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Old 03-10-2005, 12:49 AM   #1
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EGR/PCV elimination for 1990 350 TBI

What if any benefits and/or drawbacks to eliminating these smog parts? I would think that eliminating the EGR would be a positive, since it would make the intake air cooler and higher in oxygen. The PCV valve just seems to clog my air filter. What are the best ways to do this if there are no drawbacks except possible emission problems?
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Old 03-10-2005, 06:54 AM   #2
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there have been some in depth discussions on this... try a search...
iirc the consensus was absolutely leave the pvc system in place... messing with it had little benefits and lots of problems....
I have seen crankcase backpressure devices on ebay that claim to make the engine seal better.... hoooey I say.... gm would have done it for the 10 cents it would have cost them... especially if they could enhance performance and not creat more smog..
Theres been lots of talk about egr's on here... once again consensus is they are of NO detriment... and make the truck run cleaner...
there is a benefit from making the engine breath better ... even in stock configuration.... but even this is open to review... yes a filtron element breaths better.... but at what cost... filtration of particulates?
yes a tbi spacer in theory gives a more complete burn.... does it work in reality... Im not sure... I have one and it whistles nicely on my big block and I think it helps a little... but only a dyno could tell...
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Old 03-10-2005, 07:13 AM   #3
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Eliminating the PVC valve will allow pressure to build up in the crankcase and oil will leak out of every seal and gasket,and it will make a lot of sludge build up in the oil--the motor wont last very long that way--if your "bowtie" filter inside the air cleaner is letting oil build up in the air filter housing,you can remove it from the air filter and swing the hose to one side and put the bowtie back in the hose--that will keep the oil off the air filter--but it will also spew blowby fumes under the hood,and the odor will likely make the cab smell like oil burning off the exhaust..

-I had to run one down under the truck using heater hose to keep the fumes out of the cab--the motor has bad rings or pistons if your getting that much blowby--this is just a "crutch" to get you by for awhile until you can fix the real problem.. The PVC valve is a vacuum leak,and the carb or EFI is calibrated to compensate for its vacuum usage--remove and plug it,you will richen the mixture,and that will only lead to oil dilution and more wear,and poorer gas mileage...

The EGR valve should not be removed or disconnected either--it does affect performance slightly,but disabling it can make the engine start pinging or spark knocking,that leads to piston damage or other major problems--if your truck has EFI,the knock sensor will "hear" it pinging,and retard the timing to stop it--killing power and fuel economy--not a good thing....its best to leave the emission stuff alone,and keep it working right--the(stock) motor is designed to be at its peak efficiency WITH all the emission crap installed and working--taking it off or disabling it usually results in engine damage,or poor power and economy--not to mention it might make getting an inspection sticker impossible...
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Old 03-10-2005, 07:23 AM   #4
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Unless you program the EGR function out of the ECM you must have a operating EGR for the best all around performance and fuel milage.

The ECM looks for a functioning EGR when you are at cruising speed. It cycles the EGR open and closed and looks for changes in the 02 sensor readings. If it sees no change in 02 sensor readings Throws a trouble code. No or not functioning EGR will affect both timing and fuel ratio. The EGR helps cool the combustion chamber allowing for more timing advance with out pinging. If the egr is not functioning The ECM will not allow timing to go full advance. Theis will affect fuel milage and performance at cruise speed. At full throttle the EGR closes and has no effect on performance.
so its best to leave it there
Same with the PVC valve if it is working correctly it has no effect on performance.
TBI is made to work with all the sensors and emission controls intact. revoval of any of them without changing the programing will have a negitive effect on performance.
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Old 03-10-2005, 09:26 AM   #5
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EGR and PCV cost you nothing in performance.

The "clogging" you see from PCV is oil vapor condensing on the filter (hey, cheap K&N! lol) and isn't going to hurt the performance of a mild motor.

EGR is *not* functional under circumstances where you want performance...it *is* detrimental under some circumstances, automakers were smart enough to know this and made sure that wasn't an issue, at least as long as EGR is functioning correctly.
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Old 03-14-2005, 04:49 AM
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Thanks for all the input. I guess I'll leave good enough alone.
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