Why were Pontiac V8s problematic with emissions?

[King_V]

All,

Ok, there's been bits and pieces of information I've picked up here and there.... but, what was the particular issue with Pontiac engines?

I mean, ok, it was more than just for emissions reasons that the 301 was dropped in lieu of the 305, despite similar power levels and greater fuel economy from the 301.

Also, I've come to discover that some cars had Buick/Olds engines in them and not the available Pontiac engine because, in particular in California, the Pontiac engine couldn't meet emissions standards despite being more or less the same displacement.

So, what was going on? Was it the cylinder head/combustion chamber design? Something else? What specifically about the design of Pontiac engines made their emissions more problematic than other makes?

I don't want to get into a political argument about emissions control, etc., I'm just curious from a physics/design viewpoint.

 

[Bonnewagon]

Actually, Pontiac did quite well passing emissions. In fact, in '68, when others were adding smog pumps, Pontiac went to open chamber heads, negating the need for a smog pump. Plus, by using fully machined combustion chambers, compression ratios could be more accurate as well as displacement per cylinder. Look at the '67 closed chamber heads- the casting has provisions for smog pump tubes, but were never used. In '71 all the manufacturers lowered compression ratios because of the lead being taken out of the gasoline. Good ol' Pontiac went ahead anyway and developed the SD-455! AND passed emissions- with points ignition, EGR, and no CAT! As emissions and more important, C.A.F.E. (Corporate Average Fuel Economy) regulations tightened up, dooming the big motors, Pontiac then developed the 151 and 301 motors. Did you know they had the same bore and stroke, and shared piston/rods? Those motors were designed to pass emissions, sip gas, and cover the small and large cars then in development for years to come. Buick had a lock on the V-6 market with the 231, and deservedly so. I personally use a 301 in my wagon and I love it, and I am a 350/400/455 guy. To ask why GM ditched the 301, and even Pontiac itself, is futile, since they bowed to Chevy all the time. Oldsmobile? Same thing. What would a Turbo 301 in a 3rd gen Firebird have been like if Pontiac was allowed to refine it? Think of what EFI and OBD2 could have achieved with a 301. The weak crank? Use forged parts. We'll never know will we?

 

[King_V]

Yep, I always figured, based on the same bore/stroke, that the Iron Duke was in a way, a sort of 301 cut in half (well, not like the old 195 vs 389, but a similar concept).

Weird, though, that I came across references saying that California Emissions had a problem with the Pontiac engines, hence why similar displacement Oldsmobile (403 in place of 400), and Chevy (305 in place of 301) were used there. Maybe the latter info isn't as accurate as I thought?

I had come across references that the Olds head designs were emissions-friendly to the point that they were still able to get away with using a carburetor up through 1990 (though, my own opinion is GM should've had them going EFI before that point)

One would think that, if the 301 was better than the 305 in terms of emissions and/or fuel economy, it would've been to their benefit to go that route rather than the 305 - aside from the "spoiled child Chevy" corporate mentality, I suppose.

I do kinda like the 301 I've got now (though I really have to figure out my idle issues!)

 

[Bonnewagon]

Cali emissions are a horse of a different color. Lots of oddball combinations were used to satisfy Cali, perhaps the factory didn't want to waste time and money when it already had emissions friendly motors. For example, in '79, the only true Pontiac 400's available were left-over stockpiled '78 W72 models that were used in 4 speed TATA's. Would you bother with Cali emissions on a 400 when 403's and 301's were going in all other '79 TA's and the 400 was gone? The 301 got the smog pump in '80, and was gone after '81, so why invest in passing Cali standards? Never underestimate the cheap-assed-ness of GM! The '79 301 was available with a manual trans (I have two) and no smog pump. '80 had a pump but no manual trans. '81 you got a 305 with manual trans. Why? Emissions? Just ran out of flywheels? Only GM knows for sure. You know, GM killed Olds, Pontiac, and Saturn, which all had a loyal following. I have my prejudices why, but I don't want to start a war here. I'd hang onto that 301 and fix the idle. I find a 301 likes to idle best at 500-700 rpm, no higher. A clean carb should be able to do that. Use a vacuum gauge when you adjust the mixture screws.

 

[Clone TIE Pilot]

81 is the model year all US cars went to computer control. Maybe GM just didn't want to spend money to R&D a CCC system for the 301? SBC, SBO, and Buick V6s all have different CCC setups.

 

[Bonnewagon]

That's my whole point. Why not CCC the Turbo 301? That would have been a blast in the 3rd gen Trans Am! I remember an article in Hot Rod describing the 301, 305, and 307 about to appear. They raved about gas mileage, emissions, light weight, fitting under downward sloping aerodynamic hoods, etc. The future looked bright.

 

[olds307 and 403]

Pretty sure the 81 301 turbo had CCC. My understanding is the 301 is a strong block, has nice, thick mains. There is stroker cranks and a single plane aluminum intake out there for it, allowing better aftermarket heads. Those 3 things were the big problems with making decent power. EFI, better heads and a real crank would have made a potent package.

 

[tc1959]

Interesting read here about the 301, It seems that NOX emissions had a part in it's demise. http://ateupwithmotor.com/model-histori ... -am-turbo/

 

[King_V]

Interesting read here about the 301, It seems that NOX emissions had a part in it's demise. http://ateupwithmotor.com/model-histori ... -am-turbo/

Haven't read the article yet, but loved the title "Disco Inferno" - ha!... since that's one of the nicknames of my 1987 Crown Victoria Coupe. Black with red velour-like interior.

Ok, so now having read the article, one thing sticks out like a sore thumb:

Road & Track‘s April 1980 (turbo) test car was no faster than a normally aspirated Trans Am 301

What? How? Why? Without there being something actually wrong with the test car, I'm finding it difficult to believe that the NA 301 kept up with the Turbo 301 in 1980.

 

[Clone TIE Pilot]

Here is what Wiki says was a factor in the 301's demise.

The main causes of engine failure and distrust was the public's lack of experience and knowledge of care and maintenance of the new turbo engines. Often, the turbo cool-down procedure was never followed or even known to exist to some owners allowing the turbo to burn or "coke" oil onto the turbo's bearings causing early (sub 50,000 mile) failure prompting service or even complete engine replacement. Combined with the mechanic's lack of knowledge ultimately caused GM to cease production after April 1981.