FI 'S' tube screws

[Dan H.]

Hi All, have checked the archives and still have a problem defining which screws are 'normal' for 63 to 65 'S' tube attachment to radiator support. The screw called out in the 63, 64, and 65 AIM is 9417226. However, two different screws appear to have been used. The 9417226 screw is a 5/16" counter sunk hex with an 'L' logo normally. The other screw that randomly shows up is a 1/4" high top screw. This screw would be much easier to install with a driver than the 5/16" screw. I've installed both types and the 5/16 is a pain! Their is some belief that the 1/4" screw was 'acquired' by line workers to make their job easier, don't blame them. My 64 originally had the 5/16" screws in the 'S' tube. It's vin is 13708, well into March of 64. One survivor was still in place in old pictures of it's 1st restoration 20 years ago. I know of another March 64 car with the same 5/16" screws still in place. Anyone still have any 'untouched' FI cars that display these two variations. Think this is a grey area and Judges should be aware that either screw may show up. Thanks,
Dan

[Michael H.]

Re: FI 'S' tube screws

Hi All, have checked the archives and still have a problem defining which screws are 'normal' for 63 to 65 'S' tube attachment to radiator support. The screw called out in the 63, 64, and 65 AIM is 9417226. However, two different screws appear to have been used. The 9417226 screw is a 5/16" counter sunk hex with an 'L' logo normally. The other screw that randomly shows up is a 1/4" high top screw. This screw would be much easier to install with a driver than the 5/16" screw. I've installed both types and the 5/16 is a pain! Their is some belief that the 1/4" screw was 'acquired' by line workers to make their job easier, don't blame them. My 64 originally had the 5/16" screws in the 'S' tube. It's vin is 13708, well into March of 64. One survivor was still in place in old pictures of it's 1st restoration 20 years ago. I know of another March 64 car with the same 5/16" screws still in place. Anyone still have any 'untouched' FI cars that display these two variations. Think this is a grey area and Judges should be aware that either screw may show up. Thanks,
Dan

Dan,

I don't think the 1/4" hex head screw was ever used on any 63's or early 64's.
At some point in 64 production, someone got tired of fighting with the 5/16" hex head screw and used the taller and much easier to install 1/4" hex head screw instead. (found randomly on passenger car heater assy's)

As you mention, the part number in the assembly manuals did not change.

I don't think I've ever seen the original 5/16" hex head screw on a late production 64 or any 65's.

The 63 through mid 64 screw is shown on the left. Mid 64 through 65 on right.

[Mike L.]

Re: FI 'S' tube screws

Michael, I think your exactly correct. My early 64 had the screws in your left picture, and the car was never taken apart before I purchased it.

[John H.]

Re: FI 'S' tube screws

The "top hat" screw wasn't released for usage anywhere on the Corvette, but it was on the passenger car and truck lines in the "big plant" next door, and on the Corvair-based forward-control truck line up on the third floor. A couple of handfuls of them would last a long time on only five F.I. "S" tubes per day.

[Michael G.]

Re: FI 'S' tube screws

John is right on that. Misuse of screws throughout GM assembly plants was common in the 60's (and probably still is). If the line operator liked a particular part better than the one he was supposed to be using, he took what he needed from other jobs, or, the hilo driver brought him a box or two, or a whole pallet, if he liked him.

After I left GM, the fastener company I ran had many parts in wide usage at GM. I remember one particular screw that GM issued releases for 5 million annually, but , because line operators liked it much better than a similar part, the plants were ordering it at a rate exceeding 25 million annually. Manufacturing runs were incredibly difficult to schedule.

So, finding "top hat" (high hex washer head, in GM terminology) parts in 64-65 Corvettes is very possible, because its a much easier part to install.

[Dan H.]

Re: FI 'S' tube screws

Thanks all for input, I guess the bottom line is either screw should be accepted, in late 64 and 65. The JG says after 64 sn 8900 should have 'high hat' black phosphate screw. Well, I know of at least two 13XXX sn 64's that still retained the correct AIM screw, 5/16 recessed head with 'L' logo. So maybe the 'high hat' 1/4" screw was randomly used when the clever line worker could procure some more! When he went on vacation, his replacement used the correctly called for 5/16" screw? Like James Bond, never say never!
Dan

[Michael H.]

Re: FI 'S' tube screws

By the way, the 63 and early 64 "L" head screw was NOT zinc or cad plated. The correct plating was dark grey.
I see a lot of these incorrectly plated zincad. (silver)

[John D.]

Re: FI 'S' tube screws

Nice photo and info on the screws Hanson. So the plating on the 63-E64 screws must have been grey phosphate. Interesting. JD

[Michael H.]

Re: FI 'S' tube screws

Nice photo and info on the screws Hanson. So the plating on the 63-E64 screws must have been grey phosphate. Interesting. JD

This is an NOS set and they're definitely grey. Not zinc or cad. Lot of pictures of brand new 63 FI cars that show the grey also.

[Rick A.]

Re: FI 'S' tube screws

yepper - that is what my NOS set looks like that are on Lady

[Jim B.]

