I agree. I think we need to wait for him to come back now, and see what else he says.

 

Thanks to all for your help/recommendations. I did a tune-up per some of the advice and retarded the timing a bit. Like many had stated I think the truck was running rich. I had an overheat problem before and think that was part of my remedy. I'm going to hit emissions again this afternoon and I'll post results.
Guy at the parts store said to remove the vacuum advance and air filter before the test for an extra edge?
thanx again -Ole dirt McGert

 

Retarding the timing will make the overheat problem worse. Run it lean and mean with high timing. What was it at and what did you move it down to?

Advanced timing starts burning sooner, and gives more burn time to help complete combustion of the fuel.

 

Excuse me, my knowledge and lingo is still lacking. I did advance from 6 to 12
per Mr. 351s advice. -Thanks again.

 

Huh? CO's are what the carb is putting out, this makes no sense.


Put simply fuel is a molecule made up of a chain of Hydrocarbons(HCs). The engine combines in the right amounts and combusts the HCs with the right amount of O2. Ideally HCs and O2(atmospheric oxygen) break up and recombine to produce H2O(water) and CO2(carbon dioxide). Excess CO(carbon monoxide) is produced when there isn't enough available O2, lean. Excess HC is produced when either there isn't enough O2 or if combustion wasn't either initiated or complete enough to get what HC and O2 there was to combust.


I'm not going to say a compression test is a bad idea, always a good thing to know. But it is pre-mature in a process to solve the problem. There's no indications of a compression issue. <!-- / message --> <!-- sig --> __________________





What I mean is CO shows what air/fuel ratio the carb is sending the engine and by what means. I'll use your example of a Power Valve. A ruptured power valve will create a rich mixture. And they are large droplets since they did not get added to the venturi's airstream. They are added to the air entering the engine. Not mixed with it. Therefore there would be too much fuel and not be enough available O2. As you stated. Hence high co's from the carb.
As far as my suggestion for a compression test goes,we do know high HC's. We don't know condition of OP's engine. As stated, before I go throwing carb and ignition tune up parts at something I would want to make sure I'm not feeding a dying horse. Good info can come from the 60 or so minutes to do a wet and dry compression test.

 

I had to sniff my '69 in April 2014. It failed and because of that I wasn't allowed to insure it anymore until January 2015 when emissions testing was abolished. That's why I started the rebuild on mine when I did - because I wasn't allowed to drive the damn thing so I figured why not pull it apart.

Get the truck running perfectly, drive it hard with high RPM, do not let it idle, then in the parking lot of the emissions testing place retard the timing a bit and lean out the carburetor, and high idle it until it's your turn to get tested.

 

I use it as an excuse to run premium and hot rod around "cleaning the motor out" haha

 

Yep 67 and newer in Arizona if you are in Maricopa(Phoenix) or Pima(Tucson) counties.

 

As long as this thread has turned in to the basics of an ICE, I agree with Jeff. As compression is lost, the efficiency of the process degrades and you end up with excess HC. At some point you cannot dial this out with the limited range of carb adjustment because you will not be able to get the right ratio for the low compression. It's always a good idea to do a compression check on an unknown motor. It is a great measure of basic 'health.' My 86 Toyota got the the hairy edge of passing emissions simply because the 300k+ mile motor had compression so low I had to keep my foot in it until everything got warm enough to idle. And I know the emission system of that truck inside and out and that was not the cause. Rebuilt the motor, same emission system, same carb and suddenly I was well within the limits. I've seen plenty of stuck rings in FE's. The bottom one especially and they seem to cluster at the back of the motor.

 

There's a big difference between a low CR and a worn out engine when it comes to emissions. Many brand new engines in the 80s had CRs as low as 7, even NA engines. However a worn out engine can suffer from burning oil and having excessive blow-by. These can make passing emissions near impossible. It may be moot in some aspects but a compression test alone will not tell you if you are burning oil or have excessive blow-by. These things are much more noticeable via the vents/PCV and spark plugs.

 

Well, one way to combat oil blow by, If there is any, is to run thicker oil.

20-50 with a bottle of lucas stabilizer would make a big difference compared to running 10-30 or whatever.

 

Not good for the engine in other ways but yes if burning oil is a problem that would help. But so would a PCV upgrade with no negative side effects.

 

I agree with you with one addition Brute. By 1st doing a dry compression test and then a wet one will show the condition and seal of the rings as long as the top end doesn't leak. Which worn out rings or the loss of ring seal is what causes burning oil and/or blow-by.

 

Cheers
To make it clear, I'd never say it's a bad idea to do a compression test. Just that IMO as far as prioritizing efforts go to pass emissions it's below other items on my diagnostic priority list.

I get what your saying now, IMO it's still not quite completely correct though. What you are saying is true to a point, but at a point just being overly rich from the carb will produce excess HC. As the mixture gets rich at first COs will climb with HCs climbing just a little. Then there's a point where COs can't climb anymore, there just isn't enough O, at which point HCs will climb quickly, just from carb fuel.


I think what you're basically saying is high CO = too rich, and high HC = miss. This could be true if CO is only slightly high, or if CO is normal and HC is high. But if both are high it could be both rich and/or miss.


A specific example of this is seen in plug reading. An engine that emits high COs but not high HCs will not show rich on the plugs. But a flat black coating on the plugs is equal to high HC emissions but firing, while a shiny black plug equals rich fouling, missing and will also emit high HCs.

 

Hey Gertie, Are you in Phoenix or Tucson? When I take mine in I always put in about 3-4 gallons of E-85 a couple of days prior. Oxygenate the hell out of her.
Or drive to one of the outlying communities and claim residence there.
The whole smog control thing was nothing more than a fiasco when it began. Now it is nothing more than a revenue generation tool.
The levels of HC and CO that your truck is putting out are insignificant as far as smog goes.