1968 Pontiac GTO

[Rich Biebel]

A Pontiac or a GTO just ain't right to me if it does not have aTri-Power under the hood....

1966 was the last year for that option. I am sure the Q-Jets were fine but for the street the "trips" were cool.......Some extra work to keep them running right and avoid fuel leaks......but worth it to me......

I had a '67 GTO with just about every option available......400 Turbo 400 Hurst Dual Gate....Power everything including disc brakes.

I raced a friend numerous times with his 1970 GTO and beat him every time....I believe his car was heavier.
I spent a lot of time on my Q-Jet getting it to accelerate from an idle to wot with no bog or sag.......

My car would chirp the tires on the 1-2 shift and I loved that little sound.....

I think it would have run mid to high 14's at the strip. Never raced it.

[Paul Ceasrine]

The 1968 Pontiac GTO 400/366 HP 'Ram Air II',

Released in March 1968,,,,,
The new 'Ram Air II", virtually eliminated the 400/360 HP 'HO" and 400/360 HP 'Ram Air I'
from NHRA D/Stock competition at 'major meets'.

With only limited production numbers, it was highy desireable for the drag strip.

Production Numbers;
Ram-Air II, hardtop, 4-Speed,,,,,,,,,,,757
Ram-Air II, hardtop, Automatic,,,,,,,,,183
Ram-Air II, convertible, 4-Speed,,,,,,,,92
Ram-Air II, convertible, automatic,,,,,,22

[Paul Ceasrine]

Gene,

Differences between the 400/366 HP 'Ram Air II' and the other
400 engines.

'Ram Air II' 400/366 HP,, @ 5400 RPM (Tach red-line)
400/350 and 400/360 HP,,,,,@ 5100 RPM (Tach red-line)

The 400/366 HP 'Ram Air II" , 4-Bolt main block, (casting #9792968)

The 'Ram Air II' utilized;
* Nodular Crankshaft
* Special Arma-Steel connecting-rods
* Forged pistons
* Re-designed cylinder heads (w / round port exhaust)
* High-lift camshaft
* Up-graded valve train
* Re-jetted carburetor
* Revised distributor curve
* Stream-lined exhaust manifolds
* Ram-Air induction (dealer installed)
* 4.33 Gears
* M-21 Close-Ratio 4-Speed or TH-400 Automatic.

[Paul Ceasrine]

Gene,

The main performance items in the 400/366 HP 'Ram Air II',,,

Cylinder Heads
* Casting #96
* Had larger intake ports, and re-designed round-shaped exhaust ports.
* Intake port volume (155 cc),,,,,,Exhaust port volume (162 cc)
* Combustion chambers 72 cc. ('spherized design' w/ shallow combustion chamber)
* Tulip-head shaped valves (2.11 intake / 1.77 exhaust) Extended length (5.20")
* Spiral-polished valves
* Dual high-rate valve springs
* Valve spring height (1.776")
* 11/32" Push-rod guide-plates
* 11/32" Push-rods (High-strength)
* 7/16" Rocker-arm studs
* 'D'-shaped port exhaust manifolds

* Note: The #96 casting heads are considered to have the best exhaust ports of the 400 heads.

Camshaft
* Code # "041"
* .491/.486 lift,,, 308*/320* duration,,, 115* Center-line,,, 87* Overlap

Note: The first computer-designed camshaft.

Carburetor
* Rochester #7028273
* 750 CFM
* Re-jetted, w/larger #42 Main Rod

Distributor
* Revised curve
* Hardened drive-gear

General Analysis:
The 366 HP 'Ram Air II' had a hell of a lot more than only 6 Horsepower more than
the '360 HP Ram Air I'.

[oldskool]

I can't say what a stock '68 GTO would run, new.

But, I do have some numbers for a '69 RA3 366hp GTO.

Bought it new, with a close-ratio 4-speed & 3.90 gears. Since I ordered it early in '69, I ASSUME it had the "744" cam, tho I never checked it. Later in the model year, Pontiac dropped the 744, in favor of the 068. The 744 grind specs were used in the SD455 engines.

