correct size sill plate screws

[Garry B.]

Does anyone offer the correct head screws for C2 sill plates? I was told at the National that the screw should be a #6 head with #10 thread, but reading historical posts they say #8 head with #10 thread which is what I believe I have on my car. Who knows for sure?

[Gary B.]

Re: correct size sill plate screws

Garry,

According to the ‘64-‘67 AIMs, the sill plate screws are GM 9414766. David Bartush gave the specs for these in 2018 as:

GM #9414766 is a Type AB 1" chrome-bright nominal screw size 10, nominal head size 8, threads per inch 16


AMK sells a version of that screw that is stainless, then chromed: AMK Products # B-12225: #10 X 1.0 PH OV AB 8HD SS/CHROME.

Unless you’re worried that a judge will test for stainless using a magnet, I think the AMK screws would work fine. They would have the right head dimension and thread spec. Unfortunately, AMK has a $30 minimum, before shipping. You’re looking at a least a $40 purchase from them.

Gary

[Garry B.]

Re: correct size sill plate screws

Thanks Gary. Now that I know the correct size, I think I have some located. I appreciate the help.

[Gary B.]

Re: correct size sill plate screws

Garry,

[Alan D.]

Re: correct size sill plate screws

Gary, Not sure what year C2 so just to be clear (before you buy) the 9414766 screw was used in the six hole sill plate from 64L thru 67.
However a 9417945 for the four hole sill plate was used. These are easily spotted since the head looks to large.

[Garry B.]

Re: correct size sill plate screws

Alan and Gary, consensus is that the correct screw is a 1" 10 thread, #8 head oval phillips slotted chrome screw. My car was recently judged at the National and found to be a Top Flight, but virtually everyone I spoke with there got deducts on their sill plate screws. I pulled one of my sill plate screws and went to my local ACE. Using their size board, my screws are exactly 1" long, #10 threads and a #8 oval head. They also had a tray with the exact same screw, size, profile, etc. and listed as 1" long, #10 thread and #8 oval head and yes they were chrome. Same exact screw I walked in there with. So, is this in fact the correct size for my '67 sill plate. Six hole. No doubt, they do stick up above the surface. I am thinking the size may be 1" 10 thread #6 head. I seem to also recall #6 head mentioned when the score sheets were shared with me, but wasn't really paying close attention at that moment. Could it be reproduction sill plate openings not being made deep enough for the #8 screw head to countersink?

[Alan D.]

Re: correct size sill plate screws

For more conformation check your 67AIM, the section on seats. In earlier years (since I do not have a 67AIM) the bumper screws were the same.
If you search on the part numbers some good past posts can be found!

[Gary B.]

9417945 to

[Leif A.]

Re: correct size sill plate screws

Picture of my '67 sill plate and screws. I've never received a deduction during judging. The screw is slightly "domed" so it's going to stick above the sill plate a skosh.

[Gary B.]

Re: correct size sill plate screws

Leif,

Are the screws originals or repros?

Gary

[Alan D.]

Re: correct size sill plate screws

Think we have answered Garry question.
As for original screws those are on my Mar64 car, four hole sill.
Will look at the original v repo if I get the time tomorrow however search the pn, some good past discussions on these.
Alan

[Leif A.]

Re: correct size sill plate screws

Leif,

Are the screws originals or repros?

Gary

Repros from the Doc.

[Gary B.]

[Ronald L.]

Re: correct size sill plate screws

Gary
What is the head size dimension for the #8 screw?

[Garry B.]

Re: correct size sill plate screws

I have a newly rewarded '67 Bowtie car that I often check things against for my restored car. I have to admit that the level of "above the sill plate" screws on the Bowtie car is less than what is on the restored TF car. I don't plan to take any of the sill plate screws out of the Bowtie car, but that would certainly help narrow things down a bit. I am curious what you guys find when you compare originals to reproduction screws. Thanks.