1968 Pontiac GTO
 

1968 Pontiac GTO
Motor Trend's 'Car of the Year'


http://static.howstuffworks.com/gif/...tiac-gto-1.jpg

Base Price: $3101

Production numbers of 87,684 units.
Nearly double, the Road Runners 46,054.

1968 Engines available;
400/350HP
400/360HP 'HO'
400/360HP 'Ram Air I'
400/366HP 'Ram Air II'

Gear ratio's available,,,,,,,2.93,, 3.08,,3.23,,3.55,,3.90,,4.33

Note: The 4.33 Gear's were standard with the 400/366HP Ram Air II.

In 1968, the 400/350HP was classed in E/S or E/SA, while the more powerful
400/360HP 'HO' and 400/366HP 'Ram Air II' cars were classed in D/S or D/SA.
More than a few tackled SS/F or SS/FA in 1968.
http://www.scorpiocars.net/images/Po...tiac%20GTO.jpg

Re: 1968 Pontiac GTO
 

I don't have a GTO story,,,I'm curious to see if this thread will run like the Roadrunner thread, Paul. Lets find out.
Danny Durham

Re: 1968 Pontiac GTO
 

I was in school in Indy and owned a 67 Chevelle SS396 . It was stolen and never found. So I was impressed with the Ad for the car of the year and ordered one. Red with black interior and white walls. Standard engine and 4 speed. I ordered a 3.55 posi rear. This was one of the best cars I ever owned for comfort, and Performance.
I have actually looked for a restored one for fun.

Re: 1968 Pontiac GTO
 

Danny,

I think the Road Runner thread will get more hits,,,,,,,,,;)

Though the GTO was the '1968 Car of the Year', there were quite a few mixed reviews for the car.
Hot Rod Magazine called it, 'the best balanced car Pontiac's ever built'

Car Life Magazine stated, 'a nose-heavy, under-steering lump'

Performance Results;
15.93 @ 88 MPH,,,,,,(Car Life),,,,,,,,,,400/350HP, Automatic, w/3.23 Gears

15.50 @ 90 MPH,,,,,,(Car & Driver),,,400/360HP, Automatic, w/3.55 Gears ('HO')

15.10 @ 94 MPH,,,,,,(Hot Rod),,,,,,,,,,,400/360HP, Automatic, w/3.90 Gears ('HO')

14.70 @ 97 MPH,,,,,,(Motor Trend),,,,,400/360HP, 4-Speed, w/4.33 Gears ('Ram Air I')

14.50 @ 98 MPH,,,,,,(Car Craft),,,,,,,,,,,400/360HP, 4-Speed, w/3.90 Gears ('HO')

14.25 @ 99 MPH,,,,,(Super Cars),,,,,,,,400/366HP,,4-Speed, w/4.33 Gears ('Ram Air II')

Note: All performance tests were performed in a stock dealership car, with G70 x 14" tires.

When comparing apples-to-apples, the 68' GTO 400/350HP and the
Road Runner 383/335HP were pretty much equal in the 1/4 mile
with 4-Speed transmissions, but when comparing Automatic transmissions, the Road Runner could outrun the GTO.

http://i.ebayimg.com/t/1968-Pontiac-...,gNT2g~~_3.JPG

Re: 1968 Pontiac GTO
 

Is this why the 68' GTO 400/350 HP is now rated by NHRA at 325?

Re: 1968 Pontiac GTO
 

Pontiac's front end treatment worked well with the new rounded body style. They "pushed" the Endura front bumper, but iirc it was a lot heavier than the standard chrome bumper. Like with Olds, the Ram Air option had gone "mainstream" in the option book for 1968.

Re: 1968 Pontiac GTO
 

The 'most famous' 1968 Pontiac GTO print ad.

