Sooty tail pipes anyone?

[bobs409]

Calling all w-motor owners. Do these engines normally run rich?

Here's what my tailpipes look like. Notice the bumper is even stained. (it does clean off)

The exhaust will burn your eyes too. Spark plugs run from tan to dark brown in the center with a dry black soot on outer ring. Plugs are one step hotter (45's). I always run pump 93 octane premium. This engine starts in 20 degree weather without the choke and runs perfectly even ice cold. In fact, it runs it's best when the temp is under 160! Carb has been rebuilt 2 times, float level and drop settings have been checked and rechecked, jets have been changed to try an lean out but still the sooty pipes remained.

I've been told that big blocks tend to do this but lets see if anyone else has this.

 

[tripowerguy]

sooty tail pipes

My 348 with 3 carbs does the samething. The plugs always show rich. If I unplug it and run it down the drag strip once the plugs clean off and look fine. I sold a 4 barrel set up to a guy in Nevada who gave up on a tripower for his 348 because it always showed rich. I should e-mail him to see if he solved his problem. I'm hoping that this new engine with headers and 2 1/2 in exhaust will solve my problem.

 

[64ss409]

Good question Bob. I have not noticed eye burning exhaust. That sounds actually rich. Is that just at an idle?

But what I have noticed, and not only on W engines, is that it seems like the bigger the exhaust system, the blacker the tail pipe. When I went to 2 1/2 all the way on my 454 K10, I got a sooty looking tailpipe, unless I hook to a trailer and load it, then it turns brown. I have tried leaning with smaller jets, but can't go smaller without noticeing a lean feel on light acceleration.

I am thinking the smaller tail pipe is holding the heat and it is the heat that is changing the color. I have a neighbor that had 2" tailpipes on his 76 K10 350. They always had a gray/lean look. He had 2 1/2 installed and now they look a little black.

I am going to watch with interest to see if someone has a good flowing exhaust and is able to get a light brown color.

Ron

 

[bobs409]

Ron,

I too tried to lean it out by changing metering rods and jets but all I got was a bog on acceleration and a light surge at part throttle.

There's no apparent flooding inside or out of carb either.

My exhaust is 2 1/2" all the way and the tailpipes are Flowmasters with mandrel bends.

It's been like this since day 1 and I have over 7,000 miles on it now and exhausted (pun intended ) all my options.

Just wanted to see if I was alone in this. I do recall hearing that big blocks do tend to run rich but not sure why?

 

[roaminchariot]

I haven't noticed any soot on mine and I definately need choke to start the engine cold. I have the old Roch 4GC carb so it is a different animal. I do also have factory manifolds with a free-flowing 2 1/2' exhaust. If you know of any chasis dyno shops, you can put a mixture sensor into the exhaust and run the car under load across the rpm range and see what is really going on. We did that when mine was set up and the mix was about right in most places. I'm sure that street/traffic rpms on a hipo cam would also gum things up.

 

[dq409]

With the AFB type carb you should be able to dial it in right on the money!! NO SOOT !!
Rejeting , changing the rod size and spring should get it right. It takes a while but in the end it should not run rich. I have no soot or eye burning smell.
You don`t want to runn too rich or you will wash your cylinders and short live your rings,,,,dq

 

[bobs409]

Dq, I have tried leaning it out with different jets and metering rods that I got in a strip kit but all I got was bogging or surging and no improvement on the soot or strong exhaust. Plugs are dry so it's not dumping fuel so I don't think it could hurt the cylinder/rings. (or could it?)

409z28 had suggested to me to put the original jets and rods back in and try lighter metering rod springs so that's my next venture. In theory, that sounds like it could help. Especially if the richness is just at idle but without some type of a sensor, I have no idea.

 

[dq409]

Believe me when I say I`ve had my carbs lids off hundreds of times !!When I started i didn`t know a thing about this type of carb,,,but NOW it all makes sense !!
The strip kit is OK but never seems to have the combo you need. I have a box full of rods, jets and springs now. AND WORSE is having the two carb set-up !!
Keep a log of where you start and what changes you make and what the changes do. Once you get a feel on what the changes do you will start to get a real feel on what works which way. Once you nail it you will be supprised on how well you can dial in these carbs. There are so many combos to use you just have to try the trail and error method.

Start with the rods and jets . Once you get the rods and jets set then go onto the springs to get rid of the flat spots.

I`ve got mine down to where the plugs burn great ,,,no soot out the back,,,,and smooth operation all through the RPM range.
Now that I`m using the MSD trigger distributor and the MSD 6AL I`m back to adjusting my secondaries.

IF you want the best ignition posible do the MSD route and you won`t go back !!
,,,,,dq

 

[dq409]

Something else that will help is to get a Edelbrock carb manual that shows the graph on what jet and rod combo do,,,dq

PS I`ve sent this to several member. If you need one let me know

 

[bobs409]

Thanks. I think I got some type of graph like that with the strip kit. If I remember correctly, it was a copy of the manual you mentioned. Have to go dig it out.

