I should probably expand on my previous response. I guess most of my suggestions had engines a little too large to meet your criteria, but I’d still argue that they were American equivalents of the Brit sports cars :
Opel is a subsidiary of GM, but it is a German car, even though they were marketed by Buick dealers in the US. The Opel GT that looked like a miniature Corvette did have a four banger, though.
Maybe it’s a little to late for your OP but I think the Pontiac Fiero was a roadster. It was a POS but the lack of a functional back seat should qualify it as a roadster.
The insurance companies killed the roadster. Companies like Jaguar found a way to stuff in a non-functional back seat just so that the car couldn’t be classified a roadster and thus be subject to the higher premiums.
Yes the Fiero is a bit late, as I was looking for contemporaries of the ‘classic’ roadsters listed. Was there a Fiero roadster? I thought they were all hard tops. (And the Opel was a hard top as well.)
Johnny, I know you’re asking for American factory-made cars, and I have scratched my head enough trying to think of any others with no luck yet. But I did want to mention that the dad of a girl I was interested in in high school built her a “sports car” (more or less roadster) out of a Studebaker (forget which model). He modified the frame but didn’t mess with the engine (it was a 6, I think) and covered it with a fiberglass body. Most of his work was with the fiberglass and I stood around and watched him work for several weeks. When he got it built he let me drive it and I was just a short time having my license. Long story short(er), I ran into a curb and knocked a hole in the undercarriage. It took him about two hours to patch the hole with fiberglass. Needless to say, I didn’t drive it again.
All this to say I remember some Studebaker model that was close enough to a roadster for this guy to use it as a basis for his custom. Not what you asked for, but those painful memories came out.
Fascinating. Did he build the body from scratch, or was it a pre-made body (like a Woodhill or something) that he adapted to the Studebaker frame? I’m guessing that the frame was from a Lark, the compact Studebaker model; it’d be shorter (and sportier) wheelbase, and the six is also indicative.
Incidentally, the Avanti (the most beautiful car ever made) was built on a Lark station wagon frame.
It was a purchased shell he bought somewhere. He worked in a metal-working foundry for a living, but was one of those guys who could build anything. As best I recall, the frame had to be modified inward a few inches in each direction to accommodate the body, so whether it was sold for the Studebaker or he just chose the car for other reasons, I don’t know. The fiberglass was attached to the frame by way of plywood struts, so it looked as much like a boat as a car. But since the Corvette had made fiberglass a reliable body material he was okay with that. His daughter drove it for several years and took decent care of it.
Thanks for mentioning the Avanti. That may be what I was hung up on trying to remember other roadsters. And you could be right about the Lark, too. I just can’t remember that detail.
Chassis and running gear by Bristol, body by Bertone, but assembled in scenic Warsaw, Indiana, by Stanley “Wacky” Arnolt, I give you the Arnolt Bristol. Sure, it was a six but it was a high-revving, two-liter six in an absolutely gorgeous body.
Something else shared by Arnolt and Muntz were similar nicknames, Muntz’s being “Madman.” While neither received their nicknames because they started car companies, it’s a good way to make a small fortune. First you take a large fortune…
This might qualify, and I don’t think it’s been mentioned yet. The Crosley Hot Shot. Four cylinder engine, no windows at all (no doors either). I remember these being advertised in the ad pages near the back of Popular Science magazines inthe early 60’s: http://www.hubcapcafe.com/ocs/pages01/cros4901.htm
Now that I think about it, there was one other small-displacement, open, fixed-windshield roadster built in the Fifties that might meet your specification:
