Can anyone tell me if this is a casting mark and if it is normal?

No takers yet?
My 2c... I'd say it's a casting mark, A series heads are not known to crack there. And, the mark looks too geometric. I'd say it's from a mark in the pattern.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yes it is a bit weird. The rest of the head looks really good. Will get it crack tested before fitting anyway. Cheers Doc

Does it continue underneath the thermostat end? Looks weird never seen it my self before but as doc says looks too perfect to be a crack..

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The best part of fixing your mini is the test drive

Minis..

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1975 van
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any depth to the "crack"
may be worth grinding it out first then crack testing

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1275

I have one here that is the same .

Here is a photo from the underside. Visually there is no depth to the crack.

Casting mark.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I used to work in a large heavy steel foundry when I did my trade many years ago. I spent time with all the trades as I did my time including the molders and pattern makers. The last of the great craftsmen. We made things including drag line buckets and such for the mining industry, or track pads, coal crushers, ESCO mining parts, 7 meter diameter slurry pump housings, anchor chain etc etc etc.

It could be core shift, but looking at where it is and what it is I think its from the pattern insert that created the thread boss for the head. The patterns which are the male shape and can be carved of wood or cnc milled, are made up of many parts which wear out from the thousands of presses they make into thick and abrasive molding media (usually sand or even graphite). It grinds them away like sandpaper would over time.

Some hard wearing parts on the patterns are made removable so the other parts of the patterns that are still fine continue to be used, with the worn part replaced as needed. They slide into the pattern and are fixed in place before resuming the creation of the sand molds that make up the production molds and cores for the head. You can see evidence of these on other parts of the head as well. Usually leading edges or around sharp corners.

This one was either fixed poorly in place onto the pattern, or was created not quite the same.

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SooperDooperMiniCooperExpertEngineering

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