Editing Iron Duke engine (section)

==Tech IV==
[[File:GM Engine Tech4.png|right|"Tech IV" decal]]

Iron Dukes were fitted with [[fuel injection]] (TBI, via a single injector in the throttle body) in 1982. This version was christened the '''Tech IV''', though ''[[Car and Driver]]'' later ridiculed it as the ''low''-Tech IV.{{citation needed|date=August 2019}} Power output increased to {{cvt|90|hp|kW|0}}.<ref name="PopSciTBI">{{cite magazine|title=Are carburetors kaput? Coming: throttle-body injection |date=February 1982 |last=Dunne |first=Jim |magazine=Popular Science |page=52 |url= https://books.google.com/books?id=GbTTw-z6NH0C |access-date=27 August 2019}}</ref>

This was replaced by a swirl-port head with 9.0:1 (instead of 8.25:1) compression ratio in 1984 for a {{cvt|2|hp|kW}} gain. Other additions for 1985 included roller lifters, improved bearings, and a new [[crankshaft]]. Several significant changes were made in 1987, which included: an improved cylinder head, intake manifold, and [[throttle-body fuel injection]] module; a more-modern serpentine belt with an automatic spring-loaded tensioner for the accessories; and a [[Distributorless Ignition System]] (DIS). This revision to the engine increased power to {{cvt|98|hp|kW|0}}. In 1988, a [[balance shaft]] was added to smooth engine vibrations. Up to this point, the engine incorporated a 'dogbone' upper front engine mount secured to the cowling of the vehicle's hood latch, aiding in controlling the vibration. Further improvements in later years included new pistons, rods, crankshaft, and an in-pan oiling system. The most powerful variant of the Tech IV raised the rev limit to 5500&nbsp;rpm, and achieved {{cvt|110|hp|kW|0}}. The Tech IV uses the same [[Bell housing|bellhousing]] pattern as the 2.8-liter ''[[GM 60-Degree V6 engine|60-Degree]]'' V6. Over the years, the Tech IV engine has proved to be a reliable workhorse for owners when not pushed to its limits. All 1978-1990 Iron Duke engines used a [[micarta]] [[camshaft]] gear that meshed directly with a steel gear on the crankshaft. 1991-92 VIN R and U engines used a timing chain instead.

The [[Grumman LLV]] (Long Life Vehicle) built from 1987 until 1994 for the United States Postal Service for use in mail delivery were initially powered by the Iron Duke engine. The Postal Service specifications called for a 24-year service life and those with 2.5-liter engine have surpassed expectations.<ref>{{cite web |last1=Weinstein |first1=Joshua |title=GM 2.5L Iron Duke I4 Engine Guide |url=https://www.junkyardmob.com/guides/gm-iron-duke |work=Junkyard Mob |date=June 8, 2022 |access-date=January 20, 2023}}</ref>

<gallery widths="200px" heights="200px">
File:2.5l tech 4 engine.jpg|"Tech IV" engine
File:1990 GM Iron Duke engine cut-away exhibit.jpg|1990 GM Iron Duke engine with parts cut away to reveal the inner arrangement
</gallery>

{{hidden begin
|title      = Applications:
|titlestyle = background:#88FF88; text-align:left;
|bodystyle  = text-align:left;
}}
* 1982–1992 [[Buick Century]]
* 1982–1991 [[Buick Skylark]]
* 1985–1987 [[Buick Somerset|Buick Somerset/Somerset Regal]]
* 1985–1990 [[Chevrolet Astro]] Cargo Van
* 1982–1985 [[Chevrolet Camaro]] 
* 1982–1990 [[Chevrolet Celebrity]]
* 1990–1992 [[Chevrolet Lumina]]
* 1985–1993 [[Chevrolet S-10]]
* 1985–1987 [[Chevrolet S-10 Blazer]]
* 1985–1987 [[Chevrolet S-10 Blazer|GMC S-15 Jimmy]]
* 1985–1993 [[Chevrolet S-10|GMC S-15/GMC Sonoma]]
* 1985–1990 [[Chevrolet Astro|GMC Safari]] Cargo Van
* 1987–1994 [[Grumman LLV]] ([[United States Postal Service|USPS]] delivery vehicle)
* 1985–1991 [[Oldsmobile Calais|Oldsmobile Calais/Cutlass Calais]]
* 1982–1992 [[Oldsmobile Cutlass Ciera]]
* 1982–1991 [[Pontiac 6000]]
* 1984–1988 [[Pontiac Fiero]]
* 1982–1985 [[Pontiac Firebird]]
* 1985–1991 [[Pontiac Grand Am]]
{{hidden end}}