[dataway]

For those of you with a 68 ... how is the metal shroud top plate fastened? Are they sheet metal screws that just thread into the top of the core support? Or are they machine screws that thread into some kind of nut on the underside of the top of the core support?

If they are machine screws/bolts ... what size?

I think most of the sheet metal screws are like 3/8 - 10, or 3/8 - 12

Before I drill into the repop core support I need to know what size to drill

[PurelyGTO68]

Sheet metal washer hex head screws. Same as used to secure the lower valance under the ENDURA nose. Use 1/2" socket or wrench to turn fastener.

[dataway]

Thank you.

[kk68]

Originally Posted by dataway

For those of you with a 68 ... how is the metal shroud top plate fastened? Are they sheet metal screws that just thread into the top of the core support? Or are they machine screws that thread into some kind of nut on the underside of the top of the core support?

If they are machine screws/bolts ... what size?

I think most of the sheet metal screws are like 3/8 - 10, or 3/8 - 12

Before I drill into the repop core support I need to know what size to drill

For the 4 marked along front edge of top plate below, they are machine screws that thread into the rectangular nuts welded to underside of core support as shown in attached pics. I think the screws are 5/16 - 18.

You may want to use the rivet nuts like you used on the lower part of the core support which came out nice.

One tip I found helpful when you do the final installation of the top plate is cut some 1/8” or 3/16” rubber washers from some 5/16” id gas hose and place at each screw location between top plate and top of core support. This will raise the top plate just above the core support top and prevent your freshly painted parts from chipping/scratching where metal meets metal.

[PurelyGTO68]

To add to kk68s helpful post...
On my car the 4 bolts across the front and the two the next level back all have a threaded square block welded below the surface of the core support top plate. The original fasteners I removed were pointy tip course thread so I refer to those as sheet metal type screws. Maybe they are machine thread though and I might be using the incorrect term. Here is a photo of what those fasteners look like.

[dataway]

Excellent, thank you. The go-to bolt in the front end seems to be 5/16-18, and the 3/8'ish screws that go into spring nuts.

I guess what i will end up doing is using the rivet nuts in the locations that don't have provisions for spring nuts, and spring nuts where I can use them. I've got a good supply of both the screws and the machine screws. I'm going to assume that if the repop support has provisions to slide in a spring nut that that was what was used, and in the locations where you can't get to the back properly that they used welded nuts.

Your terminology is correct, the pointy screws should be sheet metal screws, usually a bit courser thread count than the same size machine screw. I'm pretty sure I have zero chance of finding the right thread count square nuts that take the sheet metal screws. That's really an odd ball thing GM did ... they would use like 3/8-12 sheet metal screws into nuts, and 3/8-10 sheet metal screws into sheet metal and normal 5/16-18 machines screws into welded nuts or the "tower" type spring nuts.

And yes ... as I was bolting things up ... I was concerned that all the nice paint work was going to get scratched up ... rubber washers would also keep things quiet.

Once again .... as careful as I tried to be taking apart the parts car ... I didn't label things or organize them as well as I should have.

And to think when I bought this car in 1976 it was absolutely factory stock, untouched .... and I proceeded to F up as much of it as I possibly could when I was kid.

[PurelyGTO68]

Originally Posted by dataway

.....

And to think when I bought this car in 1976 it was absolutely factory stock, untouched .... and I proceeded to F up as much of it as I possibly could when I was kid.

Said me for just about every car I owned in the 80s and 90s. half the fun was messing around with these to try and squeeze an extra 10th of a second out of it.

[68pongto]

The metal shroud should be bolted with 5/16-18 machine thread bolts. I'm not going to say I have never seen a coarse thread/sheet metal bolt crammed in there, because I have. But I'm sure it was a careless mechanic/bodyman driving the wrong bolt in there. Machine thread bolts always go into a nut, like the square nuts that are welded in the top plate. The coarse thread bolts always go into clips, like the fender to core support, the lower valance, the hood pop spring, etc.

[dataway]

Ok ... jeez, thanks pongto, that explains it .... the forward holes on the finger guard where I used clips ... had square holes pre-punched in the repop support underneath the top layer of metal ... I was wondering why the holes where square ... obviously they were meant to be used with the square nut-cert press in nuts, or weld nuts.

I was baffled because I did not remember the finger guard using two different types of screws. So I can pull out the clips I installed and put in 5/16-18 rivet nuts. The clips also did not fit the way they should have.

Now I have to change my how-to thread ... as I put the wrong information in there.

Next question ... what size/type were the screws that went through the finger guard into the top of the plastic shroud?

[dataway]

Does anyone know where to get that seal that goes at the bottom of the radiator?

Looks like this:

[antique69lemans]

I can't remember if 69 has that piece. There is a baffle available that goes below the radiator on the back side of the support. It is more like a dam to prevent air recirculation I think.

[dataway]

If need be I can probably make something pretty close to the original piece ... and of course first I should look through my parts ... getting tired of buying things I already have stored away somewhere.

I couldn't find this piece in the 69 assembly manual ... so you are probably right, something different used on the 69. And may be why I can't find a repop if it's 68 only ... my guess is the 69 piece would fit if I can find one.

[antique69lemans]

I think you need that piece to seal radiator on 68. On a 69 the shroud encases the radiator negating the need for it. The 69 baffle goes below the shroud, not where your strip is. Unless your seal is gooey just use it.

[Greg Reid]

I've never seen that piece, so obviously it's missing on mine.

[dataway]

I'm not sure of it's function ... it's outside the shroud. Probably another item to keep air from recirculating in the engine compartment, otherwise the front of the radiator could try to pull air from under the hood rather than out front.

They seemed to go to a lot of trouble on the 68's to make sure air came in front the front.

[Greg Reid]

I'm pretty positive that that is what it is. They even have insulators over the openings surrounding the frame rail pass-throughs and also vertically along the gaps on each side of the radiator.
I seem to recall that AC cars had more insulators than non-ac....?

Sent from my moto g(6) play using Tapatalk

[68ragtop]

I recall talking about that seal & the frame horn seals a while back. They were on A/C cars & "maybe" on the HO cars? That second part could be a brain fart, but for some reason I was thinking it was more than just A/C cars.
For what its worth, those fastening screws that come from most of the re-pop suppliers are incorrect. The originals had the hex raised edge on the screws & many of the re-pops are round on the inside. I believe I found the corrct ones through AMK. I should have kept better notes on some of these details.