Pontiac GTO Forum banner

1 - 2 of 2 Posts

4,316 Posts
Discussion Starter #1
It was these big cars that were ramping up the Super Stock wars and even the Nascar guys. So only fitting that these cars should be covered as they led the way for your beloved A-Body Pontiac's.

From Motor Trend, May 1962, "421 PONTIAC," by Roger Huntington. Jim Wangers was the driver of the 421 Catalina coupe as Roger Huntington rode shotgun, feeling Wangers was better at shifting a 4-speed than himself. The test was done in January making this more an experimental venture than the actual and later 421SD factory optioned cars with their assorted changes made for production. (This test car exists today with its number matching drivetrain)

Here is one of the most exciting and interesting observations written by Roger as he noted the sounds and physical impressions of a 1/4 mile blast down the strip:

"And BOOM. Wangers got into that big Poncho, and we went. Low gear was a rubber-burning fishtail, with the indifferent traction available. A snap shift to 2nd at 5500 rpm, and 60 mph came up in a bit over 5 seconds. The bellowing open exhausts rattled the whole countryside. Second and 3rd gears almost tore my head off. Then across the finish line in high at 5300 - stopping the watch at 13.9 and 107 mph!. And finally that delicious back-off, with the exhausts popping and banging, and the wonderful smells of gasoline and rubber and clutch lining. And here's the joker: this Pontiac had just been driven off the factory assembly line, with no more tuning than a spark advance check and valve lash adjustment!"

The article stated that all late model 421 blocks came through bored .030" over making them in reality a 428 (this was an error, the 421 used the SD389 block bored .030" over and a 4" stroke crank). The heads on this engine were the high-performance 389CI 1960-'61 heads with 1.92" intake valves, 1.66" exhaust valves, bigger ports, undercut valve heads, and 1.65-to-1 ratio rocker arms.

The cam was the solid McKellar #10 with 308 degrees duration on the intake and 320 duration on the exhaust. The maximum factory recommended RPM's with the standard dual (as delivered) valve spring set-up was 5500 RPM's.

The engine uses 4-bolt mains, forged crank, and Moraine aluminum bearings set-up between .002-.003" clearances. The heavy-duty forged connecting rods used a side clearance of .030-.035". The Mickey Thompson 11-to-1 forged pistons use a skirt clearance of .009-.013" and Huntington described their sound as "The pistons sound like a boiler factory when you start it up cold - and the slap is only slightly when warm! But it runs!" It uses a heavy duty oil pump and 6-quart oil pan.

Carbs were a pair of Carter AFB's on a matching big port aluminum intake that has no heat crossover provisions for exhaust heat in cold weather. The carbs use straight mechanical linkage, not progressive, which overcarburate the car at the lower end.

Distributor is a dual point with no vacuum advance. Factory settings were 10 degrees at the crank and 27 degrees mechanical in the distributor for a total of 37 degrees. The Royal team like to run the initial timing 5 to 10 degrees more but keep the total about the same.

Exhaust manifolds were a unique design called "pulse flow" having dual outlets pairing 2 cylinders into each outlet, then dumping into a 3" outlet. A cast adapter then went from 3" down to 2.25" to attach to the exhaust piping. A side opening could be uncapped for drag racing. Low restriction mufflers were used for the street.

The car uses a light weight flywheel, heavy-duty clutch & clutch counter shaft, 4-speed transmission with Hurst-Campbell floor shift, and 4.30 posi rear-end gearing.

Car weight as delivered was 4,070 pounds with out passengers or a full tank of gas. The cost of the upgraded engine & driveline option was $1,342.85 to the base price, but the delivered car had added extra cost options as well: HD radiator, HD battery, stiffer springs & shocks, Kelsey-Hayes aluminum 8-lug aluminum wheel-drum units, radio, heater, and interior decor group.

Here are the performance specs of the car as tested at the Detroit Dragway in January 1962 with an unprepared track and ice and water visible down the center of the strip. The Royal team installed a set of Goodyear 9.00 x 14 soft recaps and added 150 pounds of weight in the trunk for ballast putting test weight just under 4500 pounds with driver and passenger.

0-30 mph 2.7 seconds
0-45 mph 4.1 seconds
0-60 mph 5.4 seconds
1/4 mile 13.9 @ 107 mph

Huntington used the technique of "hand timing" with a stop watch. He noted that his technique was to start the stop watch the instant Wangers popped the clutch and hit the gas - which is an instant before the car actually moves. With electric timing the car is rolling before it breaks the first light beam. He has found that this makes a .2 to .3-second difference for the 1/4 mile run, making the above e.t.'s closer to 13.6 or 13.7.

Huntington also used an accelerometer to more accurately gauge the true horsepower & torque figures for the engine at the clutch - which was done under full throttle in 3rd gear. The factory rated the engine at 405HP @ 5600 RPM and 425 lbs-ft of torque @ 4400 RPM's.

What Huntington came up with was 465 HP @ 5300 RPM and 510 ft-lbs of torque @ 3500 RPM, stating that the accelerometer does not lie. He pointed out that the Pontiac advertised HP was corrected at 100 degrees, under the GM "Test 7" code. He felt the difference at 100 degrees and the cold denser 35 degree air of January accounted for an extra 30 HP difference. "Test 7" code did not call for mufflers but felt that the exhaust system might be more efficient than the factory dyno system.. With the exhaust outlets capped, the HP was down at 420-425HP. So he felt that with the denser air and uncapped exhaust that the extra 60 HP above the factory rating was possible.

Huntington noted that the engine would drop off sharply after 5400 RPM's. His accelerometer showed a drop of 100 HP between 5300-5600 RPM's. It was found that the heads had been fitted with the lower tension 348HP 425-A 389CI engine at the factory to prevent excessive cam lobe wear during initial break-in and these were to be replaced after break-in by the higher rated springs designed for the MacKellar #10 cam. The Pontiac engineers said the engine should have easily spun to 6200 RPM's.

New heads were in the design stage and being tested as the 1960-'61 389SD high-performance cylinder heads used on the engine did not have enough valve & port area to feed the the extra cubes of the 421 engine and Huntington felt this could be worth another 20-40 HP, putting a well tuned engine under optimum track condition at an estimated 1/4 mile times around 12.5 @ 112-115 mph, and 0-60 in 4.5 seconds.
1 - 2 of 2 Posts