Thought I would throw this out to the group for a consensus. 

First: '87 Westy. Last summer I my engine blew and had a rebuilt 2.3 put in. 

Unfortunately, I have not had a lot of opportunity since then to properly break her in and she has been sitting for much of the time. After my last use, I added some oil as it seemed low.

Now, the present. I was taking her out for a short trip. Checked the oil level. Looked ok, possibly a little high. The coolant expansion tank was very low. I had no coolant so I added distilled water. Then I hit the highway.

Everything felt, sounded normal. Until I got to close to 70mp on the highway. Then then there was a lot of exhaust coming out. White or gray. Not sure. It immediately stopped when I took my foot off the accelerator. And did not seem to happen when I was driving slower speeds. I did not think to look at the Tachometer. My son, in the back seat, did not see or smell anything wrong back there.

So, question: what would be causing this? Why only that speed? Is it too much oil, or too little coolant? Or something else? Should I be worried?

Thanks,

Jeremy 

Sent from my iPhone