Corroded head water holes

[Philippe-J.]

Hello,

when I separated the head from the block of my 67 OTS for the first time this weed-end, I discovered that several water holes were corroded, I guess by the coolant, or just by age. See some samples below, the worst cases indeed.
Question: do they need to be reloaded (by TIG or laser welding) or can I live with it?
Thanks for your expertise.

Philippe

[mgcjag]

What was the plan for your head...was it going to a machine shop for a scim and rebuild?....they could then advise once you can clearly see full extent of the damage Steve

[Philippe-J.]

Yes, this is my plan. However, "deux avis valent mieux qu'un" as we say in french. It's all the more true as you are dealing with a shop that may have different strategies, and you never know which is theirs: either to undertake the maximum business with you (and overestimate the work to be done), either has not the tools to do that job (and minimizing the work to be done). Hence my question here on the forum

[mgcjag]

Then you are useing the wrong machine shop....you need to have trust and confidence in the shop.....maybee if not in France than a shop in the UK?....you won't be able to tell what needs doing until all that scale is removed and cleaned up.....Steve

[Philippe-J.]

The local shop I intend to use has good reputation, not only locally. Maybe I am too suspicious ...
Anyway here is another image, shot after a brushing of the rust, and with grazing light:

[rfs1957]

Those definitely need repairing.

The procedure I have seen used involves milling them all out as far as "good metal", (curage, pour nous mon pote) then welding up those machined areas until they are proud in all senses, re-machining the orifices in the correct place and to the original dimensions, then skimming the head to get everything flat again.



If you look closely on my 3.8 you can see that they have been "reclaimed".

As an aside, and FWIIW, it's worth mentioning that on an engine with an unknown history, IMHO it is essential to do a dry-run upon reassembly - with a used head-gasket for example - and check a combustion chamber volume, to confirm what compression ratio you have.







Or do some maths and calculate head-chamber volume, and piston crown volume (see pictures), to anticipate your CR.

Heads and blocks that have been skimmed several times can quickly end up - on ostensibly 9:1 pistons - with a CR that is way over 9 ; Cometic gaskets (available from Rob Beere) come in a whole spread of thicknesses (40, 50, 66, 75, 98, 120 thou) and you can adjust the chamber volume and thus the CR with these.

As an example, with a standard 1.40mm : 0.056" (crushed) head gasket I ended up with a CR of 9.65.

On advice from Beere I ended up building it with a 0.075" one to get it down to 9.33, and it has no pre-ignition issues.

[Philippe-J.]

Thank you Rory.
Your photos finished to convince me to reload my head .
I take note of your advice about the CR.
Philippe