Engine rebuilt, Weber 32/36 running rich?

[specialk4430]

Finally finished putting my 78 1800 engine back together. Stock bore, Vick auto high compression pistons, Weber 32/36, 4-2-1 exhaust manifold with Vicks stainless exhaust, pertronix ignition with flame thrower coil, ngk plugs, fresh 93 octane. Got the timing set at 10*, idles at 1000rpm. Fuel pressure regulator set at 2psi, and I adjusted the carb float. This thing runs fantastic, but it seems to be running rich. I did all the standard Weber tuning stuff, and the weird thing is that I have a 55 idle jet installed and it runs good at 4 turns out. The number of turns tells me (according to weber) it's running lean, but the plugs are sooty/black and this thing smells like my lawnmower. Maybe it's supposed to smell, I dont have a lot of experience with catless vehicles, but the plugs have me concerned. No smoke from the tailpipe. I just made the switch to the 55 from a 60 idle jet, a d other than tweaking the timing, it made no difference. All other jets are what came on it. What gives?

[samakijoe]

Was the engine "broken in " by the book? Did you use "brake in " oil? How many hours on the engine. There are a lot of reasons for a newly rebuilt engine to run "rich" or seem to run rich. Doing a "plug chop" will tell the real story. The short story of a lug chop is, run the piss out of the engine, put it in neutral, turn off the engine, and coast to a stop without any "idle" time. Pull the plugs and take a look at them. This will give you an idea of the condition.

You mentioned that it was a "catless " engine. That smell could well be a cat. You might ask around of your neighbors to see if they are missing tabby.

[18Fiatsandcounting]

SpecialK, just checking here: the holder for the idle jet (the 55 size that you have) is screwed all the way in, right? When you refer to "4 turns out", you're referring to the idle mixture screw located at the base of the carburetor? I have to ask because many moons ago, I tried adjusting the screw that holds the idle jet and found that is not the right way to get the carb set up right...

If you're good on the above, do try the test suggested by Samakijoe.

-Bryan

[specialk4430]

That's correct, the screw that is 4 turns out is the idle mixture screw, not the screw holding the idle jet. Lol, sorry for the confusion. I did install an o2 sensor and an air/fuel gauge and it reads about 13.8 most of the time. It fluctuates when I give her some gas, so I guess it's working. I did the above mentioned test but I still gotta pull the plugs and take a look. I just drove it around and put it away. I'll let you know what I find. Thanks.

[SteinOnkel]

13.8 is a tad rich, but not by much for a curb'ed engine from the 70's. Honestly I would run it and not worry about it. If you want to run wild with it, sure, lean it out some more. But you are never going to get perfect AFR values from any carburettor. Otherwise, we'd still have them on cars today, wouldn't we?

For this reason alone I dislike using a wideband on a carb. It will just drive you nuts.

[samakijoe]

13.8 is not "rich"

[specialk4430]

I agree that 13.8 is good enough. I put the o2 sensor in after my original post and a couple more tweaks. I'm leaving it alone now. Next step, fix the interior. Anybody know anyone with a good decent dashboard for sale? Thanks, everyone.

[18Fiatsandcounting]

I agree that 13.8 is not rich. 14.7 is the stoichiometric ratio (14.7 grams of air to burn 1 gram of fuel), but this assumes pretty much ideal conditions (including the gasoline), no effects due to the difference in mass or inertia between fuel and air, no intake inefficiencies, no fuel additives, no temperature or pressure variations between or within the cylinders, etc. In practice, somewhere around 13.7 is considered a good all around number for a typical car engine, whereas around 12 is best for power output and around 16 is best for fuel economy. If your air/fuel gauge is accurate, 13.8 would appear to be just fine, although sooty plugs and the smell of unburnt gas would still concern me.

As for the dashboard, how much are you willing to spend? There are reproductions, covers that fit over your existing dash (usually just over the top part), decent quality used ones, and so on. Anywhere from $100 to much more than that. Try looking at some of the usual places, including Vick Auto, Midwest-Bayless, Auto Ricambi, Ebay, etc.

Suggestion: Try searching for "dash" instead of "dashboard" as the former brings up more relevant hits.

-Bryan