Missing TCS Solenoid on my 70 LT1

[Kenneth H.]

While troubleshooting another problem, I discovered that the TCS solenoid and vacuum plumbing were missing. The TCS relay and wiring are in place, the temp sender is gone and I have no reason to believe that the transmission sender has been removed. Eventually I plan to put everything back the way it's supposed to be, but in the mean time what do I do?

Currently the vacuum port on the front passenger side of the Holly carbuarator is capped, and the port on the distributor vacuum pot is open. Is this the configuration that I want in the interim, should I run a hose between the two ports, or should I additionally cap the port on the distributor pot? I've checked out all of the previous threads, and read the Restorer article, but I can't figure out what the correct temporary configuration should be. Any help would be appreciated.

Thanks.

[Jack H.]

Re: Missing TCS Solenoid on my 70 LT1

For a temporary OR long term but factory concours 'incorrect' fix, simply convert your distributor to a full time vac system. That means run a hose from the distributor, bypass the TCS control solenoid, and connect it directly to the carb.

Now, the distributor will have vac advance 100% of the time vs. the factory original design that selectively 'killed' vac advance (via the vac solenoid) when the car was being driven in low gear(s) or in response to specific engine coolant temperature.

That's the way Corvette engines functioned in the early to mid 60's before designers started to 'tinker' with improving their emission profile...

[Kenneth H.]

Re: Missing TCS Solenoid on my 70 LT1

Jack,

Thanks for the advice. I'll do that. Will I need to make any adjustments to the carb or the distributor once I attach the hose?

Thanks.

[Jack H.]

Re: Missing TCS Solenoid on my 70 LT1

Expect your curb idle RPM profile to rise as a result of giving the distributor full time vac. It's just a 'tweak' with a screwdriver to set 'er back to correct/normal...

[Steven H.]

Re: Missing TCS Solenoid on my 70 LT1

Ken

And if you like the way it runs now but want the hoses hooked up for appearance, a little trick is to stick a ball bearing inside a given hose. While it will still appear to be hooked up and working; it really isn't, of course make your bearing choice big enough not to enter the vaccum source port.

Steve

[Jim T.]

Re: Missing TCS Solenoid on my 70 LT1

Kenneth my 70 Corvette with 350/300 solenoid was disconnected a month after I bought it new. I have enjoyed the benifits of full time vacuum like the 60's Corvettes.
What benefits? Better gas mileage for city driving and lower engine temperature during city stop and go driving.

[Kenneth H.]

Re: Missing TCS Solenoid on my 70 LT1

Thanks, everyone, for the insight. I'm looking forward to completing the job. I do care about originality and judging, but that will be left for the future. By the way, does anyone know offhand what diameter hose I'll need between the ports?

Thanks.

[Steven H.]

Re: Missing TCS Solenoid on my 70 LT1

Ken

Not sure of the size; but I believe it has a white stripe.

[Les G.]

Re: Missing TCS Solenoid on my 70 LT1

Go To The Dr. Rebuild Site Or Look In Their Catalog, And They Have A Diagram They Also Sell The Hose Kit.

[Kenneth H.]

Re: Missing TCS Solenoid on my 70 LT1

Les,

Thanks, I've been to Dr. Rebuild and plan to purchase most of the components from him once I figure out what I need. I'm just trying to come up with a temporary fix based on previous suggestions (hose between the two ports) and the kit from Dr. Rebuild appears not to have a hose long enough to accommodate this fix.

Thanks.

[Jim T.]

Re: Missing TCS Solenoid on my 70 LT1

Kenneth just drive your LT-1 to a auto parts store, lift the hood and take the cap from the carb into the store and tell them you need a vacuum hose with the caps inside diameter and install it right there for the benefits.
Before you drive off, after starting remove the new vacuum hose from the vacuum advance and reconnect. You should notice a reduction in rpms when you remove it and rpms should increase when the vacuum hose is reinstalled

If nothing happens, one of two things wrong. Vacuum hose to connected to ported vacuum on carb or the distributor vacuum advance unit has a ruptured/leaking diaphram.
Tell us how you like full time vacuum! A LT-1 with 4:11 and standard equipment of posi-traction, take-offs from a stop should really plant your back to the seat. Would like to take this ride.

[Kenneth H.]

Re: Missing TCS Solenoid on my 70 LT1

Jim,

Sorry I didn't get back to the thread earlier. It's been busy around her. I'm going to do exactly as you suggest (probably tomorrow), and get back to you on results. Thanks.