Ran it on the street for a little over 60k miles. Put it on the track in '73. Only non-stock parts were a Weber alum flywheel & clutch. No slicks allowed. Had hard compound street legal tires. Best time was 13.95, with considerable wheel-spin.

In '74, special soft-compound tires were legal. They were basically just slicks, with a couple of very small grooves. Put in a Hays steel flywheel & clutch. It would then hook up & run 13.50's. Heads had never been off. Still had the original cam & Q-jet.

Guessing that 4.33 gears would have put it in the real low 13's. But, those would not have been as street friendly.

[Stan Weiss]

Originally Posted by oldskool

I can't say what a stock '68 GTO would run, new.

But, I do have some numbers for a '69 RA3 366hp GTO.

Bought it new, with a close-ratio 4-speed & 3.90 gears. Since I ordered it early in '69, I ASSUME it had the "744" cam, tho I never checked it. Later in the model year, Pontiac dropped the 744, in favor of the 068. The 744 grind specs were used in the SD455 engines.

Ran it on the street for a little over 60k miles. Put it on the track in '73. Only non-stock parts were a Weber alum flywheel & clutch. No slicks allowed. Had hard compound street legal tires. Best time was 13.95, with considerable wheel-spin.

In '74, special soft-compound tires were legal. They were basically just slicks, with a couple of very small grooves. Put in a Hays steel flywheel & clutch. It would then hook up & run 13.50's. Heads had never been off. Still had the original cam & Q-jet.

Guessing that 4.33 gears would have put it in the real low 13's. But, those would not have been as street friendly.

I have never done a 3.90:1 to 4.33:1 gear change. But IMO I would be very surprised if you saw anymore than a .1 of second improvement.

Stan

[NSSGTO]

Originally Posted by Stan Weiss

I have never done a 3.90:1 to 4.33:1 gear change. But IMO I would be very surprised if you saw anymore than a .1 of second improvement.

Stan

Agree, I swapped from a 3.73 to a 4.10 and ran the exact same #. Swapped to a 3.90 and picked up about .05 over the 4.10.

[Bob F]

Dad bought a 68 gto loaded with an auto 350hp engine,rear gear 2.93 in may of 1968.
Bone stock it ran 15.1 at Vargo I believe was the track.
Always thought it was a little funny his 73 455 gto ran the same number 1st pass ever.
That car was J/SA.

[oldskool]

Originally Posted by Stan Weiss

I have never done a 3.90:1 to 4.33:1 gear change. But IMO I would be very surprised if you saw anymore than a .1 of second improvement.

Stan

Assuming max traction, I suppose the ET difference caused by a gear change would strictly depend on the torque & power range of the engine.

If the engine is already well passed it's peak power range BEFORE the finish line, then obviously, if you add more gear, the engine will pass it's peak power range even farther from the finish line & slow the ET.

On the other hand, if you are way under-geared, & you cross the finish line a 1000 rpm below your engines peak power range, then adding more gear will obviously utilize more of the engines potential, & lower ET.

If the car is just barely under-geared, & you changed the ratio enuff to make it slightly over-geared, then the ET change would likely be very small or may even go slower.

So, the amount of ET change would depend on several factors.

Back in the old days, the Chevy street guys who had sbc power would say they had a "three quarter cam & 4.11 gears". It seemed that was the hot "Street/Strip" set up.

Since 4.11 gears seemed to be so popular, I've wondered why Pontiac seemed to skip that ratio & go from 3.90 to 4.33 gears. Had to be some reason they chose 4.33, assuming that many of those who ordered that ratio would be drag racing the car.

I have to assume that they did a lot of testing & had determined that 4.33 was the best ratio for drag racing a 400 Pontiac A-body, with the factory RA cams. Otherwise, they would have offered 4.11 or 4.56. But hey, what do I know ? They may have stopped at 4.33 because that's all they thought the cast rods could stand, crossing the finish line.

