The old vaccum lines on my truck is starting to dryrot and crack up. I want to put a 4 barrel/ intake on it someday but dont have the funds to do so right now. I was wondering if I eliminated the egr valve and such and just set the carborator on the intake and run it if that would work. Motor is a 302 2 barrel. and i dont have a emmissions inspection where i live.

 

It's better to have the valve than not. Especially if your carb is setup for EGR operation. It's going to be too lean and could cause problems. The best thing to do is replace the vacuum lines and valve if need be - you'll get your best performance/economy that way.

 

F100beatertruck is right, removing emissions equipment can cause some problems.

The EGR's main purpose is to reintroduce exhaust gases into the combustion chambers to further burn off nitrous oxides, hydrocarbons, and carbon monoxide, as well as any unburnt fuel that might be present in the exhaust stream. To do this, it relies on manifold vacuum, hooked to a water heated thermostat at the front of the motor that only lets vacuum go to the EGR when the motor is fully warmed up, and it also relies on a certain amount of back-pressure in the exhaust stream to help open the valve when at higher RPM cruising conditions when manifold vacuum is most likely to be lower.

When the EGR valve was first put on a motor, engineers quickly realized that the valve would allow them to run leaner fuel mixtures due to the cooling nature of exhaust gases. The exhaust gases also displace the air and fuel mixture that goes into the cylinders of a motor, causing a motor to behave smaller than it really is until you step on the gas pedal and get into the enrichment circuit of a carburetor. Lean fuel mixtures are also prone to causing detonation and making a motor run hotter than normal, so the engineers had to retard the ignition timing in order to run a leaner fuel mixture that is being cooled by exhaust gases introduced back into the motor by the EGR valve.

The result is slightly lower power levels, lower emissions levels, a potential for higher gas mileage, and slightly lower vacuum and throttle response due to changes in fuel mixtures and timing.

Until you get your 4bbl carburetor and intake setup ready to go, run the motor just like it is unless you encounter a problem that impedes the way the vehicle drives. It's not hurting anything, and you won't gain anything with the stock setup by removing emissions equipment.

 

I disagree with the lower power comment. The EGR valve only functions at cruise and mild acceleration. Under full acceleration, vacuum drops off and the valve closes.

Now onto economy. Every revolution the engine draws in a certain amount of air. On a non-EGR engine all that air must be drawn past the throttle blades. At low throttle settings that is a big restriction. With EGR some of the "air" needed is drawn in without having to go past the throttle blades. This reduces pumping losses. Additionally, since the EGR "air" is inert you don't have to add fuel for that part of the air. To oversimplify it - when EGR is active your engine acts like it's smaller than it is.

If you replace the EGR "air" with air that contains oxygen without adding fuel for that air then you're going to run lean. Deleting EGR requires tuning changes to your engine.

If it's not working now and parts are missing, the simplest way to hook it up is to get a blue 2-port vacuum control valve. It threads into your manifold into a coolant passage and opens at 128°. Hook a vacuum line from the EGR port on the carb (or spark port) to the valve. Then from the valve to the EGR.

EGR, Evap and PCV do not effect power in any way. Modern, properly sized catalytic converters also have a negligible effect on power. Smog pumps are the worst offenders but still only account for 5-8hp.

The worst part about emissions equipment is that after 30 years it probably needs some maintenance and when not working property it can cause driveablity problems. This causes people to assume it's needless junk and hack it off...

Right now the emissions system on my Supercab has been all hacked off. It's a non-catalylist truck so no cats for me but I fully intend to restore the EGR, PCV and Evap systems. The smog pump... Well, I don't have emissions testing so I figure 3 out of 4 ain't bad...

 

I'll agree with that. Power loses are really minimal when running properly tuned with an EGR vs properly tuned without one. However, the slightly reduced ignition timing (and in some cases, cam timing as we see with the 351 Modifieds and 400's) and the leaner fuel mixtures that came on our smog era engines still cause a minimal power loss. Whether it can be felt is debatable. What confuses the topic even further is how the horsepower ratings switched to net ratings during the start of the smog era. My inline 6 came from the factory with the timing set at 6* BTDC. It benefits greatly from advancing the timing a hair.

I recall old timers telling me one time that when the smog era first set in, people would pay mechanics to remove the emissions equipment from their vehicles. Back then they got away with it because inspections weren't a widespread thing, and our country was still coming out of the power era.

It's really a shame what people do when they're uninformed. Look at voters.

 

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We goin' to a hundred?