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General Motors / Chevy 191/3.1L

When this engine was used in the plastic mini-vans, it came with cast iron heads and the old, original, carbureted, non-H.O. cam. This cam was used because the reduced lift and overlap gave it a smoother idle. It’s a GM p/n 10118675, or a Wolverine CS715.

Rebuilder’s survival tip: Don’t put the H.O./EFI cam in the iron-headed, FWD 191 or you will have idle problems along with possible emissions problems, too.

Chevy 191/3.1L Heads And Rockers
When Chevy switched over to roller rockers on the 3.1L VIN M, "Enhanced" motor in ’96, the head was modified to accommodate the new, unitized, roller rocker assembly. The ’96 heads (c/n 24503769) have slots machined in them for the tabs on the rocker pedestals that keep the rockers properly aligned when they are installed. This eliminates the need for the pushrod guide plates, so the pushrods are not hardened.

Rebuilder’s survival tip: Don’t install the soft pushrods from an engine with roller rockers in an earlier one that had the guide plates and hardened pushrods or you will end up replacing them when they get eaten up by the pushrod guide plates.

Chevy 191
There are some Chevy 191s with the 10110519 casting that have two extra holes – there is a large open one and a small threaded one – in the top of the block just behind the timing gear. See Figure 1.

They are used for the cam position sensor that picks up a signal from the tab on the cam (See Figure 2) and indexes the computer for the sequential fuel injection.

Rebuilder’s survival tip: If the engine has sequential fuel injection, it has to have the block with the holes and the cam with the tab or it will not start and run. SEFI engines were used in some 1993 and ‘94 "A" bodied cars with NB2 California emissions and the M13 four-speed automatic transmission, as well as the 1994 Z24 Cavaliers.

Just for the record, this is the same flat tappet cam (GM p/n 10166324) that is in the 3.4L RWD engine with SEFI that was used in the ‘92-’94 Camaro and Firebird. GM sells it for about $160. Most aftermarket suppliers are planning to add this tab to all of their 173/191 cams if they haven’t already.

Chevy 173/191 V6 Oil Leaks
Many of the oil leaks on these engines that are diagnosed as rear seal leaks are actually caused by oil seeping up around the distributor housing and running down the back of the engine. The distributor is supposed to be sealed in the block with an O-ring that fits around the distributor housing, but it doesn’t always do the job, especially if the installer reuses the old one when he installs the rebuilt engine.

Rebuilder’s survival tip: When a customer calls with a rear seal leak on a Chevy 173 or 191, have him replace the O-ring on the distributor housing and install a paper gasket from a small block Chevy distributor between the block and the distributor housing. Then have him recheck the oil leak. Using both the O-ring and the gasket will seal up the distributor and eliminate most of these "rear seal leaks."

Chevy 173/191 Blocks Cracking
The Chevy block that was used for the FWD173/2.8L with aluminum heads in ‘87-’89 (VIN W) and the FWD car 191 in ‘89-’90 (VIN T) is very prone to crack. It almost seems like the engine is making more power than it can stand, so it tries to rip the deck right off the top of the block.

Rebuilder’s survival tip: There are three blocks that should be carefully checked for cracks. The 10065459 is especially bad, but both the 14092219 and the 10118618 have been known to crack, too. Check the cylinders just down from the top, look for cracks around the head bolt holes, and watch for cracks parallel with the deck surface just below the deck surface on the outside of the water jackets. You can expect to see about 30% of them cracked in one or more places. There is no way to fix them.

Chevy 2.2L
In 1994 when Chevy introduced the "Enhanced" version of the 2.2L/134 cid engine, they installed it in their S10/S15 pickups as the standard engine instead of the 2.5L Pontiac that had been the base engine. This was the first RWD application for this engine, so we expected to find some differences in the block, head or water pump. But we were surprised to discover there is only one major change: The FWD and RWD engines use different head gaskets.

