one in the show. 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 Tonawanda 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 pretty shallow;
•If it's a Romulus engine, it will have an "R" stamped on the machined surface on the block. The ID number will comprise a series of dots, and the cylinders will have a deep chamfer.
Some 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 spot is there when it's needed.
LIFTER RETAINERS
The roller cam motors have used three different lifter retainers. All 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 engines 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 were bolt-in replacements for the tunnel-shaped version. Some later intakes 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 with the four bolt holes.
FRONT COVERS
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 ten bolt holes that were 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 with the wide flange and only six bolt holes drilled in it. The plastic cover fits on the earlier balance shaft blocks but 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 installed on the engines that came with OBD II.
CRANKS
Chevy has used several different cranks in the 262. They came with one- or two-piece rear seals in both light and heavy versions 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 used only for heavy applications. See photo.
1988-'98: The Tonawanda cranks were all 10105865 castings that came in light and heavy versions.
1988-'98: The Romulus cranks were all 10055480 castings that came in light or heavy versions.
All 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 installed in the engine; it's essential 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 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 heavy pistons.
•If a 10105865 Tonawanda casting came without a hole in the first-rod pin, it's a heavy crank. If there's a hole in the first-rod pin, it's probably a lightweight crank. However, a few early 10109865 cranks 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 to both ways, too. If it has a hole in the first-rod pin, it's the lightweight version; if it doesn't, it's always a heavy crank.
The heavy cranks were used in all 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 the' 96-'98 VIN "X" engines. Using the right crank in a suitable machine will help prevent balance problems in the field.
However, you should also be aware that all 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 muffler and flywheel/flexplate 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 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 with the crank position sensor.
RODS
There are four different rods in two different weights that come from two other engine plants, so there's plenty of room for confusion, but it all works out if you follow these two rules:
Rule 1: Keep similar rods in sets by both appearance and weight;
Rule 2: Use only Romulus rods with Romulus cranks.
Then, the question is, how do you tell them apart so you can follow the rules? Start by sorting them by engine plant based on the shape of the balance pad on the big end. If the rod has a cast pad that's only machined on the face, it's a Tonawanda rod. These rods don't have a forging number and may or may not have a dot on the shank. See photo.
If the weight pad on the big end is long and narrow and has been machined on all five surfaces, including the sides, the lots and the face, it's a Romulus rod. All these rods will have an 818 or 045 forgings number on the shank, so they're easy to identify.
After you have separated the rods by source, sort them by weight and put them in sets. The lighter ones will weigh around 662 grams, and the heavier ones should weigh about 675 grams.
The light and heavy rods can be interchanged in engines in sets, but it's best to use the Romulus rods only on Romulus cranks because you may end up with a ticking noise if used with a Tonawanda crank. The Romulus rods have a wider face adjacent to the parting line that can hit on the side of the split pin rod journal, so the Romulus cranks are machined to provide additional clearance for the rods.
The Tonawanda cranks aren't relieved in this area, so there can be light interference and noise problem. The Tonawanda rods have a narrower face at the parting line so that they can be used with either crank.
PISTONS
Five pistons have been used in the 262, along with two versions of the lightweight piston.
1) The original heavy piston used in the 262 was the same as the one used in the 350 V8, except that the pin boss was opened up slightly for the offset rod. It weighed about 745 grams with the pin and had a 9.1:1 compression ratio. It was used in all light-duty engines without the balance shaft from '85 through '94 and in the VIN "Z" balance shaft motors from '93 through part of '95.
The parts catalogue identifies the '95 VIN "Z" engines with this heavy piston as the "second design" version, even though they were built during the first part of the year. They will have one of the following engine codes: ALH, ALA, ALB, ALC, ALD, ALF, ALH, ALJ, ALL, ALP, ALS, AJS, AJT, AJW and AJU.
2) The lightweight piston weighs about 675 grams with a pin. It was used in all the high output, balance shaft engines (VIN "W") from '92 through '98 and in all the VIN "X" engines from '96 through '98. It was also used in the "first design" VIN "Z" engines that were built during the latter part of the model year '95, including those with the following engine codes: AAB, AAC, AAF, AAJ, AAK, AAL, AAP, AAS, AAW, AFC, AFD, AHC and AHD.
The lightweight piston was originally a Mahle, full-round design (p/n 2753), but GM switched to its own "RPM" (Revised Permanent Mold) plan with a short slipper skirt and a narrower pin boss in '95. Both pistons have very short skirts, so the clearance must be correct, or they tend to make noise at startup.
