Buick 225 - V6

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1967 Sportsman LDFV © L.Shuster

Last Updated:

22 December 2006

The Buick 90-degree V6 - 225 CID, or The Story of the Little Engine that Could
a.k.a. "The odd-fire "Nailhead"

Buick 225 CID, Odd-Fire V6 © L. Shuster

In 1966, Evinrude and OMC offered a choice of three engines in the Sportsman. All were Inboard-Outboards using the OMC electric-shift "stringer" stern drive. The outboard versions (Sweet '16 and Sport '16) were discontinued for the 1966 Evinrude boat model lineup, after a two-year run. OMC was years ahead of the marine-industry in offering turn-key, ready-to-run boat-trailer-power packages, that required no dealer rigging or setup.

  1. The OMC-outboard-derived, two-stroke, 90 hp - 90 CID - V4
        (est. wet power-head weight: 120 lbs., est. outdrive weight: 170 lbs)
  2. The GM-built, four-stroke,  Chevy II-based, twin-carb, 120 hp - 153 CID - I4
        (est. wet power-head weight: 375 lbs., estimated HD outdrive weight: 215 lbs)
  3. The four-stroke, Buick-designed/Kaiser-built  "Dauntless" Jeep, 150 hp - 225 CID - V6
        (est wet power-head weight: 442 lbs., estimated HD outdrive weight: 215 lbs))
    Complete 225-V6 engine specifications here.

Note the classic Buick "nailhead" overhead valve covers in our Sportsman. OMC pioneered the use of V6 marine engines, an engine format that continues to be popular some forty years later. Ward's Automotive has rated the Buick V6 as one of "The 10 Best Engines of the 20th Century."

"General Motors Corp. Buick V-6 (1962):  Buick's 90-degree V-6 is the poster child of a bad idea turned good through fastidious refinement. In 1962, this engine was rudely chopped from a V-8 to supplant a troublesome all-aluminum (Fireball 198) V-6. Unequal firing intervals caused so much idle shake that Buick soon dumped its V-6 and tooling was sold to Kaiser-Jeep in 1966. When the first energy crisis prompted a rethink, Buick's V-6 returned home. A continuous refinement program began with a split-throw, even-firing crankshaft in 1978 and culminated with a top-to-bottom overhaul for 1995.

In spite of GM's hidebound adherence to a pushrod valve train and cast-iron construction, Series II 3800s' still excel in packaging efficiency, fuel economy, smoothness and reliability."

In fact, the current EFI Series II 3800 Buick V6's (L67 -- supercharged) & (L36 -- normally aspirated)  have been successfully adapted for marine applications by Wasp Marine, Ltd., of New Zealand. Wasp Marine offers complete supercharged marine Buick V6's or conversion kits (manifolds, cooling, drive adaptors, etc.) for the current Series II (even-fire) Buick V6 engine.

Improving performance and reliability of the  Odd-Fire Buick V6

Holley four-barrel carburetor and Offenhauser Intake Manifold

Our Sportsman (as shown above) has been retro-fitted with an aftermarket Holley Marine 4160, four-barrel carburetor, rated for 450 cfm on an Offenhauser 360-degree manifold. Setup features an electric choke and vacuum-actuated secondary barrels. Estimated brake horsepower is now 175 - 180 horsepower @ 4400 RPM, roughly a 20 percent increase over the stock Rochester 2-barrel carb and original points-coil-distributor ignition system. Torque was originally specified as: 225 ft-lbs @ 2400 RPM.

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GM HEI "High Energy Ignition" (electronic) System

The original 1966 (2-amp), coil-points and distributor ignition can only output about 20-kilo Volts to the spark plugs. General Motors introduced the (4-amp), 30-kilo Volts, HEI electronic ignition system in 1974-75.  GM engineers designed the original HEI system to replace the coil-points ignition that had been around for decades. By the mid-’70s, leaner mixtures for tighter emissions demanded greater voltage and more spark energy to initiate combustion. An HEI distributor is still an inductive-discharge ignition, but it exchanges the points for a solid-state electronic switching device called a module. Since this system produces more HT voltage and draws a higher amperage current, it demands a larger-diameter distributor cap to minimize arcing and cross-firing between adjacent spark plug terminals inside the distributor cap.

This larger cap also offers space to position the coil internally, making the HEI "system" a self-contained (coil/distributor) unit. All you have to do to run this system is to apply 12 volts from the ignition switch via 10 or 12 gauge wire, directly to the distributor and you’re ready to run, bypassing the original coil and ballast resistor. The hotter and fatter spark results in faster, more reliable starting (something I like in my boat), increased horsepower, torque, and improved fuel economy as well as leaner and cleaner emissions, especially at higher altitudes (we typically run at 6000' Above Sea Level). 

Remember to increase spark spark gap from .035" to .045", but you CAN thankfully forget about ever setting the distributor points again. The firing order is 1-6-5-4-3-2. The even-numbered cylinders are starboard, while the odd-numbered cylinders are port-side. The heads feature an unusual valve arrangement: E-I-E-I-I-E (port bank, stated from front to rear, or starboard bank, stated from rear to front.)

