We get frequent questions about this subject and I thought it would be a good addition to the archives under the title "Steam observed in the exhaust". This info will be posted in the 427, Small Block Chevrolet, and Lincoln motor sections of the
Chris Craft Commander Forum MASTER INDEX FILES
in the near future.
(ABOVE): Unfortunately, Chris Craft didn't use as good a grade of iron as Chevrolet or Ford did for their motors and cylinder heads. As a result, exhaust manifolds and risers don't last as long as motor blocks do.
The recent thread about Bill Policastro's cracked block uncovered some very good diagnostic information too, and it is referenced below.
Steam can be caused by a crack in the head, a faulty intake manifold, cracked internal cylinder wall to cooling chamber, bad head gasket, or a small small crack in the exhaust manifold water jacket. It can also be caused by a failed gasket in the exhaust manifold system too. You can also get steam from some motors due to improperly sealed head bolts, the SBC is particularly prone to this.
If you have a cracked head or defective head gasket, water will be going through your combustion chambers and you will experience some poor running characteristics, and your plugs will reflect the fact that they have been steam cleaned.
A small crack in your exhaust manifold water jacket will allow drops of water through and of course this will manifest itself as steam at the exhaust pipes.
If you are ingesting water through a crack or rust hole in your intake manifold, it will form a thick brown goo on the intake valve stems. The goo in the sump won’t be doing the main bearings, cam, or other critical parts any good either!
Check your dipstick, pull the valve cover, see if you have a chocolate milkshake, if not, then the steam is probably coming from a crack in the exhaust manifold or riser. Although the latter seems less critical, this can be a problem with some exhaust systems that allow water draindown and a buildup of enough water to pour into a cylinder and cause hydrolock.
I keep a pyrometer on board, and I check my manifolds from time to time, one engine versus the other, just to see relative temperatures. This assures the water flow internally is still functioning as intended. Otherwise, if you do get a blockage somewhere, it could cause a hotspot and that may also lead to some degree of steam. If you have low flow through your intake impeller, or if you have pressure valves clogged, you may be seeing steam as a result of overheating.
Check that dipstick first, pull the plugs, and pull the valve cover. If all looks well, and especially if you still have decent compression too, then it’s most likely a leak in the exhaust manifold or riser.
Exhaust logs and risers fail in two ways, freeze damage and just plain wear and tear. Sometimes they freeze a bit, the damage isn't really apparant, and then they rust. Most of the time the freeze damage is outward, and they can be weld repaired under some circumstances, but a replacement is always best if freeze is suspected because you just don't know what happened inside.
If the exh manifold froze, then internal motor parts may be close behind.
These parts are big and heavy, and unless you disassemble the riser from the exhaust manifold, you'll probably have to use some sort of a winch or get a buddy to help lift them out. I'd pull the ones on the steaming motor, check em out. If they looked really bad then it's time to search for replacements for both motors. My hunch is you have a leak in the exhaust manifold, riser, or in the GASKETS that put the numerous parts together. The cheapest fix would be a bad exhaust manifold gasket!
Regards, good luck,
Pau1 P1etcher
Bill Policastro has a very informative thread on this subject. His first observation was milky oil, and NO STEAM. This thread explored numerous other ways water could get into the oil system, and it is a great reference thread. In the end, Bill discovered a 2" crack in the cylinder wall, allowing water from the water jacket to creep in. This was a result of freeze damage by the previous owner (or previous owners mechanic). That thread can be found here:
http://www.network54.com/Forum/424840/message/1181165248
In a marine exhaust system, a little bit of steam is natural, After all, you’re exhausting pre-heated water that cooled down a V8 motor, and that hot water is coming in contact with a super-hot blast of exhaust gas from the motor at the point where the exhaust water dumps into the system at the riser. A little steam is normal. A lot of steam, or just steam on one motor and not the other, is not normal.
Regards,
Paul
