Re: 1974 TCS Configuration
That type I have seen with a sponge filter and wire connector holder in both black and white.
That type I have seen with a sponge filter and wire connector holder in both black and white.
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Lyle
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Re: 1974 TCS Configuration
Well Mike I am still learning too -- or I am trying to. The one you post pictures of sure is different. I guess I'll stick with ending my knowledge at 1972 -- it is much simpler. You guys have fun.TerryComment
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Re: 1974 TCS Configuration
Put a star on your forehead, John! That's exactly the concept of 'switching' vac to the distributor's advance mechanism via the heat switch...
This isn't something we actually test in a PV, but I had one occassion to verify the operation on my '71 equiped with CEC.
We put a number of NCRS cars in a Colorado local 4th of July parade. It was a HOT day (90F ambient). During the parade (release clutch slide forward 10-12 feet, stop, wait, repeat), I watched my temp gauge wander up from 180 into the red zone...
Around 230F, 'click' the CEC fired based on the temp switch and engine idle climbed about 180 RPM. The temp gauge stabilized and then began to fall on its own. Around 195F, another 'click' and idle speed dropped.
From there, coolant temp began climbing again, slowly. The process repeated itself 5-6 times and the car did NOT overheat and pop the rad cap!
Other classic Corvettes in the parade (NOT NCRS cars) DID overheat, blow their rad caps and were pushed out of the parade to the side lines...Comment
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Re: 1974 TCS Configuration
Jack,
I am still trying to understand the TCS. Forgive my ignorance. Are you saying that ported vacuum at idle caused the temp rise and at ~230*F the temp sensor triggered a change to manifold vacuum and that lowered the temp? And that cycle repeated.
When I look again at Dr. Rebuild's diagram for the 1974 L-48 automatic it seems that Mike W's filter snout is hooked into the driver's side ported vacuum, on the other side the straight-on goes to manifold vacuum at the choke area, and the 90* goes to the vacuum advance. Your observation seems to follow this logic.
Sorry to be a pest. I'll do a mock-up to illustrate.
*Edit* - This is my interpretation of Dr. Rebuild's diagram.
Last edited by Paul L.; March 16, 2010, 03:05 PM.Comment
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Re: 1974 TCS Configuration
On the number of ports, it's pretty simple. Suppose you're in the 'engaged' mode with the solenoid passing vac to the distributor. The distributor responds to changes in vac pressure, but there's always some level of vac present.
Now, for whatever reason(s), the system wants to switch the solenoid and deny the distributor vac advance... Without a 'vent' or 'third port', how does vac get out of the distributor?
Simple leakage bleeding around the imperfect seal of the solenoid plunger is lousy way to get a 'crisp' response... Hence, a third port 'somewhere' to vent stored vac.Comment
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Re: 1974 TCS Configuration
Well, I'm more confused than ever.
The typical 4 speed set up has a solenoid with two ports with tubes attached, plus a vent with screen. The solenoid controls the flow of vacuum to the vacuum advance canister. The vent allows air to enter the tube leading to the vacuum advance canister when the solenoid is de-energized.
Why then does Paul's auto trans solenoid have THREE ports, with a tube attached to the third port (instead of being a vent as above) leading to ported vacuum? Seems to me that vacuum would then be supplied to the advance canister under all conditions except normal idle.Comment
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Re: 1974 TCS Configuration
Mike,
My mock-up is simply an interpretation of Dr. Rebuild's diagram and may not be correct.Comment
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