How should I handle the vacuum port on the N* throttlebody ran on the Gen 3 blower with my 3800? Do I cap it off? Run a vacuum line to it? PCV? I have the ZZP throttle body adapter if that changes things at all.

Thanks preemptively for the answers.

Edited as I used a Gen 5 blower for reference, someone here must have the answer

[This message has been edited by jelly2m8 (edited 06-04-2023).]

That's a Gen V supercharger

[This message has been edited by MichiganReefer (edited 06-15-2023).]

MichiganReefer, what year Supercharger do you have?

[This message has been edited by jelly2m8 (edited 06-04-2023).]

AFAIK the vacuum for the fuel pressure regulator and the MAP sensor is taken right off the lower intake manifold. The vacuum for the bypass valve is taken form the top of the supercharger. I will look at my setup tomorrow but I believe that it is capped off. Are you also using the larger early LS1 or LQ4 MAF? If so the MAF tables need to be adjusted to compensate for the higher flow.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Edited out for incorrect information.

[This message has been edited by jelly2m8 (edited 06-04-2023).]

My supercharger is from an 2005 Monte Carlo SS- still a Gen 3 L67. I have a LQ4 MAF and have already had Darth Fiero flash my PCM for it. Thank you guys, I appreciate the effort to find the answer.

I did some reading into this as it may be something I might need to deal with in the future. As Dennis explained, all of your vacuum needs are dealt with via the nipple in the LIM on the pulley side and the vacuum Tree on top of the blower.


That Vacuum port port on the N* TB is for your Evap system, the L67 TB's have that port on the opposite side. If you are running EVAP, hook it to that vacuum port, if your not running EVAP, plug it off

quote Originally posted by jelly2m8: I did some reading into this as it may be something I might need to deal with in the future. As Dennis explained, all of your vacuum needs are dealt with via the nipple in the LIM on the pulley side and the vacuum Tree on top of the blower. That Vacuum port port on the N* TB is for your Evap system, the L67 TB's have that port on the opposite side. If you are running EVAP, hook it to that vacuum port, if your not running EVAP, plug it off

Yes confirmed. On my install the N* TB vac line is plugged off using no evap system.
BTW, great to see you posting here again Anthony. We have missed your thoughtful posts. The forum is now a much different place than it was 20 years ago as most of us are now a bit older. I recall an old post you made where you replaced the dew wipes by lifting the window to reach the hidden screws that was very helpful. Thats how I now do it.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Thank you guys so much. I am running the evap system, so I will be using the LIM vacuum port.

quote Originally posted by jelly2m8: I did some reading into this as it may be something I might need to deal with in the future. As Dennis explained, all of your vacuum needs are dealt with via the nipple in the LIM on the pulley side and the vacuum Tree on top of the blower. That Vacuum port port on the N* TB is for your Evap system, the L67 TB's have that port on the opposite side. If you are running EVAP, hook it to that vacuum port, if your not running EVAP, plug it off

Be aware that the nipple on the pulley side of the LIM is after the supercharger so it will see vacuum AND boost! Only the fuelpressure regulator, the MAP (=2Bar) and BBV if used, should be connected.

My Northstar TB vacuum port I planned to connect it to the brakebooster line so I can eliminate the T on top of the SC for a cleaner look.

As I said in my last post, the purpose of the vacuum source in the LIM is as Dennis previously stated. We were discussing the OP's question about the vacuum port on the Throttle body. Dennis's info is correct so is mine, I'm not sure why you feel the need to try and correct either of us.

If you read well; I was just adding information. Why? Because every swap has custom work on the top of these motors and we are talking about vacuum ports and swapping vacuum lines. So I only made clear that vacuum taken from the TOP T is not the same "vacuum" taken from the right side of the LIM, in fact that is a boost port. That is important to know when swapping and connecting stuff.