CRT Performance, of Buzzards Bay, MA, offers rebuilt HEI units, modified for odd-fire V6's, complete with HT wire kits, modified and ready to drop into your 225/V6 Buick-powered boat or Jeep 225/V6. Ask for Glenn, he knows his stuff. It's a great service, considering how very few odd-fire V6's were originally built with HEI. The larger HEI distributor is a tight fit on a marine installation, but with a little work it can be made to fit.

Another electronic ignition upgrade alternative is available from Pertronix, Inc. Their Ignitor electronic module replaces the points and fits inside the stock distributor, retaining stock appearance.

And oh, by the way, at least with this odd-fire V6, there's no bothersome idle shake.

Buick V8 HEI Conversion Info -- 

Buick V6 and V8 Engine Parts Directory --

History of the Buick OHV Nailhead

In 1953, in the beautiful Harley Early-designed Skylark,  Buick engineers introduced a unique V8 featuring a vertical Over Head Valve (OHV) head that featured a "pent-roof" shaped combustion chamber. This head design permits excellent low-end torque and fuel economy characteristics with a free-flowing (45-degree) intake tracks, but the design does compromise the exhaust ports' ability to breath at higher RPM's with restrictive 135-degree bends. It earned the nick-name "Nailhead" from the unique, vertical orientation of the valve covers, making it easy to identify Buick 264, 322, 364, 401, 425 CID OHV V8's prior to 1970. See Buick Engine specifications.

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Buick Introduces the first mass-produced V6 in the 1962 Buick Special & Skylark

Source: Buick Motor Division, 
Copyright © General Motors Corporation,
all rights reserved

The V-6, one of the most popular engine designs in use today, was first developed by Buick for its 1961 Special. It was the first use of a V-6 in a mass-produced U.S.-built car. (Note: the GMC Truck Division had successfully introduced a 60-degree V6 in 1960.)

Joseph D. Turlay, Buick's top engine designer of the period, responding to Buick's need for an engine for the new small car, said he could build a 90-degree V-6 quickly by simply eliminating two cylinders from Buick's 215 aluminum V-8. (Note: Buick sold the 215 V8 aluminum tooling to Rover in 1967; and the Buick-designed aluminum-V8 only recently (2004) ceased production in the Land Rover Discovery.)

"We got it into full production in less than a year," Turlay said. "It had a new crankcase (and a cast-iron block instead of aluminum), but the rods, pistons and valves were nearly the same as those of the V-8."

The new engine resulted in the Special earning the "Car of the Year" award from Motor Trend magazine for "pure progress in design, originative engineering excellence and the power concept for the future expressed in America's only V-6 automobile engine."

In the muscle-car era of the late 1960s, Buick phased out the V-6 and sold the tooling to another company (Kaiser Jeep). But in the fuel crisis of 1974, Buick re-purchased the tooling, re-introduced the V-6 and began a series of improvements and design changes which led to the powerful, smooth, responsive and fuel-efficient power plants of today.

In 1976, Buick's pace car for the Indianapolis 500 was powered by a turbocharged V-6 -- the first V-6 ever used in any Indy 500 pace car. Buick's first front-wheel drive car, the 1979 Riviera, was offered in two models -- a standard version with a V-8 and an S Type, with a turbocharged Buick V-6. The S Type won Motor Trend's "Car of the Year" award.

In 1986, when Buick offered an intercooled turbo V-6 in the Regal Grand National, auto magazines labeled the Grand National as America's quickest automobile. The Buick V-6 became a major factor on the race tracks of the country as well as a mainstay among production power plants.

It all started with the 1961 Buick Special & Skylark.

"If someone had told me in the sixties that the Buick V6 would be the most common engine found in all GM cars -- I would have laughed at them."  -- www.BuickStreet.com

More Compact B-O-P V6-V8 Engine Development History -- www.442.com

But why an odd-fire V6?

Solving the 90-150-90-150-90-150 mystery and why this engine sounds so unique. Hear and view the Buick odd-fire V6 pushing our Sportsman below:






Buick engineers first introduced the 90-degree "Fireball"198 CID V6 for the Buick Special & Skylark in 1961. In 1964 Buick bumped the V6's displacement to 225 CID. The 90-degee 225 CID V6 engine was essentially the 300 CID V8 with two cylinders removed.  A 231 CID odd-fire V6 was offered from '76 - '78. For smoother idling, Buick switched to a (weaker) split-pin crankshaft, resulting in an even-firing V6 with the 231 & 252 CID V6's midway through the 1977 model year.  See Buick Engine specifications.

The Utah Connection -- Hayes Brothers Jeep; (Read how GM sold the V6 engine to Kaiser-Jeep)

The Life & Times of the Buick V6 (The Little Engine That Could)
By Ken Mosher