1967 Pontiac GTO - Supercharged Silver Streak

Sure, the late-model guys are saying, "Big deal, a supercharged Pontiac; we see superchargers on LT1s and LS1s all the time. The current Grand Prix GTP even has one factory installed!" That's all well and good but how many supercharged vintage Pontiac-engined street cars that run 10s have you seen lately? Well, as the editor of this magazine and after having traveled the country each year to many different events, I can tell you that I haven't seen a lot. Therein lies the hook for this story. Here is yet another avenue for would-be Pontiac throttle jockeys to have their cake and eat it too--on the street and on the track--even if it's not exactly a new idea.

Bob Whitcher was searching for something a little different a few years back when he decided to run a supercharged Pontiac engine. As a result, today the Newton Junction, New Hampshire resident enjoys a street car that is docile in traffic but will run 10.90s at 123 mph at the track on slicks. For Bob, however, the road to double-duty weekend fun was paved over land mines.

Before we proceed with his tale of woe, let's get some background information. Whitcher's story begins with a 1953 Chieftain he acquired as a hand-me-down from his Dad. Bob then moved up to a '62 Catalina with a dual-quad 389 and a stick, in which he perfected his drag strip technique, and split ownership with a friend. By 1969, he was hunting for a Goat to race and when finances allowed, he scored a 1965 Tri-Power GTO for $650 out of a junkyard. He stuffed it with a 428 and went drag racing, posting consistent 12.90s at 107 mph back in the day on 7-inch wide cheater slicks. As years passed, more GTOs and Pontiac-powered machines filtered through the caring hands of Bob Whitcher including oddities like a pseudo "GTO" wagon and even a 455 Tri-Power 1961 Chevy pickup, of all things.

In 1990, Bob stumbled upon this Goat at the swap meet where he regularly sold Pontiac parts. He couldn't pass up the bright gold machine and it followed him home after he plunkd down $6,000. "It was your basic 400 automatic GTO," Bob related. "But it did have power steering, power brakes and A/C as well as a vinyl top." Soon after the purchase, Whitcher installed a 3.55 Safe-T-Track rear and swapped in front disc brakes from a 1971 Cutlass. These mechanical enhancements were followed by two years of comfortable cruising around Newton Junction. Then Whitcher's son began to race his own '67 GTO and with times in the low 14s it was quicker than Dad's. "That would not do!" Bob quipped.

So out went the 400 and in went a 421 short-block with #62 heads up top and a hot Ultradyne cam, all of which came as a result of an order Bob gave to his buddy who built it at Protech Machine (Nashua, New Hampshire). "I want to run 12-second quarters with this GTO!" Mission accomplished. With all Pontiac parts save cam and headers and with the addition of a 10-inch converter, and a shift kit for the Turbo-400, the GTO promptly twisted the stock axles into pretzels.

Next came a 9-inch Ford rear with 3.89:1 gears, Moser axles and a Detroit Locker to combat the axle twist problem and with these parts and still the factory iron intake, rejetted Q-jet and points distributor came 12.18 ETs with 111.57 trap speeds. This should have been enough for any Pontiac hobbyist to be proud of. And Bob was, for four glorious years. In that time the GTO was as reliable as an anvil and 10 times as fast. And then his luck turned. "I should have known better than to mess with a good thing but I wanted to go faster."

After reading about someone bolting an ATI ProCharger onto a Pontiac V8 in a car magazine, Whitcher ordered one up for his. He also enlisted the services of Ponti-Action Racing to build a 428 engine that would complement the supercharger. "The new [at the time] Edelbrock aluminum heads were recommended, which caused me some irritating problems early on," Bob recalled. "First, I couldn't find headers to fit. Then the slots in the heads for the pushrods were too short to work with my high lift cam so the engine bent or broke pushrods all the time." The header problem was fixed with a proper set of Hedmans from Jim Butler, the slots in the heads were modified and the engine ran great--but ...

"Another problem was that with the new engine and the blower, the GTO was actually slower than before I started. My son Matt and I tried to get it to go fast for a whole summer with no luck. Finally, at a race I met a ProCharger distributor who checked out my installation and told me that the bracketry (supplied by a different aftermarket company) placed the tensioner on the wrong section of the blower belt, which resulted in no boost from the blower." Bob then contacted SD Concept Engineering Inc. in Warwick, Rhode Island (401-732-4047). SDCE supplied him with a spring tensioner; an SDCE blower-prepped 750 cfm Holley, and also installed an SX fuel system to handle the increased load.

Whitcher finally worked out the mechanical gremlins and coaxed the GTO to 11.25 at 119.58 mph properly exploiting the efforts of Ponti-Action and the ATI ProCharger. Everything was going great. The combination had finally come together to Bob's liking and it was time to celebrate. Then came the accident. In 1999, en route to the East Coast Hot Rod Power Tour, Bob and his son were traveling on Rte. 495 when they were cut off by a stupid driver. As Whitcher explains, "I swerved to avoid hitting the other car and my GTO spun on the wet pavement. It crossed two other lanes of traffic and hit the guardrail in the median. First the right front hit and then the car spun and the right rear hit." Harrowing, yes, but thankfully no one was hurt except for Bob's wallet to the tune of $9,000. Lucky for him and the GTO, it was properly insured and the company came through on the claim. During the repairs, Bob decided to have the GTO painted 2000 Neon Bright Silver Metallic instead of gold and Zeke at Autobody Techniques (Kingston, N.H.) handled the job. The front inner fenders were powdercoated silver for longevity and good old Rustoleum satin black protects the chassis and floors.

