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Remanufactured American Motors 2.5L L4 Engine - Concord, Spirit; Chevrolet Monza; Jeep CJ5, CJ7, DJ5, Scrambler; Oldsmobile Omega, Starfire; Pontiac Astre, Phoenix, Sunbird, Ventura
2.5L · L4 · Part DP01
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We'll confirm availability and your price on this remanufactured engine — warrantied, with a refundable core.
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4-year no-fault nationwide warranty — includedOn gas engines in non-commercial use, at no extra charge. The builder’s standard cover is 3 years, parts only. Every gas engine we sell includes the 4-year no-fault warranty with labour, at no extra charge.
- “No fault” means we do not investigate why it failed — if a covered engine fails inside the term, it is covered.
- Labour is paid up to CAD $95.00 per hour — a cap on the rate, not a flat payout — and only for the remove-and-replace hours in the Mitchell labour guide. Diagnostic time is covered up to 2 hours, and fluids up to CAD $200.00. Towing and a rental car are not covered. Anything not listed here needs to be agreed with us before the work starts.
- The 4 years start the day the engine is installed, and a claim needs proof that a professional shop installed it.
- Unlimited kilometres, and no deductible.
- Call us before any warranty work starts, so we can authorise it. Labour paid on a repair we were not asked about first is not covered.
- A claim starts with a call to us. We file it with the manufacturer, and the manufacturer pays it.
Diesel engines, and engines put into commercial service, are not covered by this 4-year warranty — the terms vary by engine, so call us for the terms on the unit you’re pricing.
Fits
- American Motors Concord, Spirit 1977–1981 · 2.5L L4
Not sure it fits? Call (780) 473-2424 with your VIN and we'll confirm.
4-year warranty included
Refundable core
Ships Canada-wide
Engine guide
GM Iron Duke / Tech IV 2.5L Inline-4
Also known as: Iron Duke, Tech IV, Pontiac 151, GM 2.5, 2500, Super Duty 4 (racing)
Overview & history
The Iron Duke — officially the Pontiac 151, later badged Tech IV — is a 2.5-litre (151 cu in) overhead-valve four-cylinder built by Pontiac from 1977 through 1993. GM designed it as a rugged, economical base engine after the aluminum-block Vega four soured buyers on experimental engineering, and it went all-in on cast iron: iron block, iron head, five main bearings, and a gear-driven camshaft with no timing chain or belt to service. It was never a performance engine — output ranged from about 85 to 98 horsepower — but it was tuned for low-end torque, easy service and long life, and it ended up in nearly everything GM sold in the 1980s: X-cars, A-body sedans, S-10 pickups, base Camaros and Firebirds, and the mid-engine Pontiac Fiero. GM also supplied it to American Motors, where it powered Jeep CJs and the four-wheel-drive AMC Eagle from 1980-83. Somewhere between 3.8 and 4.2 million were built. Fuel injection arrived in 1982, when the throttle-body-injected version took the Tech IV name. Its toughest assignment came near the end: powering the Grumman LLV postal truck.
Specs & engineering
- •Cast-iron block and cylinder head with five main bearings — the all-iron construction is where the Iron Duke nickname comes from.
- •Pushrod OHV valvetrain, two valves per cylinder; camshaft driven by gears (no chain or belt) from 1978-1990.
- •Notably oversquare at 4.00 in bore x 3.00 in stroke, yet tuned for low-rpm torque with a roughly 5,000 rpm ceiling.
- •Original reverse-flow head replaced by a crossflow design in mid-1979, alongside the Vara-Jet two-barrel carburetor.
- •Single-injector throttle-body fuel injection from 1982 — the start of the Tech IV era.
- •Swirl-port cylinder head introduced in 1984 raised compression from 8.25:1 to 9.0:1.
- •1991-92 VIN R and U engines swapped the fiber cam gear for a timing chain; 1988-up blocks are roller-cam compatible.
- •Roughly 375 lb dressed; output spanned about 85-98 hp and 123-135 lb-ft across the production run.