Rebuilder’s survival tip: The FWD 2.2L continued to use the original 2.0L head gasket (GM p/n 10101236) that is found in all aftermarket FWD gasket sets. However, the head gasket for the RWD engines was modified to restrict the flow of coolant in the front of the block and between the cylinders to make it flow out through the front-mounted water outlet. Be sure to use the correct head gasket (GM p/n 10141913) and remove the frost plug on the front of the head when rebuilding one of these engines for a RWD application.

Chevy 2.8L
In 1988 and ‘89, Chevy offered an optional gauge package on its A (Celebrity), J (Cavalier) and L (Corsica) models equipped with the 2.8L engine. In order to have a variable gauge instead of just the idiot light, Chevy had to run a second oil pressure sender; the original on/off sender was still needed to turn off the electric fuel pump in case of an accident and loss of oil pressure. So, another hole was drilled and tapped in the top of the bellhousing, just off to the left of the distributor hole.

Rebuilder’s survival tip: Be sure to ask the customer if there is an extra hole in the block before you sell him one without it. Or better yet, drill and tap every block so it can be used either way.

Chevy 3.1L
When Chevy introduced the "enhanced" version of the 3.1L V6 in 1993, it used a roller cam and lifters. The lifters are the same diameter as the regular small block lifters, but they are about .300" shorter. They measure 2.20" in overall length compared to 2.50" overall for the regular V8 roller lifter. They are available from GM as a p/n 17120070 or in the aftermarket as an HL 118.

Rebuilder’s survival tip: Don’t mix up these lifters with the regular roller lifters or you will have serious clearance problems one way or the other. Just for the record, these short lifters are also used in the "enhanced" 2.2L and in the late 3.4L V6.

Chevy Pickups With The "Mysterious Code 43"
It’s not uncommon for Chevy pickups with injected 350s to set a Code 43 indicating erratic spark or a detonation problem after the installation of a remanufactured engine. The installer usually blames it on the engine because it has "the wrong heads" or "the wrong compression ratio" after everything else seemingly checks out okay.

Rebuilder’s survival tip: The main wiring harness runs along the right valve cover. It has a "dip" in it that is supposed to go under the heater hose. If the installer turns the harness upside down so the "dip" goes over the heater hose, the harness is close to the plug wires and it will induce a small current into the harness when the engine is run hard.

This small voltage in the circuit for the knock sensor is all it takes for the computer to "think" that there’s erratic spark or detonation present, even though there really isn’t a problem, so it sets a "Code 43" after a road test. The computer always checks the spark control circuit at start-up and sets a Code 43 if there’s a problem in the electronic spark control circuit, but it should never set a Code 43 after it’s been running down the road. If it does, then you’ve got the "Mysterious Code 43" that is probably caused by the high voltage plug wires inducing a current into the harness. We have fixed several of these pickups with this problem by rerouting the harness under the heater hose.

Chevy 262 V6
Chevy has used three different retainers to position the roller lifters in the 262 V6 since 1987. The original retainer was basically a flat stamping (p/n 10046165) with three bolt holes in the middle and three spring loaded fingers on each side that held the lifter guides in place. See photo.

This design wouldn’t work when the balance shaft was installed above the cam in 1992, so Chevy introduced a tunnel-shaped version with six fingers that used four bolts on the outer edges to hold it down. It’s a p/n 10105916. Unfortunately for engine rebuilders, GM used the tunnel retainer on some of the ‘92 and up non-balancer engines, too, and there’s no way to know for sure which one was used until you actually see the engine.

In 1994, Chevy replaced the tunnel retainer and the metal lifter guides with a pair of plastic lifter guides that also hold the lifters in place. They were bolted down using the same holes that held the tunnel retainer in place, so they are interchangeable. These plastic guides are available under p/n 12551431. See photo.

Rebuilder’s survival tip: In order to avoid problems when selling a short block, you must either identify the retainer or sell the engine with the lifters, lifter guides and retainer installed. However, you can still end up in trouble if you sell an engine with a tunnel retainer to replace one that originally came with the flat retainer, because the bottom of the intake hits the top of the tunnel retainer on some applications. The best way to avoid problems is to sell the customer exactly what he had, or use the plastic guides instead of the tunnel retainer on the non-balancer engines.

