exhaust spatter
 

I have recently made quite a few changes to my system, but I am still noticing exhaust spatter with dark matter in there. I searched the site and think I am on the right path, but was looking for some more tips.

What I did,
Rebuilt Carb, New Fuel tank/lines/pump, HEI, Plugs, Wires, New Headers, new exhaust/mufflers, Engine has 70K

Last week I figured out that I had some trash in my carb from the week I ran it before the tank change. It wasnt letting my pin valve seat right AND I never adjusted my timing for HEI so I was running fat and the bowl was overflowing. I was backfiring it was rough. I got those adjusted Sunday.

Thursday while testing something I noticed a lot of gas smell when it first fired up so I figured it was still running fat.

Friday I was installed a Tach and while I was testing it I noticed yet again water out the exhaust and black spatter.

Here are my thoughts:
It was cool out last night (probably 50) I am not getting a Ton of smoke of any color. The water coming out the back was not antifreeze, my AF is green and it wasnt green at all. So I think that the water was natural condensation because I didnt "run" the engine. I was just sitting at idle messing with the tach. I think black spatter is because I am still running FAT so I adjusted the mixture screws down to rough idle and then back up a half turn each. I set my fast idle at 1100 and my idles at about 700.

Do you guys think I am on the right track? some of my buddies do but some of them also believe in the tooth fairy I am pretty sure ;)

Re: exhaust spatter
 

What carb you got?
Have you got pics of your motor?

Moisture out your tail pipe is normal. Black spatter can be from several things. Poor combustion, lack of timing, leaking guides etc.

I assume ‘pin’ valve means needle/seat. How did you adjust it.
What did you set your initial timing at?

Re: exhaust spatter
 

When I had that symptom of black water splatter on cold starts and odor of gasoline, I couldn't figure it out. I took my truck to my shade tree mechanic, who is a retired GM mechanic. He found it was a bad choke pull-off, which is the little vacuum operated thingy on the carburetor that helps the choke open. Sometimes they are called a choke break. He tested it with a Mityvac. Replaced that choke pull-off and fixed the problem.

Re: exhaust spatter
 

A carb when 1st started will put rich sooty, carbon through the exhaust system till warmed up and the choke opens. the black stuff coming out the tail pipe is just condensation mixed with soot. once warmed up you should see it no more. EDIT" doubled with dmjlambert....

Re: exhaust spatter
 

Thanks guys, sounds like I am on the right track.

The Carb is a quadrajet, Timing is 14 BTDC now. I didnt realize I had to change it when I did the conversion so before it was running terrible.. learning as I go. Yep, I am calling it the wrong thing, the carb was professionally rebuilt buy a guy who does nothing but quadrajets... good reviews, but I dont know what the float is actually set at. There was rusty residue in the bowl from where i ran the old gas tank before I realized all that was a problem. I cleaned it out with carb cleaners etc... and I think that took care of the loading problem in the bowl.

Re: exhaust spatter
 

Maybe you should do the two ounce tune up.
Trickle a couple ounces of water in the carb while at a high idle (1500 rpm) and that’ll steam clean all the carbon outta your combustion chambers.

Re: exhaust spatter
 

Really? Thats a thing? Sounds like your messin with me at first but it makes sense and I always trust the folks on this site. Ill give that a go if the problem persists now that I have leaned it out even more.

Re: exhaust spatter
 

Back in the day that was an easy 50 bucks for a shady mechanic. Customer would bring his vehicle in for a tune-up, scammer mechanic would clean it out with a little water, no parts cost, a couple minutes of time and a cup of water. Easy Peazy!
I bought a used motor once and was giving it the water treatment (using atf instead)when the local fire department showed up at my shop. Neighbour thought I had a fire going. Called 911. Good for a chuckle.

Before you do the water thing, do a test.
Look inside the carb below the choke blade while it’s idling. If you see any raw fuel then your float is set wrong and it’s flooding a bit.

Re: exhaust spatter
 

I just went through this battle myself with a quadrajet on my 71 blowing really rich fumes, smoke and black soot. So bad it was spraying the walls and floor of my garage.
I adjusted the timing to 15 BTDC and used a vacuum gauge to set my air/fuel getting about 17 inches of vacuum.
It did not help the black soot on startup but it ran great once it was warm.
I turned my attention to the choke and ended up just having to adjust my electric choke. It starts right up and no smoke or soot now. For reference, at 7500 feet in elevation my choke is at about 12 o'clock now. Previously it was at about 10 o'clock.

It sounded like a few above already mentioned choke but that is where I would look if the vehicle runs well once warm.

Re: exhaust spatter
 

All good news guys, it sounds like I am headed down the right path, its just a matter of getting it tuned right.

Re: exhaust spatter
 

As said the water is condensation. If your truck ran for several hours or more with the rich conditions your entire exhaust system is coated with soot it may take some time before it is all cleared out. Taking a highway trip for an hour or so will help with that.
Here is a link to my repair page. Scroll to post 618 for information on my choke adjustments that may help you.

https://67-72chevytrucks.com/vboard/...698377&page=25

Re: exhaust spatter
 

This is fantastic, thanks!!

Re: exhaust spatter
 

When you trickle the water in, trickle it SLOWLY. You can cause serious damage if you dump it in too fast.

Re: exhaust spatter
 

I'm glad someone said that... Keep in mind water is essentially not compressible (or at least it can't be compressed in a combustion chamber). Pour VERY slowly indeed.
Personally, I wouldn't bother. Bottom line, what you're seeing is pretty normal phlegm. Black smoke, different story, but soot colored water, not an issue. Best way to clear soot is on an empty stretch of highway. With nobody around. :)

Re: exhaust spatter
 

I have to agree with the no water crowd. It's more of a cheap fix for detonation in worn engines that were built with low compression, poorly designed combustion chambers and running on bad fuel. In other words engines that were built in the 1950's and earlier. The listed conditions can cause large carbon build ups inside the combustion chambers which will cause detonation.
Short of pulling the head(s) off of the engine there isn't really a better way to break down the carbon and get it out of the combustion chambers. That being said I don't believe that water will help in the exhaust manifolds or pipes. Not to mention once those big chunks of carbon break free your relying on luck that they don't jam in the space between the piston and the cylinder wall and start scuffing the bore before going out the exhaust valve (hopefully not getting caught between the seat and valve when it closes.)
I'm not paranoid!
It's just that bad things happen to me and I'm out of coupons.

Re: exhaust spatter
 

First the water through the carb thing I have done many times before a top end rebuild. It works, for cleaning out the combustion chambers.

I will not prevent the soot buildup as that pertains to a rich fuel situation.

Laugh if you will, I hate pulling plugs and cleaning them. Some old school stuff still has its place in certain applications.

Keep in mind my opinions change, at will, with no rhyme or reason, depending if the dog needs to go out for a walk as she will not poop in my own backyard!

Re: exhaust spatter
 

If you're worried about carbon build up and don't want to do the water trick, we use this stuff in the marine industry with great results:
https://leadersrpmshop.com/mercury-q...MaAibaEALw_wcB