Re: FI 'S' tube screws

For those of you who can't get enough of this stuff (probably me included)...I have in my possession 3 pages from the General Motors Engineering Standards (no date, unfortunately) that I obtained from an un-named employee of a well known Corvette vendor. I scanned these and tried to upload them here, but wasn't smart enough to make it work. So if anyone would like emailed JPEG copies, email me and I will forward them. In a nutshell...the part no. for these screws shown in the '63 AIM is 9417226 (I don't know what part number is specified for '64 or '65). When cross-referenced to Page D-2.721 of the Engineering Standards, this part no. screw shows as Nominal Size 10, 16 TPI, Hex Head Tapping Screw. It states it is "phosphate coated" (although it doesn't specify grey or black phosphate) per "GM 4435-M, Code A". Pages D-2.701 & D-2.702 are the General Specifications for these screws (and others). Page D-2.702 states, in part: "Phosphate coating on steel: Unless otherwise designated, GM 4276-M specification shall apply. It requires phosphate coating plus subsequent treatment with a compound other than paint and 24 hours salt spray. Where so indicated by part number, GM 4435-M, Code A. specification shall apply. It requires phosphate coating plus subsequent oil type treatment and 72 hours salt spray." That's all the light I can shed on the topic.

[Michael H.]

Re: FI 'S' tube screws

For those of you who can't get enough of this stuff (probably me included)...I have in my possession 3 pages from the General Motors Engineering Standards (no date, unfortunately) that I obtained from an un-named employee of a well known Corvette vendor. I scanned these and tried to upload them here, but wasn't smart enough to make it work. So if anyone would like emailed JPEG copies, email me and I will forward them. In a nutshell...the part no. for these screws shown in the '63 AIM is 9417226 (I don't know what part number is specified for '64 or '65). When cross-referenced to Page D-2.721 of the Engineering Standards, this part no. screw shows as Nominal Size 10, 16 TPI, Hex Head Tapping Screw. It states it is "phosphate coated" (although it doesn't specify grey or black phosphate) per "GM 4435-M, Code A". Pages D-2.701 & D-2.702 are the General Specifications for these screws (and others). Page D-2.702 states, in part: "Phosphate coating on steel: Unless otherwise designated, GM 4276-M specification shall apply. It requires phosphate coating plus subsequent treatment with a compound other than paint and 24 hours salt spray. Where so indicated by part number, GM 4435-M, Code A. specification shall apply. It requires phosphate coating plus subsequent oil type treatment and 72 hours salt spray." That's all the light I can shed on the topic.

Thanks Jim. That's great information. You have mail.

[Joe R.]

Re: FI 'S' tube screws

Dan,

I don't think the 1/4" hex head screw was ever used on any 63's or early 64's.
At some point in 64 production, someone got tired of fighting with the 5/16" hex head screw and used the taller and much easier to install 1/4" hex head screw instead. (found randomly on passenger car heater assy's)

As you mention, the part number in the assembly manuals did not change.

I don't think I've ever seen the original 5/16" hex head screw on a late production 64 or any 65's.

The 63 through mid 64 screw is shown on the left. Mid 64 through 65 on right.

Michael,

Here are four screws removed from the S-tube of 1964 14,XXX. Cad plated by mistake but the center screw has the correct finish. The center screw is wrong for the S-tube and was removed from the cable clamp on a heater of a Corvair.
Notice that the four original S-tube screws have the self-tapping feature described below in a GM publication.
The screw you show is pointed and probably has some other application along with the center screw in my picture below. The center screw although it has the correct finish, is not a Corvette screw and does not have the self tapping feature.

JR

[Michael G.]

Re: FI 'S' tube screws

Lets put the finish part of this issue to rest. I served on GM's fastener finish committee for many years, so this is the real scoop on how these should look:

These screws should have a grainy medium gray to black appearance. When new, the "oil" probably made the surface wet in appearance, but 48 years later, they will most likely look dry. At the time of delivery they very possibly looked wet. If they were in the bottom of the box of screws, they most likely looked very wet.

Please note that color variations for new "phos and oil" coated screws such as these typically ranged from black all the way to fairly light gray when installed on the car. The difference between shades of gray is caused by common variations in phosphate grain size and/or wide discrepancies in types of oil used by individual platers. NOBODY should suggest that a phos and oil (GM 4435, Code A) coated part is not "as delivered" because it is the wrong shade of gray or looks wet.

Some "phos and oil" was also very smooth (fine grain) other batches were very rough (coarse grain), and all variations in between were acceptable and common in production. One box might be smooth and almost black, another on the same pallet might be rough and light gray.

By the way, the ones on my cars are hex head, type AB (threaded to a point), with medium grain and darker gray finish. I hope this helps

[John H.]

Re: FI 'S' tube screws

Michael,

Here are four screws removed from the S-tube of 1964 14,XXX. Cad plated by mistake but the center screw has the correct finish. The center screw is wrong for the S-tube and was removed from the cable clamp on a heater of a Corvair.
Notice that the four original S-tube screws have the self-tapping feature described below in a GM publication.
The screw you show is pointed and probably has some other application along with the center screw in my picture below. The center screw although it has the correct finish, is not a Corvette screw and does not have the self tapping feature.

JR

Joe -

When I ran the overhead Chassis Line at Willow Run from '64-'66 (Corvair & Chevy II), the first half of my line installed the five-foot-long sheet metal lower tunnel cover on the Corvair underbody, and the second half installed the large rubber bellows seal all the way around the Corvair engine shroud that attached to the body rails on four sides with loose steel retainer strips.

The Corvair engine-to-body seal retainers were close to impossible to assemble using the specified 5/16" screws (same as the "L" screws for the '63 F.I. "S"-tube), but a blind man could do that job if he used the "top-hat" screws that were specified for the underbody tunnel cover. We mis-used those top-hat screws by the THOUSANDS to keep that job going (28 screws per car); drove the Material Control guys crazy, but avoided filling the Final Line with seal retainer repairs.