Best chemical metal

Helping a mate build his race engine and there's a buggered thread on the water pump in the aluminium block. Someone's had a thrash at it in the past with a drill and tap so there's not enough material left for a helicoil. We decided to make a stud by cutting the head off a bolt and bonding that into the hole with JB Weld. After 24 hours I tried putting a bit of torque onto the nut that fits the stud and it just pulled out. The JB Weld had set to about the consistency of plastic but nothing like rock hard or enough to hold the stud in. BTW I've ground undercuts in the hole so any filler that sets hard can't pull out.

So maybe the JB Weld was a bit old, my mate had had it sitting around for ages with a bit left in the tubes and perhaps it's gone off. What's the best stuff for a rock hard bond that might hold a stud in well enough to let us put a nut on and torque it up?

Reply to
Dave Baker
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I presume that you mean that the hole is already too big for a helicoil which fits the original bolt size?

Is there enough meat around the hole to drill and tap for a much larger size? Could you make your own 'fat' "helicoil" consisting of a short length of internally and externally threaded bolt which could be loctited into the enlarged hole, and the original bolt (or same size replacement) screwed into that?

Or could you use an actual helicoil - but a larger size - and use a larger diameter bolt to hold the water pump on? [That assumes that you could drill a larger hole in the water pump flange without any undue problems].

I would have thought that you'd struggle to glue a plain stud in firmly enough to withstand the tensile force created by torquing up the nut. [But, having said that, resin fixings in masonry seem to work ok].

Reply to
Roger Mills

Can you not take it to someone with a TIG welder and get them to fill the hole with fresh ali then drill and tap?

Reply to
pcb1962

7mm hole, 20mm deep, no way in for a welder. It's either chemical metal or leave that bolt out.
Reply to
Dave Baker

Enlarge hole with a taper reamer. Machine suitable tapered plug, insert with hammer---gently. Drill and tap hole to original size or under. Works for machine tools and hips! I leave it to you to decide if you wish to stay with aluminium or switch to steel. May pay to drill and tap hole first or just machine a tapered stud.

Reply to
Capitol

I'd be surprised if anything was strong enough for that. other than welding.

Rover used to recommend Belzona for repairs to ally blocks etc. But didn't mention threads.

Reply to
Dave Plowman (News)

Is the hole currently 7mm, or is that the intended size?

Any thought of filling the hole with lumiweld or something similar?

Can you direct a oxy-accetylene or oxy-propane fine torch into the hole and fill?

Of course it would need dressing afterwards.

Given the force a bolt can exert, I can't see any "glue" holding.

Reply to
Fredxxx

Actually it can just about.

two thoughts..

1/. TIG aluminium welder with wire down inside hole can deposit metal. 2/. use polyester resin and actual metal filler powder.

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is a high temp polyester that MUST be heat cured but will then take the temperatures without softening

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has aluminium powder that will have the right rate of thermal expansions not to crack out under heat stress.

Whether this is cheaper than a new block is moot.

Reply to
The Natural Philosopher

From my experience: JB Weld does set up harder than that.

Hard enough? Don't know -- maybe time for a fresh batch...

Thomas Prufer

Reply to
Thomas Prufer

I'd not trust anything like that on such an item. The thermal cycling and vibration will make it fall to pieces faster than you can say, bugger me.

I think I'd go with the oversize bolt idea, even if it means adapting the mounting hardware. Brian

Reply to
Brian Gaff

Assuming it's not got a dozen bolts holding it in:

Where is the bolt in relation to the direction of the belt run? If bolt and belt are on the same side then the missing bolt wouldn't be under a lot of tension (if anything the action is to push that side of the pump into the block) and it ought to be ok. If opposite then it'll be trying to "peel" the pump boss off the block.

And: Any spare flats on the pump boss big enough to get a new bolt hole in?

Reply to
Scott M

I've used epoxy resin mixed with aluminium filings to put bolts/studs into aluminium blocks subject to heat/cold. They all held.

Reply to
Peter Parry

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