Motorhome carb and California Smog!

[KeyAir]

Hi Everyone!
First post here...

My 1984 Airstream 345 Motorhome came into my life with a strong running rebuilt Jasper 454, an Edelbrock carb, and most of its original smog gear disconnected/missing.

To enable me to pass Smog here in CA, I needed to find all the right parts, and get them back to Federal Smog spec. Please don't post that I should register it somewhere else, or complain about CA Smog... it is what it is and the challenge to to make it work as it was built!

So, the first line item was to find and rebuild the correct Quadrajet, and for that, I came to Cliff, a couple of years back. He had the correct carb, and rebuilt it fully for me.

The Carb was mounted, and the engine started, idled and ran ok, right out of the box.
I had previously installed a Innovate Fuel/Air Gauge in the drivers side header collector, and have been using that to help me fine tune it getting ready for smog. I have not driven the beast yet, only static tuning due to brake issues.

So, untouched, the carb was reading about 12/1 at idle and about 14/1 at 2000/2500 rpm.
The reason I am testing these engine speeds is because that is where the Smog Station tests the emissions, so my aim to to simulate that to adjust the carb to the best emissions settings, and I'm reading that is 14.7/1 or so.

Some background info...
Rebuilt 454.
Banks Headers, Banks Intake
Newer plugs, and wires. Stock HEI Distributer.
Timing is not checked as I cannot see the timing marks... working on that this week!
All smog gear is disconnected, and ports capped, except Vac advance port which I put a Vacuum gauge into.
No Vacuum leaks that I am aware of.
Smog pump is disconnected, as I dont want it injecting air yet until I get the Carb set correctly.

So, this week, I was out there, and wanted to try to set the idle mixture.
Ambient temp was about 50f.
I pumped the gas peddle twice and the motor fired first time.
Gas(20g+) has been in the tank about a year, but has heavy dose of Stabil in it, plus I bring a 5 gallon can of fresh gas and tip it in whenever I go.
Warmed up until the temp gauge was 200f or so, or about 15/20 mins.
Idle was set at 750rpm.
Banks Air Filter assembly was removed.
Confirmed Mixtures via the Innovate gauge were as above, and decided to adjust the Idle mixture via the baseplate screws.
Adjusted both in clockwise by about 1 turn, and brought the mixture readings to fluctuation of between 14.8 and 15.1. Figured a touch lean would be compensated by putting the Air Filter assembly back on!
Vacuum gauge was reading pretty steady at 19hg.

I was good... I was happy...
I then revved the engine to see if anything had changed on the 2000/2500 rpm range...
Its now reading 12/1 at those speeds!
Allowed it to go back to idle, and its also reading 12/1 now!

My time was up, so I called it a day(Motorhome is in storage 40 miles away from home).

Can someone tell me what I did wrong or suggest a better procedure?

[Cliff Ruggles]

The first thing I would do is to get rid of the old gas and put fresh fuel in it for testing.

Stabil will NOT keep fuel in a vented system from loosing octane.  I see this all the time with generator that folks drag up to the shop that will not start or barely start and run poorly. 

The story is always the same, used in a year or so ago, put Stabil in the fuel and back in storage.

I've drained out some and dumped the fuel in the gravel driveway of the shop and had difficulty lighting it with a torch and even when it did get going it burned like kerosene instead of gasoline!.....Cliff

[KeyAir]

Got it!
I will be out there this week, so as I have access to the rear mounted fuel pump, I will run the motor from a fresh can of gas for the tuning, while I figure out what to do with the gas in the tank.

With what I am trying to do, is there a tuning procedure you suggest?
 
Do you suggest regular grade gas for this motor, or premium?

This is my project for reference!

[Cliff Ruggles]

I recommend low octane fuel as it will burn easier in a low compression engine than the higher octane varieties.

For tuning you need to get the engine fully up to temp and well heat-soaked.  Adjust the idle speed and mixture screws first.  Turn the mixture screws in until the engine just starts to slow down (going lean) them back just a tad for highest RPM.  To get thru smog testing you may need to keep them a little lean until you get thru the testing.

Set the fast idle on the highest step and adjust the engine RPM's to apprx 2000.  "Tip-in" the choke flap and see if the engine speeds up some.  Adjust the APT if/as needed until you get a slight speed increase tipping in the choke flap slightly.  Usually around 50-100rpms is a good place to start.

Do some driving and evaluate engine performance, especially at light part throttle and light engine load.  This is where the APT system is tuning and has a big impact on smoothness right off idle, power in the "normal" driving range and fuel economy.......if there is such a thing with a Motorhome powered by a big block N/A engine!........Cliff

[KeyAir]

Thanks again Cliff!

I am going to concentrate on the idle
For the record, when I drove the beast back from Dodge City, Kansas, it had the Edelbrock, and a simple pancake filter on it.
It weighs in at around 16,500lb, and you feel every pound of that, but it still performed very well, taking us up over the Continental Divide... the sound of the secondaries fully open as she toiled up those climbs was memorable!
My log has tank averages of 6.29 to 8.42mpg... and I had a leak at the filler neck, so maybe a touch more was the reality... The Forum boys say thats about the span they expect, this side of FI and an OD transmission, where they gains about 2mpg.

