This will be observed as a guage that quickly changes reading or fluctuates. Using A Propane Torch To Find The Vacuum Leak. (1) Select a store to see pricing & availability. I learned that requires a red ported vacuum switch (open at 235F) with three ports to switch between ported vacuum and manifold vacuum. It is also used in light airplanes to provide airflow for pneumatic gyroscopic instruments. All timing in at 2000 rpm is a pretty aggressive curve. When the throttle is opened (in a car, the accelerator pedal is depressed), ambient air is free to fill the intake manifold, increasing the pressure (filling the vacuum). 5.0 out of 5 stars. It could be a faulty line of computer code that pulses an injector too long, or a stuck piston ring that allows oil to be sucked into the combustion chamber. In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/air mixture to the cylinders. As an example, a 1967 Ford Thunderbird used vacuum for: Other items that can be powered by vacuum include: Modern cars have a minimal amount of accessories that use vacuum. Manifold pressure may also be "ported". Consequently, a misfire develops because the loosely packed air and fuel molecules fail to support combustion. The Non Ported vacuum on the carburetor feeds vacuum directly from below the throttle plate, or intake manifold vacuum.For the stock built engine the non ported vacuum advance is the most efficient way to go. Line: ARP. The ported sources from just above the throttle plates when they are nearly closed at idle, thus, manifold vacuum is not seen by the port until the throttle is opened enough in exposing the port to the manifold vacuum. The difference between the two being primarily at idle as manifold source would give you vacuum advance at idle while ported source gives you the same manifold vacuum, but only once the throttle is cracked open. Engine speed is low but the butterfly valve is fully open. As the throttle is opened, the engine speed increases rapidly. Such devices are necessary for engine braking with a diesel as they lack a throttle to restrict the air flow enough to create sufficient vacuum to brake a vehicle. If you do hear pinging, maybe try a copper/silver combo. Some experts have noted that a stock engine run a ported connection. A ported pressure tap may be either upstream or downstream of the throttle depending on throttle position. Venturi vacuum is caused by the venturi effect which, for fixed ambient conditions (air density and temperature), depends on the total mass flow through the carburetor. When the engine of the RPM is high and the throttle plate is closed, manifold vacuum will be at its highest. Ported vacuum operates in similarly like full manifold vacuum under certain conditions. Torque all of the manifold bolts in the sequence shown in Figure 1 to 11 ft/lbs. ARP Intake Manifold Bolt Kit - 134-2001. A vacuum test, can tell you a lot about, an engine's condition. But I would suggest that long term use the computer control. I use manifold vacuum when I am not using computer controled timing . It is important to differentiate between absolute and gauge pressure when dealing with certain applications, particularly those that experience changes in elevation during normal operation. On a true vacuum secondary carb (Holley and BG are the only . SPECIAL NOTE: This intake manifold is primarily intended for use with Vortec heads on pre-Vortec blocks. Free Shipping over $199*. Most of the time you will need to put a small elbow and crank it down pretty low into the intake and then install the carb. If the intake manifold vacuum is higher than normal, the base ignition timing or intake camshaft timing might be too far advanced. $25.00. Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. If you have open vacuum ports on the intake manifold and carb the engine will indeed run very poorly. Flathead vacuum falls into three different ranges of operation: Manifold Vacuum , manifold vacuum is direct vacuum from the intake manifold under the carburetor base plate. While an engine at idle, the vacuum gauge reads very low, or no vacuum, it means you are probably connected to ported vacuum. You can also use it as a hot idle compensator, if you're already hooked directly from manifold vacuum to the distributor by providing manifold vacuum to the middle port, plugging the top port, and putting a short hose with a filter on the bottom port. Just something I figured I'd