Went down for a smog here in orange county and failed, on nox. 1185 I think. Hc were like 24 and co was 0. pretty close on both speeds.

1985 2.6 mechanical valve lash adjusters.

Motor is new 150 lbs compression, cat is 2 years old and check good by doing the 10 second crank with cat hot and coil disconnected. Egr valve checks good, vacuum applied at idle, motor stumbles.

The head was milled considerable when the motor was rebuilt and the cam is lower profile than stock. (low performance) 19-20 mpg hwy. I have picked up a stock cam out of a 86 caravan, and will install it soon. Will this fatten up the mixture enough to bring down the nox? I'm close enough to passing that I don't want to make it worse.

Engine runs slightly on the cool side 180 therm I believe.

I checked previous smogs certs and the nox has always been over 1000, they just tightened the standards.

What can I do to lower the nox prior to my retest. Will runing premium help? Gas additives? Timing? (allowed 2 degree varience). Or just hook the egr up to manifold vacuum to keep it wide open? It functions at different rates at different RPMS now, but will opening it full bring my nox down enough. If I can drop 100 I can pass.

Any suggestion will be apreciated.

I also have an 87 exhaust maifold and y pipe (not installed yet), to get rid of the provision for the cat in the manifold, how will this affect it? No cat in manifold at present, just welded in downstream