Chevy 262
In 1993, Chevy offered the 4.3L VIN Z engine with throttle body injection, with and without a balance shaft. This made it difficult to know which engine the customer needed unless the intake was off, until we realized that these engines use two different front covers, depending on whether the engine has a balance shaft.

Rebuilder’s survival tip: If the engine doesn’t have a balance shaft, it has the traditional small block Chevy front cover. If it has a tall front cover that is squared off on the top with a small hump in the middle, it’s a balance shaft motor. See photo. It’s even easier to spot the difference after ’95 because the front cover for the balance shaft motor is made out of plastic (p/n 12554557).

Chevy 262 Blocks
Some of the 262 blocks with the balance shaft that came out in early 1992 didn’t have the two extra bolt holes for the transmission support brackets that were used with some applications. The first design blocks, c/n 10105903 or c/n 10224834, don’t have these extra holes. All second design blocks with a 10224534 or 10224535 casting number had them.

Rebuilder’s survival tip: The blocks without the two extra holes can be used in the C/K full size pickups and Blazers in ‘92 up through ‘94, but they shouldn’t be used in an S/T pickup or small Blazer because some of them with two-wheel drive models and all of the four-wheel drives require the two support brackets. These brackets are available from GM under p/n 15672797 and p/n 15672806.

Chevy 262 Rockers
Chevy has used two different rocker setups on the 262/4.3L V6. The engines built in the Romulus plant have pressed-in adjustable rockers with 0.370" studs. The engines built in the Tonawanda plant have a non-adjustable design with a screw-in, shouldered stud that measures about .390".

That means that there are two different rocker balls for the two different studs, so someone can mix them up. Don’t try to force the one with the small hole or the big stud, or use the one with the big hole on the smaller, pressed-in stud, or you will have a comeback.

Chevy 262/4.3L/V6
Chevy used two different rocker covers that require two completely different gaskets on the 262 V6 in ’94 and ’95. Some of the engines came with a stamped metal rocker cover that used a flat, rubber gasket and others came with a plastic rocker cover that used a thin, "spaghetti-style" molded rubber gasket. See photo.

Most gasket sets don’t include the spaghetti-style rocker gaskets, so it’s best to keep them on hand and include them with the engine when the customer has the plastic covers. All of the ’96 and later engines use plastic covers with the spaghetti-style gaskets.

Chevy 262/4.3L Block, Front Cover Differences
In 1995, Chevy installed a "composite" (plastic) front cover on the 262 V6 engines with a balance shaft. It was a unitized design with a rubber gasket molded into the cover. In order to accommodate the molded gasket, the cover had to be wider, especially around the bolt holes. So, the flange on the front of the block had to be made about 0.300" wider with "bulges" around the bolt holes, too. See photo.

Rebuilder’s survival tip: Be sure to use the 1995 block (c/n 10227196) for a ’95 engine. Don’t use any of the earlier blocks for an application that uses the composite front cover because they will allow oil to leak out around the middle bolt holes on both sides. See photo.

Chevy 262/4.3L Engines With Balance Shaft
When this engine was introduced with a balance shaft in 1992, it came with an all new block with room above the cam for the balance shaft. The balance shaft was supported by a roller bearing in the front and a needle bearing in the back; both were lubricated by the oil mist from the lifter valley.

Unfortunately, there were some noise problems with the "first design" engine, so it was replaced by a "second design" version that used a sleeve bearing instead of the needle bearing on the back of the balance shaft. The blocks were similar, but there was an additional oil hole drilled at an angle from the rear balance shaft bore into the main oil gallery to provide pressurized oil to the sleeve bushing for the "second design" engine. See photo.

This "second design" engine included two other changes: 1) The wear sleeve on the balance shaft for the needle bearing was no longer needed, so it was left off; 2) The teeth on the drive and driven gears were modified to help reduce the possibility of noise.

The "second design" gears can be identified by the narrow ledge on the edge of the teeth instead of the more pronounced, squared off ledge that was found on the "first design" gears.

Rebuilder’s survival tip:
•The first and second design blocks must be built with the right bearing and balance shaft or they will have serious oiling problems.

