Vacuum ports in a TPI plenum

[BBShark]

There are 4 ports for vacuum fittings in the back of a TPI plenum. 3 1/4" pipe and 1 3/8" pipe. There are also vacuum ports on the throttle body. So you need vacuum for the brake booster, MAP sensor, fuel regulator vacuum reference, PCV...........

Somebody have a map for where this stuff goes?

 

[JeffP1167]

Map, hvac, F/P regulator (passenger rear)
brake booster (drivers rear)
egr solenoid (under throttle body)
PCV (goes to lower intake manifold not plenum)

 

[Twin_Turbo]

 

[Twin_Turbo]

damn that diagram is not even correct where it says to brake booster is only a small nipple next to the one for the FPR that's for HVAC controls & t-ed to cruise & vac reservoir w/ 1 way valve, the brake booster is the large one on the drivrs side rear of the plenum., it sits at an angle in the rear most part. Can't miss it.

 

[mrvette]

damn that diagram is not even correct where it says to brake booster is only a small nipple next to the one for the FPR that's for HVAC controls & t-ed to cruise & vac reservoir w/ 1 way valve, the brake booster is the large one on the drivrs side rear of the plenum., it sits at an angle in the rear most part. Can't miss it.

All that complicated canister purge crap didn't exist on my '72, and so I never had to mess with it on my '87 ....the purge canister valve took one control line to the bottom of the tbody, then it went to the large TOP ported line at the pass side of t-body, along with a line from one of the valve covers....., I never ran EGR, PCV is as shown....now upon finding my canister purge valve was in fact stuck open, I eliminated one more line ...
and just cap the small port on the underside of the t-body.....

:smash::surrender:

 

[BBShark]

OK, so in this picture the fuel regulator vacuum reference is the 3/8 NPT hole at the top right and the brake booster is the 1/4 NPT at the bottom?



And the one of the 1/4 NPT in this picture go to HVAC and (I assume) one goes to the MAP sensor?

 

[Twin_Turbo]

The one on the right is for the intake air temp sender, the one on the bottom is for the brake booster fitting

[/QUOTE]


Those 2 are hvac/cruise/vac reservoir and FPR for the other one. Are you using a later style upper plenum? They have a boss cast on the side to mount the map sensor and it goes to the same location as the hvac stuff.

It uses a dedicated hose on those, the hvac/cruise/reservoir stuff is moved to another location...and I forgot where. The other fitting is always used for FPR with a dedicated hose also, no T-ed off stuff. It may have been that the hvac was T-ed off the brake booster line. Anyone have a stock speed density car I can't check my 90 vette right now and the other ones are all not stock anymore.

 

[mrvette]

I have NEVER seen any car with the booster vac line T'd/shared with any other use......

:huh:

 

[Twin_Turbo]

but there are no more ports on the manifold, where to hook up hvac/reservoir/cruise then??? You sure don't want to t off the FPR and certainly not off the MAP sensor!

 

[mrvette]

but there are no more ports on the manifold, where to hook up hvac/reservoir/cruise then??? You sure don't want to t off the FPR and certainly not off the MAP sensor!

Got me there Marck, I don't remember, I do remember the FPR had it own dedicated line at all times, the brakes always had a dedicated line, and I know the MAP was mounted on the firewall, and so by default I T'd off that line, OR maybe used that fitting on bottom of the throttle body....I maybe T'd off that one with the emissions canister....while searching for that bad cam, I went through SO many setups on that thing, I just can't remember now, only been 18 years since I hit the first install on the OEM engine, had a setup with aftermarket runners and large mani base, put the LT1 setup on it years ago.....I remember a T fitting in the vacuum lines and this is all from up north yet, all my controls have been modified for years now....

:friends::ghost:

 

[JeffP1167]

here are the 90-92 tpi plenum ports



90-92 top 85-88 bottom. 89 was a one year only plenum dont have pictures of it.

 

[JeffP1167]

Here is the PCV vacuum port on all TPI's

 

[mrvette]

here are the 90-92 tpi plenum ports


90-92 top 85-88 bottom. 89 was a one year only plenum dont have pictures of it.

AH, looking at those smaller ports there, I remember what I did now, the plenum fitting I used to feed the MAP and mechanical shit, was a larger ID fitting, which allowed increased airflow, and I never had a issue with it, I went out to the garage and looked at a old mani I have setting around....

BTW, I have a nice set of undinged stock runners available.....:friends: