Anyone know the size of the battery hold-down bolt? I think it is either 5/16"-18 or M8. Length? Maybe 2" or 2.25" or 2.5"?

This is an '86 V6.

 

M8-1.25 x 60, hex head SEMS, all thread with a pilot point. The OEM came with zinc phosphate coating, but a standard zinc or cadmium plated fastener would probably work fine, and no one would know the difference.

 

Wow! That's a lot of information. Thanks. I was actually able to uncover the marking on the top with a hard-bristled brush. But I sheared the head of the bolt off trying to take it out and for 4 days I've been trying to get the other half out with no success and regardless of how much penetrating lubricant I use.

 

MAP Gas. Heat tends to get those frozen bolts real nice like. Must have been a lot of corrosion on the bolt or its cross threaded in there. A nice pipe wrench or vise grips help good too.

 

MAP Gas?

Tried the pipe wrench and the vise grips. The M8 bolt is now only 6mm in diameter because it's been chewed off so much.

 

Propane

 

Yeah. A torch was my next idea, but I'd have to get my hands on one first.

 

When I busted the hold down on my Caprice, I just cut it off to get the batt. out, then filed down 2 "sides" on the hold down bolt shaft to give the vice grips something flat to bite on. Heated up the threads nice and hot and it came out fairly cleanly. Junkyarded a new hold down.

 

That's a good tip.

 

I tried propane and still am having NO luck. Stupid rain isn't making things any easier. And I need a hold down before I take her to a track .

 

If nothing else works, just drill it out.

 

Never did try heating it up, since I didn't have anything to heat it up with. Right now it's mostly drilled out. I just have to re-tap. Hope that works okay.

 

Change out the battery tray. Call the dealer.

Last time I bought one, it was like $8. That was a long time ago, maybe they're twice that now; so what? Still mighty cheap, compared to all the rest of that hassle.

 

I don't know what car you have, but my battery tray is part of the car's sheet metal... welded on. I just finished up and actually got the remnants of the bolt out after working it for over an hour with an 8mm tap.