1988 Prelude S - white/black(?) smoke and power loss

First, I'm not quite sure about the color of the smoke: at first glance at the tailpipe end, it seems white, but looking at the billowing cloud you think it could pass for black. One could even suspect blue, but
that could be an illusion due to the green foliage in the background.
As to cause: my research suggests likelihood of coolant leak into the engine (most likely through a busted head gasket). I have read that in such cases the smoke "smells sweet". Having no experience here, i can not be certain what "smelling sweet" is, but i would be willing to describe this smell as sweet.
However, the facts with this car are: According to the driver, the smoke problem began right after the car was driven over a sidewalk elevation whereby the muffler was impacted. (I am not ruling out that the sidewalk may have bumped some other part, but the driver seems certain it was the muffler). Currently the muffler has an old, corroded exterior, with a good-size hole where the outer metal shell is lacerated a couple of inches. Coinciding with the start of the smoke problem and the impact, the car also noticeably lost horse power. There are soft, low rumbling noises coming from the muffler area.
I do not know enough to rule in or out the possilibity that the muffler is the one (and only) cause of the problem. Could it be a cause at all?
In case this is relevant: with a recent replacement of ignition stuff (sparkplugs, wires, distributor) the engine sounds great and runs smoothly. (Could it run smoothly with a blown head gasket?)
thanks
Andrew
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snipped-for-privacy@flight.us wrote: <skip>

--- additional details: ----
When the muffler was hit the car was going in reverse, steering clockwise. It hit the pavement and scraped for a couple of seconds, with the force pushing the muffler toward the front of the car.
--- new development: ----
today when I examined the running engine, I noticed a tiny bit of steam rising from the engine, along the mating surface of the cylinder head (I *think* I am describing the locus correctly, but not 100% sure. It's definitely along *some* mating surface, along the length of the engine block). Very small wisps/puffs, which one would not know about without looking under the hood. It starts after a couple of minutes, when the engine gets sufficiently hot (and continues for a short while after shutoff). Blown head gasket? Warped head?
--- plea ---
can someone please say if my question is extremely stupid and the answer is obvious, or if it truly presents a strange riddle - the only two reasons i can think of to explain the lack of replies.
--- theoretical question ---
if this car is deprived of coolant, could it suffer head warping and nothing else, or would the consequences of lack of coolant be, without exception, much more severe than JUST a head warp? Or, perhaps, **some degree** of coolant defficiency could cause just the head warping?
(An Advance Autoparts attendant suggested the head warping possibility today)
TIA
Andrew
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wrote:

Head warping is probably the most common result of lack of coolant. The aluminum head expands in length more than twice as much as the iron block, and typically lifts in the middle to do that. In Hondas, the solution is normally to remove and mill the head.
Mike
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Pull out the spark plugs and look at the electrodes. Are they wet or discolored in any way? Sometimes when an engine is burning coolant you'll find little white crystals on the electrodes. Also, burnt coolant produces white smoke which, in my opinion, tends to be acrid smelling. For comparison, burnt oil produces a blue-grey smoke and if the engine is running too rich it will produce a black smoke. Is the engine missing on any of the cylinders? Often times a blown head gasket will produce a misfire. Pull the spark plugs one at a time with the engine running while watching a tachometer. The one that produces the least amount of rpm drop has the misfire. A compression test can be helpful sometimes. If a head gasket is blown between two adjacent cylinders then both will be low. However, if the head gasket is blown on just one cylinder going to one of the water jackets, then that cylinder might be low. There are also chemical tests that you can do to the coolant which will reveal combustion byproducts. Anyways, there are lots of tests you could do...
Eric
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