another broken bolt 280z

[Dave WM]

I was replacing the remaining old FI hose (short pieces around the regulator) and while I was doing that I wanted to check the spray pattern on the FI's

what a pita to get it all off, but the worst part was a snapped the bolt on the front of the head that is used to attach the metal hard lines for the FI rail. The one on the side is ok (shares the lift plate).

The one that broke only has one function, and frankly I don't think it would be a problem if I did not use it.

But...

I was wanting to get a welder (wire feed type) and I have seen it used to weld on a nut to the broken bit. There is some of the bolt still sticking out but no way is it coming out, the vice grips are just chewing it up so I stopped while there was still some left.

Now the question, will the alum heads be at risk from the welding heat? my plan was to use a washer 1st over the broken bit, then a nut that fits over it, weld from the center of the nut.

I have never used a welder like this, did use an stick welder back in HS but that was 40 yrs ago..

I would of course practice on some scrap bolts etc.. to get my technique down.

Other dangers would be electronics (I presume disconnect battery completely and unplug the ECU maybe even the ign module), not sure how the current in the weld process may effect those.

fire from fuel. Will make sure the reinstalled rail is leak free tomorrow morn, too late to crank it up now to check my work.

Its all back together, while I had it apart I pressurized the fuel rail with some FI cleaner using a pressure bottle at about 35 psi. turn on one injector at a time with a low volt AC supply (60hrz)

The spay pattern was consistent for all the injectors, Not very much of a pattern I expected more of an aerosol effect the spray was maybe 1" wide at about 4" out. I ran several a couple oz of the cleaner thru each injector. but since I lack a frame of ref, not sure if they are good. but they are consistent.

Back to the bolt, am I ok with using the mig welder? Just don't want to crack the alum head.

 

 

 

 

 

 

 

[grannyknot]

Before using the mig I would try heating up the bolt with a Propane torch, get it nice and hot and cool immediately with WD40, repeat that 4-5 times then try the visegrips again but only try to get the bolt to wiggle a bit back and forth. You may have to go through the heating/cooling process again, funnily enough the WD40 wont ignite when sprayed on the hot bolt, you will only get a small flame when you put the torch back on it and it burns off quickly. You have to break the corrosion between the steel bolt and the aluminum head so clamp the visegrips on very tightly and only try to get the bolt to wiggle a bit in both directions.

Welding a nut on can work too and wont harm the aluminum head but if you haven't used a mig before this bolt isn't the place to learn.

[Namerow]

As a footnote to Grannyknot's discussion, I would add that there seems to be some magic temperature that you need to hit before the corrosion bond along the length of the threads will break down.  It's been my experience that a regular propane torch may not be able to get the job done -- especially when you're dealing with a huge heat sink in the form of the cylinder head.  Try MAPP gas instead.  An oxyacetylene torch would be ideal (but then, I don't have one and you probably don't either).  I like the MIG/welded-on-nut strategy because of the massive amount of localized heat that it puts directly into the threaded piece.  However, even a cheap MIG is going be an expensive solution here... unless you can borrow or rent one.

For reference, I wrestled for days with a snapped off bolt (a measly little 6mm guy) that was stuck in a distributor mount casting.  I tried everything, including alternating heat heat from a propane torch ('swirl' type head) with spray applications of 'liquid freeze', followed by light blows with a hand-held impact wrench (I was using a Crafstman ez-out).  I had let the casting soak in penetrating oil (acetone-ATF mix) for a week before I got started with the torch.  I never got the stud to shift even a tiny bit. 

I then tried to carefully drill out the core of the stud so that I could pull the thread remnants out of the hole, but the corrosion bond was still so bad that when I pulled on the thread curl, it would just snap off.  I had to run a thread tap through the hole to chase out the remnants and even that wasn't a happy process.  In the end, I had to drill out the hole and install a threaded insert.  Message:  That steel-to-aluminum corrosion bond can sometimes be really strong.

 

[Dave WM]

Well the upside to the story is the car started and runs fine after I messed with it, so no harm at least (no noticeable change either way). The main issue I had was with that very short piece of hard to get fuel line that was starting to show a gas leak, no engine fires please. I did use FI rated line (had to go to 4 auto parts stores, all they had was reg fuel line before I found it at oreily's), all looks good. I am going to take a break on the nut for now. I do want to get a mig welder, but need to do some research. I want a decent one, ok to spend some $$$ I just don't want to by twice. I know good tools make the job easier. I guess my next post will be about good welders.... I have always wanted to learn how to weld.

 

[hr369]

Have you considered Tig? I sure like the bead you can lay down with tig on thin sheetmetal and you don't have to set wire speed on tig like you do on mig. One less thing to fine tune.

 

[Dave WM]

I will have to look into that. I had  stick welder 30yrs ago, never used it.