EGR valves for 1976 400
 

there are 2 egr valves posted for 1976 pontiac 400 . Standard Motor Products part #egv 308 and 312. Both are shown for Federal emissions. What is the differance ?

I got rid of my EGR years ago. Why would you wa t all that heat going to the carb.

You may want to look at your carb set up. Heat from egr does not go to carb but rather into intake to combustion chambers. It reduces pinging on acceleration

The difference is likely vacuum actuation points and/or metered flow rates.

Similar to the variances seen in vacuum advance canisters, different combinations required different EGR valves to reintroduce the proper amount of spent exhaust gas at the right time of operational load.

For instance, according to the 1976 Pontiac Engine Assembly Manual, Pontiac used a total of (4) different EGR valves for 400 4-barrel applications and (1) EGR for 400 2-barrel applications.

And if anyone is counting, Pontiac used (6) different EGR valves for 455 4-barrel applications that year--only one of which is shared with the 400 4-barrel applications.

Good information Rocky, also the aftermarket replacements come with a selection of different size washers to very the size of the EGR opening, and you have to install the correct size washer. They usually come with an application chart to select the correct ID washer. I went through this process several years ago on my 78 Catalina with a 400 4bbl V8.

Thanks for the info guys. I just got through ordering one from SMP. its the egv312. which cross referenced to my original .Will see if it comes with washers or not. e-mailed SMP to ask what the difference was between the two, reply was just use the correct replacement.
As Rocky said it has to do with measured amounts.

got the egr replaced and yes came with 10 different washers. now need to replace choke tube gasket. Does anybody have a fell pro number? Internet shows several but none seem to fit 400. Most show a rectangular gasket. mine is more of a 1/2 moon shape