EGR Valve

[ChevyMan]

I'm not certain but I think I need to replace a component within the EGR system.It's what's known as THERMAL VACUUM SWITCH which screws into the intake manifold near the radiator thermostat. There are 2 hoses, one connects to the EGR valve and the other to the carburetor. The switch itself is broken in half so I have it tied down with plastic ties, but I think I'm losing some vacuum when I start the car cold, although it doesn't affect the operation of the carb.

[DonTom]

I'm not certain but I think I need to replace a component within the EGR system.

The EGR should stay closed until you have a warm engine well above idle. If it does that, you're okay. You should be able to put your fingers on the bottom of the EGR at one of those holes and feel the valve move up and down when you get the RPM's up with a warm engine.

If the VGR stays open at idle, it won't idle well. It should always be closed at idle. If it is stuck closed at a high RPM's (above 3,000), you will never know the difference unless you need to get a smog check.

-Don-

[Jim Rose]

>> The switch itself is broken in half so I have it tied down with plastic ties, but I think I'm losing some vacuum when I start the car cold, although it doesn't affect the operation of the carb.<<

If the switch is not thermaly activated when the engine warms up, the EGR valve will not operate and could cause detonation and excessive NOx emissions.

[Eric]

I'm not certain but I think I need to replace a component within the EGR system.It's what's known as THERMAL VACUUM SWITCH which screws into the intake manifold near the radiator thermostat. There are 2 hoses, one connects to the EGR valve and the other to the carburetor. The switch itself is broken in half so I have it tied down with plastic ties, but I think I'm losing some vacuum when I start the car cold, although it doesn't affect the operation of the carb.

This is very un-PC, but:

The EGR (and emissions systems generally) on a car of your vintage really screw up driveability. I'd do the following (and have done so on at least half a dozen cars of similar vintage):

Plug the EGR valve with a nipple; do the same to the ports at the thermal vacuum switch. This disables the EGR system - but th only thing you will notice is better driveability and maybe even a bit more power, too.

If you want to see a real improvement, lose the original "pellet" GM converter; they ar e incredibly restrictive. Replace it with a modern "honeycomb" unit and you will see a noticeable increase in mileage as well as power.

[mrblanche]

If you really don't care about the emission, you don't even have to "lose" the pellet converter. There's a plug on the bottom of it, which you can remove. Hit it with a rubber mallet until all the pellets are out. Or drive it 20 miles.

Put a freeze plug back in it, and no one will be the wiser.

[Eric]

If you really don't care about the emission, you don't even have to "lose" the pellet converter. There's a plug on the bottom of it, which you can remove. Hit it with a rubber mallet until all the pellets are out. Or drive it 20 miles.

Put a freeze plug back in it, and no one will be the wiser.

Yep! Done that myself...

[Jim Rose]

>>If you really don't care about the emission, you don't even have to "lose" the pellet converter. There's a plug on the bottom of it, which you can remove. Hit it with a rubber mallet until all the pellets are out. Or drive it 20 miles.

Put a freeze plug back in it, and no one will be the wiser. <<

All well and good as long as there is no emission test required of this year vehicle!

[DonTom]

The EGR (and emissions systems generally) on a car of your vintage really screw up driveability.

What negative effect does a properly operating EGR valve have on any vehicle? For the rest of the smog junk, it sure does screw things up in older vehicles. Our 1978 RV has no smog junk at all. No C. Converter, no air pump, no EGR Valve. It had "light duty emissions" and was originally sold in Utah.

Strange how this all reversed and all the smog junk now helps make a much better car in the last 20 years (IMO).

But I am especially happy that our 1978 400 CID small block Chevy does NOT have an EGR valve. In Washoe County, NV, all vehicles (except boats, motorcycles, etc) must be smogged every year, regardless of age. Because the RV has no EGR, the engine cover does not have to be removed to check its operation. This makes the required yearly smog check very cheap and fast. After 1980, they had the EGR valves in the RV's. So starting with 1980, the engine cover has to be removed.

Here in CA, a smog test is often a real hassle, but it only needs to be done every other year and that's only if the vehicle is more than five years old. If more than 30 years old, no smog check is required.

I registered the RV in NV so I could put in the MPFI. But next year, it will be 30 years old anyway. I will keep it registered in NV, since the smog check is not a big deal and is cheap compared to CA. Besides, we now leave it parked in NV so it should be registered there.

When we get back from our China trip, the RV will start being put to some use.

-Don-

[Eric]

>>If you really don't care about the emission, you don't even have to "lose" the pellet converter. There's a plug on the bottom of it, which you can remove. Hit it with a rubber mallet until all the pellets are out. Or drive it 20 miles.

