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Hi C6DM,
What year is your car and what year is the AIM?
I looked at my 71 and it has the #4 bracket mounted to the header support with 3 bolts near the hood, and then the relays mounted to the bracket.
Obviously your support was different.
I'd think you could carefully drill 4 holes in the support to mount the relays with short self tapping bolts.
Regards,
Alan
Hi C6DM,
What year is your car and what year is the AIM?
I looked at my 71 and it has the #4 bracket mounted to the header support with 3 bolts near the hood, and then the relays mounted to the bracket.
Obviously your support was different.
I'd think you could carefully drill 4 holes in the support to mount the relays with short self tapping bolts.
Regards,
Alan
71 for both. I might give that a try. Obviously being VERY Careful to not drill too far.
Hi Duff,
I'm sorry but no.
I tried to get my camera in there but it just too crowded. The lense ends up about 3" from the relays and can't focus.
I agree that you need to be VERY careful to control the depth of the drill bit.
Regards,
Alan
Hi C6DM,
What year is your car and what year is the AIM?
I looked at my 71 and it has the #4 bracket mounted to the header support with 3 bolts near the hood, and then the relays mounted to the bracket.
Obviously your support was different.
I'd think you could carefully drill 4 holes in the support to mount the relays with short self tapping bolts.
Regards,
Alan
I would put in four new holes about a half inch left or right.
You could put tape on the drill bit to keep from going too deep. I have also seen hard stops that you put on with a screw. I think the home improvement stores have them.
Those hard stops are nothing more than a set collar. I have never had good luck getting a set screw to bite onto a drill bit. Cut a piece of metal tubing about an inch shorter than your drill bit. Slip it over the bit after inserting it into the chuck and adjust the visible end of the bit for as much depth as you need. Once tight, the drill can't pull into whatever you are drilling any deeper than the exposed length of the bit.
Those hard stops are nothing more than a set collar. I have never had good luck getting a set screw to bite onto a drill bit. Cut a piece of metal tubing about an inch shorter than your drill bit. Slip it over the bit after inserting it into the chuck and adjust the visible end of the bit for as much depth as you need. Once tight, the drill can't pull into whatever you are drilling any deeper than the exposed length of the bit.
I'm with jcloving. Just move the location of the relays a bit and drill new holes. By the way, you do need to buy a can of PB Blaster; and the proper use of it is to soak those bolts for a day or two before you try to remove the screws. No big deal, really. But 'Blaster' takes a while to work and loosen the rust.
Why worry about the broken off screws? They are rusted in well, at least.
I'm with jcloving. Just move the location of the relays a bit and drill new holes. By the way, you do need to buy a can of PB Blaster; and the proper use of it is to soak those bolts for a day or two before you try to remove the screws. No big deal, really. But 'Blaster' takes a while to work and loosen the rust.
Why worry about the broken off screws? They are rusted in well, at least.
I was considering using PB Blaster, but I've heard that grease, wd40, etc is bad to get on the back side of the fiberglass. I wasn't confident that I could spray the bolts and not get any on the fiberglass. Seems like a fairly easy fix by drilling new holes.
I had to drill new holes in mine and I just used a small drill to get a pilot hole and then drilled to proper size for self tapping stainless screws. If you use good drills there is no need to push hard and it's easy to stop drill before fiberglass. Good luck
My 71 does not have the #4 plate as well and both relays were pop riveted on.
Alan mentioned he had the plate but I think his car is an early 71 and I know mine is around mid year so could that plate have been removed from production (early/late 71 differences) or is it more likely it has just been tossed some time over the last 40 years ?
I had this problem also. There is nut plate either pressed or welded onto the back side of the header bar. If you change the location of the holes, you will miss that plate and the mount screws wont have much to bite into because the header bar isn't very thick. I suspect they would vibrate loose.
Anyway, the nut plate forms a divot on the out side that the drill bit sits nicely in. I just drilled out as much of the old screw as I could and retapped it with a 10-24. I did this with the header bar in the car, and it was difficult to get the drill bit perpendicular to the header bar, as you can see, I was unable to even reach one of the original holes.
The picture is from a later time when I removed the header bar for refurbishment. I included it because it shows the nut plates I'm talking about and the holes I drilled in it. Hope this helps and good luck.
Those hard stops are nothing more than a set collar. I have never had good luck getting a set screw to bite onto a drill bit. Cut a piece of metal tubing about an inch shorter than your drill bit. Slip it over the bit after inserting it into the chuck and adjust the visible end of the bit for as much depth as you need. Once tight, the drill can't pull into whatever you are drilling any deeper than the exposed length of the bit.
Hi P,
"I know this is an old thread, but does anybody know the part number of the #4 plate?"
The bracket that the relays mount to is part number 3966703.
I'm not sure if I've seen new brackets available but I'd think the Corvette parts recyclers would have it.
Regards,
Alan
08-28-2011, 05:02 PM
Need advice with headlight vacuum relays - bolts broke
