I was looking at the numbers for Pontiac engines over the years, specifically 350s, cause I like 350s!! I can't help but wonder where they got these numbers from? I guess they just thought nobody paid any attention.

All #s as advertised. (source is a Chilton's from 1981)

1968 the base 2bbl 350 arrives on the scene: 265 hp 355 torq. 9.2:1 comp Ok lets take that at face value. It wore #17 heads which have proven to be fairly nice. This was a good engine.

1969 the same 2bbl 350 now wears #47 heads (no idea why) and 265 hp but drops to 325 torq. Although they claim the same 9.2:1 compression. Hmmm Same everything but we lose a chunk of torq. Well... different head, that can happen. OK mystery solved.

1970 same 2bbl 350 Here's where the numbers start to get weird. Pontiac now puts #11 heads on and gets 255hp but now likes 355 torq once again? But the comp is now 8.8:1. We lose compression and hp but gain torque. I ain't buying it.

In 1971 we start to see the first sign of the smog era and things go down hill fast but again they weave a fancy tale. They now put #94 heads on the poor 350 and get only 250 hp and a only 8:1 comp. But still somehow claim 350 torq.

And the amazing thing is that the 1971 350 would look like a screamer for about the next 15 years!! The poor 350 would drop to 155 hp in 1974!!! But if you opted for the 4bbl you could make 200hp!

See why the 1st gen birds were beasts!! Even the base 350 2bbl was an absolute monster in stock form in less than 10 years!!

Yeah, low compression really kills power, especially in small cube engines. The big cube, long stroke engines, like the 455, still had decent power & torque, especially the 455HO & SD455.

You can't really put any stock in factory hp & torque ratings. GM had different reasons, in different years & car models, to rate an engine either higher or lower than it actually was.

Some of the 350 & 400 engines were rated higher in the A-body than in a Firebird.

The RAIV was rated at only 370hp, which was only 4hp more than the 366hp RA3 engine. So, they were saying that the bigger 041 cam & the round port heads were only good for a 4hp increase. That's ridiculous.

Another thing that has been proven wrong is the advertised compression ratio. Many of the heads had bigger combustion chambers than advertised.

I think it would be interesting to gather a set of real numbers. What was the actual hp, torq and comp of each engine... each year. Heck so many guys have rebuilt them to factory specs over the years and dyno tested them we must have real numbers by now? I know there is still some variation from head to head etc it would be pretty close.

Since you mentioned that, I happened to think of a rebuild & dyno test of a '69 350HO engine. It made real close to the 330hp adv number.

https://www.hotrod.com/articles/hppp-1102-350-ho-engine-build/

"...so many guys have rebuilt them to factory specs over the years and dyno tested them..."

I'm guessing that VERY few 2-barrel stock rebuilt engines have seen any dyno time. And, most who just build to factory specs aren't really interested in the dyno numbers. Dyno time is not cheap.

But, there are probably lots of dyno tests of rebuilds of some of the most popular high performance engines, such as RAIV, 455HO, & SD455.

Another reason why accurate numbers are not available is because most rebuilds will include, larger than stock bore size, less than stock deck height, different pistons, & a different cam. So, the cubic inch, compression ratio, quench distance, and cam specs are not close enuff to factory specs to be a good comparison.

The other thing is most are done on chassis dynos so that's all pretty subjective to finding real numbers to compare.

They basically used math, knowns, etc, they also went from gross to net @ 71, but they also lied especially on the hit motors like the HO's and RA's because GM had a corporate rule that said nothing over 1HP per 10LBs of vehicle weight shall sail, period, so if you check your weight you'll find the hot motors suspicioulsy top out at @ 360, 366, 370 HP WHICH IS NO WAY, NO WAY, A 400 with good heads and 10.75-1 comp and the 068 or 041 cam is going to be in the 400-425HP range, has to be, I laugh when I read about the factory comparing a 69 RAIII at 366 HP and the RAIV at 370, right it only jumped 4HP with the 041 cam and 1.65 rockers and round port heads, yeah right.

What's the story with changing the heads every year? You would think if you had a good product with good performance in the range they wanted they would continue production? Just using the base 350 as an example they changed heads every year from 68-76. I understand the later years with smog considerations but 68-70? It's like they made a bunch of #17s and said oh well... for one year we're good and then the fun is up. Unfortunately the next head (#47) although essentially identical, had bigger chambers and less compression. And the next one (#11) continued the trend, same valve size but even bigger chambers for once again lower compression.

Yeah, there were lots of Pontiac heads that were very similar. The 12, 13, 48, 62, & 16 big valve heads were all very similar.

I suppose that the 6x-4 & 6x-8 heads were used longer than any other Pontiac heads. And, the 6x-4 heads were used on both 350 & some 400 engines.

#46 heads were used in both '73 & '74. 4X heads were also used in '73 & '74. But they came in more than one chamber size.

Here's the thing. These were smart guys. Pontiac had good engineers, everybody did. They were given a set of parameters and they built cars to fit them. The problem was the guys building the engines and cars and the guys crunching the numbers and the guys marketing the cars often had different objectives. And the rules sometimes changed mid project. The goals was seldom if ever to build the absolute best... fastest... most powerful car etc.

It’s all about the heads!!

No doubt about it. But the heads in the suits made a choice to use certain iron heads in a given application, or to make changes to it that resulted in more or less performance. And then in many cases were "creative" about the numbers. They didn't publish an honest compression number... ever. I would have liked to be a fly on the wall in those meetings.