I noted your comment during our Email back and forth of the carb rebuild about NOT changing the intake to an Aluminum Edelbrock that I had planned. The comment about the cast iron stock manifold running hotter to aid in vaporization of fuel droplets makes sense.

My Motohome is missing its Smog/Emissions sticker, and so that has been the battle to figure out what it should have fitted, and then find the missing parts.
This is the one off someone elses Motorhome from 1984, and its what I'm running with!


I've had to work off this "Vintage" Smog testers manual to figure it out.



The only thing I am struggling with, is the Smog pump diverter valve, that is NLA, and finding a used functioning one has proved impossible. For now, I have the pump on, but the pulley off, so its not spinning. Smog rules say that all the parts have to be "Present", but they cannot, and do not test them for functionality. My plan is to have a "Correct" Diverter valve present, even if its not working.

What is your opinion/experience of the impact of the smog pump air injection into the exhaust manifolds on mixture and emissions readings?

Oddly, the Federal Smog version of my Motorhome for 1984 model year does not have an EGR fitted, but CA did, as well as a charcoal canister.
I just want this thing thru smog, and my understanding is that it struggled to hit the required numbers when new! would you believe I thought about fitting a CA legal, Hi Flow catalytic convertor on it to clean up the emissions, and ensure a pass, but that is an instant fail!

And finally... What is your opinion on what Fuel/Air reading I should be aiming at for idle and 2000/2500rpm?
I know 14.7/1 is "Perfect", but your input and knowledge of this carb, and the BBC in this fitment might make a difference.

[Cliff Ruggles]

There really isn't a "perfect" A/F ratio for idle as every engine will have it's own deal going on.  So basically you have to tune it for best idle quality, typically at the leanest settings to make it happy.

Some folks use a vacuum gauge, which IMHO is a waste of time.  Others use a tach and lean each side up until they notice a slight RPM drop.  This is the "lean tip-in" point mentioned in many Service Manuals and other literature on tuning early N/A carbureted engines.

Basically you must do ALL tuning with the engine fully warmed up and well heat-soaked.  Timing is set first, then idle RPM, then idle mixture, then you may have to re-adjust the idle RPM, in that order.

The FIRST thing removed from most emission years engines were the smog devices.  Not surprised that some are difficult to find, they went straight into the "round-file" back in those days.

Pumping air into the exhaust should help the CAT some, or at least I think that was the plan the engineers had trying to get less PPM of pollutants exiting out the tail pipes.  It certainly isn't helping anything on the front side of the engine.

It's interesting that starting around 1971 we saw compression ratios lowered to help emissions.  It didn't make any sense to me back then more than it does today.  Ya, I understand the idle deal and retarding timing, etc, but it never has made sense to me to kill combustion efficiency with lower compression then try to make the engine perform better and use less fuel, etc.

Then they started installing tiny little cams, retarded cam timing, hotter thermostats, air pumps, CAT's and other devices to clean things up.

Common sense tells me that improved efficiency should start inside the engine with "optimum" compression ratios for pump fuel and very close control of timing/fuel curves.

Those big HD 454 engines from that period are "sleeping giants".  A few simple improvements starting with tuning and the camshaft really wake them up.  I've taken several of them and tightened up the squish and increased the compression a tad, better cam choice and custom tuning.  They feel like they make another 100HP and everything gets better in a HD/towing application.

Never smog tested any after the modifications but I'll bet they are cleaner out the tail pipes as well.......Cliff

[KeyAir]

Last trip out there, I drained almost exactly 15g of old gas out,using the rear mounted electric pump. That pleased me, cos I only had 3x 5 gallon cans with me! Gas smelled ok, but then over the last few months I had added at least 2x 5 gallon cans of premium to the tank, as well as extra Stabil, and at least 1 can of seafoam.
Then ran the 454 until it stalled out.
Should be ready for when I go back, to try the setup again.
Plan to put 10g of fresh, quality 87ron in.
I think I will pull the O2 sensor and recalibrate before I start too.

[Cliff Ruggles]

I'm not sold on Stabil or Sea Foam with this new fuel.  The ethanol is still in there, and it will separate over time and absorb water. 

The octane goes down pretty quickly with modern fuels. 

Had a Honda generator brought in here a few months ago because it refused to start, not even a hint of trying to fire over.

I just figured the carb was plugged up with "apple jelly" from sitting a few years so pulled it off for a good cleaning.  Turns out the generator had an automatic fuel shut-off and the carb had dried up shortly after the last use so was perfectly clean.

I proceeded to dump the fuel tank and put in fresh gas.  It fired right up but "hunted" and wouldn't pull full load, but that's another story.

I dumped the old fuel (about 3 gallons) in the gravel driveway outside the shop and told Ray to light it.  He made several futile attempts to get the fuel to burn.  I joined in and it became a mission to get that gas to ignite.  We finally got brave enough to light a paper towel and drop it right in the middle and it very slowly took off but really didn't flame-up light most gasoline does in open air. 

It ignited and burned very slow, similar to kerosene or diesel fuel.  It didn't have a stale smell or any indication it was bad, and the owner did mention putting Stabil in it........Cliff