In '75, I had a 400 built to 350hp Stocker specs. Changed to 4.56 gears & ran 12.90's right off the bat. Put that engine in my girlfriend's '68 E/SA Bird, with a 330hp Lunati Stocker cam & 4.56 gears, & it turned 12.80's. The Bird was a MUCH more competitive combo. NHRA rated basically the same engine 20hp LESS, in the Bird. And the Bird was 200lbs lighter. It was a perfect fit for E/SA. 3300 lbs/330hp = 10 lbs/hp = E/SA.

The '68 Birds have been a popular & competitive combo right up to the present time. I suppose Julie Biermann drives one of the quickest, today. She runs a little more than 2 secs quicker than we did. The round port '68 Birds have also been very competitive, thru the years.

Anyhow, I never changed JUST the gear ratio ONLY, to see the ET difference it made. So, any numbers I mention would be strictly a guess, or estimate.

[DeuceCoupe]

Originally Posted by oldskool

Assuming max traction, I suppose the ET difference caused by a gear change would strictly depend on the torque & power range of the engine.

If the engine is already well passed it's peak power range BEFORE the finish line, then obviously, if you add more gear, the engine will pass it's peak power range even farther from the finish line & slow the ET.

On the other hand, if you are way under-geared, & you cross the finish line a 1000 rpm below your engines peak power range, then adding more gear will obviously utilize more of the engines potential, & lower ET.

If the car is just barely under-geared, & you changed the ratio enuff to make it slightly over-geared, then the ET change would likely be very small or may even go slower.

So, the amount of ET change would depend on several factors.

Back in the old days, the Chevy street guys who had sbc power would say they had a "three quarter cam & 4.11 gears". It seemed that was the hot "Street/Strip" set up.

Since 4.11 gears seemed to be so popular, I've wondered why Pontiac seemed to skip that ratio & go from 3.90 to 4.33 gears. Had to be some reason they chose 4.33, assuming that many of those who ordered that ratio would be drag racing the car.

I have to assume that they did a lot of testing & had determined that 4.33 was the best ratio for drag racing a 400 Pontiac A-body, with the factory RA cams. Otherwise, they would have offered 4.11 or 4.56. But hey, what do I know ? They may have stopped at 4.33 because that's all they thought the cast rods could stand, crossing the finish line.

In '75, I had a 400 built to 350hp Stocker specs. Changed to 4.56 gears & ran 12.90's right off the bat. Put that engine in my girlfriend's '68 E/SA Bird, with a 330hp Lunati Stocker cam & 4.56 gears, & it turned 12.80's. The Bird was a MUCH more competitive combo. NHRA rated basically the same engine 20hp LESS, in the Bird. And the Bird was 200lbs lighter. It was a perfect fit for E/SA. 3300 lbs/330hp = 10 lbs/hp = E/SA.

The '68 Birds have been a popular & competitive combo right up to the present time. I suppose Julie Biermann drives one of the quickest, today. She runs a little more than 2 secs quicker than we did. The round port '68 Birds have also been very competitive, thru the years.

Anyhow, I never changed JUST the gear ratio ONLY, to see the ET difference it made. So, any numbers I mention would be strictly a guess, or estimate.

Agree on the gear comments - that's what I see in the Gonkulator. A "rule" often used is "gear it so the engine hits peak HP thru the traps" - but even then, less gear might be better if you're just frying your street tires.

Maybe 4.33 was a compromise - barely driveable on the freeway if you limp along at 55-60mph (we used to run our Model A Ford on the freeway at 50-55mph, MAN that got hectic even back then!)
But also a decent gear for a big block with drag tires.

On the factoring: That's consistent with what I have down that Paul C once said here:
RamAir1 GTO: 360hp
RamAir1 Firebird: factored to 340hp

I often wondered why they weren't BOTH factored to 360hp - with headers and a carb fully opening, arent the GTO and Firebird identical engines then?