Drilling and tapping JB Weld

[creia]

Has anyone ever had any success doing this? I'm trying it for the first time (The JB weld still needs to cure another 8 hours)
I have a Briggs 5HP where the threaded boss on the aluminum block partially broke off that receives/retains a tiny 8-32 X 3/8" long bolt that secures the wrap around tin that diverts air around the cylinder. I have rebuilt the end of the boss and waiting for the JB weld to cure before I try drilling and tapping it.

Give it to me straight guys (I know you will!). Is this a futile attempt? If this fails I suppose my only resort left would be to have the boss rebuilt with weld then grind it down then drill and tap.
Michael

[KE4AVB]

To me JB Weld is some of the worst stuff on the market. But that may be my bad luck every JB Weld product I tried. And when my machinist repair shop bars it from their shop it tells me something too.

[bgsengine]

Agree with KE4 , the stuff is good for some applications such as filling in holes, but it does not bond well to the metal, so structurally, it won't last. to repair broken off tabs like that (I've had blocks welded to repair broken or cracked intake mounting boss on 5 HP briggs) you need something that actually integrates with the existing metal casting - Nothing else would make a suitable bond to hold up under vibration & torque. Not to mention, you're going to see the JB Weld separate due to differences in thermal expansion rates (JB Weld won't have the same thermal properties as Aluminum, so it'll move differently from the rest of the block.)

For those tins, however - notably the little square tin that screws in at the back PTO side of the engine in between cooling fins, I have used fabricated nut & spacer after using a dremel tool to cut little slots in the fins further in, and a wing-shaped "nut" (1/8" steel drilled & tapped to 8-23) and an identical piece in a cut-out over top of fins, then a spacer (piece of copper or brake line tubing) to support the "wings" from being bent too far inwards and coming loose - It was a really complicated repair and took several hours of fussing with it to get it to work right, but it did save from having to have the standoff re-welded (which would mean we'd have to tear down & rebuild engine and bore it out, since welding in that area would be sure to warp the cylinder bore) Other than that for those broken tins, if there simply were no where else to bolt them on they were left off - It does not seriously affect engine cooling all that much as far as something that isn't gonna be running hours at a time non-stop... But in my 30 plus years experience, JB weld repairs NEVER worked Either our shops' attempts or even other professional machine shops using it, it just didn't last - even the best of them eventually broke away in a couple years.

[creia]

Thank you both for the "tough love" talk about (not) using JB Weld- I needed that, and kind of thought that may be the case. I was not aware that welding a blob on the outside of the cylinder fin would warp the cylinder bore! Soooooo.... my option # 2 (welding) is out because this bore is real nice, in specs, and was just honed for installation of new rings- really do not want to do the bore again.

This particular cylinder tin is the (large) "wrap-around" one on the 5HP that completely encircles the cylinder and diverts air over and around the cylinder fins- pretty important to proper engine cooling, no? It is not the little square 2" X 2" tin like on the 3 HP. Add to that the fact that this is a restoration, as all my engines are, and I want it have the OEM factory look of the tin in place.

OK, that leaves me with option # 3 (My only option?)- Brian's suggestion of the "wing-shaped nuts" that are (notched?) into the cooling fins. Please forgive me Brian, but I am not following you as to how they look and how they are secured. Can you please educate me further? If not appropriate here, perhaps you can PM or email me? I would be MOST appreciative
Michael

[bgsengine]

Oh THOSE little spots , yeah those tins are kinda must-have. If you have a local pro welding shop with a good reputation for Aluminum welding, you might ask them for advice - I am not 100% sure whether welding would cause bore warpage, but it WOULD be something to keep in mind (I'd bet a pro shop that has welded aluminum heads on cars and the like might be able to mitigate that by way of heat sinks) I don't know as the wing type fix would work all that well (It definitely wouldn't be restoration worthy work) since you'd have to drill new holes in the tins, and it'd be hard to get them to line up right - Basic idea is to create a "sandwich" of steel bridging across 2 fins (IT took me 2 hours with a tiny dremel to get slots cut in cooling fins for the "inner" slice , and countless more of patiently filing down and fishing around with tiny pieces that I could never do now with my age and vision, and even then the engine ended up getting tossed on the junk pile 4 months later when the guy ran it out of oil and it threw a rod through the side... so I couldn't attest to how long it would hold up....

So my first suggestion would be to check in with a solid machine/welding shop that has capability to weld aluminum (ask around at local auto shops or auto parts jobbers perhaps - or if you are lucky, there's a speed shop around that can point you to someone - lot of those guys go by word of mouth - - It isn't WHAT you know, but WHO you know.... ) if they know someone who can weld aluminum heads, (or motorcycle jugs) that'd be who to go with. Easy enough to weld aluminum - even some auto repair shops can do that, but the real skill is in welding it right, and managing heat/warpage usually via heat sinks, or pre-baking, etc. If done right, odds might be good that you could get away with welding and not have the bore go out of round.

[creia]

Update,
I have a local welding shop that I have been going to for years. He is an older guy (73 years old) one-man shop, very meticulous, and does great work. I brought it in to him and he stated that he can definitely weld it with no problem using a TIG welder. Now, all I have to do is get all of that JB Weld "blob" off of there that I applied and get the area cleaned up real good for him, using a small wire wheel on a Dremel tool.

Just for kicks I tried drilling and tapping the JB Weld I had applied for the tiny 8-32 X 3/8" bolt6 that secures the cylinder tin. I have got to tell you, I was rather impressed! It drills and taps very well with good threads. Then I installed the cylinder tin and torqued down the tiny bolt and lock washer and it held just fine. Then I kept tightening it down until failure (bolt pulled out), however, that was WAY more than I would have ever normally tightened it.

In summary, my feeling was that while JB Weld was not appropriate for THIS application, I would consider using it in the future where heat and vibration are not a factor- "Your mileage may vary" It is important to note that I used the "Original" (much higher strength and heat-rated) version that takes 24 hours to cure, NOT the (weaker) "Kwik" Weld that only takes 6 hours to cure.

Thanks to all for the interest and replies to this thread.
Michael

[creia]

Update:
Success!!
I took the engine to my welder today and he TIG welded the broken threaded boss. Got it home and checked the bore- all within specs just the same as before the welding - NO BORE WARPING!! (I feel I got lucky ) I then grinded down the weld a bit to a nice flat surface , then drilled and tapped it for the 8-32 bolt which (now) snugs up real nice on the shroud tin.. The engine started and ran very well. = A good day....
Michael

[bgsengine]

Update:
Success!!
(I feel I got lucky )

Not lucky - I'd say you got a good welder. Those guys can be worth their weight in gold. Tried welding cast iron once , myself (with the proper rod for Cast Iron) - block cracked right through the cylinder - Obviously because I didn't have the skill or know-how at the time - I since learned from a Pro welder, they will roast the block in an oven to like 350-400 degrees or something before and after welding and then turn off "oven" and let it cool down overnight gradually over like 24 hours or something - Not anything I have the capability for, and I always assumed the same sort of issue might apply with cast Aluminum, but perhaps to a lesser degree. In any case, welding an engine block or head, etc. is something I'll always take to a professional, and generally assume I may need to machine the block afterwards, so it usually goes from the weld shop to the machine shop (assuming they are not one and the same) and have it bored oversize, valve seats done, etc.

[SUKI]

That is why I prefer an experience doctor than some witch doctor when it comes my health.

Although, I will probably be getting my a TIG welder later this year but I train myself on scrape metals before even trying to do something like that on a good unit.