# Horse Power Ratings for 1967 GTO "Standard" 335 HP 400



## 3rd1967gto (Jun 12, 2011)

I am wondering if anyone else ever questioned the factory rating of 335 HP for the "standard" 1967 GTO engine. It had eleven more cubic inches than the good old 389. The new 670 Cylinder Heads had larger valves and was able to flow more cfm than the old 421 heads used on the 389. The intake manifold was better flowing and it used a Rochester QJet that flowed about 250 CFM more than the Carter AFB. I also noticed that the 350 HP 400 in the Grand Prix used the 670 heads but used the Carter AFB and older design intake manifold, but was rated 17 HP more than the "standard" GTO 400. I would have loved to see a dyno test of a "standard" '67 400 and the 360 HP HO and the "360" HP Ram Air engine with the '744' cam. Too me the differences in the "standard" 335 HP and the 360 HP HO was the 068 cam in the HO and the better exhaust manifolds and larger exhaust pipes. Thoughts?
Thanks!
3rd1967GTO


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## Instg8ter (Sep 28, 2010)

seen a dyno test of big blocks built to factory specs 409 chevy vs. 421 SD Pontiac....both rated from factory around 410 HP. 409 hit 408 HP, the SD topped out at 476 hp, that should give you an idea of the games Pontaic played with rating their motors....big brother would have slapped them down if they knew they were building Bowtie killers.


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## jetstang (Nov 5, 2008)

They rated the HP as 310 HP at 4000 RPMs, but at 6000 RPMs the motor makes 450. They did this to fool the car insurance, and all competitors. Just think what the LS-7 454/450 HP actually pushed, or the aluminum L-88 BBC.


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## Instg8ter (Sep 28, 2010)

Jet these were actual dyno numbers of factory spec motors....rules were that all motors were to be built like they would have came off the line, granted they both had dual quads , but they could have been ordered like that.....the chevy motor performed to rating at max RPM/HP, the Pontiac was underrated 75 HP at max RPM/HP granted the 421 has a few more cubes but 75 HP more? i think i saved it somewhere it was a whole series of all the big blocks but i only caught the chevy pontiac one been trying to dig up the rest with no luck. Curious where the pontiac stands against the Mopars and Stage one 455's


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## jetstang (Nov 5, 2008)

I just made an example of how they rated HP. No doubt the SD motors from Pontiac put out stupid power. I used to wish I could have lived during the muscle car era, but realize now that we got those cars for peanuts in the 80s. My buddies and I all had big CI cars and it was fun!


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## Richard Boneske (Jul 29, 2008)

It was fun!! I love my '64 GTO with a 428 & Tripower setup. But, the new Mustangs, Camaros, and Chargers will run circles around our old muscle cars--and get 20+ MPG on the highway!! Even the 454 Chevelle with 450 HP wouldn't match the new muscle cars.


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## geeteeohguy (Feb 2, 2008)

Just my opinion: Pontiac under-rated it's engines, Chevrolet over-rated them. Back in the day, I _completely_ waxed a '66 SS396 Chevelle with the 375HP engine and an automatic with my automatic 2 speed 335 horse, 4bbl Capri Gold '65 GTO. My car was bone stock with 64,000 miles on the clock. The Chevelle was bone stock, too. I also beat a '70 LS6 454 Chevelle _badly_ with my 4 speed, 389 powered '66 GTO with a 3.55 rear gear. The Chevelle was an automatic car. I was running a tripower and a Sig Erson Cam with Hedman Hedders. He was running an unknown lopey cam with headers, as well. Why did I beat a car that had 90 more HP than mine??? Also, it's interesting to note that the 360 HP HO GTO of '67 was rated the same as the ram air engine. Very sneaky. Never had a problem with Fords, either. 335HP 390 Fairlane GT's were NEVER competiton for a 335HP GTO.....not even close. And the Fairlane was a lighter, unibody car, too. This topic is FUN!!!!!


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## BearGFR (Aug 25, 2008)

:agree Like our friend Mr. PBody says, the GTO didn't gain its reputation by making a habit of _losing_ to the SS 396.

Think about it. From the get go in 1964 with the first GTO, everything about Pontiac performance had to be done "on the sly" to get it by GM Corporate. Same deal with the VOE exhaust system in 1970: as soon as that "Humbler" Superbowl commercial aired, corporate pulled what was arguably one of the "coolest" options to ever roll down the line. Same deal with advertised horsepower ratings. It just wouldn't "do" to have it widely known that stodgy old Pontiac was beating the snot out of Corvette in the power department. They didn't have to "lie" exactly --- when you consider that horsepower is actually a calculated number ( HP = [torque X rpm] / 5252 ), all they had to do was take the horsepower "reading" somewhere other than at peak torque rpm and report that as the rated figure. 

I remember a few years back when a Buick GS 455 Stage 1 flat destroyed a "mighty" Hemi Roadrunner... talk about wailing and gnashing of teeth!

Bear


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## geeteeohguy (Feb 2, 2008)

Bear, well put. I have the magazine with that article....it's an old CARS mag, I think...but early '90's. Time flies! It was an AUTOMATIC a/c equipped stock GS 455 that was loaded with comfort options and 3.23 gears and the Hemi Roadrunner was equipped with dual quads, a 4 speed, and 4.10 gears. The Buick beat the Hemi by a mile.....like .5 to .75 seconds, if I remember. Buicks get NO respect, and they're one of the baddest if not the baddest stock ride out there. The reason I personally never got "into" Chevies and Mopars (and I've owned 4 Mopars) is that they were entry level, cheaply trimmed cars, and they simply were not nearly as nicely appointed or fast as a GTO, and not nearly as good loooking, either!! Back in the early '80's, a coworker had a '69 Buick GS400 Stage 1 convertible with a factory 4 speed and a 3.42 posi. That car loooked like a luxo-boat, but it was super fast. Light blue with a white top and white interior. It was a low mile, "mint" car. I found out recently that they made something like 65 or 70 4 speed stage 1 ragtops that year.....sigh....


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## Instg8ter (Sep 28, 2010)

Back in the early '80's, a coworker had a '69 Buick GS400 Stage 1 convertible with a factory 4 speed and a 3.42 posi. That car loooked like a luxo-boat, but it was super fast. Light blue with a white top and white interior. It was a low mile, "mint" car. I found out recently that they made something like 65 or 70 4 speed stage 1 ragtops that year.....sigh....[/QUOTE]

heres one of i believe he said 18....4 speed conv. optioned out all original 45,000 miles










and an auto


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## jetstang (Nov 5, 2008)

Richard Boneske said:


> It was fun!! I love my '64 GTO with a 428 & Tripower setup. But, the new Mustangs, Camaros, and Chargers will run circles around our old muscle cars--and get 20+ MPG on the highway!! Even the 454 Chevelle with 450 HP wouldn't match the new muscle cars.


Remember, these cars were on little 78 series rock tires. Bolt some slicks on the car and the 3.90 geared cars really hauled ass. Watch pass time or other drag racing shows, these cars haul with a cam swap. New cars are fast, but it wasn't called the muscle car era for no reason. New to old, new technology really kicks the hell out of old.. 556 HP Cadillac CTS-V that gets 20 MPG, and is gross horse power over 600 HP, yeah, you got a point.. Old cars can be strong, but are not getting any MPG.


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## Rukee (Feb 8, 2007)

The closest thing to a computer in the old cars is the clock!! :lol:
How many computers does a new GTO have??


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