charliedents

Looking to buy a 1970 350/350 4 speed air convertible and it doesn't have smog equipment on it. My 70 lt1 has smog. Do all 1970s come with smog equipment? This cas was supposedly done some years back for NCRS judging but never got judged so I was assuming it could be correct by not having it. Right or wrong? Thanks in advance.

MelWff

if you mean air pump, no it doesnt use one, see pictures in the link below
https://www.corvetteforum.com/forums...needed-of.html

Alan 71

Hi cd,
The fact that the 1970 didn't have any A.I.R. equipment and STILL had the higher compression makes it to my mind a really nice sb engine to live with.
Certainly a 1970 LT-! causes more excitement, but the 350 h.p. engine is quite special too!
Regards,
Alan

JC68

All 1970 Corvettes had some type of smog reducing system in place even if they don't have a smog pump. Chevrolet used several schemes to reduce emissions in 1970.

The Air Injection Reactor (A.I.R) system was used exclusively in 1968 and 1969 on Corvettes.

In 1970 the Controlled Combustion System (C.C.S) came into use. The C.C.S system used leaner carb setting and revised timing to reduce emission in place of the A.I.R.

The A.I.R system was the least performance robbing of the two, so it was used on all special high performance engines (LT1 and LS7 if it had made it into production). The lesser engines used the C.C.S system. The 1970 350/350 used the C.C.S.

All 1970 Corvettes also had a Transmission Controlled Spark (T.C.S) system that limited in what gears the vacuum advance would work.
John

charliedents

Very interesting.Thanks for the help.

Revi

You will have a TCS solenoid mounted to the intake manifold (passenger side) that blocks vacuum to the distributor in 1st & 2nd gear. (This system also uses a relay on the firewall, a switch in the transmission, and a temp sensor in the passenger side head.)

A simple way to test if it is functioning correctly, get engine up to operating temperature;
Clutch in - put shifter in 1st or 2nd gear, idle should be in the 750/800 rpm range.
With clutch still in - move shifter to 3rd or 4th gear, rpm should increase an additional 300/400rpm above previous idle.

Syl1953

Revi, what is the location of temp sensor in passenger head?

Revi

Between #6 and #8 cyl. (Green wire)

Iceaxe

Just curious, I have a 1970 L46 that is really clean and really close to original, but it does not have the TCS solenoid or the temp sensor, so I assume they were removed at some point in the car's life.

My questions, are what is gained or lost by removing the items? What else should I look for that was part of the system?

FWIW: I've owned the car for about 6 years and the only real modification I've found to date is someone installed headers and a CD player somewhere along the way. Other than that it appears the car was well cared for and no bubba fixes that I've run across. The engine was rebuilt about 8 years ago, before I bought the car. I'm just trying to learn everything about the car that I can.

Revi

You don't need the TCS system, the car probably runs marginally better at idle with it removed. When you're driving, you won't see/notice any difference.

With the TCS solenoid removed, I'm guessing you have vacuum going to your distributor all of the time. The car actually runs better that way, it likes vacuum at idle. GM installed the TCS system to block vacuum (reduce timing at idle) which increases combustion temperature to help with emissions output. Higher temps equal less emissions.

Temp sensor removed? Was it just replaced with a plug or was the head replaced with a unit without a temp sensor hole?

The TCS relay should be mounted to the firewall just to the right (drivers side) of the wiper motor. It has three single wire plugs going to it.

The transmission switch is located on the drivers side of the transmission, just below where the forward shift linkage attaches, it has a single wire plug going to it.