OT: My tow rig failed emissions! Options

[Eddie914]

My tow rig failed emissions today in Seattle!

1983 Chevy 454 with a Quadra jet pushing a 27 ft motorhome chassis.

It failed the Carbon Monoxide at idle test.

HYDROCARBON (ppm)

Cruise Limit: 220
Cruise Emissions: 33
Idle Limit: 220
Idle Emissions: 128


CARBON MONOXIDE (%)

Cruise Limit: 1.2%
Cruise Emissions: 0.75%
Idle Limit: 1.2%
Idle Emissions: 4.78%

Unfortunately the idle mixture screws are sealed on this carburetor (for the time being). The air pump has been removed.

What is interesting is that since I replaced the heads to rectify the badly worn valve seats the HC has gone substantially down and the CO has gone substantially down.

Are the HC and CO inversely proportional?

Should I lean it out? Should I richen it up? … or should I just shoot it?


Thanks

Eddie

[Eddie914]

ERROR!

Since the head replacement, the CO went UP, not down. I'm guessing this happened since the worn valve seats reduced the actual valve lift. This is a 1983 vintage engine. I believe that it may been designed to run on leaded gas and did not have hardened valve seats. The 454 Chevy has exhaust valve rotators, and without hardened seats, some of the exhaust valve seats were erroded more than 0.175".

What is baffling is how the engine passed CO with badly worn valve seats and NO air pump ... and now with fresh heads it fails CO. Maybe the timing is too advanced.

The air pump was removed to reduce exhaust manifold temperature and manifold warping. This is a big problem with motorhomes that are used for towing due to the poor airflow in the engine compartment and the heavy load. Last time we went to Laguna Seca, the GVW (combined) was about 18,000 lbs.

I'm planning on pulling the carb and removing the idle mixture screw caps so I can get the beast through emissions and licensed befor this weekends camping trip ... when I get a spare minute ... Just need to replace the bilge pump on the boat and replace a couple of the trailer rollers before this ... and ... finish the oil cooler ducting and brake ducts on the 914/6 before next weeks track day ...

and of course ... the wife calls and says the family Suburban blew up and she's stranded with the kids!

I told her the compressor clutch was getting noisy and would soon need replacement, but when the rattling turned into screeching and white smoke starting billowing out from behind the car, she knew something was serious. Suddenly the power steering gave out and she smartly pulled to the shoulder of the off-ramp ... temp gauge was pegged too?

When I showed up and looked under the hood, I was surprised that the serpentine belt hadn't started on fire! It was fried! No amount of pounding and prying could get the compressor clutch to free up.

I sent the family home in the M5 and waited for my buddy to show up with the flatbed. Then I remembered that there was a Chevy dealer about 1/2 a mile away. I risked running with no waterpump, fan, power steering or power brakes (hydraulic boosted) and backed up the next onramp. I had my fingers crossed that the parts department was open until 6:00pm. No dice! It was 5:45 and the door to the parts department was locked and the lights were out. I caught a glimpse of a solitary sole behind the counter and rapped on the door. It was the parts manager. I pleaded with him. He very graciously opened the dooe and sold me a complete compressor. $400 ... it was ONLY money.

I unbolted the fried compressor and wired it to the fender. Bolted the new compressor in place and slipped on the spare belt. No hoses. No wires. No problem. I just needed the compressor pulley to idle. IT WORKED!

I'm home.

Thanks for all the help with the emissions.

Got to go!

Out to the garage!

Thanks!

Eddie