This ad was pulled, as the Woodward Avenue reference was all you needed to know,,,,,,,'Street Drag Racing'

GM Management realized the issue, and pulled the ad after only
'one' printing.

http://www.adclassix.com/images/68po...towoodward.jpg

Re: 1968 Pontiac GTO
 

I ran 14.25 at Orange county 99 MPH with the 350HP 400 4 spd. NO CHANGES. Full exhaust and Air cleaner on it.

Re: 1968 Pontiac GTO
 

1968 Pontiac GTO Price List;

Base Price; $3101

Primary Options:
* Power Steering: ($95)
* Power Brakes: ($35)
* Disc Brakes: ($63)
* Retractable Headlight Covers: ($52)
* AM Radio: ($61)
* Hood Tach: ($63)
* Dash Rally Guage Cluster: ($84)
* Dual Exhaust Extensions: ($21)
* Custom Rally Wheels: ($50)
* Safe-T-Track Differential: ($42)
* Special Axle Ratio's: ($63)
* Speedometer Gear Adapter: ($11)
* Center Console: ($68)
* Rear Super-Lift Shock Absorbers ($48)
* Turbo-Hydra-Matic Transmission: ($236)
* Close Ratio 4-Speed: ($185)
* Ram Air Hood Scoop: ($50)
* 400/360HP 'HO' Engine: ($76)
* 400/366HP 'Ram Air II' Engine: ($342) {available mid-year production}

Re: 1968 Pontiac GTO
 

When comparing apples-to-apples, the 68' GTO 400/350HP and the
Road Runner 383/335HP were pretty much equal in the 1/4 mile
with 4-Speed transmissions, but when comparing Automatic transmissions, the Road Runner could outrun the GTO.


B.S.



No. That's why the RR 383 is now @ 300 horsepower

Re: 1968 Pontiac GTO
 

1968 Performance Tests
Motor Trend Magazine (February 1968)

http://image.automotive.com/f/roadte...ance_Sheet.jpg

Re: 1968 Pontiac GTO
 

Also Paul,

Little known 1968 (I think 1968 only) option was a 265 HP 400 2 barrel regular fuel engine.
A girl I dated in high school circa 1970 parents had one that she got to use and actually became her car eventually.
When I got to drive it the first time on a date I could not understand what a pig it was until I opened the hood.

Re: 1968 Pontiac GTO
 

Alex,,,,,,,

You are correct sir.
The 400/350HP was the 'base engine' in the 1968 GTO.

A 'no cost' option was the 400/265HP 2-barrel,
called the 'Economy V-8'.

The only transmission available for that engine was the TH-400 automatic
You would find those cars classed in K/S A in 1968 (13.00 - 13.99 wt/hp).

That 265HP engine had no business being in a 68' GTO,,,,,,what
was John DeLorean thinking on that decision.......:eek:

Re: 1968 Pontiac GTO
 

Not a new GTO, but in '79 I look at a one for sale 'as in' for $350. Green, real clean, new convertible top, interior real good minus a small tear in drivers seat, only boldy flaw was a little rust above the wheel well openings on the rear. Owner had a new clutch put in it and after about 4+ months the car wouldn't move. I'm looking around the rear of the car with the owner and my brother is poking around with a flashlight in the hood compartment. Bro calls me over as says firmly, in a low tone, buy the car NOW! So I did and said we would be back tomorrow to take it.

We show up with a tool box and while I completed the paper work with the owner in his kitchen my brother starts the car and backs it out of the garage. The owner was steaming and asked what my brother did. The bellhousing had backed away from the block. He was frustrated that we didn't point it out to him. Oh well LOL. Sold it a short time later to a friend.

Re: 1968 Pontiac GTO
 

Now THAT is a great story,,, I can just imagine the look on the seller's face!
Danny Durham

Re: 1968 Pontiac GTO
 

Same type of story happened with me but not a GTO.I was 16 a kid in the hood had 396 375 nova someone put an 850 manual choke.The cable broke with the choke half closed he thought the cam went bad.I payed 500 while my brother flipped opened the choke,put plugs in it and drove home.

