'76 DeVille EGR Valve Confusion

[mgbeda]

As I am replacing most perupherals on Bessie's engine (500, 4 bbl, federal) I was planning on replacing the EGR valve as well.  But I am a bit confused.

The number on my EGR valve is 7049869 (see picture my_number).  According to the GM Parts Wiki that has been replaced by 17052699.

The second picture (EGR_numb_page) shows that this is correct for a '76 C,D,E,Z, except EFI Calif.  (I'm thinking C,D,E,Z means DeVille, Limo, Eldo, Commercial Chassis) So far so good.

But when I try to find a replacement for this part number I get directed to a Standard part no.  EGV 328, which looks clearly wrong (the ports are in a different place).

I can find a replacement for 17052662, aka 7030836, which just says '76 C,D,E,Z (see EGR_numb_page).  That is a Standard EGV 330.  It looks about right, but the valve itself looks a little different.  (See pictures my_valve and egr_new).

So my question is, what was the difference between a 7049869 and a 7030836?  And the big question is, will the Standard EGV 330 work right on my car?

Thank you for your help.

-mB

[Scot Minesinger]

I replaced an EGR valve with the one that looks like the unit in your picture on a 1975 Fleetwood (might be same as 76) and it worked fine.  The two issues with the EGR valve are the diaphragm leaks and causes bad running after car is thoroughly warmed up and the valve itself can malfunction.

[waterzap]

When I replaced the egr on my Eldorado,  I got a small bag full of washers. Apparently you have to put one of the washers in the hole to match the original egr.  Anyway,  didn't work,  just would not open.  So just put it on without the blocking washers, and tested it.  You can put your finger or a little stick on the moving part.  Should be no movement at idle,  and as you start revving,  it will start vibrating,  and then open. Good enough for me. 

[mgbeda]

Okay, thanks guys.  I'll go ahead and get the replacement.  I can always put the original back if the new one doesn't work right.

I'm still curious as to what the difference was between the original parts 7049869 and a 7030836, but I guess I won't lose any sleep over it.

Thanks again,

-mB

[Hankk17]

would a failed EGR valve cause the engine to wobble during idle?  my '76 CDV is shaking badly and I have yet to isolate the source.  back when I was a kid I didn't care a whit about emissions and usually just bypassed it without much concern for the consequences, and didn't really pay attention to performance afterwards... and now my addled brain can't recall.  lol

Thanks!

-Hank K.

[TJ Hopland]

I too don't really remember the results back in the day, I was likely too focused on the next piece of chrome to pay attention to how the car actually ran. 

My more recent experience with 70's cars and emissions has been you are better off trying to keep everything for the most part stock and working unless you are prepared and skilled enough to re engineer the engine as a complete system.   For the most part if you remove or disable one part of the system you will cause some sort of issue somewhere else that you then have to compensate for.  This will then cause another issue which needs to be compensated for and on and on.    The systems that are easy to remove with minimal effect on other systems tend to be the ones that have the least effect on everything anyway. 

The EGR itself assuming its working correctly does not hurt performance and actually seems to improve economy.   You can argue that an intake designed for EGR may not flow as well as one that does not have one just because they had to make some compromises to the flow just to physically route things around.  You can also argue that having hot exhaust gasses around there raises the air and ambient temps around the carb.   EGR is closed (or should be) at idle and full throttle.   It pretty much only opens at cruise.   When I built and tuned my EFI system a few years ago I originally started out with the EGR still hooked up but not directly controlled by the computer.  I kept getting flat spots in the transitions I could not tune around so part of the process I ended up removing the EGR.   Removing it didn't completely solve my issues, most of those turned out to be other things.   The really interesting thing was when I went out for my first test drive without it cruise was extremely lean.  With it hooked up cruise was a nice 14.5:1.  Without it it dropped to 17:1ish.  I say ish because it would start to misfire badly which throws off the O2 readings not to mention the detonation so I didn't let it stay there long.    If it was a carb setup and you didn't have a wideband O2 sensor the most likely fix the average person would go for is higher octane fuel and less timing.   Result from premium is higher cost.   Result from less timing, most likely less performance.   That is a loose loose.   With EFI and data logging to show me what was happening I was able to go into my fuel map and simply add fuel in the cruise area.  I would say in most of the cruise area I added 1/4-1/3 but in some areas it was twice as much fuel than when I had the EGR hooked up.   After I got my other issues worked out and with more tuning experience I had planned on putting it back on and see what happens as far as economy but other aspects of life have got in the way the last several years so I have just been driving the car when I have time rather than working on it. 

One of the things the EGR does is changes the temps in the cylinder which effects the burn or at least the resulting gasses after the burn, I really don't get that part but that is also where the A.I.R. system comes in, it adds fresh 'air' after the cylinder so the burning and or molecular conversion thing can happen in the exhaust pipes and cat converter. 

The other thing it does which I suspect is where the fuel savings comes in is it reduces the combustible volume in the cylinders.  The theory is oxygen is already used up in the exhaust so adding it to the air fuel mix does not effect the burnable air fuel ratio.  It just reduces the overall volume of burnable stuff.   Makes less power but in theory it comes into play when you are not looking for max power. 

[66 Eldo]

The difference between the two EGR valves is the flow. The new one you got is sort of a universal one to fit more than one GM car. You need to install the correct washer for your vehicle and there should be an application guide that came with the valve that will tell you which one. Leaving the washer out will allow too much EGR flow and possibly a stumble, hesitation, surging or all three.

[mgbeda]

Thanks, 66 eldo.  That makes sense.

I was pleased to find out that the instructions said mine was one that should have no washer.

Once I get the engine installed and running I can see if the new valve causes a problem.  Worst case I could always put the old one back.  It seems to work (holds vacuum).  I just got a new one because I'm sick of cleaning rusty old parts.

-mB