3) A heavy-duty engine was offered for trucks and vans with over 8500 GVW from '89 through '95. It used a heavy-duty Zollner piston with an 8.3:1 compression ratio and weighed the same as the regular heavy piston.
4) There was also a high output, VIN "B" (LU2) engine offered in the Astro van in '90 and '91. It used a unique, hyper-eutectic, strutless piston available from GM under p/n 10181389 in standard or from Zollner as an H-8269-D. It weighs about 745 grams, just like the rest of the heavy pistons.
5) There was one more piston used in the 262. It's a low compression (8.6:1), strutless, hyper eutectic piston with a deeper dish used in the turbocharged Cyclones and Typhoons from '91 through '93. The OEM standard piston is p/n 12508702, and the Zollner number is an H-8269-E.
These pistons are specific to the application, so they should not be interchanged. Building an engine with pistons with the wrong weight or compression ratio will guarantee a comeback, so it's better to play by the book.
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Ok, I've had this book in my safe for almost a year, and now ill share it with all of you. Try not to drool on your computer (they don't respond too well to that) :rock: :bang: (p.s. the picks didn't make the transition, I think. The website is www.engine-builder.com, then look at back issues. Then search for rebuilding the new 262. There are a lot of informative picks. Enjoy!!
Rebuilding the New Chevy 262, Doug Anderson, Automotive Rebuilder, April 2000
Thanks to all who have contributed information to this article, including the people at GM Powertrain - Lansing Engine.
In the late 1970s, when everyone was worried about the "gas crunch," Chevy needed smaller engines in a hurry, so it created a new family of junior-sized V6s by chopping two cylinders off its existing V8s. This enabled GM to shorten the development process dramatically because it could adapt a proven design. But it also allowed it to share much 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 was based on the 305. By 1985, both were replaced by the 262 V6, based on the 350. It was initially installed in 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 machine 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 many 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 subtle differences between the engines built in the two different plants. 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).
BLOCKS
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 the trucks still had carburetors. Just for the record, there were some '86 blocks shipped with pans for '85 service replacements so that a customer can 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 the cars and some 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 adequately 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 a tiny difference – some of the blocks came with four bolt holes for the tunnel-style retainer beginning in '92. Several different castings were 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 two extra bolt holes for the strut bosses and ten bolt holes for the tin front cover. See photo. Five castings may or may not be suitable:
•All of the 10224534 and 10224535 blocks have the two strut bosses and ten holes for the front cover so that they will fit everything in '93 and '94;
•The 10227196 castings have the strut bosses, but they came with either six or ten holes;
•The 10224834 blocks have ten 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 six or ten holes for the front cover!
Consequently, all of these castings must be checked and sorted by casting number and features 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 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 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 ten bolt holes. The later ones had the "second design" plastic cover with only six bolts so that the flange could have either six or ten holes drilled. See photo. That means that the tin cover won't work on a block that was prepared for a plastic cover, so the blocks aren't always interchangeable.
Things can get confusing in '95 because the 10227196 and 10235359 castings used in '95 came with the narrow flange in '94 and were converted to the broad flange in '95. All 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 ten 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 needs, it's probably better to make sure all the blocks have ten bolt holes so they will work with either front cover. Please do not use a previous partnership with a 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 union 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 differ depending on whether the union was made in Romulus or Tonawanda. The Tonawanda blocks use two more oversized diameter cam bearings, one in front and one in back, instead of only one large one in the show. 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 Tonawanda 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 pretty shallow;
•If it's a Romulus engine, it will have an "R" stamped on the machined surface on the block. The ID number will comprise a series of dots, and the cylinders will have a deep chamfer.
Some 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 spot is there when it's needed.
LIFTER RETAINERS
The roller cam motors have used three different lifter retainers. All 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 engines 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 were bolt-in replacements for the tunnel-shaped version. Some later intakes 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 with the four bolt holes.
FRONT COVERS
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 ten bolt holes that were 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 with the wide flange and only six bolt holes drilled in it. The plastic cover fits on the earlier balance shaft blocks but 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 installed on the engines that came with OBD II.
CRANKS
Chevy has used several different cranks in the 262. They came with one- or two-piece rear seals in both light and heavy versions 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 used only for heavy applications. See photo.
1988-'98: The Tonawanda cranks were all 10105865 castings that came in light and heavy versions.
1988-'98: The Romulus cranks were all 10055480 castings that came in light or heavy versions.
