This is the most surprising discovery I've found in collecting and racing cars.  I'm not sure I've seen these cars raced or even mentioned before.  The original Speed Demons were released between 1986 through 1989.  This series launched 11 new castings, all featuring Ultra Hot wheels (the exception being 1989 which did not have UH wheels).  I don't believe these castings made a good impression on collectors or kids, as the monsters/beasts and robots are quite tacky.  But they are very fast.

Some of these castings continue to be made today, but none of the post 1980's versions are nearly as fast as the originals.  In particular, beware of the 1994 Speed Demons 5-Pack that includes these castings with UH wheels.   The top 5 cars in this series are all from the 1986 release.  Finding them in unopened blister packs can be tricky (see picture of the blister above).

There are 4 Elite Speed cars in this series and 3 High Speed tier cars.  The 4 other castings are duds.
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Elite Speed
Top Tier

Double Demon
1986, Speed Demons
44 grams, Ultra Hot Wheels
The Double Demon runs very smooth and fast.  Not especially heavy, but very balanced and with great wheels.  This car is in my overall Top 15 beating every mainline Hot Wheels car.  The casting was brought back in the 1990's and continues to be released today.

Eeevil Weevil
1986, Speed Demons
41 grams, Ultra Hot wheels
This unusual looking casting is still produced today,  Very fast car despite its relative small size.  

Turboa
1986, Speed Demons
44 grams, Ultra Hot wheels
Another unusual looking casting.  Runs very fast with the UH wheels.  Low center of gravity.

Cargoyle
1986, Speed Demons
42 grams, Ultra Hot Wheels
Another monster looking casting that runs smooth and fast.  Was later called Grizzlor and Road Cannibal.  

High Speed
​2nd Tier

Car	Year, Series	Wheels
Vampyra	1986, Speed Demons	Ultra Hot wheels
Sharkruiser	1987, Speed Demons	Ultra Hot wheels
Fangster	1986, Speed Demons	Ultra Hot wheels

Good Speed
3rd Tier

There are no other competitive cars in this series.  Phantomachine, Zombot, Rodzilla and Ratmobile are all duds.