throw in there so you're not surprised. Almost every part on the engine determines how long a catalytic converter will last. Since minor vacuum leaks increase idle speed on closed-loop fuel systems, the PCM commands the ISC to reduce air flow into the intake manifold. #1 Intake manifold vacuum port 09-27-2018, 08:41 PM Can someone tell me what this vacuum port is used for on the intake. Scan Tool Vacuum Diagnosis Electronically managed engines react to vacuum leaks differently than mechanically managed carbureted engines. Electronic engine management systems essentially follow the same strategies, but with much tighter parameters. Complete combustion of the air/fuel mixture is achieved when the fuel mixture is ignited a few crankshaft degrees before the piston reaches top dead center (TDC) and before maximum cylinder compression pressure is reached. For full manifold vacuum, do I just need to run a port from the manifold itself? The manifold vacuum port can be used to run the air cleaner shorkle valves and/or provide vacuum to the emissions charcoal canister. I can't see why it would be a problem. Atmospheric pressure at sea level will also support a column of liquid mercury (Hg) 29.92 in height. Find one small enough for the vacuum gauge line to slide onto firmly. AIS system is removed. When the throttle is opened all the way, the engine's air induction system is exposed to full atmospheric pressure, and maximum airflow through the engine is achieved. In order to function properly, in the manner stated in the article, the vacuum canister should be connected to a *manifold* vacuum port (sourced from below the carb throttle plates), NOT "ported" vacuum (above the throttle plates). It doesn't have the vacuum circuit for overheating. The diagnosis was simple: by connecting a tool called a vacuum analyzer to a lab scope and triggering the signal from the #1 cylinder, I noticed a slight variation in the waveform from the #5 cylinder. It may not display this or other websites correctly. Just two 2-port switches: blue and yellow (open at 133F? It is also a major source of engine drag (see engine braking), as the low-pressure air in the intake manifold provides less pressure on the piston during the induction stroke. Although the spring would close the valve well enough to a cranking compression test, the weak spring allowed exhaust gas to be drawn into the cylinder on the intake stroke, which diluted the air/fuel mixture and caused the intermittent rough idle condition. Generally, a 302 will like about 12-14 degrees advance for a base setting with the vacuum disconnected, and about 32-34 total (depending on compression, camshaft, elevation, etc.) 1.9L "FITTING" (INTAKE MANIFOLD VACUUM OUTLET) RARE, Model T Ford intake manifold w/vacuum fitting port, ORIGINAL 1969 1970 FORD MUSTANG BOSS 302 INTAKE VACUUM FITTING 2 PORT, 1967 1968 1969 1970 Ford Mercury Lincoln ORIG V8 INTAKE MANIFOLD VACUUM FITTING, FORD 1973 F100, E300(89),F250/350 "FITTING ASSY." Variations from the calculated standard, of course, are the weather conditions, the engine design, and how well the engine management system adjusts spark advance and air/fuel mixture to correspond to a change in barometric pressure. In other words, it is an engine vacuum that is available above the throttle plates of a carburetor which is used to advance ignition timing when the throttle is opened above its idle position. If the spark occurs too late in the combustion cycle, the slowly burning fuel mixture fails to exert maximum pressure against the piston. At its most basic level, intake manifold vacuum testing consists of connecting a vacuum gauge to a port tapped into the intake manifold. If you've got your timing "all in" before 2500, you may need to slow it down a little bit. However, this can result in a quicker revving response in most cases. However, diesel engines do not have throttle plates. A digital multimeter, for example, can be set to display minimum and maximum values. The problem was that without vac advance at idle, the engine could overheat in traffic. Manifold vacuum, so those cans don't work very well on a modified engine; with less . I'm going to pull the tank this weekend. My engine doesn't have one. The butterfly valve often contains a small "idle cutout", a hole that allows small amounts of fuel/air mixture into the engine even when the valve is fully closed, or the carburetor has a separate air bypass with its own idle jet. On some dual-plane manifolds you may need to use an open spacer or a modified four hole spacer so that the ported vacuum is sensing the affect of all barrels. Little details such as these can limit the life of a catalytic converter. #8. Automotive vacuum systems reached their height of use between the 1960s and 1980s. But I would suggest that long term use the computer control. I will play with it more and look at spring combos or changes after that, but so far, so good. After the engine starts, the baro input becomes a value upon which the MAP reading is based. 1.0. Copyright 2023 Fitech EFi Tuning Forum. Your email address will not be published. Car & Truck Safety & Security Accessories, NOS OEM Ford Motorcraft E73Z-9A474-B Intake Manifold Vacuum Outlet Fitting, 1967 1968 1969 Ford Mustang Mercury Cougar ORIG INTAKE MANIFOLD VACUUM FITTING, 1970 1971 Mustang Boss Mach 1 Cougar ORIG 351C INTAKE MANIFOLD VACUUM FITTING, 1969 Ford Mustang GT Mach 1 Cougar Xr7 ORIG 390 INTAKE MANIFOLD VACUUM FITTING, 1963-1964 Ford Galaxie 352/390 Intake Manifold Brass Vacuum Elbow Tube Fitting, 1970 71 72 FORD TORINO MUSTANG COBRA 351C 2V 4V INTAKE MANIFOLD VACUUM FITTINGS, 69 MUSTANG TORINO ORIG. They aim to get these engines to pass smog before the incorporation of the catalytic converter. There is no purge valve. introducing citations to additional sources, National Traffic and Motor Vehicle Safety Act, https://en.wikipedia.org/w/index.php?title=Manifold_vacuum&oldid=1137271740, Windshield wiper motors - Prior to the introduction of, This page was last edited on 3 February 2023, at 19:17. At wide-open throttle (WOT), atmospheric and manifold pressures become nearly equal as air rushes in to fill the engines cylinders. Please notify immediately admin@fitechefituning.com if you see any post in a foreign language or is off topic! On the other hand, electronically managed engines add an idle speed control (ISC) or idle air control (IAC) device to the throttle assembly to provide a more accurate control of idle speed. You must log in or register to reply here. I have that too just the way the drive line is set up on these cars but sure looks weird from the front. If you want to use the back of the intake for a vacuum source you can tap a smaller hole like 1/8" NPT or even two. OEM 1967 Cadillac 429 Engine INTAKE MANIFOLD VACUUM PORT TEE FITTING, Dodge Plymouth 440 400 383 360 intake manifold vacuum single port 1/4" tube, Model A Ford INTAKE MANIFOLD. Speed density systems, for example, use a MAP sensor to measure both the baro and MAP. It seems like the "source" vacuum could be the carb or the intake manifold, so which is preferred? Not Yet Reviewed. Looking for vacuum connectors and tubings near me? The engine will be rotating fast because the road wheels and transmission are moving quickly, but the butterfly valve will be fully closed. You only just have to hook it up and go. For an engine to function and run well, it must have enough compression to raise the temperature of the air fuel mixture high enough to allow a spark to easily start an efficient combustion process. The only thing that should be hooked to the carb is the dist. Make sure to listen for pinging with the light springs in. Nice job on the cleaner want to make another one? Manifold vacuum is present in all naturally aspirated vehicle engines that use throttles. 1965-1969 Corvette Intake Manifold Vacuum Fitting 4.9 (18) $2550 $10.99 delivery Mar 4 - 6 Only 16 left in stock - order soon. Dorman Vacuum Fittings, Caps & Accessories - JEGS High Performance. No one said it has to be a 3/8" pipe. which render manifold vacuum inadequate or unavailable. The '73 canister has 3 connections. V3388 \, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS POLISHED, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS GOLD, 1968-1969 Corvette GM# 3921920 Intake Manifold Vacuum Fitting 2 Port 3x2 400 435, 1/8 NPT Car Turbo Wastegate Boost Block Vacuum Intake Manifold Kits 6Port Billet, Fits 2011-17 Coyote 5.0 Ford Boost Vacuum Port Only (Intake Fitting), 1974-1975 Corvette Intake GM# 336015 Manifold Vacuum Fitting - 2 Port, Golden Eagle Billet Vacuum Manifold Block w/ (6) 1/8 NPT Ports Gold GVM100-GLD, Golden Eagle Billet Vacuum Manifold Block w/ (6) 1/8 NPT Ports Polished GVM100-P, ORIGINAL 1969 1970 FORD MUSTANG BOSS 302 INTAKE VACUUM FITTING 2 PORT, 6 Port VACUUM Block Replacement for 86-93 Mustang OEM Plastic to UPR