Temperature of exhaust gas leaving the cylinder

JumbleDuck said:
Hooray. If the new head is significantly eroded below original spec in any of these places, this might be a good time to have built up with welding/spraying ...
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Trouble is, I don't know what the original spec was. I've heard apocryphal tales that on this engine, the cores moved in the sand when they were casting them and the wall of the exhaust port through the water jacket was thinner on one side than the other. Unfortunately, I can't get to both sides of the wall on the other side of the port to see if there's any truth in this, but I have now seen two D12 heads that have gone through in exactly the same place, so it might be! To be honest, I don' think I'll try building anything up. it's going to be in fresh water for the next couple of seasons at least. I'm using magnesium anodes and I might pay a bit more attention to winterising it properly with antifreeze. I'm sure there's at least 5 years to be had out of it and by then, don't know what the rest of the engine will be like (it's 25 years old now)! That should give me time to save up for a new engine. As it is, the vendor has been taunting me, about the smooth, quiet, low vibration virtues of his new 2 cylinder Beta - or as he so eloquently put it, "maccapacca maccapacca" instead of "thud-thud-thud-thud-thud"!
 
skipper_stu said:
"
A result! excellent, dont poke it!
S
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No need! It really does look almost like grey cast iron in there. Interestingly, Mine must have been well-worn for a long time, because I'd always wondered why they'd made the exhaust port a bit bigger than the hole in the gasket that was supposed to seal it. Just shoving some verniers down each of them, the exhaust port where it meets the gasket for the elbow is 38mm across on the new head and 40.6 on mine!
 
Avocet said:
Trouble is, I don't know what the original spec was. I've heard apocryphal tales that on this engine, the cores moved in the sand when they were casting them and the wall of the exhaust port through the water jacket was thinner on one side than the other. Unfortunately, I can't get to both sides of the wall on the other side of the port to see if there's any truth in this, but I have now seen two D12 heads that have gone through in exactly the same place, so it might be!
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I see the problem. I was really thinking of clearly visible corrosion but if it looks OK then, as you say, you should get a few years out of it. With luck you'll be able to sell the head on again when you get your nice new engine ... maybe at a profit!
 
I'm glad it's turned out well. I didn't post this earlier as it might have worried you, but I bought a spare exhaust manifold for my smaller BMW, just in case - it looked ok when I unpacked it, but somehow crumbled away with hairline cracks within a week of my receiving it - it's under my workbench now as a sad reminder.

Luckily it was only a fiver!
 
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