Put a freeze plug back in it, and no one will be the wiser. <<

All well and good as long as there is no emission test required of this year vehicle!

Many states exempt a vehicle from smog check after 20, 25 or 30 years from the date of manufacture...

[Eric]

"]What negative effect does a properly operating EGR valve have on any vehicle?"


The problem with these vehicles (mid-late '70s) is that the engines were designed in the pre-smog era; they had to be "de-tuned" (lower compression, retarded ignition timing, weak cams, etc.) to scrape by the smog standards of the time. Also, the first emissions controls were very primitive and prone to malfunction. Getting them to work properly - and the engine to run decently - could be a real struggle.

Modern engines and their emissions controls in contrast are designed to gether and work as a system. The components themselves are also much improved. And of course, the use of EFI and computers has made tailoring spark curves and air-fuel ratios a much more precise art than it ever was in the carbureted '70s!

[DonTom]

And of course, the use of EFI and computers has made tailoring spark curves and air-fuel ratios a much more precise art than it ever was in the carbureted '70s!

I never expected to hear that from you ;D.

BTW, do you own any vehicles that have EFI?

-Don-

[Eric]

And of course, the use of EFI and computers has made tailoring spark curves and air-fuel ratios a much more precise art than it ever was in the carbureted '70s!

I never expected to hear that from you ;D.

BTW, do you own any vehicles that have EFI?

-Don-

Hey now! I never denied the superior precision of EFI (or computer controls); I just prefer carbs - and no computers. They're much less expensive, easier to fiddle with and most important of all, have more personality than the hyper-efficient automatons of modernity!

I do own on vehicle with EFI and a computer, however - my '98 Nissan Frontier pick-up.

[mrblanche]

One EMP weapon fired over D.C., and those carburetors are going to look mighty good!

[Eric]

One EMP weapon fired over D.C., and those carburetors are going to look mighty good!

Yes, there's that, too!

Also, I keep my vehicles for a long, long time - and while EFI and computer controlled vehicles are very reliable relative to the cars of the past, when they do begin to fall apart, it is very hard (or more precisely, increasingly un-economic) to try to keep them going. Meanwhile, one can fix up something like an old F100 and keep it going indefnitely for very little coin, provided you are a decent home mechanic...

[mrblanche]

Of course, if your Pontiac has HEI ignition, you'll have to go find a points distributor.

[Eric]

Of course, if your Pontiac has HEI ignition, you'll have to go find a points distributor.

Nah, just a new module. It's the only transistorized component in the whole works!

But I don't run an HEI; I swapped it out for an MSD unit with a "soft touch" rev limiter set for 5,400 RPM. Don't wanna grenade my long stroke 455. That can get expensive!

[DonTom]

They're much less expensive, easier to fiddle with and most important of all, have more personality than the hyper-efficient automatons of modernity!

IMO, carbs are a lot harder to fiddle with and are more expensive to maintain than FI. I have had to replace carbs before. I never had to change much of anything with FI. The only thing I can think of is a fuel pump that needed to be replaced. But since it was FI, it was mounted in the gas tank.

I do wish they would stop mounting the fuel pumps in the gas tanks in vehicles with FI. That's my only complaint about FI. My MPFI RV proves it's not necessary to do so.

-Don-

[mrblanche]

Nah, just a new module. It's the only transistorized component in the whole works!

But I don't run an HEI; I swapped it out for an MSD unit with a "soft touch" rev limiter set for 5,400 RPM. Don't wanna grenade my long stroke 455. That can get expensive!

And you would get that new module exactly where? (Again, this is assuming the EMP attack.)

I was just thinking about it. My truck wouldn't run (all computer controlled). My F-150 wouldn't run, and the Cobalt wouldn't run. The T would run if I put the points back in the distributor, which has a Pertronix convervsion. But the speedometer wouldn't work any more on it, I think.

[Eric]

"IMO, carbs are a lot harder to fiddle with and are more expensive to maintain than FI. "

Only if you don't understand how they work; they are actually pretty easy to fiddle with. And while that's just an opinion, it's a fact that EFI is more costly to buy and maintain. A new carb costs maybe $400 - and that's for the whole ball of wax. You can rebuild a good "core" for a fourth of that. And it will function as new. In contrast, even a throttle body EFI system, with its related and necessary parts, costs $1,000 or more. A PFI system much more than that. l

" I have had to replace carbs before."

Probably because either you or the guy you took it to had no clue how to fix them! It's unusual for a carb to "go bad." Usually, it just needs a few minor pieces (float, needle and seat, gaskets, etc.) replaced.

[Eric]

"And you would get that new module exactly where? (Again, this is assuming the EMP attack.)"

Why, from my parts bin! (I keep spares of many things; just in case...)