NoTransistors

Last week, I was taken for a suprise when I found out that New York City requires the full dyno test past age 25.
As the car no longer had an installed A.I.R. system, it actually ran too dirty to pass. Also, the machine reported "Low Volume, as though the cat is clogged and/or cooked.
Foward to today. I decided to reinstall the pump, hoses, chrome injection tubes, etc.
I had these little tapered allen-plugs in the holes where the injection manifold had been installed.
All but one of the plugs came out, as they were teflon-taped. The rear-left plug had to be drilled out. Picture it. The threaded hole points to the sky.
Drilled it out, and I suppose a bit of steel went under the exhaust valve.

Why? Because the car then ran very rough, and made a very discouraging knocking noise.

After a few minutes, which seemed like hours, and a bit of gas pedal play, the symptoms went away, and now the only engine noise at all is from the mixture solenoid. Drove it for an hour. Stop and go city driving, as well as some nice take-offs from lights. No further problem.

Question is, is my acessment on track? Can a tiny mild-steel shaving totally unseat a valve?



Seth

Apeiron

It's practically impossible that drilling on the manifold could have put a shaving somewhere it could do any damage.

NoTransistors

Damage, I too doubt that scenario. But I did suspect that the location of the drilling landed a flake of metal on the top of the valve. What other explanation fits? I don't know about this particular manifold design, but most air injection tubes are designed to pump the air directly into the exhaust port.
Is that not where the valves are located?

Remember, I do not, nor have I ever, claimed to be the best, most knowlegable or experienced mechanic, so I could be incorrect, unless, of course, I am right. I honestly haven't a clue.


If it is anything else at all, it will surely reappear upon a cold start, as it first did after I caused the initial incident. I must repeat that the noise coincidentally was under the valve cover, right at the work area.

Thank You Again,

Seth

Seth

Apeiron

The valves are way back inside the head. The majority of the chips you make from drilling are going to be on the outside of the manifold, and the rest are going to fall straight down. Even if a chip was thrown into the head somehow, chances are it'll land on a closed exhaust valve, where it'll get blown clear as soon as the valve opens. Even if it somehow managed to get inside the cylinder, it'll land on top of the piston and get bounced around a bit before it gets blown back out the exhaust eventually.

Trick414

The exhaust valves are up in the head, not down in the exhaust manifold.

So no, I don't think there is a way a bit of metal got to the exhaust valve. I'm not sure the geometry is right for even a freak accident.

I'd suspect the pump itself. You said you re-installed it. That's the only thing that could have affected the engine enough to make a knocking noise.

The new air going into the exhaust stream might have played havoc with an old worn-out O2 sensor, and that might cause all kinds of problems with the computer, but I don't know if your particular car even has those.

What kind of shape is the carb in? I think you might get much better results with a rebuild on the carb and a good tune-up. Although the AIR system does help, you'll find most people here pass just fine with a well-tuned engine without AIR.

NoTransistors

I have not as yet gotten to the pump, wiring, pipe to cat, etc.

I had started the engine after installing the injector rails. They were still each opened to the air, and the engine was cold, so no closed-loop.
I rebuilt the carb two years ago, with seemingly good results. What had originally prompted me to do so was that the engine refused to run lean after it would go closed-loop. Turned out to be a well-hidden vacuum leak in the vacuum storage tank, and a bad TPS.

Interestingly, I seem to recall legitimately passing inspection last year without the pump. I wonder if the inspection computer's claim that there is insufficient volume points to a bad cat. It has been suggested by some that running w/o the air pump may, in time, overheat the cat.
That would account for higher than acceptable numbers, and the mysterious 'insufficient volume' message, I GUESS.

Seth

five7kid

iTrader: (14)

I can say unequivocally at least with an aftermarket cat, that is not true. I ran mine for 2 years without, finally got it operating when I had to get it tested again, and it passed with flying colors.

blackroc68

iTrader: (2)

After 25 years only safety is required in ny.look on dmv website

NoTransistors

Yes, look at the NYS DVM website.
What applies to NYS does not apply to NYC and immediate area. That seems to require the 'enhanced' testing, with no cut-off time. Enhanced means dyno-testing.

Also, I just returned from dinner out on The Island. Lots of Stop & go traffic to and lots of 80+ mph going home. Great acceleration, especially at higher road speed. Engine must have best torque above 3,000 RPM. No wierd noises and no problem, other than gallons per mile engine efficiency. Seems that in 80 miles, I used six gallons.
Wierd is how economically-low the tach displays at road speed. At 60MPH, the tach showed 1600 RPM, if I recall properly.

Where is the economy? My 440 Chrysler New Yorker did better with a huge 750 Holley and only three speeds. It also weighed lots more.

Seth