Re: 1968 Pontiac GTO
 

Motor Trend Magazine,,,,,,February 1968

Second performance test on the 68' GTO 400/360HP 'Ram Air I'
A 4-Speed with 4.33 gears.

14.45 @ 98 MPH

The air-cleaner top was removed,
A set of 8" wide x 28" tall GoodYear slicks mounted on
Ansen 15' x 6' rims were used.

Test performed, on a Wednesday Night (Street Racer Night) at
OCIR (Orange County International Raceway).

http://image.motortrend.com/f/featur...Grill_View.jpg
This 69' GTO also went through the same performance test in 1969.

Re: 1968 Pontiac GTO
 

I think it was 2006 I bought a full, frame-off beautifully restored '69 GTO. It was Matador Red with red interior. Factory original RAIV (400/366HP) with 4-speed and 4.33 gears. That RAIV has to be the best sounding factory cam ever installed!

http://i296.photobucket.com/albums/m...X/IMG_0718.jpg

http://i296.photobucket.com/albums/m...-interior2.jpg

http://i296.photobucket.com/albums/m...X/IMG_0015.jpg

http://i296.photobucket.com/albums/m...ader24x324.jpg

Re: 1968 Pontiac GTO
 

Soory but this is not a 1968 commercial but this 1970 GTO commercial for the VOE (vacuum operated exhaust) has to be the COOLEST muscle car commercial I've ever seen!

http://www.youtube.com/watch?v=ZccI7aQOKnQ

Re: 1968 Pontiac GTO
 

Jeff , I,m with you on the 69 RAM-AIR 4 ,wildest sounding cam that i can remember .I had a new 69 RAM-AIR4 automatic,green with gold interior ,,,thats right .:cool:
i

Re: 1968 Pontiac GTO
 

GTO Hood Tachs;

The 1969 GTO Ram Air IV Tach (only)
5500 RPM Red Line
http://i24.ebayimg.com/07/i/001/1e/34/4aeb_1_b.JPG


The early production Tach for the 1968 GTO's
(400/350HP and 400/360HP 'HO' engines)
5200 RPM Red Line
http://i21.ebayimg.com/03/i/001/1e/34/4dc2_1_b.JPG

Re: 1968 Pontiac GTO
 

I had a 68 GTO in E/SA. Could not get it to run right.
Just lacked time going to college 1974.

For the longest time none of the 68/69 GTO engines was a good class fit.
The Cams had very low lift and nominal increase with the 366hp.
NHRA and IHRA at the time were strict on HP and Weight and having the correct Emblems.

There were some advantages, combustion chamber was machined.
had the same rocker set up as the SBC and BBC.
Easy to maintain than a SBC or BBC as you could get to the Plugs easier.
The Engine seems to like the 4.33's the best with a 28 inch tire.

There was one driver who made the Firebirds rock in B, C and D Stock for a long time.
Forget his name..but ran the RA IV combination

One cool rumor was that Pontiac and Buick divisions at the time were vying for some kind of dominance.

There was a quietly publicized race that happened between a RA V and GSX.
Nobody seems to know who won that race.


Dan

Re: 1968 Pontiac GTO
 

Fred Borcherdt
'Rocky's Goat'
1969 GTO 'The Judge',,, w/Ram Air IV (400/370HP)
sponsored by Rock Hill Pontiac, Newark, Delaware

1969 Photo (Classed in D/SA) (9.00 - 9.49 wt/hp)
http://www.classracer.com/classforum...1&d=1309824796

In 1970, held the E/SA National Record (both ends)
12.10 @ 114.79 MPH,,,,,, (Set in May 1970)

1970 E/SA Class; (9.00 - 9.49 wt/hp)

Re: 1968 Pontiac GTO
 

Tiny E,

I stumbled upon another GTO site with some other performance tests done back in 1968.

Hot Rod Magazine tested a mid-year 1968 400/360HP 'Ram Air I'.
4-speed, with 3.90 gears on G77 x 14" tires.

