I'm installing a SD TPI system on my 72 el camino. Apparently it is a mix and match system. There are only 2 vacuum ports at the rear of the upper plenum. I need 3 - I think. FPR, MAP sensor and Heater/AC.

Is there an easy solution? From what I've read, the FPR and MAP both need to have a dedicated port and line. Could I safely tap the brake booster line for the HVAC? I was thinking of using a one-way check valve and vacuum reservoir.

I know that finding a later 3 port plenum is probably the answer, but I have too much time/money tied up in polishing what I have. AND I'm anxious to get this project finished. Thanx.
Rick

EDIT - Is there such a thing as a plenum with 3 ports? I thought I had seen a reference to such a thing, but searching on eBay I did not see any. If such an animal does exist, what year am I searching for? Again - Thanx.

 

The '91 TPI plenum I just got from the junkyard, as well as my original TPI plenum, both have three ports. It's got two which are recessed --one for FPR and one for MAP-- and then on the same side right next to the recessed ones on the non-recessed section (still before the runner) it's got another port with a wider diameter fitting for the HVAC line. It's also got the brake booster port on the opposite side.

 

Here is what a SD plenum looks like. The picture is from an old for sale thread, where you can see the 3rd port on the passenger side.


I have a similar issue with converting from a 165/MAF ECM to a 730/SD/EBL ECM and where to plumb the MAP. I was thinking about relocating the MAT from the bottom of the plenum to be an IAT in the TPI air filter housing. This frees up the port under the plenum for MAP or heater/AC.

 

Thank you both. My system was pieced together and I don't have the 3 port plenum, but now I know what is needed if I choose to change it out.
But moving the IAT sensor sure sounds like a winning idea. I don't have a clue yet as to what type of air intake I'll be using but I've done enough "engineering" on this project that moving the IAT shouldn't be a problem.

Let me run this by you, while doing more homework this afternoon I was reading on the throttle body. Do you think that the EGR/Vapor Canister port, on the passenger side of the TB, has enough vacuum for the HVAC in my elky. I am not running EGR and could send the T'd line to the HVAC instead of the EGR. I have a vacuum storage ball that I can install.

Thank you again for the ideas/suggestions and help.

 

You can split the vacuum line between the MAP and the HVAC. The ports are all getting the same vacuum inside the plenum anyway.