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4 bucket 67's 1967 GTO

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The 1961-1963 Trophy 4 / Indy 4 Engine

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9 hours ago, Frosty said:

The Trophy 4 engine (sometimes called the Indy 4 engine) is probably the most unique engine Pontiac every developed. Things started back in 1958 when GM was reacting to the rising popularity of imports and it was feeling the effects of the ’58 recession, GM started to develop its own version of a compact cars, starting with the Chevrolet Corvair, with its rear-engine air-cooled flat six engine. Buick, Olds, and Pontiac could have replicated the Corvair but instead chose to go their own way. The ’61 Buick Special and Olds F-85 got a new V6 (which would eventually evolve in the 3800) and a small 215 cu in aluminum V8 – both engines came from Buick. 

John DeLorean chose to take Pontiac in a different direction and build its own economic engine. The result was a revolutionary approach: a transaxle--adapted from the Corvair--mounted at the rear for good weight distribution, connected to a four-cylinder engine through a flexible steel driveshaft (often called the “rope driveshaft”). DeLorean wanted an inline four for the ‘61 Tempest. The only problem was that Pontiac did not have a 4-cylinder engine in its inventory, and not enough money in the budget to develop a new one from scratch. But it did have its celebrated, 389-cu.in. V-8. Could it be split to make a workable four?

In 1959, Pontiac had increased it’s V8’s stroke to 3.75 in, thus raising engine displacement to 388.9 cu in. This was the beginning of factory supplied performance items such as 4 bolt main bearings and windage trays to reduce friction from crankcase oil. The 389 would remain the standard Pontiac V8 engine through 1966. The 389 came in a wide variety of configurations that ranged from 215 to 368 horsepower. The 389 was the standard engine for the Pontiac GTO from 1964 to 1966. Beginning in 1961 the Pontiac V8 389 (and 421) was dubbed the Trophy V8, due to its many victories in racing after just two years.

Since the 389 was called the Trophy V8, the new 4-cylinder engine was called the Trophy 4 by extension. In some racing corners, it was called the Indy 4. The Trophy 4 was a 45-degree inclined 194.4 cu inline 4-cylinder engine created from the right bank of the 389. With an identical bore and stroke of 4 1⁄16 in and 3 3⁄4 in, it was precisely half the displacement of the 389.

Initial tests were encouraging. A Pontiac V8 with one bank of cylinders disabled was found to be capable of pushing a full-sized Pontiac over 90 miles per hour, with acceptable fuel economy for the day. By using the 389 as the basis for the 4-cylinder, the costs of preparing the four cylinder engine for production were significantly smaller--it shared its pistons, rings, connecting rods and more with the 389, and it even used the same tooling for its cast-iron block, thanks to shared dimensions. The crankshaft, camshaft, oil pan, intake, and other parts were unique to the four cylinder.

The engine was offered in three horsepower ratings:

  115hp, with 8.6:1 compression and a two-barrel carburetor

  140hp, with 10.25:1 compression and a two-barrel

  166hp, with 10.25:1 compression and a four-barrel

The Trophy 4 was not an ideal compromise or design, by any stretch of the imagination. It retained about two-thirds of the mass of the 389, tipping the scales at a quoted 557 pounds, or 200 pounds more than the optional Buick 215-cu.in. aluminum V8. And its large displacement—194.4 cubic inches, made it prone to significant vibration. There was little the engineers could do about the weight and only so much they could do about the shaking.

A downside of the engine’s design and configuration was engine vibration. An inline four-cylinder engine suffers from inherent secondary imbalance resulting from its 180-degree crankshaft. In its design, the two outside cylinders move together simultaneously, as do the two inside cylinders. Due to geometry and the ignition cycle, a piston descending from top dead center will always move quicker through the first 30 degrees of crankshaft travel than a piston moving upward from bottom dead center, meaning that more mass is moving downward than is moving upward, causing a shaking in the vertical plane. Today, engineers consider the installation of twin counter-rotating balance shafts a necessity for engines larger than 122 cu in (2.0 L). The V8-based design of the Trophy 4 lacked balance shafts due to cost (note - balance shafts didn't get popular at GM until the late 1980s/early 1990s). It was instead cushioned by a flexible rubber engine mounts designed to isolate the engine from the rest of the car, and its forces were further dampened by the Tempest's unusual drivetrain (which distributed forces by the engine being bolted directly to a rear-mounted transaxle via the solid outer tube of its driveshaft. The timing chain in the Trophy 4 was originally the same as the 389’s but was prone to stretching and breaking from the inherent engine vibration; therefore a special high-strength version was developed as a replacement.