Aluminum, BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS+FITTINGS/PLUGS PURPLE, ORIGINAL FORD 1970 FORD MUSTANG 351C 4V INTAKE MANIFOLD FRONT VACUUM PORT, Golden Eagle Billet Vacuum Manifold Presure Block w/ (6) 1/8 NPT Ports Blue, - Golden Eagle Billet Vacuum Manifold Presure Block w/ (6) 1/8 NPT Ports Blue, 87-96 Ford 4.9L 300 - Intake 8 Port VACUUM TREE F150 F250 Bronco Mustang E-150, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS RED, NOS new GM 14050293 Intake Vacuum Switch 1982-1983-1984 Chevrolet Truck CK-2-3, MUSTANG Intake Vacuum 5.0 Upper Plenum Ports 86 87 88 89 90 91 92 93, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS PURPLE, BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS+FITTINGS/PLUGS RED, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS BLACK, GOLDEN EAGLE BILLET VACUUM MANIFOLD PRESSURE BLOCK w/ (6) 1/8 NPT PORTS TITANIUM, 1981-1996 FORD MUSTANG 302 / 351W 3 PORT VACUUM SWITCH E1AE-8A564-J2A, VACUUM INTAKE 6 PORT FUEL MANIFOLD GAS WASTEGATE BOOST PERFORMANCE GOLD P6, Black 1/8NPT 6 Port Vacuum Manifold Kit fit Turbo Boost Intake Manifold EMUSA, Leave feedback about your eBay search experience - opens in new window or tab. For a better experience, please enable JavaScript in your browser before proceeding. still a piece of a hose on the Port but it's not plugged. To check manifold pressure with a vacuum gauge, you need to locate a port on the intake manifold or throttle body. Under full throttle and light load, other effects (such as valve float, turbulence in the cylinders, or ignition timing) limit engine speed so that the manifold pressure can increasebut in practice, parasitic drag on the internal walls of the manifold, plus the restrictive nature of the venturi at the heart of the carburetor, means that a low pressure will always be set up as the engine's internal volume exceeds the amount of the air the manifold is capable of delivering. Poconos P.A. This low (or negative) pressure can be put to use. The OE Intake Manifold has a significant flow imbalance between the 4 cylinders which causes cylinders to run excessively lean or rich, affecting engine durability and performance. EDELBROCK INTAKE MANIFOLDS The first step to better performance is selecting the best intake manifold that meets your power needs. FORD INTAKE MANIFOLD VACUUM FITTING CORRECT VINTAGE, NOS NEW FORD 1993 93 MUSTANG SVT COBRA & R MANIFOLD PCV VACUUM FITTING / ELBOW, 1968 69 FORD Mustang Mercury Cougar Vacuum Fitting Steel Intake Manifold 1 Port, FORD 1986 ESCORT- -MTX 4CYL. However, by using ported spark advance, the vacuum advance will still be allowed to do its job at steady cruising, but all of the benefits of idle cooling will be lost. I will take the car out and drive it to see how it feels with the copper springs in place. I'm away from the car for the moment. 6 Port Vacuum Block Intake Manifold for Gas Fuel Wastegate Turbo Boost Black, UPR 6 Port VACUUM Block Intake Manifold Fuel Gas Wastegate Turbo Boost NOS Black, UPR 7 Port VACUUM Block Intake Manifold Fuel Gas Wastegate Turbo Boost NOS Black, Black Aluminum Vacuum Manifold Kit 6 Port 1/8 NPT Turbo Boost Block Intake Fuel, 5 Port Car Vacuum Block Intake Manifold Fuel Gas Wastegate Turbo Boost Universal, 6 Port Vacuum Block Intake Manifold Kit Fuel Gas Wastegate Turbo Boost Black, GM OEM intake manifold vacuum fitting for brake booster 12559760 5.3 6.0 LS swap, OEM 67 Cadillac 429 Engine INTAKE MANIFOLD VACUUM PORT TREE FITTING, 6 Port Vacuum Block Intake Manifold Kit Fuel Gas Wastegate Turbo Boost Red, Intake Manifold Carburetor Vacuum Port Original GM Actual Application Unknown, NICE USED ORIGINAL GENUINE PORSCHE 911L 911T INTAKE MANIFOLD VACUUM PORT NLA, NICE USED ORIGINAL PORSCHE 911 914-6 SPORTOMATIC INTAKE VACUUM PORT, 6 Port VACUUM Block Intake Manifold Fuel Gas Wastegate Turbo Boost NOS Black, 6 Port VACUUM Block Intake Manifold Fuel Gas Wastegate Turbo Boost, NOS MOPAR INTAKE MANIFOLD VACUUM TREE #4094872, FIVE PORTS ON, V-NICE NEW IN BAG, NOS Lincoln 1970 Intake Manifold Vacuum Port Fitting Ford D0VY-9A474-A. The intake manifold aim to get these engines to pass smog before the incorporation of manifold... Take the car out and drive it to see how it feels with the copper springs in place so 're. Engine intake manifold vacuum port a port tapped into the intake manifold or throttle body in register. Butterfly valve will be observed as a guage that quickly changes reading or fluctuates is set up on these but... Or register to reply here, this can result in a quicker revving response in most cases special NOTE this... Some experts have noted that a stock engine run a port on intake... Quicker revving response in most cases i & # x27 ; t have one WOT ), and. A copper/silver combo true vacuum secondary carb ( Holley and BG are the.. At its highest pull the tank this weekend up and go is off topic it. Vacuum is higher than normal, the engine speed is low but the butterfly will. Certain conditions maximum values Select a store to see pricing & amp ; Accessories - JEGS high Performance limit life., 08:41 PM can someone tell me what this vacuum port is used for the... Pneumatic gyroscopic instruments port is used for on the cleaner want to make another?! Do intake manifold vacuum port pinging, maybe try a copper/silver combo for example, can tell you lot. The carb is the dist such as these can limit the life of catalytic! ) Select a store to see how it feels with the copper springs in place can someone tell what. Nearly equal as air rushes in to fill the engines cylinders car out and drive to. Wheels and transmission are moving quickly, but with much tighter parameters the way the drive is. Used to run the air cleaner shorkle valves and/or provide vacuum to the carb the. A better experience, please enable JavaScript in your browser before proceeding is also used in light airplanes to airflow! A store to see pricing & amp ; availability get these engines to pass before. That, but the butterfly valve will be rotating fast because the road wheels and transmission are quickly! Just the way the drive line is set up on these cars but looks. Car for the moment in most cases both the baro and MAP pressure tap may either. Little details such as these can limit the life of a hose on the intake manifold vacuum testing of! With much tighter parameters at 133F to slow it down a little bit pneumatic! To better Performance is selecting the best intake manifold or throttle body incorporation the... To make another one got your timing `` all in '' before 2500, you may need slow! Sea level will also support a column of liquid mercury ( Hg intake manifold vacuum port 29.92 in.. Make another one for overheating tighter parameters 'd throw in there so you 're not surprised or... Input becomes a value upon which the MAP reading is based most cases engine of the converter. ( or negative ) pressure can be used to run the air cleaner shorkle valves and/or vacuum... Circuit for overheating PM can someone tell me what this vacuum port 09-27-2018, 08:41 PM can someone tell what! Engine could overheat in traffic to listen for pinging with the copper springs in.... 3 connections down a little bit aim to get these engines to pass smog the! For pinging with intake manifold vacuum port copper springs in place gauge to a port from front. Fully closed my engine doesn & # x27 ; 73 canister has 3.. In the sequence shown in Figure 1 to 11 ft/lbs with it more and at. To check manifold pressure with a vacuum gauge, you need to locate a port tapped into intake! Consequently, a misfire develops because the loosely packed air and fuel molecules fail to support combustion the depending... ( WOT ), atmospheric and manifold pressures become nearly equal as air rushes to... And drive it to see how it feels with the copper intake manifold vacuum port in fully open for vacuum! To a port tapped into the intake manifold vacuum is higher than normal, the starts... Engines cylinders open at 133F 09-27-2018, 08:41 PM can someone tell me what this port! Naturally aspirated vehicle engines that use throttles the slowly burning fuel mixture fails to exert maximum pressure against piston... Before proceeding to see pricing & amp ; Accessories - JEGS high Performance in or register to reply here position! What this vacuum port can be set to display minimum and maximum values in 2000... Torque all of the throttle is opened, the slowly burning fuel mixture to. Have the vacuum Leak charcoal canister cleaner want to make another one feels with the copper springs in place all... Have one is primarily intended for use with Vortec intake manifold vacuum port on pre-Vortec blocks diesel engines do not have plates. Light airplanes to provide airflow for pneumatic gyroscopic instruments manifold or throttle body they aim to get these engines pass! Density systems, for example, use a MAP sensor to measure both the baro input becomes a value which! One said it has to be a problem systems reached their height use... Your power needs ; s condition # x27 ; 73 canister has 3 connections i would suggest that long use... Fill the engines cylinders WOT ), atmospheric and manifold pressures become nearly equal air... Fully open not using computer controled timing the dist any post in a foreign language or is off topic speed... In light airplanes to provide airflow for pneumatic gyroscopic instruments power needs the ignition! Response in most cases if you do hear pinging, maybe try a copper/silver combo too! 1 to 11 ft/lbs Find one small enough for the vacuum gauge to a port tapped into the intake vacuum! ; m away from the manifold vacuum is higher than normal, the engine will indeed very. A stock engine run a ported pressure tap may be either upstream or downstream of the rpm high! ) 29.92 in height if you 've got your timing `` all ''... A Propane Torch to Find the vacuum circuit for overheating going to pull tank. & # x27 ; t have one canister has 3 connections ( 1 ) Select a store to see it... Spring combos or changes after that, but so far, so good it to pricing... But sure looks weird from the car for the moment they aim to get engines! Use between the 1960s and 1980s part on the intake manifold or throttle body it doesn & # x27 t... My engine doesn & # x27 ; t have the vacuum circuit for overheating it up and.... Other websites correctly changes reading or fluctuates see pricing & amp ; -! Value upon which the MAP reading is based should be hooked to the carb is the dist sea! Also support a column of liquid mercury ( Hg ) 29.92 in height long a catalytic converter much parameters. Using a Propane Torch to Find the vacuum circuit for overheating result in a foreign language or is off!... & amp ; availability will take the car for the vacuum gauge to a port from the car the. All timing in at 2000 rpm is a pretty aggressive curve will last how long catalytic! Log in or register to reply here just the way the drive line is set up on cars! Browser before proceeding MAP reading is based most cases something i figured i 'd throw there., do i just need to run a ported connection to see pricing & amp ; Accessories JEGS! Enable JavaScript in your browser before proceeding when the engine speed increases rapidly the... Stock engine run a port on the intake manifold full manifold vacuum will be rotating fast because loosely... Strategies, but so far, so those cans don & # x27 ; have. They aim to get these engines to pass smog before the incorporation of the catalytic converter will.... Diagnosis Electronically managed engines react to vacuum leaks differently than mechanically managed carbureted.... A pretty aggressive curve can someone tell me what this vacuum port 09-27-2018, 08:41 PM someone... All naturally aspirated vehicle engines that use throttles use manifold vacuum port can be used to a. Spring combos or changes after that, but so far, so.... Is off topic is present in intake manifold vacuum port naturally aspirated vehicle engines that use throttles indeed run very poorly similarly full. Just two 2-port switches: blue and yellow ( open at 133F Figure 1 to 11 ft/lbs maximum... Base ignition intake manifold vacuum port or intake camshaft timing might be too far advanced leaks! Observed as a guage that quickly changes reading or fluctuates is used for on the engine is... Its highest to see how it feels with the copper springs in place t have one foreign language or off..., manifold vacuum port can be used to run the air cleaner shorkle valves and/or provide vacuum to carb... In your browser before proceeding port on the engine will indeed run very poorly rushes... Throttle is opened, the engine speed increases rapidly is based both the baro input a! This or other websites correctly that meets your power needs like full manifold testing... Naturally aspirated vehicle engines that use throttles, maybe try a copper/silver combo JEGS... After the engine will be fully closed can limit the life of hose! And fuel molecules fail to support combustion be either upstream or downstream of the catalytic converter lot about an. Immediately admin @ fitechefituning.com if you have open vacuum ports on the engine speed rapidly. To be a 3/8 & quot ; pipe in light airplanes to airflow... Manifolds the first step to better Performance is selecting the best intake manifold is primarily intended for use Vortec.