1968 Pontiac GTO

[oldskool]

"...arent the GTO and Firebird identical engines then?"

Yes. There are several '68 & '69 400 D-port engines that are basically the same, whether in a Bird or a Goat.

The cams may be SLIGHTLY different. But with the unlimited duration & valve spring pressures, those slight cam differences won't really make a difference.

Here's the '68 330hp 400ci Bird engine specs. Current NHRA factor is 333hp. Came down from 338, the season before.

http://www.classracerinfo.com/Engine...9&MAKE=Pontiac

1968 350hp 400ci GTO engine specs. NHRA = 325hp. This was set in 2001. Don't know when it came down.

http://www.classracerinfo.com/Engine...5&MAKE=Pontiac

'69 330hp 400ci Bird. NHRA = 345. Was raised to this in '14. The specs look just like the '68 engines, to me. So, why is the '69 NHRA factor so high ? Guessing it's because the one quick '69 Bird Stocker was running so quick. That car belongs to long time Pontiac racer John Schloe, in div 7.

http://www.classracerinfo.com/Engine...9&MAKE=Pontiac

'69 350hp 400 GTO. NHRA = 325hp. The last change is dated 1/1/27. So I don't know when the change was made, nor when it was 1st reduced from the 350hp rating it had back in '75. One thing is for sure. At the current NHRA factors, a '69 GTO with the base 400 engine should be more competitive than a '69 Bird with the base 400 engine.

http://www.classracerinfo.com/Engine...4&MAKE=Pontiac

'70 330hp 400 Bird. NHRA = 350hp. Specs look real similar to the '68 & '69 engines. Don't look to have been any hp factor changes in recent years.

http://www.classracerinfo.com/Engine...5&MAKE=Pontiac

'70 350hp 400 GTO. NHRA = 350hp. Can't see any reason for the '70 engines to be rated higher than the '68 or '69 engines.

http://www.classracerinfo.com/Engine...8&MAKE=Pontiac

I CAN see that maybe some allowance should be made for a body which is more aerodynamic. For example: A 1st gen Bird body should offer less wind resistance than a '68-'70 GTO body. But, using the '69's for an example, I don't think the Bird should get a 20hp penalty. Maybe 5hp, 10 max. That would put the '69 Bird more in line with the '68 Bird.

Under NHRA rules, cars are penalized for going too quick. Lots of guys would probably go slower, if they had it all to do over again. Many have made their combo much less competitive, because of going too quick. Sandbagging has become a major aspect of Stock/SS racing. It's just part of the game, if you wanna protect your combo, in order to avoid a hit.

As it stands now, looks like the '68 & '69 Goats, with the base D-port 400, would be just as competitive as a 330hp '68 Bird. But, I don't know of a single one still active, unless someone is racing the former Adam Strang '68 Goat. I assume Tim Gillespie still has his '68, but don't race it anymore.

[Cstockbird]

Not sure if it’s the same for 68 RAII but it was for 69 RAIV that the power to weight ratio dictated the HP be less for firebird which was taken care of mainly with the different throttle linkage bracket.

This thread needs pictures something awful.

[Stan Weiss]

Originally Posted by Cstockbird

Not sure if it’s the same for 68 RAII but it was for 69 RAIV that the power to weight ratio dictated the HP be less for firebird which was taken care of mainly with the different throttle linkage bracket.

This thread needs pictures something awful.

Nostalgia Stock and Super Stock
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Actually it needs more tech.


Stan

[oldskool]

Originally Posted by Cstockbird

Not sure if it’s the same for 68 RAII but it was for 69 RAIV that the power to weight ratio dictated the HP be less for firebird which was taken care of mainly with the different throttle linkage bracket.

This thread needs pictures something awful.

"... with the different throttle linkage bracket..."

Yeah, those Q-jets were rigged up so they would not open all the way. But, that was easily fixed by hot rodders & racers.

On a Pontiac forum, I've been scolded for not posting pics to go along with what I was saying. I suppose that's one reason why I have collected so many Pontiac pics on my computer.

I think MOST guys like pics. At least I usually see several guys thanking the guys who post pics from races.

I don't care about MOST of the pics. But, I always like to see pics of the few Pontiac powered cars that are still active.

I assume that Adam Strang & Tim Gillespie have driven the quickest '68 GTO Stockers, ever. Tim Made the field at Indy a few times. He was #83 in 2006, @ .981 under. Adam was #105 on that list, but had already switched over to his '68 Bird. Tim also later switched over to a '68 Bird. Julie Biermann has been driving it for the last few years. It now runs high 10's.

https://www.dragracecentral.com/DRCS...r2006#indextop

Don't know the best time for either of the '68 Goats. But here's a 2004 race where Adam ran more than a sec under. He ran it mostly as a stick car. Won class at some races.

https://www.dragracecentral.com/DRCS...r2004#indextop

[DeuceCoupe]

Originally Posted by 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'.

"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'"

I'm still learning and Gonkulating these combos but no doubt about THAT.
So far the Gonkulator is telling me that (refreshingly) the 400 GTO engines tended to be rated pretty close to their actual gross HP (iron manifolds, open exhaust, 60F 29.92 dry sea level air, no accessories).

