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S-Series Swap Guide

Old 11-07-2014, 11:14 AM
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Exclamation S-Series Swap Guide

saturnwiki is gone....thanx for the help over the years. RIP

Edited by Derf 11/7/14 to include transmission defs and interchangeability, condense updated info into existing sections, and to make it look prettier.
Please be aware that this guide is a work in progress. The information contained within this swap guide is believed to be correct but be aware that errors maybe present.

S Series Swap Guide

Intake manifolds and fuel delivery:

91-94 Intake manifolds interchange.
95-98 Intake manifolds interchange.
99-2k Intake manifolds interchange

91-94 throttle bodies interchange.
95-98 throttle bodies interchange.
99-2k throttle bodies interchange.
91-94 fuel rails and injectors interchange.

95-97 Fuel rails interchange however the injectors from 95 and earlier years will not work correctly in the 96-97 years. The injectors are the same size they are just of different impedance.

91-94 fuel pressure regulators were non-adjustable.
95-97 fuel pressure regulators were adjustable.
91-94 aluminum fuel rails will not fit 95-97 intake manifolds due to the bolt pattern and fuel lines being plastic.
95-97 plastic fuel rails w/adjustable fuel pressure regulators will not fit the 91-94 intake manifolds due to the bolt pattern and fuel lines being metal.

Also, the ports on the 93-94 are much cleaner than 91-92, though the 92 seemed to have a wider opening on the mouth of the intake ports. The 95 mics out close to the 93-94, though it is reshaped with a shallower curve leading down to the valve surface. The combustion chambers up to 94 are all identical.


The 91-95 injectors are peak and hold or also known as low impedance.

96-02 are called saturated injectors or also known as high impedance.

set multi-meter to measure resistance.
2-4(ohms) low impedance
4-10(ohms) weird injectors. pretty much only found on old Porsches.
10-14(ohms) high impedance

Cam covers:

The earlier cam covers seal better, as they have more bolts holding them down.


The '91 DOHC head is a freakshow-leave it alone.
91-94 Heads interchange. (compatible with any year block.)
95-98 Gen2 heads - Linear EGR valve, otherwise compatible with 91-94 heads. Compatible with any year block.
99+ Gen3 Heads are NOT compatible with older heads. Completely redesigned. Compatible with any year block.
2000 (or 1999?) - 2002 Have the roller-rocker design with the small ports.

95 Heads do not interchange with any other year correctly. While yes all the heads up to 99 will interchange physically they will not have proper electronics and egr connections. The 95 head is the first year of the electronic egr valve. And the head has two coolant temp sensors. Now the 91-94 had a vacuum controlled egr valve and also had two coolant temp sensors. The egr mount is completely different between the vacuum and the electronic. Now the 96+ heads also came with the electronic egr valve but they only had one coolant temp sensor due to the fact that 96+ years went to the obd II pcm and only called for one coolant temp sensor.

'91-'94 heads can be adapted to later year engines and use the new style EGR valve if you get the adapter from Saturn that was used on 1994 DOHC cars sold in California, I'l try to dig up the part number at a later time.

You can use a '95 DOHC head all the way up to '98 all you have to do is buy one extra temp sender and screw it in the "spare" hole. Alternately, you can install the sender from an Autometer electric coolant temp gauge-it's a direct fit.


91-94 Valves; Flatfaced. Compatible with 91-98 cylinder heads.

95-98 Valves; Dished. Compatible with 91-98 cylinder heads.

91-93 had flat faced valves.
94+ had dished valves.
Now what difference does it make? The 91-93 can be used to raise the compression slightly on the 94+ model years. While the 94+ valves can be used on 91-93 years to lower compression slightly.

Exhaust manifold:

91-92 OEM header is interchangeable for 93-98 DOHC Saturn engines
SOHC are all the same (8 bolt)
DOHC 91-98 are all 5 bolt
DOHC 99-02 are 9 bolt

Oxygen Sensor Bungs:

1991-1993 Smaller Bung = o2 Sensors/Bungs interswappable between these years but not interswappable w/ newer ones
1994-2002 Larger Bung = o2 Sensors/Bungs interswappable between these years but not interswappable with older ones


91-02 blocks are compatible with all years

1991 - 1993 (midway through '93) blocks contain an oil feed restrictor (looks like a freeze plug with a hole in it) present in the right front oil galley beneath the deck. This should be removed to prevent oil starvation to the head, as the newer headgaskets function as the restrictor.

91-99 blocks interchange externally. Now internally itís a different ball game. The 91-92 had a crank all on its own that will not function correctly in the 93-99 years due to the positioning of the crank position sensor reluctor ring notches. 93-99 cranks are interchangable
'92 to '03 blocks are totally interchangeable. The '00 and up blocks are stronger and all the accessories from previous years fit. Also, The internals from previous years will fit in the '00 and up blocks.

