Damage in squish area, safe to use?

[tony27]

I had a CZ head modified last year which to be honest came back in shocking condition, the area that locates on the liner was 2mm bigger than it should have been even though I'd written the required on the head when I sent it off, that has been corrected for me by 1 of the guys over here
What I'm really not sure about is whether the head is usable due to the porosity in the squish area, do I have a very expensive doorstop or am I safe to use it?
 
As the head arrived after modifying

Close up of some of the porosity in the squish band, liner location has been repaired


Another couple of close ups of the porosity which is not localized to 1 area

[shelpi]

consider this Yamaha used to paint the squish area,  not saying paint it, but was ammazed how long it lasted, I personaly think you will get away with it,
 but if it was me I would use appropriate material that will be able to handle the enviroment, like ceramic its not that expensive

[Tim754]

Go for it. If she goes as I suspect it will sweet ,if not um , all care but no responsibility taken 

Do not try plastic body filler and sanding.....don't work.
or epoxy glues. or a formed copper insert (no shit!) don't work either.....

[pokey]

first of all i would get rid of the termites so it doesnt get worse

Then i would  have it welded and machined back to spec
 those pockets will be hot spots and getting a good even burn would be difficult.
 You could try it and see if it pings its head off

[cemotobull]

That's not damage, that's just old school alloy mixed with new alloy. It's very hard to get a good mix during welding with all the impurities in the old alloy. That would be fine to use and with a couple of runs, those pins holes will fill up with carbon anyway. I've run a hell of a lot worse than that!! You wouldn't be able to tell the difference!!

[Mick D]

Hi Tony, were those creators, pockets there before you sent the head away?

[jimg1au]

just run as is I have seen far worse on road racing bultaco heads and gred ball showed me on jap vmx head he was moding and it was the same new and old ally don't mix to well
jim

[GMC]

Quite often you will find porosity in castings. It will look fine until you machine it and then you will find these otherwise hidden imperfections.
The same problem often comes up with trying to weld alloy that is like this, you can usually create a nice bead of weld but when you take the top of the weld off you will also have these porosity holes in the weld.

[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

[yamaico]

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.

[sleepy]

I would bead blast all over the chamber. That will help remove any extra loose bits and round off the sharp edges. Make sure that there is on oil in the porosity before you do that to help stop the bead sticking in the holes. After blasting give it a scub in boiling soapy water with a bit of steel wool to clean it up again.

It should be good to use and I very much doubt that the holes would make any difference to the performance, there are some very fast title winning motors out there with similar porosity.

Whats with the chater marks, are they meant to help or is it just poor machining?

[tony27]

The grooves are something that the company who did the modification does, they reckon it does all sorts of things to the mixture but I'll never know as they got polished off when the spigot location was repaired

[Slakewell]

First off I machine it until all the holes are gone then I bake it in an old oven overnight then boil it. Then reheat it in the oven then weld it. 

[vandy010]

the machined "chatter" marks and "porosity" holes are to give an "air" buffer between the surfaces when the big BANG happens thus creating a smoother more even platform for the BANG!
just need a piston to match...
a bit like the bubbles on the swim suits they wear in the Olympics...
if you get my drift...
 











or was i the only one in the pits with a bike that wouldn"t run right?

[Ted]

the machined "chatter" marks and "porosity" holes are to give an "air" buffer between the surfaces when the big BANG happens thus creating a smoother more even platform for the BANG!
just need a piston to match...
a bit like the bubbles on the swim suits they wear in the Olympics...
if you get my drift...
 

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.











or was i the only one in the pits with a bike that wouldn"t run right?