C3 Door sill screws won't tighten

[Dave R.]

I am in the process of reinstalling the interior of my 1969 coupe and was trying to install the door sill plates. I bought a new screw set for the car and found that the screws just drop through the sill into the car and spin. Are there supposed to be threaded inserts where these screws fasten or do they simply fasten to the fiberglas? Is there something I can do to enable these screws to tighten? Should I try to locate black screws of a larger diameter?

Also, is there anywhere that I can buy the correct screws that attach the side panels behind the seats? There are screws in the new screw set that are supposed to be for this area but, they aren't even close to the originals. Unfortunately, the previous owners must have lost some of these screws and I don't have enough to secure both sides.

Thanks,

Dave

[George D.]

Re: C3 Door sill screws won't tighten

Typically, these screw holes are stripped. If you have the correct size screws you can insert plastic type sheet rock anchors for holding pictures in the enlarged holes. These will hold the sill screws, but don't over tighten them.

[Dave R.]

Re: C3 Door sill screws won't tighten

George I was thinking about that but, didn't know if that would be an acceptable method by NCRS standards. (The car is not a show car but, I don't want to ruin anything either).

[Harmon C.]

Re: C3 Door sill screws won't tighten

Dave
I have found that the original sill plate screws have a larger head and diameter than most kits have. The sill plate holes are striped many times but the undersize screw is sometimes the problem.

Lyle

[Stephen L.]

Re: C3 Door sill screws won't tighten

Many fasteners used by GM were/are somewhat unique. An example is a screw size #8 with a head size #6 sheet metal style. You need to find these screws for proper fit.

I found these screws at a local specialty fastener store.... much less expensive AND correct for the various applications. If you live in a moderately sized city you may have a similiar store. Check the Phone Book.

[George D.]

Re: C3 Door sill screws won't tighten

Dave

I have used this method on my top flight 69. So this should not effect any standards since you cannot see anything but the screw heads. As mentioned by some of the other posts make sure you have the correct size screws before putting in the plastic inserts. DO NOT make the holes any larger. You should be able to get the insert into the existing holes.

George

[Dick W.]

Re: C3 Door sill screws won't tighten

Agree with Steve. I think the sill plate screws are #10 with #8 heads. The heads should fit flush with the sill when installed. Many kits have heads that are too large.

[Dave R.]

Re: C3 Door sill screws won't tighten

George, thanks for clarifying that; I was wondering about enlarging the hole for the sill plate screws.
Does anyone have any suggestions for the rear panel fasterners? The originals that I have appear to be some type of self tapping screw (they have two little notches at the very tip).

[George D.]

Re: C3 Door sill screws won't tighten

Dave,

If you're talking about the metal outer quarter panel retainer that hold the interior panel in place at to rear door pillar I believe they are self tapping philips oval head screw. I don't recall their exact size, but I think they are 8-32 or 10-32. There is a threaded metal retainer that is pressed into the quarter panel trim piece on the inner side. These are rather fragile and often missing (pulled out) from the panel. I have epoxied hex nuts where the retainer was and they must be flush with the surface. Again, be careful when tightening the screws. Also, make sure the screws are not to long or they will push out thru the finished side of the panel leaving a bump/hole.

George

[Jeff A.]

Re: C3 Door sill screws won't tighten

Sears hardware etc carry brass threaded inserts that will screw into the quarter panel trim and can be epxied there. These have the correct thread for the retainer screws.