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Intake Manifold Vacuum???

11824 Views 12 Replies 5 Participants Last post by  DirtFiend602
Intake Manifold Vacuum??? (Pics Added)

I'm definately a newb to this 'old school' stuff, I've played with mostly Honda/Acura the past decade. So opening the hood to my new 1985 Bronco with a 351w(2bbl) is obviously a shell shock haha. So I need help. I'm going through attempting to corrrect all the misguided vacuum lines in this thing.

So my question is: on the front side of the intake manifold, just under the carbeurator, there is what looks like a vacuum port. I was wondering if this is suppose to have a hose that runs to the manifold vacuum on the back with all ports? I'm just assuming that's where it goes because there is an open port on it. But you know what happens when you assume so that is why I'm asking the experts here.
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Is it a small port in the carb's baseplate, or is it a large one in either the intake or a spacer under the carb? The small port feeds the EGR at cruise, and the large one is PCV valve manifold vacuum, for which the PCV is installed in the oil filler cap at the front of the driver's side valve cover.
Also, is the VECI label under the hood? It will have a diagram to follow.
This port is on the Intake manifold itself. The sticker under the hood doesn't cover this, probably because its on the I/M who knows. But the PCV coming out of the oil filller cap goes to the air cleaner does it not?
Please help guys, I don't have a decent shop around me without having to drive an hour to Nashville. I know I can fix this myself, I just need the information to do so.
Do you have pictures of the vacuum ports? Some engine's can have quite a few that go several different places.
The PCV does connect to the intake vacuum port; there should be a diagonally-opposite tube on the passenger valve cover that hooks to the crankcase filter in the air cleaner, supplying fresh, filtered air to the crankcase for the PCV to correctly operate. Since my '79 Ranchero has a very close setup (351W-2V), I'll see if I can get a couple pics on here to clarify. Unfortunately, the weather's crappy, and the sun's already heading down tonight.
Thank you guys.. I'll see about getting some pics. As of right now the PCV on the passenger side is just ran to the firewall...?? I'm guessing thats wrong by the way ya'll are talking haha
Ok so here's a couple of pics:

This is of the port I'm curious of where it goes...

This is the PCV on the passenger side valve cover, you can see it just runs up to the firewall. It's also got a second hose coming out of it that runs to the back of the carb...
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Also, do all of the ports on the manifold vacuum on the back of the Intake Manifold have a home or are any of them just plugged?
I hate bumpin my threads, but I really want this fixed before I test it out on any trails or mud. You guys are the only source I have to get this fixed, no shop around me knows enough about vacuum lines to give me a straight answer.
Yeah, that front one is definitely manifold vacuum, even if it isn't used for PCV. Go to Vatozone, O'Really, Crapa, whomever you do business with and buy a package of vacuum caps (rubber or vinyl doesn't matter). Choose the size that fits snugly over it and see how it runs.
Maybe this will help;
Diagram in a 85-86 5.8 Carbureted
Source: by Chilton

acronyms (not nec. for your year/engine)
A/CL: Located in the air cleaner
A/CL DV: Air Cleaner Diverter Valve
A/CL BI MET: Air Cleaner Bi-Metallic Valve
A/CL CWM: Air Cleaner Cold Weather Modulator
ACT: Air Charge Temperature Sensor, prior to 1992
ACTS: Air Cleaner Temperature Sensor
ACV: Air Control Valve
AIR: Thermactor, short for Thermal Reactor. CA vehicles are installed with it as standard. Air Injection Reaction is what it stands for.
AIR BPV: AIR BPV is the AIR Bypass (AIRB) Valve; also called the TAB (Thermactor Air Bypass) Valve
BV: Bowl Vent (on top of the float tanks)
CARB: Carburetor
CBD: Closed Bowl Distributor
CPRV: Canister Purge Valve
DIST: Distributor
DPFE: Differential Pressure Feedback
DV-TW:Two Way Delay Valve
EFCA: Electronic Fuel Control Assembly/ (Fuel Pressure Regulator (FPR)
EGR: Exhaust Gas Recirculation
EXH HCV: Exhaust Heat Control Valve
EVP: EGR Valve Position
EGR: Valve Position
EVR: EGR Vacuum Regulator; also called EGR Vacuum Solenoid
FLTR: Filter
FPR: Fuel Pressure Regulator (check vacuum line)
HEAT VLV INT: Heat Vacuum Control Valve Intake, (next to carb)
HICV: Hot Idle Control Valve
IAT: Intake Air Temperature Sensor (Air Charge Temperature (ACT), prior to 1992
IVV: Thermactor Idle Vacuum Valve
LCV: EGR Load Control
MAN VAC: Manifold vacuum-Vacuum source; usually ref. to as Vacuum Tree atop intake manifold]
MAP: Manifold Absolute Pressure
PCV: Positive Crankcase Ventilation
PURGE: Vapor Canister Purge Valve
PV: Ported Vacuum
PVS: Ported Vacuum Switch (PVS) Valve
S: Spark port
SA-FV: Separator Assembly Fuel/Vacuum
SOLV: Thermactor Solenoid Valve
SV CBV: Carborator Fuel Bowl Solenoid Vent Valve
TCAC: Thermostatically Controlled Air Cleaner
TCP: Temperature Compensated Accelerator Pump
TK: Throttle Kicker
TVS: Throttle Valve Solenoid (aka Solepot, Dashpot)
TVS: Temperature Vacuum Switch
TVV: Thermal Vacuum Valve
or, TVV: Thermostatic Vacuum Valve (aka Ported Vacuum Switches; Thermal Vacuum Valve)
VAC: Vacuum
VCKV: Vacuum Check Valve
VCV: Vacuum Control Valve
VDV: Vacuum Delay Valve
V CK V or VCV: Vacuum Check Valve
VOTM: Vacuum Operated Throttle Modulator
VRDV: Distributor Vacuum Delay Valve (VDV, VRDV, DV-TW)
VRDV: Vacuum Delay Valve (VDV, VRDV, DV-TW)
VRESER: Vacuum Reservoir (coffee can style in earlier years; replaced by plastic style)
VRESV REST: on earlier years such as SEABRONC's 83 is a Vacuum Restictor/delay valve, it delays vacuum for a certain amount of time
VRV: Vacuum Regulator Valve
WOT: Wide Open Throttle Valve
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bump... here is my slight my header panel.. 1986 bronco 351w duraspark II non CA, non high altitude, w factory AC

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