Smelly Exhaust fumes

[HandyDan]

I finally got my 1984 Holiday Rambler back from the mechanic after one and a half months.  He had trouble getting the bolt out that holds the choke stove in the manifold.  On the 100 mile drive back, my son was driving behind me.  He said he had to fall back a ways because of the exhaust fumes that the HR was putting out.  He said it smelled somewhat like a diesel.  I know the 454 runs at a fast rpm, I averaged right at 3000 the whole trip, and at that speed it is going to run warm.  It never got over mid way on the temp gauge, but the fan came on quite a bit.  My oil gauge seems to be broke because it never moved.  I have to work on that.  It worked fine on the way down to the lake.  What can I do to clean up the exhaust?  It ran fine, idles fine (which is why it went to the mechanic), and doesn't smoke.  Any ideas?

[DRMousseau]

That "diesel" odor is usually that of "incomplete combustion",... but not necessarily from the engines internal combustion of fuel. A quick look at the end of the tail pipe, MAY lead you to look elsewhere. At higher engine speeds, any of the "oily" fluids in vehicle systems may leak slightly from aging seals, gaskets and connections. Any that come in contact with hot engine components, may smoke and fume quite a bit. Check carefully for any fluid leaks from engine areas and all other nearby systems, including brakes, steering, and transmission.

But if the end of the tailpipe is dark, wet and sooty,... you shouldn't be alarmed YET. A quick inspection of the sparkplugs will confirm a great deal of information. ALL should be dry and rather tan in color. Any problems in carburetor adjustments, choke settings, vacuum leaks and other "general" problems will show among all the plugs. But if jus ONE or two is "off" color from the rest,... then it may be as simple as a faulty plug wire, or an internal issue with one or more cylinders.

And if all sparkplugs appear normal and as they should, then your issues likely lies somewhere between the exhaust port and the tailpipe. Often, the muffler becomes "overloaded" with carbon and deposits from previously neglected and poorly maintained adjustments. I might suspect that your issues may lie here.

After a good tuneup with no other major issues, the clean hot exhaust tends to "burn out" the deposits previously left in the muffler and exhaust system. It may take some time before this clears up. But if this continues for long, then you might look elsewhere. It is POSSIABLE that a leaky exhaust valve seal is allowing some excessive oil leakage into the exhaust system. But this usually shows up as a persistent exhaust smoke when starting, and at higher speeds or right after a long run, until excess oil drains from the valve covers. From your description, I really don't think this is a big issue to be concerned with.

Jus check for "leaks", and keep an eye on ALL fluid levels for anything unusual.

[HandyDan]

Thanks for the info.  That gives me somewhere to start.  I'm going to start pulling spark plugs tomorrow if it doesn't rain.  Got to get done before the Royals game.  I know the rest of the world couldn't care less, but we in Kansas City would like to win the World Series this year.

[Rickf1985]

Exhaust valves do not have seals, only intake valves have seals.

[MotorPro]

Exhaust valves do not have seals, only intake valves have seals.

I have never seen a BBC without exhaust valve seals. Having said that the factory seals are only 1 step above useless.

[circleD]

I've had the same issue Dan. I had to readjust the carb and do a tune up. Do you have an odor in the cab after you park it and close it up for awhile, then come back?
I know it just got worked on but you know how finiky they can be. I also took all my A.I.R. Stuff off.

[DRMousseau]

OMG!!! I laughed a bunch because I corrected that from 'intake' to exhaust,... sparkplugs will show oil fouling from leaky intake seals or worn rings. Compression tests are helpful here. But worn exhaust valve STEMS and guides will also leak oil down after a hard run sometimes. Nothing that shows on the plugs, but it usually smokes a bit when started later, and disperses rather quick. It CAN sometimes load up the muffler though and be a problem.

And Rick's right,... you jus don't see any seals on exhaust guides. Any that might fit, jus don't stay there! Ya,... we tried.

I still think you jus got a drip somewhere during hot runs,...

[HandyDan]

I've had the same issue Dan. I had to readjust the carb and do a tune up. Do you have an odor in the cab after you park it and close it up for awhile, then come back?
I know it just got worked on but you know how finiky they can be. I also took all my A.I.R. Stuff off.

As a matter of fact, there is an odor after I park it.  I still have all the A.I.R. stuff hooked up.  It originally had the dual fuel system for propane, but I removed all that.

[Rickf1985]

Make sure you don't have any leaks in the large hoses to and from the evap canisters in the right fenderwell.

[circleD]

Like I said. Even ththough I had a new carb and it ran great there was an odor after I shut it off. So I turned down the jets and idle and it's fine. Did a tune up just because. The dual fuel was tak n off of mine already. I have picks in my gallery if you need a reference. The AIR was simple to remove. Trying to get the people at the parts store to understand why I need certain sizes of belts was hard. Luckily I made friends with an old school hot rodder that knew what was going on that worked ther.

[DRMousseau]

Ain't no one like an ol' "hot-rodder" in a parts store to be friends with.

He didn't sell ya on a nitrous system, did he??? They smell "funny" too. LoL!

[circleD]

Any progress Dan?