•The "first design" blocks can be identified easily because they will have either a 10105903 or a 10224834 casting number on the side.

•If you do rebuild a "first design" block, it’s best to use the "second design" gears to help prevent any possible noise problems.

•The "first design" balance shaft is a 10172748 casting with a wear sleeve on the back bearing surface.

•The needle bearing used in the "first design" engine is a J2412. It’s the same one that’s used with the balance shaft for the 3800 Buicks.

Chevy 121/134
The original 1990-’91 Chevy 134 engines had a connecting rod that measured 1.030" wide on the small end and came with a rectangular balance pad that stuck out prominently from the bottom of the big end. Most of the balance pads stick down about 1.55" below the cap, but some can be as much as 1.645" below the cap.

This limits the room between the bottom of the #4 rod and the top of the oil pump and can cause problems with some aftermarket pumps. See photo. The clearance is marginal at best, and can result in interference between the rod and the pump if everything stacks up the wrong way. The aftermarket suppliers have made changes to this housing, but there still may be some of the earlier castings left out in the field, so check it out when you buy a pump.

Rebuilder’s survival tip: Be sure to check the pump to see if the rod has enough clearance. If not, we suggest grinding off the corner of the pump housing and the plug to make sure that the rod will clear the pump on these engines. Mount the pump on the engine; roll it over and check the clearance to make sure that the rod will actually clear it when the engine is running.

You may also want to consider using the later pump with the shallow gears and the shorter housing that came out in 1994 instead of the earlier pump. GM has not superseded the early one with the late one, so it’s not officially approved. The engines, however, are the same so it sure seems like the later pump would work on the early engines, even though it doesn’t have as much volume and the relief valve is set for 64 lbs. instead of 80 lbs.

Chevy 134/2.2L
There are two blocks used for the ’96 and later 2.2L Chevys with one important difference – the plastic lifter guides that keep the lifters from rotating were changed in ’97, along with the two machined bosses that are used to bolt them onto the block. See photo.

It appears that the 24576035 blocks came with the taller boss in the block and early style lifter guide (p/n 24575182), and the 24574521 blocks came with the shorter boss and the later style lifter guide (p/n 24575541). However, this may not always hold true, so double check the block before assembly. You can tell the blocks apart because the early lifter guide is about .360" thick where it bolts onto the boss in the block and the later one is .750" thick with reinforcing gussets on both sides.

Rebuilder’s survival tip: Use the right lifter guide in the block when you assemble a long block. Supply the right one with the short block when you sell it to avoid problems in the field, too, because there’s no sure way to predict which one the customer has.

1998 Chevy 134/2.2L VIN "4"
Chevrolet made several significant changes to the 2.2L engine in 1998:

• The block is a different casting (c/n 24576039) that has one more boss (undrilled) on the passenger side;

• The piston has a shallow dish;

• The crank has the same casting number (4618) that was used in 1997, but the notches on the reluctor wheel were advanced by about .450" in 1998. See photo.

• The head is a new casting (c/n 24575507) with a heart-shaped chamber that has squared-off intake ports and smaller (1.120" vs. 1.340") exhaust ports. See photo.

• Roller rockers were used for the first time on this engine. They have locating tabs that fit into notches on the head to provide proper alignment. See photo.

Rebuilder’s survival tip: Watch out for this crank! It’s the same 4618 casting that was used for the earlier cranks, but the notches have been moved. That can be a real problem because the wrong crank will confuse the computer big time. Both versions of the crank can be identified visually if you know what to look for, so check them over carefully and know which one you have before installing it in an engine.

Chevy 454 Mark V With Roller Lifters
When the Mark V 454 Chevy was introduced in ’96, it came with a steel cam and roller lifters that aligned to the cam lobes with a holder that was unique to these big block engines. This holder locates off two flats that are parallel to the sides of the roller instead of perpendicular to the roller like they are on all the rest of the GM roller lifters. See photo.

Rebuilder’s survival tip: Be sure not to get these special 454 lifters mixed up with any other GM roller lifters or you will have a very expensive comeback.

