Cylinder #1 carbons up

[Renegade]

I installed a new rotor, new distributor cap, new wires, checked the valves in cylinder 1, both working. I tried an acid flush of the cooling system and gapped a plug at .040 and I have a clean burning cylinder one. I went through a box of 4 plugs and the last one was #5. I wonder if I had a bad box of plugs or a obstruction in the exhaust system?

In any case, Thanks for all the advice! I'l keep you posted once I get a few hours on it.

[Renegade]

I took the boat out for a couple hour motorboat ride and while it seems to run fine and carbon deposits on the plug are less, there is still a noticeable amount of black soot on the plug. The other 3 plugs are fine.

[Dave Neptune]

Renegade, once ALL of the above ignition questions have been checked and verified good all should be well there. I have only one question to answer, what plugs are you using?

Indeed a sooty single cylinder and sooty exhaust could be the carb. If the "air jets" are plugged or restricted the engine will run OK in many cases however the "fuel mix" contains to many droplets of fuel instead of "atomized fuel" broken down by the air injected into the fuel inside the carb before it gets to the venturi. This causes a poor mix of the fuel in the cylinders so the "burn" is not complete and still burning "droplets" are present when the exhaust valve opens. This effect can be worse from cylinder to cylinder as the heavier fuel will gather in places and flow in others.

Dave Neptune

[Renegade]

Dave. I believe if it was the carb, the symptoms of fouling would show on all cylinders possibly to a different degree in each cylinder. Cylinder 2, 3, and 4 are burning perfectly clean.

I took one more shot at it this afternoon. yesterday I noticed that the plug was fouled but not nearly as bad as before. I decided to pour a liberal amount of MMO in the cylinder and let it sit for a couple hours. I put a new Autolite 86 plug in and started it up. I ran it under load for about half an hour then shut it down and checked the plug. It was as clean as the others. A very nice light brownish gray. I repeated the process and ran the engine under load at 1800 RPMs and it came out clean again.

This summer during our travels when we first noticed the soot on the stern, I assumed it was due to too much MMO in gas. We put a lot of hours on the engine with the last no wind leg being about 75 miles. Now I'm wondering if a fault in the spark plug or wire to cylinder one caused so much carbon build up that it had to work its way out. I'm not an expert so I can't say for sure. I'm just glad it's back to running properly again.

[Dave Neptune]

Renegade, good news. If you are using the MMO in the fuel don't use anything else. When mixing mix at 100:1 max oil concentration. What were you mixing it at and any other additives? Also use regular grade and not premium as the regular burns faster and is designed for lower compression like in the A-4. If the soot persists try a 2 stroke oil with the TCW-3 rating instead as it lubes and mixes better with gasoline. It is designed to both 'burn and lube" while staying in "suspension" in the fuel.


Mixing fuel additives can be catastrophic if something in either doesn't get along with something in the other.

Dave Neptune

[Renegade]

I only use MMO. I eyeball the amount I put in the gas though...

[tenders]

I only use MMO. I eyeball the amount I put in the gas though...

While a little extra Marvel probably never hurt an engine, you can reduce a bit of the eyeball factor by repurposing a Sta-Bil bottle as an MMO delivery mechanism. Those have built-in 1oz dispensers, the design of which I happen to have admired since before I could read.

[Dave Neptune]

Renegade, 1 oz per gallon is what I used which is 128:1 and always a clean exhaust.

I run my D/P Hemi Challenger (140,000 miles) and my Corvette (185,000 and pulled the engine still good running for a swap and 250.000 miles on it) both on the TCW-3 at 1 oz per 4 gallons or 500:1. My compression numbers are still excellent and the valve guides don't leak.

Dave Neptune

[capnward]

marvelous

I use 2 oz. MMO for 5 gallons of fuel. That is what Marvel recommends. That is a ratio of 320:1, which is less than 1/3rd the maximum Dave mentioned. I have a pint bottle of MMO, which has marks on the side in 4 oz. increments. I buy MMO by the gallon, and dispense it into the pint bottle periodically. Half a pint bottle (8 oz.) is good for an oil change, every 50 hours. That is about 8% MMO. Marvel recommends 10 to 25%. I haven't opened the valve cover in 2500 hours of running. The stuff works. If it is snake oil, why did the old-school engineers who tested A4s at Universal in the 1960's swear by it? I read that on this forum somewhere. I'll bet it wasn't the red dye and the fragrance.

[Renegade]

MMO is great stuff. I use it in my 1978 John Deere 316 tractor as well.

[Renegade]

Just an update. We did our last Wednesday night race last night and the engine ran great and no fouling.