My shop is doing more work on my 74. They noted a sensor attaching to the block on the passenger side had melted from the heat and that there was no shielding on that side. Is there supposed to be some there like the driver's side and I'm just missing it, or was there never any for that side? Thanks!

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I wanted a Corvette my whole life, but I never dreamed of all the wonderful people I would meet because of it!

The only sensor on the pass side of the engine is the temp sensor for the TCS system, and yes, there should be the same type of metal shielding around it as you see on the driver side.






|UPDATED|4/28/2015 4:24:01 AM (AZT)|/UPDATED|


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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

If Mangets car has TCS, he'd best keep it. I have a 72' base car, that HAD TCS. It was removed before I purchased it. I, personally have not seen it on any engine, to see what I needed to put it back on. Don't know what to look  for or how to install it.   VERY few even know what I'm talking about when I mention it. Aside from Joel, now marshall has some knowledge of it.

|UPDATED|4/28/2015 5:12:19 AM (AZT)|/UPDATED|


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Mark(and all), I have, in my vast, un-organised library of useless crap, a tutorial on how/why/when the TCS(Transmission Controlled Spark) works. Not sure of the years covered on it, but I'm fairly certain it covered the '70-'73 systems. The Factory Service Manuals also have a complete theory/operation section on the systems, which varied slightly from year to year.
The main components are:
Switch on transmission
Vacuum solenoid(mounted on intake manifold)
Timer(mounted on firewall)
Temp sensor(mounted in the head)

I'll try to dig the info up next chance I get....

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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Here are some shots of the TCS components on my '73 L82 according to Joel's posting:

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John Sigmund

Tanks John! 
Yes, the timer is what you show on the firewall. The timers were different for different years, as they could be a 30 second delay, or 15 seconds....it varied. It was new technology for the time, and they were still trying to get the guv'ment required emissions crap figured out. Late '74 cars did not have a timer.
The circuit breaker next to it to the right in the pic is for power windows(or rear defog, if equipped).
The switch on the trans is correct for the later 4 speeds, but earlier cars had 2 switches there, one for 3rd, and one for 4th. Automatic cars used a pressure switch located on the passenger side of the trans, just behind the filler tube. The TCS only operated in the higher gears...3rd & 4th. The later cars, '73-up ONLY operated in 4th(or high gear on automatics), unlike the earlier cars that also worked in 3rd.

On a 4 speed car, you can see if the TCS is working by getting the engine to operating temp, clutch in, foot on the brake. Shift the trans into 4th gear(and 3rd on earlier cars), and, depending on the timer, you'll see the engine rpms rise about 200(approx) rpm as the system allows vacuum to the distributor. It's not possible to test the automatic cars like this, since the trans needs to be in 3rd gear on those, but you CAN connect a vacuum gauge to the vacuum advance line going to the dist, and drive the car. There should be no vacuum there until the trans shifts into 3rd gear.
This ALL assumes the system is working as it should. Any one failed, or non-operational component could keep it from working.


Of course, all of this has nothing to do with Marshall's original query.... Sorry Marshall....


|UPDATED|4/28/2015 1:18:47 PM (AZT)|/UPDATED|


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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

John, I have the switch from the transmission. THAT is got me looking to see what it was for. Joel put me on the correct path, and I found some info in a GM manual for the car. I have nothing else. The wire on the switch was not there, and nothing else to go by.

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I think the first photo should help Marshall out. Yes, there is shielding on that side and it shows what piece he's missing. He'll probably need a new temp sensor and wire if things have gone all melty down there. Thanks for the 4 spd TCS test info. I'll have to give that one a try once I get done with the timing chain adventure. Still waiting on some parts from Bair's.

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John Sigmund

Great stuff guys! The pix also help explain how it attaches (wing nuts) which was a bit of an open question as well.

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I wanted a Corvette my whole life, but I never dreamed of all the wonderful people I would meet because of it!

You'll have to have the metal heat shields that fit around/under the sparkle plugs to be able to install the chrome ignition shielding....plus the wingy nuts. Lots of folks remove/discard the chrome shields to make it easier to change the sparkle plugs, but they usually leave the heat shields in place....but ya never know.

Just think of all the crap people threw away off of these cars back in the day that we now have to pay through the nose to replace....

btw John.....I'm "stealing" your pics for my "future reference" files.... 





|UPDATED|4/29/2015 9:36:58 AM (AZT)|/UPDATED|


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Unless you are going to have your car NCRS judged, don't waste your time on a useless system.

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