In stock trim,,,,
14.25 @ 99 MPH

With 7" Casler Slicks
13.85 @ 102.13 MPH

Also, John DeLorean pounding the 'Endura' bumper with a sledgehammer!

http://t2.gstatic.com/images?q=tbn:A...wX8vsd0dy0AQ-b

1968 Pontiac GTO, in 'I Dream of Jeannie'
http://www.imcdb.org/t252387.jpg

Re: 1968 Pontiac GTO
 

Ray,

For 1968, Pontiac GTO w/400 engine, car weight #3504 lbs.

400/350 HP (Standard engine car),,,,,,,,,,classed in E/S (10.01 wt/hp)
400/360 HP ('HO" High Output Engine),,,classed in D/S (9.73 wt/hp)
400/360 'RA I' (Ram Air I Engine),,,,,,,,,,,,,classed in D/S (9.73 wt/hp)
400/366 'RA II' (Ram Air II Engine),,,,,,,,,,,,classed in D/S (9.57 wt/hp)

I'm no Pontiac expert, but I think this is the 68' 400/360 'HO' specifications.
The 400/360 'HO' was the first performance engine option for the 68' Pontiac.
It was also known as; the 400/360 HP 'Non-Ram Air Engine'

Block Casting #'s: WS or YZ
Pistons; 10.75-1 compression
Cylinder Heads; #16 casting's (2.11" Intake / 1.77" exhaust) (72 to 75 cc's) (Open chamber)
Cast iron exhaust headers
Camshaft; (Hyraulic) .425 intake lift / .424 exhaust lift (288*/301* duration) (119 Centerline) (63* Overlap)
Cast iron intake manifold
Rochester Quadra-Jet (750 cfm) Model #7028267

The Rochester carb on the 400/360HP 'HO' was different than the 400/350HP carb,
with a larger Main Rod, and some other minor up-grades;
Throttle openings: 1 3/8" Primary / 2 1/4" secondary
Main Jet: #72
Main Rod: #41
Spring: #7037305
Secondary Rod: #BE

The #16 Cylinder heads, had regular valves, screw-in studs, dual valve springs and 'D' port exhaust.
Considered a good general all-around performance cylinder head.

A true performance test by Motor Trend Magazine (December, 1967)
400/360HP 'HO", TH-400 Automatic Transmission, w/3.23 Posi Gears
G77 x 14" tires
15.10 @ 90 MPH

Suprisingly, 400/360HP 'HO' production numbers are quite high, only a ($76) option.
9303,,,,,,,, Manual 4-Speeds
4007,,,,,,,,,TH-400 Automatics
13,310,,,,,,Total


pc

Re: 1968 Pontiac GTO
 

That seems a touch slow, my father was turning that at Alton with his 65 Tempest. 326/285hp "HO" 4speed and a 3.36 posi. I know my father wasn't the best, but he knew his car and it is still the same one sitting in my shop. Still the same down to the original hoses. It is the car that made me a car guy.

Re: 1968 Pontiac GTO
 

im a pontiac guy but you can tell times have changed i took my daily driver 08 pontiac g5 to the track last week and ran it ,15.89@89mph 4cylinder no turbo bone stock and got 30 mpg going there!

Re: 1968 Pontiac GTO
 

Maybe a better view of the 1968 GTO,,,

Car Life Magazine
May 1968

400/360HP 'HO'
4-speed
w/3.90 Posi-Rear
G77 x 14" Tires
14.53 @ 99.7 MPH

A more presentable performance.

Re: 1968 Pontiac GTO
 

Ed,

The 1968 Pontiac GTO 'Ram Air I'.

Option Code #342,,,,,,$342.89

The 400/360 HP 'Ram Air I' was more potent than the 400/360 'HO'.

