I found a nice article on the Seven Series IV here:
http://www.simplesevens.org/anglocanadian/angloSIV.htmTwo of the pictures:
Attachment:
SIVPressRelPhoto1.jpg
The whole body is fiberglass.
The front fenders extend all the way to the back, but they also point slightly down at front instead of aiming at the sky.
The undersides of the fenders - most of the side of the car - appears to be flat black.
The tail is much longer than previous cars.
The cockpit opening is also much longer
The rear fenderwell opening isn't round
It's not apparent from this picture, but the hood and nose are all one piece and tilt forward for engine access. The dashboard is also fiberglass and not flat. And the hood latches inside at the middle, apparently with an inside release.
and
Attachment:
SIVPressRelp5.jpg
note the exhaust travels along the side, then back through the body and out the back, instead of being a sidepipe. That may have been a legislative thing; many US states have had laws requiring the exhaust to exit some specific distance behind the last openable window, etc.
the windshield appears to use cast brackets instead of sheet metal
the battery is moved to the rear
the radiator is moved back behind the rack and pinion, and an oil cooler has been added
the usual S3 front anti-roll bar is not visible. And while the A-arms still attach in single shear, the upper wishbone looks very narrow at the base. And it appears to be using a trunnion instead of a ball joint
the chassis is MUCH different. It's noticeably shorter in front, and the back is triangulated differently. It's not readily apparent if there's a structural rear bulkhead; we see a long diagonal instead of the tube arrangement on earlier and later cars
the center spine is square on top instead of being half-round, and looks to be taller than the S3
I don't see any master cylinders, so I'm assuming it has floor-mounted pedals
The press release says, "increased leg room ... Europa concept double wish-bone suspension ... collapsible steering column ... extensive sound proofing ... hazard warning light ... glass fibre body shell, double skinned at cockpit sides and fully weatherproofed ... 165 x 13 Sport radial ply tyres ... 13 in. steering wheel ... ammeter ... two speed wiper ... screen washer ... heater ... rubber mats ... diagonal seat belts ... weight from 1102 pounds ... 7-1/2 gallon fuel tank behind seats protected by chassis structure"
The earlier cars used 15" tires as far as I know. The brochure for the 4 says "13" in several places.
From the description at simplesevens.org and the drawing above, it looks like the rear axle location was entirely different than the S3 or later Caterhams, using a four link instead of an A-frame.
My eyes always slid over the Series 4 cars. The styling is a product of its time, I guess, but it always looked like someone built the buck out of plywood and rounded the corners a bit before making a mold. For a dune buggy body to go on a used VW pan, sure. But at Lotus prices, I can see why they gathered dust in showrooms.
edit:
I found this drawing of an S4 chassis:
Attachment:
S4chassis.png
http://sevener.fr/articles_redac/Design ... 4_(Type_60).pdf&sa=U&ved=0ahUKEwjnh4Gf67TJAhWGLSYKHV21DME4ChAWCEQwCA&usg=AFQjCNEU4JK7_ie5BG40buHuiqotIfiBbg