I know what it's like to have the "lid" off! What a pain. I don't mind changing rods though. And it really does get confusing. I did make notes last year when I was doing this "testing". Now to find them again. Come to think of it, where did I put the strip kit?!?

 

[dq409]

Bob, Next time I`m at the car I`ll grab my notes and let you know what I`m running. Don`t be afraid to change the springs to see what happens. I think thats where you were stuck at. That flat spot or stumble will be caused by the wrong spring.,,,,dq

 

[Gerry]

Sooty exhaust

Bob, one thing you should be aware of is that changing main metering jet sizes and metering rod diameters does not affect the idle circuit of a carburetor. The idle circuit on an AFB style carburetor is changed by changing the idle restriction size or by changing the the idle circuit air bleed size. If your vehicle does a lot of idling, you may have an overly rich idle circuit causing the sooty exhaust pipes.

 

[dq409]

DOHHH !!

 

[bobs409]

It's raining here so I can't test it but today I put back the original jets and rods and installed the orange springs from an Edelbrock spring kit I just bought as per the advice of "409z28." Also double checked the floats while I was in there.

I'll let ya's know how that works out when the roads are dry. I think I will clean the plugs before I run it so I can see if there is any difference in color with the new set up. Come to think of it, I better clean those sooty tail pipes too!

Oh yeh, I found my old notes and what I've been running since last year was the original rods and springs but with .098 jets. With this combination, I have a very light surge at cruise and a bog on acceleration. Comparing the .098's against my original jets shows a big difference! I bet I can really whoop those Mustangs with these in there! :eek:

 

[dq409]

Bob, That surge and bog thing is caused but the wrong spring. I think you want a stiffer spring. I`ll check my book,,,I always get it backwards,,,dq

Just checked and it is the heavier spring that brings in the power mode sooner. I have the manual if you want me to send it email to you,,,let me know,,,,dq

 

[bobs409]

Ok, here's my road test report:

Cleaned the plugs and tail pipes and road tested it. WOW! No more bog/hesitation/surge what so ever. Completely smooth through all ranges from cold to fully warmed up. It's like a totally different engine.

The exhaust still has a strong smell and I still didn't need to use the choke to start. A few pumps and it fired right off and idled fine with choke wide open.

It's gonna take a few rides to see if the pipes soot up but no signs as of yet.

I snapped a pic of the plugs before I cleaned them. The porcelin is almost white, the center electrode is a dark brown and the outer rings are sooty black. See:

 

[65Impala409]

Hey Bob,

You will have to let me know how it all works out... My 65 409 could almost gag you.... The current setup is a mallory ignition system and is set up with a 650 cfm holley carb(not a double pumper but has a secondary?).... Has dual flowmasters that stop just shy of the back seats with little chrome tips on them pointing towards the ground.... Not only are the little tips black with soot but the concrete is stained black from the exhaust.... Not to forget to mention, just sitting in the car makes you feel like you bathed in the exhaust. Just try to get the smell off of yourself, it doesnt happen without a serious shower.... I had no idea if this is something that is to be expected or not.... Good luck
Ned
65Impala409

 

[dq409]

You should run your ehaust pipes all the way out the back or have them exit out the side in front of the rear tires. Even with the engine running (buring right) you will never eliminate the exhaust stink with that set-up.,,,,dq

 

[62SS409]

My '62 has always had soot in the tailpipes. There are several contributing factors. Lots of short trips prevent the exhaust from getting hot; the use of resonators does the same thing but worse, resulting in condensation in the tailpipes which catches the hydrocarbons like a filter and sticks them to the pipe walls. Multiple carb set-ups make the car run rich (I lean mine out as much as I can while maintaining decent idle). Leaded gas is dirty - so is lead substitiute. Modern fuel with the alchohols, esters, and ethers burns hotter with much lower hydrocarbon precipitation. The burning eyes comes from lack of catalytic convertors which take nearly all of the sulfur dioxide out of the exhaust on modern cars. When sulfur dioxide hits water (like your eyes, nose, and throat), it forms sulfuric acid. The same principle as acid rain. If you don't have convertors, you're making lots of sulfur dioxide. I don't notice the burning unless I run
a few minutes in an enclosed space - then WHEW!!

 

[dq409]

I`m running dual fours and a complete exhaust system and don`t have any "soot" out the back. The soot is a sign of rich running no matter what. Granted a little black "inside" the pipe is ok but what I`m seeing and hearing is an excess of unburned gas.
Also you will get a stink with a non-cat system but not to the degree mentioned here. I can run my car in the pole barn and NOT get the caustic eye burn or heavy smell.
It`s tuff getting the carb or carbs dialed in. I`ve got hours and hours of rejetting and adjusting but I know I`m close enough to be happy at this point. Once I get the the track that`s another story but it will just be jetting of the secondaries.
I guess what I`m saying is ,,,,,,spend the time and get those carbs and engines running as close as possible to perfect !!

Did I just say perfect,,,,,,,,,,,,,,,,,OK,,, I said as close as possible,,,dq