Thread:

'83 Chevy Motorhome - Passing CA Smog Check

I'd like to register my Dad's 23' RV that I brought to CA from AZ recently. It has a 454 BBC (65k miles) that I tried to smog last week....and it failed. The smog tech said not to touch the carb as it was dialed in, but that it has a miss that's the likely culprit of why it failed. Looking at the smog report, the motor did excellent at the 2500 rpm test, but registered as a gross polluter spewing twice the legal limit if hydrocarbons during the idle test.

So I'm thinking of doing a basic tune up and testing it again, but want to get some feedback about whether it's worth putting any more $ into this beast. All in all this RV is in decent shape, it handles well, and it towes the toys well. So I'd like to keep it.

Besides changing plugs, wires, cap, rotor, points and setting the timing....do you have any other suggestions? Also, what should I set the timing to here in San Diego?

Thx

Depending on the year, it may have an HEI distributor. Being '83, it SHOULD be. If not, I would stick one in. As long as it is a stock, direct replacement piece, it would still pass the visual inspection. If you end up replacing a points dist with HEI, that will take care of most of your tune up. You would need new wires anyway (for the HEI) and plugs are really the only thing left.

If it DOES have points, you can go another route and put in a Pertronix module kit. It would be even safer, as the distributor would appear stock, but be similar to HEI inside.

Either way, it would probably be the last time you would ever have to tune it.

Motorhomes are notorious for vacuum leaks, make sure to try and find all of them, typically when they fail the idle test its do to high hydrocarbons (unburned fuel), if you have the data sheet, it should say what it failed on..

You can use an ultrasonic leak detector to find the leak (sometimes called a vacuum sniffer), also if you can find a place in your area that sells methanol, try mixing about 25% methanol in the fuel and make sure she's hot as hell when you do the test, 454's intakes tend to get intake leaks fairly easy, especially if they have an alumunim intake, does this one have an EGR?, might check that out too.

I have a 1984 454 motorhome with an Air Sensors Inc. Fuel injection system on it and it passes with flying colors, has EGR, Evap, Air injection, everything but a damn CAT. Vacuum leaks are its only downfall.

Do you guys have the option of a pre test, we can do that here for about $30? Basically it makes sure it will pass before putting into the system.

Good luck!

edit; I want to say the initial ignition timing is like 4* BTDC but not sure.

GT

You should be able to to a pre test (you need to ask them) smog only technically can't, but might if you ask them.

HC or hydrocarbons is a dead miss, causes are many, low compression, vacuum leak, bad plug or wire (a scope would find this in a heartbeat), a wet or bad cap/rotor, wrong idle adjustment on the mix screws etc....

As far as the hesitation it almost sounds like a stuck open EGR, but I can't see one in you're pics, this would also cause the high HC, the EGR should be totally closed at idle.

I would get it cleaned up (steam clean in your area?) and spray some WD40 or carb cleaner around the carb base and the intake manifold to see if the idle changes...If the canister purge valve is jacked that will cause high HC also, it's just unburned fuel, I'm betting a carb problem...

I would throw some basic tune up parts at it and see what sticks, you can always keep the good used stuff for spares.


GT

I would bet just an HEI tune-up kit; cap, rotor, module, coil, wires and plugs would make a tremendous improvement. Especially since the engine looks like it hasn't been touched since 83. Probably easiest just to get a rebuilt distributor, since it would also include the vacuum advance which could also be rotten.

I don't like the routing of plug wire three, there is a good chance for cross firing, just another opinion...

GT

What it's supossed to look like

GT

Wow. AirSensors! That brings back memories. I used to work for a company that was in the back of an RV service center. They installed these things all the time. Worked really well, given the technology of the time.

Originally Posted by Beer:30

Wow. AirSensors! That brings back memories. I used to work for a company that was in the back of an RV service center. They installed these things all the time. Worked really well, given the technology of the time.

Yeah she runs good, just wish it was a closed loop system, can't figure out how to convert it...It has bigger injectors now, runs like it's scared and still gets 12+/- MPG if you drive it like an old man..

GT

Originally Posted by GT Jets

Yeah she runs good, just wish it was a closed loop system, can't figure out how to convert it...It has bigger injectors now, runs like it's scared and still gets 12+/- MPG if you drive it like an old man..

GT

Yeah, I don't know of any way to closed loop that. About the only thing you could do is run an a/f monitor and adjust accordingly. Sounds like it is pretty dialed in, though. I never knew them to get much better mileage than that on big blocks.