Pontiacthunder

Degreeing a Camshaft

THE FOUR CYCLE ENGINE
Indeed, cam degreeing is simple, but first let's make sure you have a good understanding of the cam's function in the four cycle engine. You probably already know the four basic strokes of the four cycle engine: INTAKE, COMPRESSION, POWER, and EXHAUST. Each stroke represents one-half of a revolution of the crankshaft or 180 crank degrees. 4 cycles x 180° = 720° or two revolutions of the crankshaft. Two revolutions complete one sequence of the four strokes. The camshaft is connected via the timing chain and sprockets at a 1:2 ratio to the crankshaft and therefore revolves once for every two turns of the crank. Its purpose is to operate the intake and exhaust valves in the correct timing with the piston as it sequences thru the four strokes.

EARLY SLOW SPEED ENGINES
In the old days, the first four cycle engine had very short valve timing, but rightfully so because these were slow speed engines. The engineers of the late 1800's were only concerned with harnessing power of the gasoline and air explosions in an internal combustion engine to propel an automobile, hopefully, a little faster than a horse. They were merely concerned with getting the engines to run at slow speeds. Even in their wildest inspirations they would never have believed that a quhttp://www.iskycams.com/ARTer or half century later, with better structures, these same engines would be revved five times as fast and produce many times more power.

EARLY SLOW SPEED VALVE TIMING
The old valve timing then was: Intake valve opens at T.D.C., and as the piston lowers, it draws in the fuel/air mixture; the intake valve then closes at (B.D.C.) hence, the intake stroke. The piston rises, with both valves closed to compress the fuel/air mixture. hence, the compression stroke. The spark plug fires and ignites the fuel/air mixture which drives the piston down to B.D.C. (again the valves are closed)... hence, the power stroke. Also, the exhaust valve opens at B.D.C. The burnt gases, due to their high pressure, virtually expel themselves, and the piston drives the last of the gases out; the exhaust valve closes at T.D.C.. hence, the exhaust stroke. These early engines had Oo overlap or no overlap whatsoever.

1970 Trans Am

1970 Pontiac Firebird Trans Am

by the Auto Editors of Consumer Guide

Firebird and Camaro grew more European in nature with their second-generation redesign, but the scooped and spoilered 1970 Pontiac Firebird Trans Am was pure American muscle car, and more immodest than ever.

With the introduction of the second-generation Firebird, the 1970 Pontiac Trans Am came into its own as a bare-knuckles brawler. Functional spoilers
and vents abounded, while super-tough underpinnings and
quickened steering gave it corner-hungry handling.

The 1970 Pontiac Trans Am's standard engine, the 345-horsepower Ram Air 400-cid V-8, furnished low-14-second elapsed times at the dragstrip. That apparently satisfied most buyers, because just 88 of the 3,196 Pontiac Trans Ams built that year got the optional Ram Air IV. That one added bigger ports, better heads, swirl-polished valves, and an aluminum intake manifold for 370 horsepower, 25 more than in '69. Rarer still was the Ram Air V, an over-the-counter, special-order piece that counted among its tricks solid lifters and tunnel-port heads for as much as 500 horsepower.

1969 GTO

The new 1969 model did away with the vent windows, had a slight grille and taillight revision, moved the ignition key from the dashboard to the steering column, and the gauge faces changed from steel blue to black. In addition, the rear quarter-panel mounted side marker lamps changed from a red lens shaped like the Pontiac "V" crest to one shaped like the broad GTO badge.

The previous economy engine and standard 350 hp 400CID V8 remained, but the 360 hp engine was dropped in favor of a pair of new Ram Air engines. The 400CID Ram Air III was rated at 366 hp @ 5100 rpm, while the top option was the 370 hp Ram Air IV, which featured special header-like high-flow exhaust manifolds, high-flow cylinder heads, a specific high-rise aluminum intake manifold, larger Rochester QuadraJet four-barrel carburetor, high-lift/long-duration camshaft, forged steel crankshaft plus various beefed-up internal components capable of withstanding higher engine speeds and power output. Unlike the big-block Chevy and Hemi motors, the Ram Air IV utilized hydraulic lifters which allowed the engine to remain civilized during everyday driving. It didn't overheat in traffic, and it also didn't foul spark plugs, which set it apart from the large-displacement performance engines seen in other muscle cars.

12 Second 400CID Pontiac Build

Pontiacthunder has collected data and tested many Pontiac engine combos and has come up with, what we feel, a nice collection of builds to make your Pontiac perform to your needs.
Over the next several months we will list detailed builds with performance levels from 12 second ET's from a relatively stock 400, to deep into the 9's with a 455. We�ll even take you through the build of a 517CID Pontiac Monster destined for sub 8 second quarter mile times from one of Pontiacthunders very own members.

