Internal npt thread repair

[rlitman]

Automotive castings are typically A356 grade aluminum, which has about 7% silicon and 0.35% magnesium added. Silicon is added to increase fluidity for the casting during the pour. Magnesium is added for strengthening. Neither are added for corrosion resistance. ER4043 has slightly less silicon (5%), but not enough difference to cause a corrosion issue with automotive coolant that already has corrosion inhibitors. Not enough difference to worry about. There are plenty of welded aluminum intakes that have no corrosion issues.

I'm not remotely worried about corrosion on the inside. I'm just talking about the color difference on the outside as it begins to oxidize.

 

[zmotorsports]

Personally, I'd drill out to a uniform size/shape, then machine a slug that would press in after drilling/tapping the new NPT thread in it. Weld around the perimeter and good to go. Solid repair with new threads and leak proof. I have repaired a lot of motorcycle cases, some intake manifolds and hydraulic manifolds in this manner with great success.

 

[VC455]

JB weld for me. It’s easy, cheap, quick and works. About 20 years ago, I got a pinhole in the dry sump oil tank of my race car. I used JB weld as a temporary measure that weekend at the track. 20 years later, still not leaking. Oil temps sometimes hit 300 degrees.

Yep, heat cycles, pressure cycles, vibration, dissimilar materials, 'One & Done, next'

 

[bwringer]

We use a metallic epoxy putty at work called Devcon for metal repair. If JB weld has a formulation with metal in it, probably same thing. Don't expect to be able to unthread the plug again...

FWIW, JB Weld does contain iron particles. If you use it on magnetized parts like a motorcycle rotor, it will try to "creep" into the shape of the magnetic field.

Devcon is a very good brand. They make lots of specialized epoxies for all sorts of things, and they may have a more specific product that would be a little better for this use.

Make sure and use the JB Weld and not the JB Quick.

Agreed, if you decide to use JB Weld, use the original stuff.

 

[lilscorpion]

Ok, working on an intake manifold that someone thought would be a good idea to put a steel 1/2 npt plug in a nice polished intake. The motor sat for years, and coolant severely corroded this plug to the point that it was basically fused into the aluminum. I drilled it out with the largest bit I had which was 43/64. I made a couple light cuts with a hack saw blade and went to try and break it out and it sheared off below the surface. I kept working at it and finally got it out, but I ended up cutting into the aluminum more than I wanted to. I ran a tap in a thread or so deeper than it was, which is now about as deep as it can go. It cleaned up all the threads pretty nicely other than my cut. What are my options here? Structurally it is good. I just want to make sure it won't leak. It is an engine so it needs to be good for 250 plus degrees. Do I go to some sort of epoxy and retap? It is is not as deep as it looks, but is still deeper than I wanted. I think it looks worse than it is. I can't really go bigger, or deeper. Of course the brass plug next to it can out with a little heat and an impact. Looking for ideas and you guys always seem to have good ones.

Thanks.

John

Intakes are welded all the time. TIG the bottom 1/2 of the threads and re-tap using the top 1/2 as a guide. The way a pipe thread works, it shouldn't leak with only the bottom 1/2 fixed. If the threads don't seat deep enough, just tap the hole slightly deeper.

Edit: Mike's recommendation above is the right solution. Make an over-sized aluminum plug, tap it, drill the manifold to fit, and tig perimeter in place. Good as new. If you can machine a recess around the plug, you could also metal finish it so no one would ever know (but you). That said, that would be just for looks.

 

[joe49]

Reality check for the welder-up, throw it on the mill, turn a press fit bush with new threads, press that in, then weld that, and likely chase the threads. So lets reach out there and suppose we don't own all that equipment. Then what is the cost to farm out ''your best way to do it'' going to be? Sure seems like a new manifold would be more cost effective.
Edit: machinists would you please chime in on real cost not buddy work.

 

[lilscorpion]

Reality check for the welder-up, throw it on the mill, turn a press fit bush with new threads, press that in, then weld that, and likely chase the threads. So lets reach out there and suppose we don't own all that equipment. Then what is the cost to farm out ''your best way to do it'' going to be? Sure seems like a new manifold would be more cost effective.
Edit: machinists would you please chime in on real cost not buddy work.

if you took it to someone you don't know who's doing it as a business thing and charges you his hourly rate, there's a good chance it'll cost more than a new intake. If the guy/woman says "throw me a $50 and I'll take care of you", it's less. If you have a buddy deal then it's a 6-pack.

There were other options recommended above that don't require welding which would work. There's part of me that would probably slap it together and see if it holds and I do have the ability to weld it.

Unless the OP posts up what's in and what's out, think the crowd usually provides multiple options. There's no way we could know if he does or doesn't have a buddy..

 

[ez-duzit]

...what is the cost to farm out ''your best way to do it'' going to be? Sure seems like a new manifold would be more cost effective...

Hacking up expensive parts should hurt.

 

[joe49]

if you took it to someone you don't know who's doing it as a business thing and charges you his hourly rate, there's a good chance it'll cost more than a new intake. If the guy/woman says "throw me a $50 and I'll take care of you", it's less. If you have a buddy deal then it's a 6-pack.

There were other options recommended above that don't require welding which would work. There's part of me that would probably slap it together and see if it holds and I do have the ability to weld it.

Unless the OP posts up what's in and what's out, think the crowd usually provides multiple options. There's no way we could know if he does or doesn't have a buddy..

My point is telling someone how it sould be fixed with a fully equiped machine/weld shop is not complete without indicating the real cost. Everyone doesn't have the shop of dreams or the knowledge to use it.
By the way, the buddy deal isn't a six pac anymore, you should be starting with a case of the prefered beverage, and going up from there.

 

[lilscorpion]

My point is telling someone how it should be fixed with a fully equipped machine/weld shop is not complete without indicating the real cost. Everyone doesn't have the shop of dreams or the knowledge to use it.
By the way, the buddy deal isn't a six pack anymore, you should be starting with a case of the preferred beverage, and going up from there.

I hear ya, point taken.

Dunno about the case thing on a buddy deal...you're diggin' into social dynamics. If it's my buddy it should be free and that rate should also always be mutual and keeping score shouldn't even cross our minds. If the offer involves a case (or a 6er) then they're a buddy of a buddy trying to figure out how to pay me very little instead and are just starting cheap as a negotiation tactic. A nice person says, "yeah sure" since it's a buddy of a buddy because the actual buddy is a real buddy. Either way, if it's a quick thing, I do it for free regardless. If it's fairly time consuming I go the "not for hire" route. Not b/c I'm an *** but because they can't pay me for what I really need reimbursement for - time.

whoa...too real for a Saturday.

 

[joe49]

Nope never free it's his hourly rate in beverage or the you owe me which I prefer when I help others. But to be fair when I get that owe me it's a project worth more than they can afford or I won't take payment over the they owe me.