Still working on empting the gas tank. All the above mentioned things are good to do. Being that I take resonably good care of my ride, the maintanance things will not be the trouble.

The big change was on the engine rebuild, shaved head and new low profile cam. I still need to check o2 sensor and maybe mechanical advance, and vacuum routing to distributer, it's always had a flat spot for the past, well, since I've owned it, but it always passes smog, but lately only after a second try.

I get sent to a smog only on renewal and I called the number at the bottom of the test. Because I have been sent to a smog only and failed, I can apply for finacial assistance and get it. The state will pick up $400 of the smog repair, after I spend $100. (has to be smog certified shop). But while on the phone the tech guy, told me to run methanol and I should be OK as the methanol doesn't "pop", it "burns", keeping combustion chamber temps down. He also said that retarding the spark will help also, but you have to stay within manufacturers spec. So cheap and easy, (my middle name) Denatured alcohol it is.

Awhile back I read the thread on shaving heads and cam timing varience.

I think this is what is happening with my motor. $150 psi compression should not be trouble, but the timing could be.

Kevin, when I'm done I can post the results in your previous thread.

My take is the flat spot could be a lean condition and that will make the NOX bad. If you measure the O2 sensor voltage it should show if you are going lean or not. In closed loop you should get a swing in voltage from rich to lean.

Here is a decent blurb on testing one:

http://www.autozone.com/servlet/UiB...900823d/80/04/f6/02/0900823d8004f602.jsp

If during the flat spot the voltage shows lean you know you have a carb problem.

Milling your head retarded your cam a bit. This makes the overlap period of the cam happen later. It should give you a slightly lower cranking pressure more exhaust contamination of the intake charge at low to mid RPM (lower NOX).

However the tamer cam profile and milled head will decrease the amount of exhaust left behind increasing NOX ( and raise cyl pressures and temps).

I would go after the flat spot first, see if it its from a lean mixture. Alcohol in your fuel will make the mixture even leaner. It still may burn coolerà. But its asking a lot if you are already lean.

I would look for any vacuum leaks or exhaust leaks at the manifold.

I donÆt think you have modified your motor to the point that it wont pass if its running right. I kow of others that have put in torquer cams and passed emissions (that does not say that that putting the stock cam back wont help, just that something else is up).

Good luck,

Kevin

I measured the voltage when hot and it appears to be lean, .06 idling, .1 when revved with a .6 or so spike during acceleration. I still have the high altitude setup so if anything it should be running rich, which it isn't. how to fatten up a mid 80's mikuni, is there even and adjustment for the higher rpms? Re jetting right?

I remember when the float sank, boy did it run rich then, so I replaced it with a metal one and fairly sure that the level is still proper.

While I was at the boneyard I did pick up some of the little actuator diaphrams that attach in the carb. All the external vacuum controls are OK, but coould be connected wrong. I had a though time finding vacuum diagram for this engine. I went right to the dealer and couldn't get a conclusive diagram. I guess the best thing is to know how all the actuators and sensors all work together.

I just changed a vacuum hose around to lessen the draw on the advance and dumped a gallon of alcohol in. I'm getting ready to go get it hot and inspected. I'm still debating hooking the egr to a direct vacuum source to force it wide open all the time, at least for the test anyway. It works and actuates but may not open enough as I watch the diaphram move under different rpm ranges.

I had to check for values to make sure the O-sensor was ok and it appears to be.

Well wish me luck, I'll post the numbers when I get back. If it fails I get a free retest, so I may change the cam at that point, as I am suspect of the cam, I did't really like it when I built the engine, but it was the only one I had with clean bearing surfaces, and I figure it isn't to bad of a job to change later. Performance has always been sub par with this cam, but it is hard to argue with 19 mpg.

So here are the new test results running 6 parts gas 1 part denatured alcohol. And a lower vacuum pull on the distributer advance. (I took the vacuum line from the canister purge and switched it with the vacuum advance) Extremely gutless.

rpm1725 15 mph
co2 11.9
o2 6.3
HC max137
ave43
meas 7

CO max .94
ave .16
meas 0.00

NO max 1107
ave 406
meas 294
PASS @ 15 mph test


2799 rpm 25 mph

co2 13.3
o2 3.8

HC max 109
ave 32
meas 3

CO max 1.19
ave .15
meas 0.01

NO max 1163
ave 349
meas 750

PASS @ 25 mph

Plus a pass on all visual etc.
I'm good to go for 2 more years, YIPPEE!

So I guess the new cam goes in and a comprehensive test of all the vacuum controls and hoses.

Aslo need to know how to fatten it up at mid rpm range.

Ha Ha, I told you the secret formula works <img src="/forums/images/graemlins/notooth.gif" alt="" />

<img src="/forums/images/graemlins/cheers.gif" alt="" />

A mighty fine one at that, thanks much, I'll have to buy you a beer. Was it supposed to go in the tank? <img src="/forums/images/graemlins/ignore.gif" alt="" />

This has to be the most amusing and informative post I have read. The denatured alcohol trick is a good one. I'll have to use it myself. My 90 3.0 has an exhaust leak somewhre before the catalyst. This has caused an increase in NOX due to the lack of a rich condition in the catalyst and has also caused the O2 sensor to read lean and try to fatten up the mixture. Double whammy. I smogged it for change of ownership myself and barely passed. Rather than repair it I ran it early in the morning so the NOX would be lower. I know I won't get away with that again though. Even though everything I did was legal the DMV is going to see that I own the truck and then see my smog license number next to my name and "Presto" test-only next time. Happens to every smog tech I know. In fact, every tech at my shop, whether or not they smog has there cars flagged test-only. Even the service writers and the service manager. His wife's Tahoe is not a test=only but it's in her name and she doesn't have anything to do with the auto repair business.

If anyone cares, a lower than stock temperature thermostat may prevent a vehicle from going into closed loop or at least from staying there. This usually results in higher than normal HC and CO but may at times result in higher NOX as well though usually not all at the same time.

The biggest culprit for NOX on this blog, as I see it, is those shaved cylinder heads. I understand that there is really no viable alternative and replacement heads are prohibitively expensive but I didn't set the limits either. And expect the limits to get even tighter. CARB still sees automobiles as the primary contributors to smog gasses and even though we all know that industry pollutes FAR more than we do, getting government to see the truth is never easy unless the truth is spetacular or appears to defy common sense. Until then expect our plight to become worse, not better. Sorry.

The Kalifornia <img src="/forums/images/graemlins/patriot.gif" alt="" /> smog check is quickly becoming a game of "see what you can get away with" and it's being made more difficult by the fact that it's getting harder and harder to find a smog tech who will cheat. I won't and I don't know anyone who will. The price is too high and the penalty too severe.

Good luck!

I just did the denatured alcohol thing to pass smog test. I was passing everything with the exception of the Nox. I used a 1-to 4 ratio (1 part alcohol). 1994 Suburban 454- All NEW ôChevy crateö motor, cat, O2 sensor, EGR valve, plug and wires and oil change. And it still would not pass, until I tried this trick! I found this same advice on two other sites but was still a little reluctant to try. So IÆm posting my story to help build the confidence of others to try.