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72 CS 350 4 bbl AC. So I am trying to sort out the vacuum highway. Found the CSM. Yeah. So I think I have where the lines should go from the CSM, the question is what are they suppose to read or pull vacuum wise when properly operating? All three read zero on vacuum gauge, car running idle. The Port D to distributor would increase on throttle bump but back to zero at idle. Port V and MT did not jump on throttle bump. I did this test in park ( by myself) since the transmission is involved I’m thinking that is why nothing seems to be happening in park or the engine was not overheating. Allot of stuff going on with this switch the biggest question is the port D to Dist.. doesn’t seem right. No vacuum in idle, bump in vacuum when throttle advance. ? If that is the case why do you have to cap VA when setting initial timing in idle. ( that’s how this all started BTW). Timing right on at 12 on initial reading. Thanks. Blue cap On back carb Vent D? Blue cap port C? Bonus. I found this on top of drivers IM.
If you think that is a "vacuum highway", try working on a 1980s 307 with CCC...
As for your TCS functionality, turn to page 6K-9 in your CSM and read the paragraph in the lower RH corner of the page. The short answer is that the DVCS serves two purposes. First, it is part of the TCS (transmission controlled spark) system that prevents any vacuum advance unless the trans is in high gear. That's what the electrical connector is for. Second, since your car uses ported vacuum to operate the vacuum advance anyway, the DVCS also serves as a fail-safe to switch the distributor to full manifold vacuum if the engine starts to overheat. This advances the distributor at idle, allowing the engine to run cooler. The normal ported vacuum doesn't provide vacuum at idle or small throttle openings, so if you are gauging vacuum at idle, you won't measure any. And that rubber tip is part of someone's vacuum testing tool and has nothing to do with the car.
Keeping TCS is a personal preference. I'd personally rather do without it, but in its day it made the Feds happy. Ported vacuum advance does more for cruise gas mileage than performance anyway.
I had a bunch of blow guns that the rubber tips were dryrotted and busted. Then I went to Carlisle and found tool vendors who had replacement rubber tips without having to buy the whole blow gun! Made my day...bought enough to last the rest of my lifetime. Now watch those dry rot before I need them again!
Ya I’ve read that para a bunch of times as well as most of the posts on this switch. Since basically a newb thought I just try to get a little more clarification. Trying to grasp the vacuum relationship of the three ports on the switch. Thanks Joe that helps this product of the Missouri public schools. One of steps in tuning is the timing. After dwell of course. It says to disconnect vacuum line from the carb. In this scenario it isn’t connected to the carb it’s connected to the DVCS which doesn’t pull any at idle. Either way timing right at 12 so hooray. Back to the books on this switch to see what I gaining with or without it. I read on one of the other post to just remove the electric and keep the other for overheating. I’ll look into this relationship. Thanks.
Ya I’ve read that para a bunch of times as well as most of the posts on this switch. Since basically a newb thought I just try to get a little more clarification. Trying to grasp the vacuum relationship of the three ports on the switch. Thanks Joe that helps this product of the Missouri public schools. One of steps in tuning is the timing. After dwell of course. It says to disconnect vacuum line from the carb. In this scenario it isn’t connected to the carb it’s connected to the DVCS which doesn’t pull any at idle. Either way timing right at 12 so hooray. Back to the books on this switch to see what I gaining with or without it. I read on one of the other post to just remove the electric and keep the other for overheating. I’ll look into this relationship. Thanks.
Keep in mind that TCS is an early emissions control system designed to reduce NOx. The way the system is wired, without power the valve is open and vacuum gets to the distributor (allowing for the fact that there is no ported vacuum at idle). Simply pulling the wire off means that you are getting ported vacuum to the advance in all gears, not just in high gear. The other option is to bypass the system completely and just run the distributor from straight manifold vacuum. You'll really want to recalibrate the distributor's advance curve to take full advantage of this, but since the OEM advance curve likely isn't optimum for today's fuels anyway, that isn't a bad idea. Running straight manifold vacuum also means that you'll want to play with the initial timing setting in addition to the advance curve.
December 21st, 2020, 04:35 PM