There were 2 dipstick tubes used, not entirely sure when they changed, but 91-92 I know for sure had a dipstick tube that positioned itself away from the block, and I know that my 99+2000 have a dipstick tube that hugs the block. The actual dipsticks are the same length so you can use either tube to move the dipstick out of the way of the turbo, or supercharger.


1991 - 1998 Rods are the same.
1999 - 2002 Rods are the same.
1999-02 rods are longer than the 91-98 rods, and have to be used with the 99-02 pistons which have the wrist pin moved up.

The 99-02 rods are 5.863" long vs 5.712" for the 91-98 rods.

91-92 Crankshafts only work with 91-92 PCM's. Avoid at all costs.

93-98 Crankshafts are essentially identical; compatible with any year block.

99-02 Crankshafts were redesigned; heavier. Compatible with any year block.


So 91-93 Pistons + 94-99 valves equal lower compression.
94-99 Pistons with 91-93 vales equal higher compression.
Now with these compression changes they are slight not drastic. It is about a 2-2.5 point change in compression. So do not expect huge gains.

The 91-93 model years came with the lower compression piston than the later years. The way they maintained the 9:5:1 compression was using the flat faced valves. The 91-93 pistons also came with thicker ring lands which is a plus. Now the 94+ years came with a higher compression piston but it also came with thinner ring lands which is not good. The way they maintained the 9:5:1 compression was by using the dished valves to lower the compression down to its 9:5:1 state.

91-94 Pistons; Slight dish, thickest dome of all years. (Yields 9.5:1 compression with 91-94 flatfaced valves) Compatible with 91-98 rods.

PCM and Harness

1991-1999 = Manufactured by Delco
2000-2002 = Manufactured by Motorola
1991-1995 = OBD1
1996-2002 = OBD2

91-92 PCMs are grouped together. The wiring harness for them is slightly different (two wire type oil pressure unit). If using a 93+ block the oil pressure unit must be changed in order for the harness to hook-up.
93-94 PCMs are grouped together.
95 PCMs are year specific.
Years after this, I'm not sure.

91-92 PCMs are grouped together. The wiring harness for them is slightly different (two wire type oil pressure unit). If using a 93+ block the oil pressure unit must be changed in order for the harness to hook-up.
93-94 PCMs are grouped together.
95 PCMs are year specific.
Years after this, I'm not sure.

MAP/Pressure sensors

There are several varieties of pressure sensors from GM: Map sensors in 3 varieties (1 bar, 2 bar, 3 bar), and a barometric pressure sensor. 1 Bar sensors are good for NA engines, they measure from 0 (vacuum) to approximately atmospheric pressure. A 2 Bar sensor is good for 15 PSI of boost, and a 3 Bar unit is good for 30 psi of boost.
They all share a common pinout, although the connector keying may be different:

Pin A -- Ground
Pin B -- Sensor output
Pin C -- +5 volts

Version Part numbers Description

1 Bar GM part # 2503679
standard part # AS-5
Pretty much any normally aspirated TBI GM car, plus plenty of others

2 Bar GM part # 16009886
Wells part # SU-129
standard part # AS-4
91-93 GMC Cyclone & Typhoon 4.3 turbo
87-90 Pontiac Sunbird Turbo 2.0
84-86 Sunbird (actually any J-car) turbo 1.8

3 Bar GM part # 16040749
1989 turbo Pontiac trans am

When swapping heads from tbi SOHC to DOHC the engine side of the wiring harness needs to be swapped to the same year harness as the PCM/head. The SOHC PCM needs to be changed to the DOHC PCM of the same year grouping as the head (no matter what). If you have an auto, you must swap to the appropriate year DOHC tranny also.

If going from mpfi SOHC to DOHC, the harness doesn't need to be changed.

95 used OBD-II style closed loop operation. If you want to boost and plan on having the stock computer be a part of things, pre-95 is better. You can run rich at boost/part throttle. 95 and later you can't, 99+ is even more sensitive.

When doing my swap from 95 SOHC to 96 DOHC I used the same wiring harness, but the 95 DOHC PCM I bought would not connect due to the connectors so I cut the little guide tabs off with some tile nippers and slid the connector in the PCM it snapped in and no service engine. The only problem was the 95 head has 2 temp sensors and the 96 only has one so I left the gauge sensor out.


1991 - 1999 Have the original clutch design.
2000 - 2002 Have the self-adjusting hydraulic POS.
1991 - 2002 Have the same flywheel and throw-out bearing.