Block Casting #'s; WS or YZ (4-Bolt Main Blocks)
Pistons; 10.75 compression,,,, (same as the 'HO')
Cylinder Heads; Casting #31 (2.11 Intake / 1.77 Exhaust) (72 cc's) (Open chamber)
Cast Iron Exhaust Headers,,, (same as the 'HO')
Camshaft; (Hydraulic) .425 Intake / .424 Exhaust (301*/313* Duration) (119 Centerline) (76* Overlap)
Rochester Quadra-Jet (750 cfm) Model #7028275
Cast Iron Intake Manifold (#9790140 same as the 'HO')

The main engine differences between the 'Ram-Air I' and the 'HO' were,
the 'Ram-Air I' had a 4-Bolt Main Block, and the #744 camshaft, which had more duration
and overlap.

The #31 casting cylinder heads had the same valve and port size, but the combustion chambers were a true 72 cc's. (Generally regarded as better casting cylinder heads).

The cast iron intake manifolds (#9790140) were the same on each engine.

Both engines had the special long-branch cast iron exhaust manifolds.

The Rochester 750 CFM carburetors were almost identical, except the
# 7028275 'Ram-Air I' carburetor had more jet area.
---------------------------------------------------------------------------------------------------------------------------------

All GTO Ram-Air cars were to be equipped with 4.33 gears.
But the mandatory Safe-T-Track Differential option (Code #361) was required ($63.19)

The M-21 close ratio 4-speed was an option (2.20 1st, 1.64 2nd, 1.28 3rd, 1.00 4th),
Code #358 for a cost of ($184.31)

The 'Ram Air I' 400/360HP cars were built between December 1967 thru March 1968.
--------------------------------------------------------------------------------------------------------------------------------

The 400/360HP 'Ram Air I" did make its mark early.
At the 1968 NHRA Winternationals, Gary Brookshire out of Visalia, California
won the D/Stock Class with his new 1968 GTO.
Ran 12.70's @ 110 MPH.
As he took out a host of 68' Mopar GTX 440's, and 68' Olds 4-4-2's.

Re: 1968 Pontiac GTO
 

Super Stock & Drag Illustrated Magazine
October 1967

http://66.154.24.154/jal_attachments...b?d=1267199334

In November 1967, Royal Pontiac (Royal Oaks, Michigan) did a performance test for the editors of Super Stock & Drag Illustrated magazine.

The car was a 'new' 68' GTO 400/360 HP 'Ram Air I', 4-Speed (with P/S and P/B) and
4.33 gears.

The GTO underwent a 'Royal Bobcat Level I' up-grade.
The car had the 'dealer installed' Ram-Air hood scoop package.

The cylinder heads were removed, and replaced with a set of Royal Pontiac
(Casting #31) prepared 'blueprinted' units;
* 3/angle valve job
* milled and cc'd
* valve spring shim height set
* rocker-arm lock nuts
* thin cylinder head gaskets

Note: Compression ratio was estimated at 11.5 - 1 (over the stock 10.75 -1 ratio)

* The distributor mechanics were replaced with a performance re-curve kit.
* Larger jets were installed in the Rochester 750 CFM carburetor.
* Colder Champion J10Y spark plugs were installed.
* A heat-riser block gasket was used for the intake manifold.
* A set of Doug's Headers were installed.
* The exhaust pipes, mufflers and tail-pipe extensions were removed, to lighten the car.
* A set of M & H Slicks (8.00" wide x 14") were installed on Hurst (14" x 6") Rallye wheels.

The performance test was supervised by Milt Schornack, Head of the High-Performance
Division of Royal Pontiac.

Driver; John Kosmala of Royal Pontiac

Results: 12.93 @ 108.05 MPH

This was the supposed car;
White with gold rocker panel moldings, and a gold stripe painted
down the hood center, an Endura front bumper, hidden headlights, and Hurst (14" x 6") Rallye wheels.
http://ultimategto.com/1968/68roybo.jpg

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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'.

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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.

Re: 1968 Pontiac GTO
 

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?