Generations & variants
- •1977-78: original carbureted 151 with reverse-flow head (Pontiac Astre, Sunbird, Phoenix; Chevrolet Monza; Olds Starfire).
- •1979-81: major redesign — crossflow head, Vara-Jet 2-bbl carb, relocated distributor, smaller oil pan.
- •1980-83: AMC/Jeep-spec GM 151 supplied to American Motors for Jeep CJ, Spirit, Concord and Eagle.
- •1982-92: Tech IV — throttle-body injection across GM's FWD A/N-body cars and S-series trucks.
- •1984-93: swirl-port head with 9.0:1 compression; vibration-reducing refinements followed in 1988.
- •1991-92: VIN R and U engines replace the gear-driven cam with a timing chain.
- •1980s Super Duty 4 racing variants from 2.1 to 3.2 L; rights later sold to Kansas Racing Products.
Vehicles it powered
- •Pontiac Fiero (1984-1988)
- •Chevrolet S-10 (1985-1993)
- •GMC S-15 / Sonoma (1985-1993)
- •Chevrolet Celebrity (1982-1990)
- •Chevrolet Citation (1980-1984)
- •Pontiac 6000 (1982-1992)
- •Pontiac Grand Am (1985-1991)
- •Buick Skylark (1980-1991)
- •Buick Century (1982-1992)
- •Oldsmobile Cutlass Ciera (1982-1992)
- •Oldsmobile Calais (1985-1991)
- •Chevrolet Camaro / Pontiac Firebird (1982-1985)
- •Chevrolet Astro / GMC Safari (1985-1990)
- •Jeep CJ-5/CJ-7, AMC Spirit/Concord/Eagle (1980-1983)
- •Grumman LLV postal truck (1987-1994)
Casting numbers
| 10012189 | 1979-81 GM 151 block; commonly found on Jeep CJ applications of the era |
| 10044311 | 1988-93 block (S-10/S-15, Astro, postal LLV); roller-cam compatible and regarded by builders as the strongest production casting |
| 10112514 | Mid-1991-up 'A'-code crossflow cylinder head (S-10/S-15 trucks and 1990+ 'R'-code cars) with the improved intake port design |
| 10044485 | Mid-1991-up 'A'-code crossflow cylinder head, near-identical to 10112514 |
Known issues & fixes
Fiber (micarta) camshaft timing gear failure (1978-90 gear-drive engines)
What to watch for: Sudden no-start, backfiring through the intake, or an engine that cranks but won't run — classically around the 80,000-mile mark.
The fix: Replace cam and crank gears as a matched set. Reman engines get a new timing set as standard; 1991-92 chain-drive engines avoid it entirely.
Cylinder head cracking on early engines
What to watch for: Unexplained coolant loss, overheating, white exhaust smoke, or coolant in the oil.
The fix: Pressure-test the cooling system; a cracked head is replaced rather than repaired. The flaw was largely engineered out of later crossflow and swirl-port castings.
MAP sensor and EGR faults on TBI Tech IV engines
What to watch for: Rough idle, stalling, hesitation and poor acceleration — often mistaken for a tired engine.
The fix: Replace the MAP sensor and clean or replace a sticking EGR valve. Both are inexpensive, bolt-on fixes worth checking before condemning the engine.
Inherent vibration and rough idle
What to watch for: A buzzy, shaky character at idle is normal for this big-bore four; excessive shaking usually points elsewhere.
The fix: Check engine and transmission mounts, plugs, wires and ignition timing before suspecting internals.
Did you know?
- ★A 2.7-litre Super Duty version of the Iron Duke powered the 1984 Pontiac Fiero Indianapolis 500 pace car to over 138 mph.
- ★It is the engine behind the Grumman LLV mail truck (1987-94), spec'd for a 24-year service life — many were still on delivery routes decades later.
- ★Super Duty 4 variants raced in IMSA GT, NASCAR's Dash Series and even powerboats, and in 1987 Cosworth built a 16-valve DOHC head for a 3.0-litre version (Project DBA).
- ★When throttle-body injection arrived in 1982, GM rebranded the engine 'Tech IV' — Car and Driver promptly nicknamed it the 'low-Tech IV'.