Pre-cups - a solution?

[Smokey Eddy]

Can you TIG the cups to the head somehow? could you get enough penetration between the alluminium and unobtanium to fuse them together? then get the head "decked" until the welds are flush with the rest of the head?

[Mark(The Miser)UK]

I dunno, all the obsession with precups. I assume they can only come out piecemeal.
Here's mysolution, why not pull them out, machine a few thou off, reinsert, and THEN spring-punch the head around them.

[honda_is_the_best]

Can you TIG the cups to the head somehow? could you get enough penetration between the alluminium and unobtanium to fuse them together? then get the head "decked" until the welds are flush with the rest of the head?

cant weld dis-similar metals.

[rabbid79]

You can research "friction stir" welding to see if that might work.  There are some pretty neat videos of it on youtube.  In Wikipedia there are references of welding aluminum to copper, and aluminum to galvanized steel.  You may not need to do the whole circumference either.  Maybe just "spot" weld a couple of areas that are outside of the combustion chamber.  Who knows, maybe it could be done at home with a large drill press and a one of these friction stir probes?

[Mark(The Miser)UK]

I have a BOC welding book somewhere from the 1950's and I'm sure it says you can weld inconel to ally
I'll have to dig that one out eh

[Smokey Eddy]

the purpose would only be to run propane or LNG in an IDI engine without the cups falling out.
but ... now im thinking why not just find any old ALH and use that...
i don't like my IDI

[RabbitJockey]

precups can't fall out unless they melt o crack to pieces, and if they melt or crack to pieces, welding them won't help either

[honda_is_the_best]

precups can't fall out unless they melt o crack to pieces, and if they melt or crack to pieces, welding them won't help either

dude, i been wondering why people are all worried about cups.. there is no way for a WHOLE pre-cup to fall out of the head, unless the head were to lift. the cup has to come out of the head almost 3/8" before it comes fully out of the bore.
and it sure aint gonna turn sideways in the bore and fall out. aluminum does not expand THAT much.

the block and head gasket hold the cup in, and they cover almost half the surface of it.

i dont see how a useable pre-cup can grenade an engine.

only a cracked, melted, or broken one will kill an engine.

and like was mentioned already, welding them in wont help if they break apart.

[TPW]

I've had cups fall out from what I believe now to be caused by too much advance.  (I tried to set timing without a gauge)

[RabbitJockey]

what did the destruction inside the engine look like?  i'm curious to hear from people who have experienced this

[Mark(The Miser)UK]

I have a BOC welding book somewhere from the 1950's and I'm sure it says you can weld inconel to ally
I'll have to dig that one out eh

The technique is to abrade the cups, then tin them, then oxy the cup until the ally just fuses...I'm still  with the I  can't believe  they fall out whole, brigade though

[TPW]

what did the destruction inside the engine look like?  i'm curious to hear from people who have experienced this

It mushroomed one cylinder, one other was cracked on top.  The engine was making harsh noises until I shut it off, then it was locked up almost solid.

[jackbombay]

  The cups can't "fall out", bu they can certainly become looses enough to wear through the HG and then start chewing away the edge of the cylinder knocking sand sized grains of cast iron into the cylinder which get drug up and down the walls by the piston and then your engine is smoked.

   It happened to an engine in a car that was in my driveway, the car was run hard daily over a long steep pass, 3 miles of %10 grade, this pass ruins cars for a living.

  I don't have pics anymore, but running these IDIs hard for more than a short time will eventually loosen the pre-cups...

[Mark(The Miser)UK]

 
   It happened to an engine in a car that was in my driveway, the car was run hard daily over a long steep pass, 3 miles of %10 grade, this pass ruins cars for a living.

 

That is one hell of a big driveway Jack. Requires a QSyncroTD IMO

[TPW]

They can fall out (or be blown out).  I've had first hand experience with this happening!