C3 emissions control systems

[Tom R.]

did a 70 454 with automatic come with the air injection reactor system
the build date is june 1970

[Terry M.]

NO *NM*

[Tom Freeman]

Re: C3 emissions control systems

All Vettes in '70 used CCS (Controlled Combustion System) for emissions control with the exception the LT-1s which used A.I.R.

tom...

[Tom R.]

Re: why?

Caught my curiosity and couldn't help but raise the question "Why?"

In 68-69...everything got smog. Then in 70 we see the hiatus and in 71...smog begins to creep back in until 73 when everything gets A.I.R. So what' going on?

A.I.R. was expensive and alternatives were being sought...thus we get the controlled combustion system or CCS which is what was equipped in 1970.

Also...70 model cars were actually 69 calendar year cars produced from 69-70 and the new emission standards were effective in the 1970 calendar. So the 69 cars weren't quite really subjected to the new regs...yet! I'm speculting here. And those regs toughenged through 1975 so we see subsequent years get equipped with A.I.R. to comply with the stiffened emission standards.

Simultaneously, to meet the requirements, we see reduced compression ratios and therefore reduce horsepower (or was that just a shell game on paper), carb calibrations and something else I don't recall off hand.

Its safe to say that those early years...were subjected to much tinkering with emission controls to meet the federally mandated standards effective in 1970...or the 1971 model year.

Curious to hear the perspective of others...who were around and involved at that point in time. Go ahead jump out there and admit your age!

[Duke W.]

Re: why?

Beginning with the first federal tailpipe standards in 1968, emissions limits
tightened every two to three years, and it took time for Detroit to figure out
how to meet them. The effort was focused around reducing emissions by
changes in combustion chamber shape (which affected compression ratio), modified timing maps, and more precise fuel flow control to reduce "engine out" emissions, however, some engines required "aftertreatment", which was the purpose of AIR - to provide air for additional
oxidation in the exhaust system. NOx formation had to be controlled during combustion, which dictated lower CRs to reduce peak flame front temperatures, where NOx is formed, but later in the seventies EGR systems had to be implemented on some engines as NOx standards tightened.

Very stringent standards were proposed in 1970 to become effective in 1975,
and the engineering consensus was that catalytic converters would be needed
to meet them. Catalyst materials would be poisoned by leaded fuel, and EPA was
considering TEL reductions and ultimately banning TEL, so GM took a leadership
role by designing ALL their engines to operated on relatively low octane
unleaded fuel beginning in 1971, which gave the petroleum industry time to
develop refining and distribution prior to the absolute necessity for unleaded
fuel in 1975.

Duke

[Terry M.]

Re: why?

Tom,

"Also...70 model cars were actually 69 calendar year cars produced from 69-70 and the new emission standards were effective in the 1970 calendar."

What 1970 model cars are you referring to? No 1970 Corvettes were produced in calendar year 1969, and 1969 Corvettes were produced until at least December 17, 1969, and possibly a few days beyond.

Not to hijack this thread, because it was about 1970 emissions controls, but:
Folks commonly attribute this 1970 production delay to "strikes" during the 1969 model year, but my extensive examination of the available 1969 automotive press fails to provide a reason for the delay of 1970 introduction of Corvettes and Camaros.

Could it have been for emissions reasons? Who knows? I personally doubt that emissions are the cause, but I also doubt that it had to do with "strikes." I wouldn't mind seeing some hard evidence of the reason for the delay of 1970 Corvette and Camaro production.

[Jack H.]

Don't think we'll know...

why '70 Corvettes didn't start production until Jan, but I'm on your side with the hunch...it wasn't due to the long over strike in '69 as all other Chevy cars/trucks launched at traditional Summer '69 model year changeover.

I'd bet it was a strategic move based on the California emissions requirement and since Corvette was the 'flagship' performance vehicle in the line, Chevy chose to strategically wait until the 11th hour to see how NA9 equipped cars were received in California (approx 10% of sales) before committing Corvette to the 1-state unique emissions rules.

[John H.]

Re: why?

Terry -

Don't know the reason behind the late Corvette introduction, but the '70 Camaro introduction was delayed due to failure of the quarter panel draw dies during the Pilot die tryout program. Fisher Body couldn't make the quarters without wrinkles and splits from the beginning of die tryout, and after many changes to the draw punch clamping rings, they finally gave up and had to build new draw rings from scratch, which delayed the production launch by four months. I was there, and it was a genuine nightmare. The PR flacks gave it a different spin for public consumption, but internally it gave Fisher Body Die Engineering a huge black eye - first time Fisher Body had ever caused Chevrolet to miss a launch date.

[Terry M.]

Thanks John

Thanks, John, for your usual candor. I had been trying to find some commonality between Camaro and Corvette that would reveal the root of the delay, but you have blasted that idea.
It is remarkable that all the 1969 announcements about the delay that I could find lack a reason, and the automotive press let the PR folks get away with that. I doubt that would happen today.