1970 smog need help
Thread Starter
Instructor
Joined: Jan 2012
Posts: 156
Likes: 24
1970 smog need help
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.
Race Director
Joined: May 2006
Posts: 18,710
Likes: 2,574
if you mean air pump, no it doesnt use one, see pictures in the link below
https://www.corvetteforum.com/forums...needed-of.html
https://www.corvetteforum.com/forums...needed-of.html
Team Owner
Joined: Sep 2006
Posts: 31,237
Likes: 4,328
From: Westminster Maryland
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
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
Racer
Joined: Nov 2014
Posts: 463
Likes: 129
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
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
Last edited by JC68; Apr 18, 2016 at 08:16 PM.
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
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.
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.
Last edited by Revi; Apr 19, 2016 at 12:43 PM.
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Safety Car
Joined: Sep 2013
Posts: 4,355
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From: Draper Utah
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.
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.
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
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.
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.
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.
Last edited by Revi; Apr 23, 2016 at 10:31 AM.