Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Motorhome carb and California Smog!

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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

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