What killed the Trophy 4 was not its tendency to shake, or its habit of snapping timing chains, instead it was Pontiac's decision to move away from the transaxle design when the Tempest was re-designed from a compact to an intermediate for 1964. The slant-four was dropped as the base engine, replaced by the 215-cu.in. straight-six overhead valve engine from Chevrolet (this Chevy straight six lead directly to the development of Pontiac's OHC 6 engine in 1967).

Today, the Trophy 4 can be made to produce 300hp in normally aspirated form, and more than 500hp with either a turbocharger or supercharger, if balanced and built with modern parts and techniques. These motors are much smoother than new too. They are very strong engines that weigh about the same as a small block Chevy",according to Ken Freeman, owner of East West Auto Parts in Tulsa, Oklahoma.

https://books.google.com/books?id=0tsDAAAAMBAJ&pg=PA4&lpg=PA4&dq=pontiac+"trophy+4"&source=bl&ots=in8hgEZRl9&sig=Ya4PU_4exyy5QmhqctXM3-qnf4o&hl=en&sa=X&ved=0ahUKEwjC-aat95vZAhUJbK0KHXYzAHY4FBDoAQguMAI#v=onepage&q=pontiac "trophy 4"&f=false



Cut Away of the 194


The 194 in a stock Tempest



Blown Trophy 4



4-barrel intake manifold

Great job of covering the whole design, front to back. I never thought Delorean got enough credit for his other work.

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Excellent and thorough article , Frosry! :cheers:  The "Indy 4" is indeed a forgotten engine, thanks for the reminder. When I was a kid, my older brother (by seven years) had a '62 Tempest with the 4 cylinder. That's all I remember about it, because he had an Austin Healey 3000 before the Tempest and I couldn't believe he got rid of the really cool Healey  and got this (in my 12 year old kid's opinion, lol) 4 cylinder grandma car...This was the first Pontiac in the family and I was not impressed! The Healey of course, being British, required constant "tinkering", and I think my brother got sick and tired of it and just wanted something that was cheap, reliable transportation as he was in college at Virginia Tech. Alas... no more being the cool kid riding around in an Austin Healy, lol!

Here's Mickey Thompson's Indy 4 racers...


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Thanks stratman.

A few years before John Sawruk passed away, the Michigan Widetrackers asked him to select a car for "Best Engineered" car at their annual Spring Dustoff car show,. Ater all John was a certified professional engineer (P.E.). John picked a red '63 Tempest convertible with the Indy 4 and the original rope driveshaft. John said he selected it because it was the only car at the show with this unique drivertrain combination. No other Pontiac ever had something like this - before or since.

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Great story, thankz for sharing!

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14 hours ago, Last Indian said:

Great job of covering the whole design, front to back. I never thought Delorean got enough credit for his other work.

Thanks. DeLorean was a maverick by GM standards of the day, so he ruffled a lot of feathers. So a lot of things he did have gone under appreciated.

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On 3/17/2018 at 6:00 AM, SPRINT 6 said:

IMO, this engine was an exercise in design. It was conceived at a time with no real market, it just seems someone said what if or wonder if and they decided to give it a go. More of a lets see if we can exercise. I like them due to this odd ball factor but I also have collected and built several OHC's ;)... enough said :D  

I guess I will have to write an OHC 6 piece next for you and add what Mac Mckellar told me personally about the OHC6 program.

DeLorean asked Mac to do a lot with next to nothing budget wise on the Trophy 4 program. I learned more from Sawruk on it. 

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