Classic75

I am currently working on my headlight/vacuum system for my 75' (which I have another thread going on), but last night at about 2:30am when I was dead tired, I just had to remove and replace the 2nd Relay valve. I don't know if both of the bolts on it were that stuck or that weak, or if I was just at a weird angle.... either way, I broke the heads off of both bolts.

Where they are is hard to get to with drill etc.... though it can be done... anyway, first does anyone know exactly what size these bolts are? They appear to be #10-24, but I am not sure.

Second, anyone had this problem before? Any tircks or suggestions?

Also, if you know the bolt size, you have a drill bit size recommandation on this?

I am too tired to mess with it anymore today, but I want to look at it fresh tomorrow and figured it would be worth a shot to ask for help. Drilling out a screw/bolt in any circumstance is a pain in the a$$, but where these are located makes it particularly difficult, at least for me.

Oh, and I did stop by Home Depot to see what they had tool wise, but they didn't have any left handed bits or any extractors that looked like they would work well for this. Also stopped by Advance Auto, they had nothing at all....

Thanks in advance!!

CCrane65

I broke one bolt off from each of my headlight relays. I tried to get along with just one and some automotive double faced tape but that didn't last long.

So I borrowed a 90 degree close quarters drill from my friend and drilled new holes in the mounting plate. I used a 1/8" drill bit and sheet metal screws. If you recall, the original screws are machine screws which screw into welded nuts so you can't replicate that. I have lots of broken screw extractors but none that small.

I just make sure the drill bit is slightly smaller in diameter than the screw and allow the screw to make it's own threads in the sheet metal.

Use slow and steady pressure and you will feel when you drill the holes and you will know immediately when you have made it all the way through the mounting plate.

You can buy the same drill I used at Harbor Freight.

cc

corvette kitty

I did this same repair on my 79, 4 months ago. When I bought the car both relays were tie-wired in place. On closer examination I found all four bolts were broken off. I moved the relays about a half inch off their location and drilled and tapped four new holes. I used a No. 25 bit and 10-24 machine screws. Its a hard area to access, 18v battery drill too large. I used a small 90 degree drill.

Good Luck
Richard

Classic75

Thanks for the tips guys! I think I am going to try and get these bolts out first before I move the bracket... I am stubborn.

I am pretty sure the bolts are 10-24, and I am ordering a set of left hand drill bits. I know I want to go smaller on the bit than the size of the bolt, or hole. I have been searching on line and it looks like either 5/32 or 5/64 would be right, but I am not sure. Looking at these drill bit size charts is making my brain hurt. Anyone know for sure the best size bit to drill this out? I am going to try and drill a pilot hole first (hoping of course the bit catches and unscrews the bolt when I do this), but if not I am going to try one of these Screw Extractor deals, where I tap it into pilot hole and then use wrench to turn it out.

Any suggestions or tips would be appreciated!!

Edit - looking at the charts again, I think 5/64 will make a good pilot, and 5/32 would be the actual tap out size.... Any confirmation or corrections would still be appreciated!!