All 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 installed in the engine; it's essential 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 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 heavy pistons.
•If a 10105865 Tonawanda casting came without a hole in the first-rod pin, it's a heavy crank. If there's a hole in the first-rod pin, it's probably a lightweight crank. However, a few early 10109865 cranks 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 to both ways, too. If it has a hole in the first-rod pin, it's the lightweight version; if it doesn't, it's always a heavy crank.
The heavy cranks were used in all 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 the' 96-'98 VIN "X" engines. Using the right crank in a suitable machine will help prevent balance problems in the field.
However, you should also be aware that all 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 muffler and flywheel/flexplate 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 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 with the crank position sensor.
RODS
There are four different rods in two different weights that come from two other engine plants, so there's plenty of room for confusion, but it all works out if you follow these two rules:
Rule 1: Keep similar rods in sets by both appearance and weight;
Rule 2: Use only Romulus rods with Romulus cranks.
Then, the question is, how do you tell them apart so you can follow the rules? Start by sorting them by engine plant based on the shape of the balance pad on the big end. If the rod has a cast pad that's only machined on the face, it's a Tonawanda rod. These rods don't have a forging number and may or may not have a dot on the shank. See photo.
If the weight pad on the big end is long and narrow and has been machined on all five surfaces, including the sides, the lots and the face, it's a Romulus rod. All these rods will have an 818 or 045 forgings number on the shank, so they're easy to identify.
After you have separated the rods by source, sort them by weight and put them in sets. The lighter ones will weigh around 662 grams, and the heavier ones should weigh about 675 grams.
The light and heavy rods can be interchanged in engines in sets, but it's best to use the Romulus rods only on Romulus cranks because you may end up with a ticking noise if used with a Tonawanda crank. The Romulus rods have a wider face adjacent to the parting line that can hit on the side of the split pin rod journal, so the Romulus cranks are machined to provide additional clearance for the rods.
The Tonawanda cranks aren't relieved in this area, so there can be light interference and noise problem. The Tonawanda rods have a narrower face at the parting line so that they can be used with either crank.
PISTONS
Five pistons have been used in the 262, along with two versions of the lightweight piston.
1) The original heavy piston used in the 262 was the same as the one used in the 350 V8, except that the pin boss was opened up slightly for the offset rod. It weighed about 745 grams with the pin and had a 9.1:1 compression ratio. It was used in all light-duty engines without the balance shaft from '85 through '94 and in the VIN "Z" balance shaft motors from '93 through part of '95.
The parts catalogue identifies the '95 VIN "Z" engines with this heavy piston as the "second design" version, even though they were built during the first part of the year. They will have one of the following engine codes: ALH, ALA, ALB, ALC, ALD, ALF, ALH, ALJ, ALL, ALP, ALS, AJS, AJT, AJW and AJU.
2) The lightweight piston weighs about 675 grams with a pin. It was used in all the high output, balance shaft engines (VIN "W") from '92 through '98 and in all the VIN "X" engines from '96 through '98. It was also used in the "first design" VIN "Z" engines that were built during the latter part of the model year '95, including those with the following engine codes: AAB, AAC, AAF, AAJ, AAK, AAL, AAP, AAS, AAW, AFC, AFD, AHC and AHD.
The lightweight piston was originally a Mahle, full-round design (p/n 2753), but GM switched to its own "RPM" (Revised Permanent Mold) plan with a short slipper skirt and a narrower pin boss in '95. Both pistons have very short skirts, so the clearance must be correct, or they tend to make noise at startup.
3) A heavy-duty engine was offered for trucks and vans with over 8500 GVW from '89 through '95. It used a heavy-duty Zollner piston with an 8.3:1 compression ratio and weighed the same as the regular heavy piston.
4) There was also a high output, VIN "B" (LU2) engine offered in the Astro van in '90 and '91. It used a unique, hyper-eutectic, strutless piston available from GM under p/n 10181389 in standard or from Zollner as an H-8269-D. It weighs about 745 grams, just like the rest of the heavy pistons.
5) There was one more piston used in the 262. It's a low compression (8.6:1), strutless, hyper eutectic piston with a deeper dish used in the turbocharged Cyclones and Typhoons from '91 through '93. The OEM standard piston is p/n 12508702, and the Zollner number is an H-8269-E.
These pistons are specific to the application, so they should not be interchanged. Building an engine with pistons with the wrong weight or compression ratio will guarantee a comeback, so it's better to play by the book.