Pontiac 1.8L/2.0L
The cranks for all ’82-’86 1.8L Pontiac OHC engines and ‘87 through ‘91 2.0L engines have two small steel pins embedded in the second counterweight of the crank. See photo. They line up with a hole in the block that has a bushing (p/n 90091049) installed in it.

The pins and bushing are used for a crank position sensor that indexes the sequential fuel injection each time the engine is started (See photo). The ‘92 and up 2.0L cranks don’t have these pins even though they have SFI, because they use a special reluctor wheel to trigger both the ignition and the fuel injection.

Rebuilder’s Survival Tip: The turbocharged engines were the only ones that used sequential, multi-port, fuel injection from 1982 through ‘91, so they are the only ones that require the pins in the crank and the bushing in the block for the sensor. A word of caution though: Don’t use a ‘92 and up 2.0L crank without the pins in an earlier turbo engine, because it will not start without the signal from the crank position sensor.

Pontiac 2.5L Balancers
The balancers for the Pontiac 2.5L/151 can be rebuilt if the gears and the housing haven’t been damaged.

Rebuilder’s survival tip: Disassemble the shafts by pressing them apart with a punch from the oil pump end. Clean and inspect the housing, shafts and gears for damage. Replace the bushings with the OEM bearings that are presently available from Enginetech (1-800-869-8711) under p/n BG-371U. Time the weights by bringing both external weights to the top when reinstalling them. Then press the shafts back together. Be sure to use a .165˝ to .185" shim between the gear and the housing while pressing the shafts together to ensure that the shafts are installed correctly (see photos).

2.0L Pontiac OHC Reluctor Wheel
The 1992-‘94 Pontiac 2.0L OHC engine (VIN "H") came with crank-triggered spark. The computer gets a signal from the stamped steel reluctor wheel that is bolted onto the front counterweight and a sensor that sticks into the crankcase through a hole in the side of the block. This can create a problem, because the reluctor wheel is bigger than the counterweights and sticks down below the pan rail where it’s easily damaged during shipping and handling. If the reluctor is bent or nicked, the engine may not start and it definitely will not run right if it does start. See photo.

Rebuilder’s survival tip: Be sure to inspect every reluctor wheel carefully before installing it in an engine. If it’s bent or burred, replace it with a new one. It’s available from GM under p/n 90265094 for about $40. We install a homemade steel shield over the reluctor wheel at assembly (see photo) to protect it during shipping and ask the customer to put it back on the core before they return it to us.

Buick 204/3.3L
There are at least three different Buick 204 engines out there. When this engine was introduced in 1989, it had a two-piece rear seal. The very same block, (c/n 25532062) was used in 1990, too. In 1991, GM switched to a new casting (c/n 25534816) with a one-piece rear seal. Then, in 1992, GM added a bulge to the front of the block (c/n 24500498 or 24502090) where it mates with the front of the intake manifold.

Rebuilder’s survival tip: Be sure you know the exact model year of the car and double check the casting number before you sell a Buick 3.3L or you could end up with big problems.

Saturn DOHC Heads
The DOHC Saturn head was revised in 1995 so it isn’t interchangable with either of the earlier versions. The EGR mounting pad is parallel to the deck surface on the ‘95 head (c/n 21006937) instead of being canted at a 45° angle like it was on the ‘91-’94 head (c/n 21006469). See photo.

Saturn Front Covers
Saturn has used two different front covers for the SOHC and DOHC engines, and two versions of each. The original covers that were used in ‘91 had a narrow ledge on the top for the rocker cover gasket. They were replaced in ‘92 by two different covers that had wider flanges with three additional, large, threaded holes (10 x 1.5mm) in them. See photos.

When the engine is installed in the car, there are three studs that stick up about 2-1/2" for the torque axis motor mount that was added to reduce "noise, vibration and harshness" (NVH). These later covers can be identified by the three big bolt holes or by casting number. See the chart

ENGINE	1991	1992-‘97
SOHC	21006108	21006370
DOHC	21006109	21006371

To see more pictures click here.