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Deciphering The Differences In The Chevy 2.2L Engine

The very popular Chevrolet FWD/RWD, 2.2L/134CID, OHV four-cylinder engine has been a solid steed in the GM stable. But even after all these years, it still manages to raise questions surrounding the Gen II engine casting configurations, in particular the cylinder head.

By Roy Berndt
Since its birth in 1990, when the old Chevy 2.0L engine was upgraded with a stroke increased from 3.15˝ to 3.46˝, the 2.2L powerplant has been upgraded several times: the block has been revised four times and the head has been changed three times (it was discontinued after 2003, replaced by the 2.2 L Ecotec). Let’s start in 1994 and see if we can’t clear up some of the confusion.

In 1994 the 2.2L Chevrolet became the base engine in the S-series truck line, replacing the 2.5L Pontiac engines. This presents us with the 2.2L now being both FWD and RWD, which you would think would mean numerous differences. Actually, that’s not so. GM used two different head gaskets through 1997, and in 1998 went to a common head gasket for both FWD and RWD. Using the incorrect head gasket will result in almost immediate overheating. The castings made changes in those years but they followed suit in both FWD and RWD alike.

In 1994, the valve stem diameter went from 8 mm to 7 mm as well as going to a roller lifter and assembled camshaft. The FWD requires the use of a 34.4 mm soft plug in front of the head while the RWD is open and must have the bolt holes drilled and tapped (see below). The 1994 motor could have casting number 10112391 or 10112391S that is the service replacement. This same pattern was followed throughout the 1997 production cycle.

In 1998, head c/n 24575507 arrived with a heart-shaped combustion chamber against a D shape. The engine also had smaller 1-1/8˝ diameter exhaust ports vs. 1-3/8˝, and a triangular top of the intake ports vs. a smaller eyebrow top. This version of the GM 2.2L engine – a single-year configuration – must have an open and drilled EGR port.

Since 1999 to present, cylinder head c/n 24576146 has been used and is basically the same as c/n 24575507 except for crucial long flat bosses that are now between the first two and last two exhaust ports (see illustration below). The latest exhaust manifolds have a balance channel that runs between ports 1-2 and ports 3-4 that must seal against the cylinder head. As you can see, that exhaust manifold configuration assembled against the 507 head would leak.

One last quirk, the 146 head may also be drilled for the EGR port as a service replacement for the 507 head in 1998. All later applications would require the use of an EGR block-off plate (GM p/n 24575919) when used without EGR.

Well, there you have it, clear as a bell. No? Well perhaps the chart included on page 30 of this issue will help! Good luck and remember it is always easier to build it right the first time.

2.2L OHV L4 GM, CHEVROLET CYLINDER HEADS

OE PIN #	1994 12363166	1994-’97 12360424		1998 12563766		1999-2002 24577648
OE SUPER #	12360424
CASTING #	10112391	10112391S		24575507		24576146
7mm Valve Stem	X	X		X		X
8mm Valve Stem	*
Roller Rocker Arm				X		X
D Combustion Chamber	X	X
Heart Combustion Chamber		X		X
EGR Drilled w/Bolt Holes	Xc	Xc		Xc		Xc
EGR Not Drilles w/o Bolt Holes	Xc	Xc		Xc
Eyebrow Intake Port	Xa	Xa
Triangle Intake Port				Xa		Xa
Large 1.340˝ Exh. Ports	X	X
Small 1.120˝ Exh. Ports				X		X
Exhaust port balance boss						Xd
FWD water port closed with 34.3mm soft plug and no bolt holes	Xb		Xb
RWD Water open 34.3mm with 2 mounting bolt holes			Xb
FWD/RWD Water port open 1-21/64˝ with two mounting bolt holes				Xb	Xb
Lost foam casting	X		X	X	X

* prior to 1994 8mm valves were used

Notes:

1. letter after X indicates illustration attachment
2. Intake manifold EGR port on intake side in rear of head, the port goes around the back where EGR valve assembly connects, the channel than goes around on to exhaust ports down other side of head.
3. #24576146 can be WOW drilled EGR port and bolt bosses, but is the only head that has exhaust manifold port balance boss between front two and rear two exhaust ports; this head w/EGR can be used as a replacement for 24575507
4. 1998 is a stand alone MY application with heart shape chamber and roller rocker head with open EGR.

Special Note: 1998 applications all required an open EGR port; 1999-2002 are closed EGR, w/exhaust manifold port balance mounting face, (see Illustration D and observe area that arrows are pointing to). #24576146 cylinder head may also have open EGR port and will retro for 24575507 in 1998, or may be used 1999-2002 with the use of EGR block off plate part # 24575919.