Overview
Weather sealing is something you take for granted in OEM car. However, it takes some forethought and effort to get it right in any car, especially a component car, and the SL-C is no exception. Even if you will never drive in the rain, simply washing your car can result in a flooded interior without proper seals.
Good sealing will also make the car more pleasant to drive by keeping out heat from the engine and radiator areas. In the summer, an unsealed car can overwhelm the AC system, leading to a sweaty driver. And nobody wants that.
Finally, you might be surprised by how much quieter the car is with adequate sealing. Good seals throughout the car will make for a more enjoyable driving experience, and so care should be taken to completely seal all openings from the outside to the cockpit.
Water intrusion, heat rejection, and noise reduction are all important reasons to go over the car with a critical eye, looking for places where good sealing techniques need to be applied. It's an inexpensive way to really improve your car.
In addition, other kinds of seals and films can make a huge difference in how your car looks after a few miles. Check out the details below for more info on how to protect your SL-C. It's easy, relatively inexpensive, and rewarding.
Seal Sources
There are many sources of these kinds of moldings, including McMaster, SoffSeal, Metro Moulded Products andSteele Rubber Products. Other ways to seal unwanted gaps include the use of tape and foams. These can be sourced at your local home improvement store.
Doors
Bulb seals such as McMaster 93085K16 work well around the doors. In addition consider using 1" wide by 1/16" felt or foam as well to help seal the door edges, making a kind of double seal.
In addition to bulb seal, experienced builders are careful to use 3M or Xpel or similar clear film on the edges of the doors. These small pieces of film (the same stuff used to make front-end bras for cars) reduce chafing of the door edge against the spider. Failure to protect the spider from door edges will always result in paint or gelcoat damage- trust us- we've seen it in way too many cars. You can buy the film in 3/4" widths for edges.
Body and Chassis
McMaster-Carr's Gap-Filling Expandable Sealing Foam Tape is fantastic for sealing irregular openings between the body and the chassis. It comes off the roll about 1/4" thick, but expands to an inch or so over 24 hours. Using expanding foam like this to seal the body from the chassis in the dash area, around the engine bulkhead, and anywhere else there is a gap between the body and chassis will help reduce noise, heat transmission from the drivetrain, and reduce rattling as well. Use it liberally.
In addition to gap filling approaches as described above, the careful builder will also want to protect the paint around the rest of the body parts. For example, if you don't apply some sort of protection there, the front clam will rub the paint right off the front of the spider. Some cars are doubly protected - 3M film on the front clam, as well as 3M film in larger sheets along the bottom of the spider where the front edge of the front clam rides.
The same applies to every part of the car where body panels mate, or could rub together.
Fuel Filler Area
This is called out separately because it is often overlooked until the spider has gotten a bad case of the uglies from the rear clam rubbing on it.
You can't really stop the chafing of course, but you can do a lot to prevent it from actually causing damage. One way to do that is to cover the BACK of the rear clam where it can hit the fuel filler area with a soft material. That softer material then rubs on the spider, instead of bare, rough fiberglass typically found on the back side of the panels. Some have used soft felt with an adhesive backing.
You can double-down with more 3M film around the fuel filler as well.
Edge Sealing
Unfinished edges abound in all cars. OEMs take the time to finish off the edges, for reasons of appearance and safety (it's pretty hard to cut yourself on a rubber seal).
SL-C builders can do the same thing, by finishing off the body edges on their cars. A specific Trim-Lok profile has been proven to be useful for some of the 1/8" edges, especially around the back of the spider. This gives an OEM look, and reduces the risk of cuts. This is the preferred approach when you have room. If not, use the 3M film discussed above to reduce the effects of chafing.
Using Edge Trims
Edge trim profiles are generally pretty consistent in their dimensions. Unfortunately, the body edges aren't and can easily vary by 1/8" in thickness. But too thick edge thickness can make the seal unreliable, and prone to falling off.
The solution is to use a Dremel tool as sort of a router to precisely route the thickness of the edge to a consistent thickness. The routing only needs to be done to the depth of the leg of the rubber trim. Because Dremel tools are ubiquitous, accessories are available everywhere. This author used a modified accessory as shown below to make a tool that reliably routed the back of the body edges for perfect edge trim fit.
Sealing Other Areas
Experienced builder Allan U discovered that a significant amount of noise in the interior could be traced to air rushing through the portion of the body under the doors (and extending the full length of that opening from the scoop just aft of the front tires, all the way to the engine compartment).
He fabricated thin aluminum strips to seal the gap between the body and chassis, bolting them to the chassis. If cut properly, and fitted with edge seals, these aluminum "seals" have proven to make a significant contribution to noise reduction in the interior.
If you fabricate these, use a structural vibration dampening material to cover at least 50% of the surface to reduce drumming.
Body Openings
It's important to seal the sides of the body under the doors, especially where the coolant lines enter the body. Failure to do this will mean that leaves, water, and assorted trash will enter the body cavity under the doors. If you have wiring there, it will get wet, and possibly cause a short circuit (and maybe a fire).
Allan U has pioneered a neat sealing approach to this area that is easy to do and effective. He tapes up the opening with clear package tape, then mixes FG resin with a thickener, and saturates woven FG cloth and lays it over the area. When it hardens to the "green" stage, he removes it, trims the edges, and lets it harden completely. Then he uses screws or other fasteners to hold it in place. This also reduces noise.