Manual Transmissions:


MP2 and MP3 have different gear ratios

Automatic Transmissions


*Swapping Auto trannys betw SOHC and DOHC and vice versa will lead to many issues which you don't want to deal with

*Auto to manual swaps require many things in addition to the tranny. DO YOUR HOMEWORK regarding ALL of what's needed before you start. The info is on the net and is not re-typed here.

Fuel System:

1991 - 1997 Have the wonderful fuel return line.
1998 - 2002 Have the returnless fuel system.
1999(?) - 2002 have a plastic test port.
91-94 fuel pressure regulators where non-adjustable.
95-97 fuel pressure regulators where adjustable.
91-94 aluminum fuel rails will not fit 95-97 intake manifolds due to the bolt pattern and fuel lines being plastic.

Return type fuel rail used on 2003-04 Cavalier and Sunfires will convert "returnless" type fuel rail on 2003-04 ION. You will need to convert/replace tank unit AND route a return line back to the fuel tank as well (or at least as far as the T-fitting at the fuel filter) The 2 line JBody filter can then replace the 3 line version in this mod.

Also, I understand the axles are larger on post '98-'99 cars?

The spline pattern for 98 and up seems different. I know '98 to '93 are different, as I have parts for both. I pulled the '95 axle real quick and it has the same spline pattern as the '93.

Of course, the ABS axles are thicker, and are preferable to the non-abs axles for anyone who's ever launched their car. They should be able to be used w/ or w/o abs, I'll verify that when I go to the parts yard.

The rear disc brakes from any s-series with abs will fit any non-abs s-series.

Oil pans:
91-98 oil pans have a clearance problem when installing the windage tray from a 2000+up into your engine so get the oil pan along with the windage tray. The last 2 nuts hold the oil pan up about 1/4" off of the rail

Belt Tensioner:

The belt tensioners from 91-97 are manufactured by Gates. From í98-í02, they are manufactured by Dayco. The OE Gates tensioners fit any year, the OE Dayco tensioners do not fit 91-94, Iím not sure about the 95-98 blocks though. The tensioner is too deep for the hole it sits in, 98+up have a bigger hole in them to accommodate the new tensioner. The aftermarket Gates tensioner should be avoided if at all possible, OE is best.

"What belt bypasses the P/S and A/C?"

Survey says: Saturn part# 21007093. Gates part# (for SOHC, donít know about DOHC) K050551

Instrument cluster:

1991-1992 Instrument clusters can't be used with the 93+ wiring harness unless the wires are moved to the proper places in the connector face (some of the wires are in different places).

Disk Brake Conversion

Yeah for some reason Saturn decided to change the E-brake cables six different times. The models listed below each have their own style E-brake cable. There are two different lengths (short wheelbase, and long).

Also, in '95 Saturn decided to change the connector at the E-brake cable. This continued till midway through '97, then they went BACK to the original style.

91-94 SC/SC1/SC2

91-94 sedans and wagons and all 97-02 cars (97 with VIN#s VZ334256 (sdn) VZ334335 (wgn) and VZ334269 (cpe) & higher

95-96 SC1/SC2

95-96 sdns, wgns, all 97 models with VIN #'s VZ344255 (sedans) VZ344334 (wagons) and VZ334268 (sedans) and prior


Fel-Pro Gaskets & Seals:

Head Gasket: 9968 PT
Intake Gasket: MS 95632
Intake Gasket: MS 95630
Throttle Body Gasket: 60998
91-94 Vacuum EGR Valve Gasket: 70978
(94 CA)95-98 Linear EGR Valve Gasket: 70789
Valve Stem Seals: SS 72867
Front Crank Seal: TCS 45958
Rear Main Seal: BS 40615
Water Neck Seal: 35087
Water Pump Seal: 35090

Spring Rates
OEM Springs: 126 lb/in front, 129 lb/in rear
Dropzones 450 lb/in front, 350 lb/in rear
H&R Race Springs: 310lb/in front, 250lb/in rear
H&R Sport Springs: 205 lb/in front, 195 lb/in rear
Eibach Pro Kit: 149 lb/in front, 91-159 lb/in rear
Progress Group: 200 lb/in front, 170 lb/in rear
Sprint 2" Springs: 200 lb/in front, 140 lb/in rear
Sprint 2.5" Springs: 200 lb/in front, 140 lb/in rear
KYB GR-2 front: 30% stiffer than stock
KYB GR-2 rear: same as stock

ARP studs (from Jegs or Summit)
Main Studs: Part #165-5402
Head Studs: Part #165-4202

Motor Mounts
Prothane inserts. They're only $25.99 from Summit. And that will do both dogbones. Part # PTP-7-510. Caution: Engine Vibration may significantly increase over stock.
Document adapted from
Swap Guide ('06)

Please be aware that this guide is a work in progress. The information contained within this swap guide is believed to be correct but be aware that errors maybe present.
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