Here is my list of the worst engines ever made (ill add the worst first, but after the first few they won't be in any particular order). I might have forgotten a few, but I left out some clichés on purpose (like the Caddy V8-6-4)
I appreciate additions and CSBs about bad engines
1) Chevrolet Vega 140ci aluminum engine. Problems associated with not using steel liners as well as cooling problems. Timing belts weren't sturdy yet and often snapped prematurely.
2) Triumph Stag 3.0l V8. Why use the perfectly good Buick 215 when you can mesh 2 dolomite engines together? cooling, durability and timing chain problems.
3) Cadillac HT4100. fuel injected aluminum V8 with... 130 hp. And a litany of reliability problems.
4) Olds 350/4.3 diesels. Gasoline engine parts like con. rods and head bolts that aren't built to the pressures of a diesel, soured the diesel brand in the US for good. Great MPGs, though.
5) Toyota 3ZVE. Poor reliability and power for a V6 Toyota.
6) Chevrolet 200 and 229 V6s (who remembers those?) . Awful boat anchors.
7) Ford Powerstroke 6.0L.
8) Pontiac 3.4 DOHC.
9) The "renesis" RX8 engine.
10) whatever the hell was in the land rover discovery.
11) Any twin turbo BMW
12) Saab 3.0 V6
-The Audi engine in the 924. I believe with the US emissions, it only made 95 HP, and it was almost twice the price of an RX7.
-Delorean PRV V6. expensive exotic with a 130 hp V6.
-GM 2.8 and 3.1 V6s.
-GM iron duke and pushrod 2.2.
-Buick 231. (125 hp)
-ford 255ci V8 (debored Windsor with 120 hp)
-Olds 260 V8 (weak 110 hp but economical and reliable)
-BMW "e" 2.7l engine. Again weak but economical
-Ford Vulcan V6.
Good performers with bad reliability.
Buick 231 turbo. For the malaise era, it had great power but having a non cooled turbo with a 2bbl carb gave it poor reliability.
Oldsmobile Quad 4. Very fast (190 hp) 4 cylinder, but not terribly reliable.
Cadillac Northstar. Great power and V8 MPG, but unreliable, especially early on.
VW/Audi 1.8t (MK4/B5-B6 generation). Especially mounted lengthwise with the shallow oil pan.