I have a LOT of history with that engine. Actually, THOSE engines. There were three incompatible versions of those engines between 1989 and 1995. My team was responsible for developing the dealer service procedures and service tools and parts kits for each iteration, and then for taking the engine out of production when the car and engine ended.
Actually, GM’s history with DOHC engines goes back before the LT5 to the Quad 4 that was used in Grand Am and other vehicles for several years beginning in the mid ‘80s and then every 4- cylinder engine product that followed. Then the 3.6L V6 products that started in 2007.
That was a WTF? engine to most people back in the day. I had just purchased a L98 powered Iroc in 87. And I remember most of the gear heads turned their noses up to the Lotus motor. Most of that was probably due to the complexity of working on it. Compared to the tree50s.
That and the new GM manual transmissions out of the Muncie, Indiana plant were my introduction to the fact that US automakers do a lot more to protect the customer’s service costs than European companies. Lotus designed that engine for the best performance they could get out of it. Serviceability was an afterthought. Then, when a better way to do something came along, they went for it and could care less if the change could service backward. A lot of the parts that can service a ‘94 engine cannot be used to service the ‘89 - ‘91 engines.
I've heard this same thing said about the Camaro - that GM was working on it before Ford came up with the Mustang and that the Camaro wasn't released as a reaction to the Mustang and Ford's huge success with it. I must be a cynical and skeptical person, because I didn't believe the Camaro thing either.
that'll be tough unless they go oversquare. 101x86mm (5512cc) to 8500RPM would do nicely if a bit nuts on piston speed. Question is can they do a better job of balancing the engine than Ford did and can they get the manufacturing right to support large production rates instead of crippling availability that 'hand-building them in a specialist environment' leads to. Unfortunately I doubt GM will elect to go with high RPM, keeping it around 7000 since long-stroke is what they do and the fuddy-duddies who buy these things in large numbers are too accustomed to 30 year old tech power delivery to tolerate deviating too far from it.
There is no denying that in both cases, Mustang vs Camaro launch and affordable FPC launch, Ford got there first. It does not mean GM wasn't working on it before knowing what Ford was doing. It means they both got an idea at roughly the same time, but Ford got it to market first.
Huh? The only major change was adding 4-bolt main caps in 1993. Other minor changes was to bump up horsepower. Hardly incompatible. BTW, Lotus Engineering designed the LT5 engine. Engineered in England but produced and assembled in Stillwater Oklahoma by Mercury Marine.
The 4-bolt main was the big change. What most people would not know, though is that in making those changes and the hp upgrades, the heads and crankshafts also changed. Head casting suppliers and crank forging suppliers changed. Can’t remember what year, but it was after ‘91. Most of the volume of ZR1 was in the ‘89 - ‘91 timeframe and the new cranks and heads were not backward compatible without changing a bunch of other parts. To top it off, a lot of the original ‘89 - ‘91 suppliers went out of business. I had to work with purchasing in the US and the UK to find a casting source for ‘89 - ‘91 vintage heads.
I thought everything was produced in-house at Mercury Marine, and only the electronics & fuel related parts were outsourced.
Nope. MM made relatively few parts compared to a more typical engine plant. Most actually came in from the UK. At least the castings and forgings. Can’t remember if machining was done in UK or US for most parts. I think MM did assemble heads and they may have made the exhaust manifold and some other sheet metal parts like brackets and such. Some light machining.
