1976 2.0 engine rebuild, Euro Pistons Options

[Allan]

I need help from the California members. Will going to the euro flat top pistons during a rebuild effect the emissions on a '76 2.0. And can you still meet emissions with a mild cam? (IMG:style_emoticons/default/confused24.gif)

[pbanders]

Euro pistons increase compression, the effects on emissions should be negligible. Things that affect emissions are:

1. On a '76, you've got a cat converter, and I'm pretty sure that you have a lower CO standard to meet than earlier cars. Make sure your cat is in good condition, actually working, and that when you go in for the test that your engine is FULLY WARMED UP. Your cat doesn't work properly until it's hot, you'll have higher CO with it cold.

2. Valve adjustment must be spot-on to meet the HC standards. If your valves are too tight, they stay open longer and your HC is higher. An associated problem is if you have a non-stock cam. The factory cam has no overlap (-2 degrees, IIRC) whereas most aftermarket cams have some overlap to increase performance through exhaust gas scavenging. Unfortunately, this overlap significantly increases HC. If you go with an aftermarket cam with overlap, before your emissions test, adjust your valves so that they are looser by 0.002" or so. Yes, it'll rattle like hell, but the increased clearance will effectively decrease the overlap and reduce HC.

3. Ignition timing must be spot-on, and your vacuum retard must be working. To pass the idle portion of the test, the ignition timing must be retarded through the action of the vacuum cell. On a '76, your vacuum advance is inactive.

Other tricks people use to pass emissions are to slightly lower the fuel pressure and/or use a fuel oxygenator additive to effectively lean out your mixture (that's what the state does for us in AZ without asking when they add ethanol).

While it's true that a car in stock condition, properly tuned, should pass the standard, these cars frequently need a little "help" to get a passing grade