Damage in squish area, safe to use?

[Lozza]

With porous heads sometimes its hard to avoid especialy as over time the oil has gone deep into the casting. When welded the oil seeps up to the surface with the heat no matter how careful the preparation is. There is only one way to find out

I always boil heads, cases etc. before welding which gets a lot of the imprisoned oil out. Makes life a lot easier.

Cheers thanks for that. I had a suspicion there was a trick to it.

[Mick D]

I get your drift Mick. I've seen it proved. Nearly 40 years ago I saw my girlfriends father ( dirt tracker ) polishing the inlet of a cylinder with a toothbrush and toothpaste. In walks his brother in law ( surfboard maker ) and asks him what he is doing. He says I'm polishing it up to get the gas to run over it quicker. Brother in law says leave it rough, it will flow quicker. Bullshit says the father. Brother in law goes to the kitchen and comes back with water and food colouring. He pours some water on the rough sloped driveway. It goes about two feet and stops. He then pours same amount on the coved ( smooth ) edge of the driveway and it goes about four feet in about half the time that the rough surface would permit and stops. The father says I told you so, it travels faster over smooth surface. The brother in law then pours water on rough driveway to the same length as the smooth surface and it stops. He then adds a bit of food colour to the water and puts a couple of drops on the rough surface water and it gets to the end way quicker than the water did on the smooth surface. His theory was water runs over water with less friction thus speeding up the flow. The pits in the rough surface trap the water, allowing the water to run over unimpeded.

Not a bad way of putting it Teddles,
Although some things or effects are small?
Nevertheless, every difference in result is measurable. It is only invisible when using a closed mind.

[Mick D]

I will never be as competent a welder as Mr Slakewell is,
nor will I ever be certified to his elite pipe and pressure welding level.

But as an apprentice, your first weld is broken in a press to expose voids and inconsistencies in your run.
The rest of your welding career is to recognise and adjust the causes which are producing less than an optimal outcome.

If you are happy with voids, you are in the wrong career.




These very from early days, things have improved out of site since then.

[Mick D]

[Mick D]

I have found that to exhume and force out all of the oil from Aluminum Alloy castings, that it is necessary to remove the paint or coating first.

Then even boggy Japo repairs can easily be rectified without voids.





 

[Mick D]

If these voids are only a result of a poor sub-standard welding outcome?
I would just go a head and use it. As others have suggested that alone will not have much of any noticeable effect.

Can see why you would have been majorly disappointed though, who wouldn't be?
particularly the bit about the wrongly machined diameter??
Enough to make a saint blaspheme.

BUT, if the head had suffered a foreign material impregnation from a collapsed big or little end cage failure etc.
Then it would have been a different story.
I no longer use heads with such history unless I machine them back first.
A lathe tool will soon help you find every little foreign body.
If the engine is shut down promptly and only a small amount to search for?
you can just do that with a rotary burr in a die grinder or dremel.
But don't forget to Bleed it of oil before you start welding it back up

I would love to see independent dyno testing on this style of finishing chamber surfaces

Keeping the TDC chamber volumes consistent as a part of a "controlled experiment" of course.

[yamaico]

 

Very nice job Mick.
Pete.

[tony27]

Finally got around to trying it over the weekend, seemed ok running on avgas as a precaution, had the standard head to refit after practice if needed but didn't need to.
Will take it off in the next couple of days & check out how it looks & whether there are any differences on top of the piston, will see what the squish measures as well

[bruce g]

I will put my 10 cents in on the spirals in the squish band
there there to promote a horizontal vortex where as the ungrooved chamber will produce vertical tumble there are some arguments on which is the best ,and i'm with you Mick dyno testing is the only way to find out for sure
let alone all the variables of fuel type and ignition and compression
these mods are done so when MSV is reached just before TDC the burning fuel in the centre of the head starts to mix with the cooler mixture getting squirted from the squish band this is where the horizontal vortex or vertical tumble helps to make detonation less likely

If these voids are only a result of a poor sub-standard welding outcome?
I would just go a head and use it. As others have suggested that alone will not have much of any noticeable effect.

Can see why you would have been majorly disappointed though, who wouldn't be?
particularly the bit about the wrongly machined diameter??
Enough to make a saint blaspheme.

BUT, if the head had suffered a foreign material impregnation from a collapsed big or little end cage failure etc.
Then it would have been a different story.
I no longer use heads with such history unless I machine them back first.
A lathe tool will soon help you find every little foreign body.
If the engine is shut down promptly and only a small amount to search for?
you can just do that with a rotary burr in a die grinder or dremel.
But don't forget to Bleed it of oil before you start welding it back up

I would love to see independent dyno testing on this style of finishing chamber surfaces

Keeping the TDC chamber volumes consistent as a part of a "controlled experiment" of course.

[Lozza]

There are no vortex's or tumbles there is only turbulence more turbulence better it is