Engine aluminum or cast iron?

On a 1990 Ford Explorer the engine block is cast iron, and the cylinder heads are aluminum .

You need a repair manual, Your favorite Auto parts store, or try filespeep.com or manualslib.com

Block and Basics
Displacement: 350 cubic inches, 5733 cubic centimeters, 5.7 liters
Block Material: Cast Iron
Main Bearings: 2-Bolt Centers and Ends (The Corvette LT1/LT4 had 4-bolt mains)
Stroke: 3.48"
Bore: 4.00"
Compression Ratio: 10.4:1
Combustion Chambers: 54 cubic centimeters
Factory Redline Rating: 5700 Rotations Per Minute

Bottom End
Piston Material: (10159437) Eutectic Aluminum/Silicon Alloy
Connecting Rod Material: (10108688) Powdered Metal
Crankshaft Material: (12556307) Cast Iron

Top End and Valvetrain
Cylinder Heads: (10168448) Cast Aluminum, 2 valves per cylinder/16 valves total, ~212 CFM flow (Impala SS and Caprice heads were made of cast iron*)
Valve Diameter: (intake- 10241743, exhaust- 12550909) 1.94 intake, 1.50 exhaust
Valve Overlap: 41*
Valvesprings: (10206040) 85 lbs, seated
Camshaft Specs (12551705): 205/207 duration @ 50*, .447/.459" lift, 117 Lobe Seperation Angle
Rocker Arms: (10089648) 1.5:1 Stamped Steel
Timing Chain: (10128485) Powdered metal link

Intake and Fuel Delivery
Fuel Delivery: Electronic Fuel Injection, sequential port
Injector Size: (17124248) 3.0gps, 22lbs/hr speed density (1992-1993), 24lbs/hr mass airflow (1994-1997)
Throttle Body: 48 millimeter twin butterfly
Intake Manifold: (12552137) Aluminum

Factory Power Ratings
92-96 LT1 Corvette: 300bhp, 330lb-ft
1996 LT4 Corvette: 330bhp, 340lb-ft
1992 LT5 Corvette: 375bhp, 370lb-ft
93-95 LT5 Corvette: 405bhp, 385lb-ft
93-95 LT1 F-Body: 275bhp, 325lb-ft
96-97 LT1 F-Body: 285bhp, 325lb-ft
96-97 WS6/SS: 305bhp, 335lb-ft
93-97 Firehawks: 315bhp, 340lb-ft

Factory LTX Camshaft Specifications**:
1992 Y-body: 205/207 0.451/0.450 lift 117 LSA
1993-1995 Y-body, F-body: 202/207 0.450/0.460 lift 116 LSA
1994-1996 B-bodies (including L99 4.3L): 191/196 0.418/0.430 lift 111 LSA
1996 Y-body, 1996-1997 F-body: 200/207 0.447/0.459 lift 117 LSA
1996 Y-body, F-body LT4: 203/210 0.476/0.479 lift 115 LSA


hope this helps

Freeze plugs are round, metal/aluminum plugs located in various spots on the engine block. Their purpose is to prevent the engine block from cracking in freezing weather IF you don't have anti-freeze in your car/truck. The plugs will pop out as the water freezes (and expands) releasing the water from the engine block. Kind of a safety-valve device.
I am questioning your "mechanics" dstatement that they are 'shot'. They are either good (not leaking) or bad (leaking). If they are "shot" then you should be loosing antifreeze all over the place. Ask your "mechanic" for a reasonable explanation for his diagnosis.
I would suspect something else other than the freeze plugs causing your overheating problem (i.e. stuck thermostat, clogged radiator, cooling fans not working, blown head gasket)...
I would try ANOTHER mechanic, maybe one recommended by a friend. Lots of so-called mechanics out there that couldn't fix a pedal car....

3 choices, 4.8L, 5.3L, or 6.0L. All small blocks Generation III GM Vortecs. I need the RPO code from the sticker inside the glove box to determine which you have or the emmisions sticker on the fan shroud under hood should label what the engine size is. They all look the same but the 6.0 L has cast iron heads. All others are aluminum, Hope this helps

1990-1991 OBD0*
Engine: B18A
Cylinder Arrangement: Inline 4 Cylinders, Transverse
Type: Water cooled, 1.8L, 4 cylinder, 16 valve, DOHC
Displacement: 111.9 cu in (1834 cc)
Bore & Stroke: 3.19 in x 3.50 in (81mm x 89mm)
Compression Ratio: 9.2 : 1
Valve Train: Double Overhead Camshafts, Belt Driven
Fuel System: Programmed Fuel Injection (PGM-FI)
Horsepower: 130 hp @ 6000 rpm
Torque: 121 lbs.-ft. (16.8 kg-m) @ 5000 rpm
Redline: 6500 RPMs
Engline Block: Aluminum Alloy with Cast Iron Cylinder Liners
Cylinder Head: Aluminum Alloy

No.

the head gasket go in these cars because of what they call "dissimilar metals" all that means is you have an aluminum cylinder head and cast iron block. the problem is, the both expand and contract at different rates when driving and cooling down. and sometimes this actually creates the gasket to fail over time..there is a revised gasket you can get right from the dealership. its un upgraded head gasket..and if you can't find a 2.4L engine, check a local auto wreckers...

Yes, These engines are a combination of aluminum castings and cast iron castings. The orange dexcool is designed to control the acidity of the coolant. If you put in green it is going to eat away at the aluminum. It could cause leaks in your head gaskets, intake gaskets, water pumps and promote clogging of important coolant areas in the block.

use a magnet on it if it sticks it is cast iron, if not it is aluminum