Note that under that standard Gross HP definition of the 1960s, Ram Air adds ZERO gross HP - since all engines are dyno rated with 60F air into the carb. Ram Air adds NET HP, which is not how they were rated in the 1960s.

Of course that Gross HP varied a little since so many cams were used.
So far, a certain rough set of numbers comes out of the Gonkulator. These are NOT factory ratings, they're computed from my own Gonkulator model, based on flow, dyno data, etc. About +/- 3% typically.

335hp 066cam, log exhaust
340hp 067cam, log exhaust
344hp 068cam, log exhaust

347hp 067cam, HO/RA exhaust iron
358hp 068cam
370hp 744cam

394hp Ram Air II (041cam, heads, RA exhaust)
424hp Ram Air IV (041cam, 1.65RR, heads, RA exhaust, alum intake)

Note I can't distinguish between the RA1 and RA3 - is that about right?
RA1=360hp, RA3=366hp, but are the head flows etc really any different?
Comments welcome on all this!!

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

Well we can't ask Paul about that comment but he must have got it from somewhere. I've searched quite a bit for cylinder head EXHAUST FLOW - very hard to find especially on the #96 RamAir II heads.

I'm trying to compare factory exhaust flow, from the D-Ports vs RA2 vs RA4 (and even 455HO and 455SD) heads. Anybody know?

[Stan Weiss]

Originally Posted by DeuceCoupe

"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'"

I'm still learning and Gonkulating these combos but no doubt about THAT.
So far the Gonkulator is telling me that (refreshingly) the 400 GTO engines tended to be rated pretty close to their actual gross HP (iron manifolds, open exhaust, 60F 29.92 dry sea level air, no accessories).

Note that under that standard Gross HP definition of the 1960s, Ram Air adds ZERO gross HP - since all engines are dyno rated with 60F air into the carb. Ram Air adds NET HP, which is not how they were rated in the 1960s.

Of course that Gross HP varied a little since so many cams were used.
So far, a certain rough set of numbers comes out of the Gonkulator. These are NOT factory ratings, they're computed from my own Gonkulator model, based on flow, dyno data, etc. About +/- 3% typically.

335hp 066cam, log exhaust
340hp 067cam, log exhaust
344hp 068cam, log exhaust

347hp 067cam, HO/RA exhaust iron
358hp 068cam
370hp 744cam

394hp Ram Air II (041cam, heads, RA exhaust)
424hp Ram Air IV (041cam, 1.65RR, heads, RA exhaust, alum intake)

Note I can't distinguish between the RA1 and RA3 - is that about right?
RA1=360hp, RA3=366hp, but are the head flows etc really any different?
Comments welcome on all this!!

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

Well we can't ask Paul about that comment but he must have got it from somewhere. I've searched quite a bit for cylinder head EXHAUST FLOW - very hard to find especially on the #96 RamAir II heads.

I'm trying to compare factory exhaust flow, from the D-Ports vs RA2 vs RA4 (and even 455HO and 455SD) heads. Anybody know?

It has been a number of years since I gave Dwight / Class Racer Info a number of files of flow data, so I don't know if this data is there or not. Also you need to be careful with flow data. I believe this exhaust flow data is without a pipe.



Pontiac 96 '71 Flowtech - Steven Magnotti
2.11
0.10000 - 76
0.20000 - 135
0.30000 - 177
0.40000 - 199
0.45000 - 204
0.50000 - 206
0.55000 - 208
0.60000 - 210
1.77
0.10000 - 50
0.20000 - 95
0.30000 - 128
0.40000 - 148
0.45000 - 153
0.50000 - 161
0.55000 - 164
0.60000 - 166


As far as Ram Air. That is correct you will see no difference on the dyno. The amount of HP increase from Ram Air will be a function of how fast / MPH the vehicle is going. The increase is not linear so @ 200 MPH it will be much greater than at 100 MPH and at 50 MPH almost nothing.


Stan


PS - Let me just add what I think you can see (positive intake track pressure) from a "Good" Ram Air setup.

50 MPH - 0.0444 PSI
100 MPH - 0.1776 PSI
200 MPH - 0.71 PSI

[DeuceCoupe]

Stan,
Thanks for that - I had looked in your database (which I use a lot) already, but arent those the 1971 #96 heads, ie casting 481196, 96cc stock?

The RA2 #96 are casting 9793596, 71-72cc stock, those are the ones I can't find. I'd GUESS the exhausts are close to the RA4 heads but can't find any numbers.

For sure on the "Ram Air" - I find about a 4% plus-up just for the cooler air works well, if it's a good system- just as those smogger IMCO Snorkel things can heat the air up a little, even when the flapper is open. The late-60s-up IMCO snorkels cost about 2% power from testing I've done.

And of course the "ram" effect, if any, depends on where & which direction the scoops are. The Cobra Jet shakers look totally cool (got my 1st one at a swap meet for $20) but dont get much ram, if any. I suspect the grille and cowl systems have a little edge there, even for "sensible" speeds like 100mph or so.

Thanks again for your head flow database it does the community a great service.