OLD SKL 69

When I get around to it, I am planning on bypassing the TCS switch (on my 71 Supreme) so I am getting more performance from my engine. Has anyone done this and if so, do you have a picture of it bypassed or at least remind me how you hooked everything up? Thanks!

jensenracing77

i don't know that it will give you more performance other than in high gear. to bypass it, (assuming you have them ran correct now) the vacuum line from the carb to the TCS, take it off and run the line from the distributor to the carb port you just unhooked. the third line on the TCS just runs to the top back of the carb for a fresh air vent, take it off and cap the port on the back of the carb. i would also take the TCS off with it being unhooked to have a cleaner look.

Olds64

x2

OLD SKL 69

Thanks, I will do that. It was my impression that the TCS only allows for full vacuum advance in high gear so you are not getting full advance in 1st or 2nd. It feels to me that it needs more advance and my initial timing is already set at 14 btdc. Before I change the distributor weights, I wanted to do this 1st.

Lady72nRob71

The TCS allowed for ported vacuum (from carb) to the disty in high gear. Full manifold vacuum was applied to disty only if the engine temp rose to above 210* or something like that.
The PO of Lady routed manifold vacuum directly to the disty and capped off the rest and left the TSC switch in there. It only looks like it is hooked up. She runs good, so i am hesitant to do anything differently with it.

MN71W30

Rob,
It seems that they would want to retard the timing at a high temp in 4th gear to prevent pinging.

joe_padavano

The timing advance provided by the TVS (which also bypassed the TCS) was intended for use at idle under overheating conditions. The retarded timing at idle was good for NOx emissions reductions but bad for engine temperature. Running full vacuum to the advance canister let the engine run cooler.

MN71W30

Thanks Joe,
You would think that changing the timing at idle would cause an irratic idle from time to time.
I think I'll leave mine dissconnected.

88 coupe

Assuming you mean at WOT (wide open throttle).

Under WOT conditions, there is not enough manifold vacuum to advance the spark, regardless of how anything is connected. Other than the "placebo effect" there would be no power increase.


There are only two ways to do that:

• Change the initial
• Move the vacuum source to the intake manifold.

Problem with changing to manifold vacuum is that initial would need to be retarded, to compensate for the added vacuum advance.

Erratic idle would not be an issue, under any of the above circumstances. The exception would be: If, under any circumstances, advance is already at optimum, adding more (whether initial or vacuum) will cause the engine to misfire.

Norm

507OLDS

I haven't had a TCS switch on my 72,since I built it. A better bang or improvement would be to remove the vacuum line from your distributor,& let the distributor advance itself mechanically.plug the vacuum port wherever the distribtor is connected to.You might have to bump-up the idle a hair when you do this.The port on the distributor can be left open.Get one of those spring kits for the distributor,& install the lightest set of springs.We have heavy cars,& need the advance to come in as quick as possible.You should achieve total timing by 3000-3300rpm. You want to focus on the total timing,& not initial,for maximum performance.With a timing light on your timing tab,& the engine at 3,000rpm,rev the engine higher.If the timing moves,it still wants to advance.If it stays put,you're golden.

BlackGold

Allowing vacuum advance to operate in first and second gear (by disabling TCS) WILL give most cars better throttle response in normal city driving (which is generally not WOT ). But if you've got a lot of rear gear and/or a high-stall converter (as I suspect Brian has), you won't see much difference, because the engine will already be at a higher rpm and have plenty of mechanical advance.

OLD SKL 69

I did that earlier tonight and took it for a test drive. Definitely has better throttle response off idle.

Thanks for the advice Brian. I will try that to see what difference it makes.

507OLDS

Yes,I run 3:73's,but if you have 2:56's,you're gonna need all the help you can get.In the earlier days,I did still get a better overall performance when I did what I mentioned above.I have also ran the vac line to the carb instead,& that was a good result as well.

OLD SKL 69

Your right, I have the 2.56 peg leg. Believe it or not, if I stomp on it, it will smoke it right up without a problem. (Had to make sure I set my carb up properly)

I will want to get a 3.42 posi at some point and maybe a 200r4 if my budget allows, so I do have more performance in mind.

But for now, at least the rear ratio I have cruises real nice at 70-75.

mmurphy77

A couple of more questions on this. I have a correctly installed TCS in my '71 442/auto. Does this prevent vacuum advance when hitting the throttle from idle? My car 'feels' like it's not getting advance when I jump on the throttle. I would think with all that torque I should be able to obliterate the 225/70 tires when flooring it off idle but it just takes off. It WILL pin me to the seat the whole time but I guess I just expected a more crisp response. If the TCS is supposed to allow vacuum advance like a non-TCS car on initial throttle is there a way to check it other than watching with a timing light? If it does NOT allow for initial advance, I think I'll also bypass it to allow for full advance on throttle for more off-idle response.

joe_padavano

Yes. That's exactly what it does.

mmurphy77

Thanks Joe. Then I think I'll cleverly re-route the vacuum line from the advance. With the air cleaner on nobody will be able to tell. According to the previous posts, I should run the distributor advance to ported vacuum off the carb correct?

mmurphy77

Forget that!! What am I crazy. The reason I bought this particular car is because of it's un-molested originality. It runs exactly the way Olds wanted it to run so I'm fine with that. My 200' burnout days are over anyway. The car still pulls like a freight train (in fact it's probably quicker WITHOUT all the wheelspin!) Sorry for my momentary lapse in judgement! Now back to your regularly scheduled programming....

BlackGold

Yes, a working TCS prevents vacuum advance in any gear except high, regardless of throttle. However, disabling it will not give you vacuum advance when you floor the accelerator pedal -- because there is no vacuum at WOT. Disabling the TCS will likely give you a little crisper throttle response at part throttle. It shouldn't be too hard to disable it without making it visible. You just have to figure out whether the solenoid should be engaged or disangeged full-time and wire it accordingly.

compedgemarine

Old Skl originally stated that his initial timing is 14 degrees. the part that always suprises me when people bring up wanting to play with the vacume adv. is that no one ever seems to know what the total timing is. 14 degrees may mean nothing if the weights are stuck and the mechanical does not work and they are using the vacume adv as a crutch. none of mine have used the vacume adv. in years. I set the mechanical up to come in when I want it and to give me the amount of advance I am looking for. maybe I am just too old and still remember how to work on a distributor with out a computer but seems to me that a lot of people need to read the service books and learn how the systems in these old cars work. not meant as an attack on anyone so no disrespect to anyone but I think we may need a tech section with lessons on the various systems.

OLD SKL 69

My initial concern when I brought this up was maximizing my ignition system for optimum performance. If the TCS switch does not allow for vacuum advance in 1st and 2nd gear, then it does hurt performance. (I know that this system was put in these cars for better emission control)


I did not mention this information because that was already set up correctly. Initial is set at 14 degrees btdc and I am getting another 22 from the mechanical and vacuum advance for a total of 36 by 3000rpm. So timing is set up properly and now with the TCS bypassed, it does have a better "seat of the pants" feel when accelerating.

BlackGold

To be fair, vacuum advance was also put there for better emission control. Its purpose is to help achieve a more complete burn (and better fuel economy) while at cruise, not to give you better acceleration. It's just that once they added vacuum advance to the distributor, they had to recurve it to not add the mechanical advance as quickly. Thus the point that Compedgemarine made: it is possible to recurve a distributor for great performace without using any vacuum advance at all. But then you're missing out on the benefits vacuum advance can give you on the highway.