From the book Dodge Viper by Daniel F. Carney:
Looking back, it seems astonishing that Team Viper was also building a radical new engine from a nearly clean sheet of paper, to a deadline pace. Ruling out the truck engine meant the team members had to build what they wanted themselves.
Said Francois Castaing "It was already April 1989. If we wanted the car to be ready by January 1992, we needed to really get going. But the timing for the truck engine was a year later. It also became obvious, when we looked at it more thoroughly, the weight of the iron engine was too high and the power we would get from it wouldn't be sporty enough." Francois was in charge of truck engineering at the time.
Said Roy Sjoberg , Team Viper's new executive engineer,"We rapidly ascertained, the truck guys and myself, that where we wanted a 6,200-rpm redline, the truck guys didn't really care to go over 4,200 rpm. They were interested in low-end torque, not horsepower at high-rpm levels where we were. They were not concerned about weight. Truckies don't like aluminum blocks. They're not as forgiving, and truck people like to have things that are pretty bulletproof.
"Not a lot could be learned from our truck V-10 development. Both engines were V-10s, but one was aluminum and one was iron; ours was sequential-fire individual-injected, and the truck's was group-injected, so it ended up having air pumps and things. We only needed EGR to meet the initial emission requirements, as well as a catalyst. The truckers had to put some other things on it. We ended up with the same dimension pushrod and that was it. But even there, we used a higher-grade material because of our power and rpm requirements."
In the end, there wasn't a single shared part with the Ram V-10 that was being built elsewhere within Chrysler.
As the notion to use the truck engine quickly faded, Team Viper went through a nervous period asking "Now what?" Said Castaing, "Bob Lutz was very anxious for the car to proceed, so he said maybe we can use the 5.9 V-8 instead. I said, "No, no, no, the V-10 is so magic as part of this car. We have to find a way to do an engine, even if it is a derivative of the truck engine. we have to explore a way of doing that."
"I was convinced that if we didn't make too many mistakes, there was a chance for us to have a better engine, a very distinctive engine in the V-10 and not another pumped-up V-8 like in the Corvette. Over the course of the summer, finally, Bob Lutz, who was concerned that this was not cutting it timing-wise, started relaxing. Obviously the engine was way more powerful than a V-8, so it was good from that perspective. The engine turned out to be, in my view, part of the legend of the car. I'm glad we insisted at the beginning that it had to stay a V-10." But the engine wasn't just part of the legend of the car, it was the car.
"At the time, we owned Lamborghini, so I called them and said, 'I need your help to convert as quickly as we can the drawings of a truck engine into an aluminum design from a cast-iron design. And I want your very fast prototyping sources to produce a math casting so we can start prototyping an engine for the Viper as quickly as we can.'
"They agreed to do that, so [engine manager] Jim Royer took the design and flew to Bologna, Italy, where Lamborghini's Formula One team was. Lamborghini assigned a couple [of] engineers and a drafter, and they modified quickly the block design, a casting of the block and the head to make it more like a car engine."
But it wasn't that simple. "Lamborghini was an acquisition we had," Sjoberg said, "so Francois thought that perhaps Lamborghini could help us in converting an iron V-10 concept to aluminum, because they should know about those things. They were designing the basic individual components from iron to aluminum. Our contract with them was to produce five aluminum engines, our basic design. They were to deliver five engines, running. We ended up getting one set of engine parts, nonrunning. At that point we separated."
"They were very oriented to high rpm, not oriented to torque, but oriented to horsepower at high rpm, they were not so worried about produceability and not so worried about reliability, and I was very insistent that we were going to have an engine that met all the basic Chrysler Corp. engine life and durability requirements, both dynamometer and vehicle. They weren't worried about that at all."
"Lamborghini did help with the base concept of how to convert to aluminum. and they provided some aesthetics of the outward part of the engine, how it looks. But the components we got from them, we ended up redesigning substantially to assure adequate durability. They weren't worried about 300 hours of dynamometer durability at wide-open throttle. That wasn't their concern. So, yes, they helped us with some directional issues, but in the end, none of their components lasted and were totally redesigned."
The Viper's engine program had now gone in opposite directions: too much truck-like torque and not enough rpm or power in the Ram engine, and in the Lamborghini execution there was too much rpm and not enough torque or reliability. The Viper eventually found its middle ground between Clydesdale and Thoroughbred By Team Viper's simply doing it themselves.
The frustrating relationship with Lamborghini aside, the bare engine block is a work of art. There is an Italian influence. Its massively deep-skirted design, with six-bolt main bearings, seems intended for racing. The block is unique in having an external water manifold to carry coolant to each cylinder individually. The thermostat was originally mounted at the back of the engine, so coolant hoses snaked over the engine to the radiator. The head casting was designed to provide a good swirl of the intake charge for efficient combustion to reduce emissions. At the bottom end, the Viper engine substituted a forged crankshaft with enlarged bearing journals for durability.
The weight-saving aluminum construction whacked 100 pounds off the original engine's weight compared to the cast-iron truck engine. But the engine weighed a still-hefty 716 pounds; 80 pounds more were trimmed for the 1996 GTS Coupe.