This month, check out a simple build for a 400CID Pontiac that is geared for the budget minded! This combo has run in the mid 12�s at 110MPH in one of our own cars and is reliable enough to be street driven on pump gas!

Nitrous Tuning

The best advice when getting started with nitrous is to be conservative. If an adjustable kit has been purchased, start with the lowest horsepower setting and progress steadily - one step at a time.

Regarding fuel settings, it�s always advisable to err on the rich side- irrespective of the horsepower level. With an adjustable kit, use either the largest recommended fuel jet at that level or raise the fuel pressure to the maximum recommended setting. Larger fuel jets together with a higher fuel pressure will richen the mixture. Smaller jets cause leanness - the opposite effect. If the kit is not adjustable, perform the first test using slightly reduced bottle/cylinder pressure. Then gradually increase the pressure until the optimum performance is achieved.

1968 GTO

The 1968 GTO

By 1968, the musclecar segment had exploded, with entries from nearly every brand. The GTO entered the model year with an absolute knockout of a new body, as well as some performance upgrades. In fact, all four GM intermediates had been redesigned for 1968, and all upped the ante in performance. The Chevelle SS396, which was more than a match for the Pontiac on the street and strip, couldn't match it in sales, though.

Pontiac moved 87,684 GTOs for 1968 (including 9980 convertibles), compared to 62,785 SS396 Chevelles and 33,607 Oldsmobile 4-4-2s.
Prices for the '68 GTO started at $3103 for the hardtop and $3327 for the ragtop (there was no post coupe). Adding an optional transmission and luxury options such as air conditioning, cruise control and stereo could easily push a GTO over $4000. That kind of pricing helped Plymouth sell 44,599 of its new back-to-performance-basics Road Runners. The Road Runner started at $2870 for a post coupe and included a standard four-speed transmission a $184 option on the GTO

1967 GTO

The 1967 GTO

So the '67 GTO actually marks the beginning of the marque's de-emphasis on all-out performance. Gone was the tripower engine option. Now, the hottest setup available was a single Rochester Quadrajet on a high-rise intake manifold. But all was not lost. Pontiac saw fit to drop the 389 engine and introduce an enlarged, bored-out version that displaced 400 cu. in. In addition, many new engine pieces had been developed since '64 and were all introduced in a group on '67 engines. For one thing, a new set of cylinder heads was designed. These heads were sorely needed and replaced the antique heads that were originally designed for the '55 287-cube V8. The new heads sported clean combustion chambers and ports, 2.11-in. intake valves and high flow capacity. Pontiac felt that the increase in displacement plus the new heads warranted a retention of the 360-hp rating despite the drop from three 2- barrels to one 4-barrel carb. The 360 hp was the high-performance option with the HO cam, long-branch exhaust manifolds, etc.

1966 GTO
In '66, Pontiac made some improvements to the engine. The division went to larger carbs on the tripower option, now using Rochester 2GC carbs at all three locations. There was also a cold-air package on top of the tripower setup. The single 4-barrel engine was unchanged, still rating 335 hp at 5000 rpm and 431 ft.-lb. of torque at 3200 rpm. The tripower engine was still rated 360 hp at 5200 rpm and 424 ft.-lb. of torque at 3600 rpm, despite larger carburetors. Even the optional ram air setup didn't change the horsepower rating, in Pontiac's opinion.

1965 GTO
The 1965 GTO

In 1965, Pontiac increased the rating of the standard 4-barrel engine to 335 hp but brought out a real goodie of an engine option. It was still 389 cubes, but a new cam that had 292° intake duration, 302° exhaust duration and more streamlined cast-iron exhaust headers added up to 360 big ones. And they meant it. Those weren't just paper ponies. In the May 1965 issue of Car Life magazine, Roger Huntington took some of his famed accelerometer readings in a 360-hp GTO and found that the car was being propelled by 345 actual horsepower at the clutch. And the true torque reading was 420 ft.-lb. compared to the factory rating of 424 ft.-lb. By the way, that issue was the first time the word "supercar" was used to describe the new breed of big-engine intermediates.

1964 GTO
Legend has the conception like this: The scene is Pontiac General Manager Pete Estes's office. The time is early 1963. The man walking through the doorway is Jim Wangers, Pontiac account executive for MacManus, John and Adams, the Pontiac advertising agency. Wangers is also an avid performance enthusiast, drag racer and part-time product planner for Pontiac.