1985 Saab 900 Cylinder Head: Decoding the 8-Valve vs. 16-Valve Transition

Critical 1985 Compatibility Warning: 8-Valve vs. 16-Valve

Before purchasing, you must identify your engine. Here’s how to tell the difference:

• Valve Cover: The 8-valve engine has a simpler, more rounded valve cover. The 16-valve engine has a more complex, squared-off valve cover, often with "SAAB" and "16 VALVE" cast into it.
• Spark Plug Location: On the 16-valve B202 engine, the spark plugs are located in the center of the cylinder head between the two camshafts. On the 8-valve B201, the spark plugs are on the side of the head.
• External Oil Pipes: Early 16-valve heads used external oil feed pipes for the camshafts. If you see small metal pipes running along the top of the head, you likely have an early B202. Later versions integrated this oiling system internally.

Common Symptoms of a Failing Cylinder Head

Symptoms of a cracked cylinder head are often identical to those of a blown head gasket, as both failures allow coolant, oil, and combustion gases to mix. Look for these signs:

• Engine Overheating: This is a primary symptom. A crack can leak hot combustion gases into the cooling system, overwhelming it and causing the temperature gauge to climb.
• White Smoke from Exhaust: Sweet-smelling white smoke from the tailpipe, especially on startup, indicates that coolant is leaking into the combustion chambers and being burned off as steam.
• Milky, Foamy Oil: If you check your oil dipstick or oil filler cap and see a milky, frothy, or mayonnaise-like substance, it means coolant has contaminated your engine oil. This is a serious condition that compromises lubrication and can destroy the engine.
• Oil in the Coolant: Conversely, you might find a dark, oily sludge in your coolant reservoir or radiator. This happens when high-pressure oil is forced into the cooling system.
• Bubbling in Radiator/Coolant Reservoir: With the engine running, visible bubbling in the coolant is a sign that combustion gases are being forced into the cooling system through a crack or gasket failure.
• Loss of Power and Misfires: A leak between cylinders or into the cooling system can cause a loss of compression, leading to a rough idle, engine misfires, and noticeably poor performance.
• Unexplained Coolant Loss: If you are constantly adding coolant but can't find any external leaks (puddles under the car), the coolant may be leaking internally through the head or gasket.

Buying a Used 1985 Saab 900 Cylinder Head: A Buyer's Guide

Finding a new cylinder head for a classic Saab 900 is nearly impossible. A quality used OEM head is the best option, but careful inspection is mandatory. A used head should always be taken to a professional automotive machine shop for cleaning, pressure testing, and resurfacing before installation.

Physical Inspection Checklist

• Check for Cracks: This is the most critical inspection. Look very closely for hairline cracks, especially in the areas between the valve seats and around the spark plug holes. These are common failure points.
• Check for Warpage: Place a certified straightedge across the deck surface of the head (the flat bottom part that mates with the engine block). Try to slide a feeler gauge under the straightedge at various points. If you can fit a feeler gauge thicker than about 0.004 inches (0.10 mm), the head is warped and will need to be resurfaced by a machine shop. Check diagonally as well as lengthwise.
• Inspect Camshaft Journals: If the head includes camshafts, check the bearing surfaces (journals) for deep scoring or scratches. Minor wear is normal, but deep grooves indicate oil starvation or contamination.
• Look for Corrosion: Examine the coolant passages for heavy corrosion or pitting. Minor surface corrosion can be cleaned, but deep pitting, especially around the fire rings (the metal rings on the head gasket that seal the cylinders), can prevent a proper seal.
• Verify All Parts are Present: Ensure all camshaft bearing caps are present and in their correct locations. These caps are machined with the head and are not interchangeable.

Known Issues, TSBs, and Recalls

There are no specific NHTSA recalls or Technical Service Bulletins (TSBs) for the 1985 Saab 900 cylinder head. However, the most common known issue for the Saab B-series engine is head gasket failure at high mileage, typically after 150,000 miles or more. This is often caused by the natural stress of many heating and cooling cycles on the aluminum head and cast-iron block design. Overheating the engine significantly increases the risk of both head gasket failure and a cracked cylinder head.

Replacement Overview & Difficulty

Replacing the cylinder head on a Saab 900 is a complex and time-consuming job, not recommended for a beginner or DIY mechanic without significant experience.

• Difficulty Rating: 5 out of 5 (Very Difficult)
• Estimated Time: 10-15+ hours for a professional.
• DIY Feasibility: Not recommended for novices. This is an advanced repair that can cause catastrophic engine damage if done incorrectly.
• Special Tools: You will need a special E-16 external Torx socket for the head bolts, a reliable torque wrench, and an angle gauge for the final torque-to-yield tightening sequence.

Frequently Asked Questions (FAQ)