Having some more time to think about the mechanical aspects of the GTO while the body was being repaired, Bob soon decided that even more power was in order so he once again consulted SD Concept Engineering Inc. Scott Dickinson of SDCE went through the engine and then installed an SDCE custom sheetmetal intercooler. At the same time, an Action Automatic (Brookline, Mass.) full-manual valvebody switch-pitch Turbo--400 built by Mark Brown was installed with an Ultra Bellhousing, an SFI flexplate, a Chrysler Imperial external cooler and a custom 12-inch JW switch-pitch converter with 1500 low and 3000 rpm high stall speed. The result of the trans swap and the SDCE rebuild and intercooler installation was the GTO running 10.92 at 123.87 on M/T 28x10.5x15 slicks (weighing 3,750 lbs. with driver and 3,550 lbs. at the curb).

So, what's under the valve covers now? Mostly it's the freshened 428 with some more touches added by SDCE. Though Scott had to retain many of the parts that were brought in by Bob, he built a potent combination even if the parts selection for the current application isn't optimized. Here is how it all shakes out.

The .030-over 1969 428 block and 4.00-inch stroke 1965 421 crank (held in with Indian Adventures steel 4-bolt main caps) combination results in 434 cubic inches. Childs & Albert forged steel rods connect to thermal-coated KB hypereutectic pistons wrapped in Total-Seal gapless rings. The oiling system consists of a stock pan modified with kickouts, and a Melling pickup and high volume oil pump. A Racer Brown solid, flat tappet cam checks in at 240-degrees /250-degree duration at .050 with .485 lift and 114-degree lobe separation and was installed at 104-degrees. According to Scott, "The cam was actually ground for 1.65:1 rockers but Bob wanted to retain the valve covers that he brought us so he stuck with the Comp Cams roller tip 1.50:1 rockers. The result is that the cam only has .485 lift instead of .550." Lash is set to .012-.014.

Stage II port work by SDCE on the Edelbrock heads includes, "as much porting as possible without welding," according to Scott. The intake ports were enlarged to 233 ccs and the exhaust was opened up too. Valves are 2.11 stainless Ferrea intake and 1.79 stainless exhaust by SDCE. The valve job consists of a 45-degree seat and a 30-degree and 60-degree cut, all of which are blended to a radius. Comp Cams valve springs feature a seat pressure of 140 lbs. and an over-the-nose pressure of 330 lbs. (with .550 lift, less with .485 lift).

The compression ratio is 9.67:1, a bit higher than Scott would normally use--he would rather see about 9:1. The reason is that Bob wanted to use the off the shelf pistons so Scott went with a flattop. He cut valve reliefs in them and worked the chambers in the heads to get 84 ccs. But since the ProCharger is currently putting out just 5-6 lbs. of boost, the GTO still runs strong on pump gas without detonating.

Then there is the focal point of this engine, the P600B billet impeller ProCharger centrifugal supercharger, that can produce up to 24 lbs. of boost but Scott relates that 9 lbs. would be the practical limit for this application. Given the fact that only 5-6 lbs. of boost are used now, there is still more potential power in the combination. Different sizes of pulleys can be installed to raise and lower the boost and the unit is driven via a 12-rib belt that connects it to the crank. This installation offers another power producing element--an air to air intercooler.

What the intercooler does is drop intake manifold air temperature, up to 200-degrees in some cases, over non-intercooled installations. The cooler denser air makes more power. As a result, more timing can be dialed in as can more boost, and octane tolerance is increased at the same boost level as compared to the supercharger alone. Low-end power is also increased.

Induction comes by way of an SDCE Holley 750 Double Pumper carb with #73 jets up front and #80 jets in the rear, not to mention solid floats installed so that they don't collapse under boost pressure. After the intake air is compressed and intercooled, it enters the carb via a large diameter hose from the intercooler that dumps into a chromed hat over the airhorn.

An SX electric fuel pump (80 GPH at 40 psi, 130 GPH at 10 psi at 12 volts) feeds a Mallory boost-referenced regulator. With the compressed air and fuel combined in the Holley, the mixture is then introduced to a Torker II intake that has been port-matched and the water passage has been cut so the intake can be removed without having to take it off too.

A Pontiac HEI provides spark with the aid of a Jacobs ignition controller, boost retard, coil, wires and rev limiter and NGK plugs. Timing is set to 18-degrees initial with 35-degree total all in by 1800 rpm and the engine runs on a steady diet of 89 pump gas on the street and at the track mixing Cam 2 at 110 octane and 92 octane super unleaded, according to Bob. However, Scott says the GTO would probably be faster without the 110 octane Cam 2.

Spent fumes are handled by the aforementioned (Jet Hot coated) Hedman Hustler Hedders from Jim Butler with 2-inch primaries and 3 1/2-inch collectors. And 3-inch mandrel bent pipes from Custom Tubes (Woburn, Mass.) with 3-inch 3-chamber Flowmasters tune the tones.

At this point Bob has a real animal on his hands, capable of 10s, so he has outfitted the GTO with needed safety parts. Some are front and rear driveshaft loops to assure that the Goat won't pole vault should the U-joints fail, an SFI-approved balancer and flexplate, a roll cage, a battery cut-off switch and a safety harness.

According to Whitcher, the GTO is well behaved on the street. Since a rules change to street tires only on weeknights at his local track, he has been spending considerable time trying to get his Pontiac to hook on the required drag radials, with little success. His 60-foot times increased by nearly a 1/2-second and the ETs are up to the high 11s. Bob isn't too upset. "The GTO is a street car that I happen to race," he explained. Wouldn't it be nice to have a street car that just happens to run 10s? Maybe the late-model guys with superchargers are onto something?

Bob would like to thank Zeke at Autobody Technques, Scott at SDCE (SD-concepts.com), Mark at Action Automatics and Dick at Ponti-Action Racing and Indian Adventures for all of their help with the building of his GTO. For more information on ATI ProChargers visit www.ProCharger.com