hi, i was hoping someone could help with some advice. i have just started to rebuild my stag engine which has been living in my garden for the last 20 yrs and having removed the cylinder heads i have found a deep amount of corrosion where the middle cylinders water passages come to a dead end with the cylinder head, if that makes sense. the aluminium in the 'crater' is also very soft. i have access to a machine shop so could / should i machine slots in the head so there is no longer a dead end for the water or should i just weld up the craters. any suggestions would be much apricated . ta.
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I wouldn't machine them out so that there is no dead end as it will affect the water flow. I suspect the Triumph Design Engineers created the "dead ends" and also some of the restricted holes in the gaskets to adjust the water flow to try to even out temperatures.
Ideally weld them up and skim the heads, depends how bad it is and more importantly how close to the cylinder gasket fire rings they are and also to the edge of the gasket. If they just go deep (ish) but have not spread much sideways you could leave them. When I did my heads a few years back they had some quite deep pits but I judged that the gasket would still seal adequately so I have left them with no issues so far. Others may have a different view.Now Stagless but have numerous car projects
So many cars, so little time! -
many thanks, i think i will have a go at welding them up, they are well clear of the fire rings etc. i would have thought the two middle chambers would need more cooling than the outer two if anything but you are right im sure they knew what they doing. there must be reason to their madness. thank you.Comment
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Could you post a photo or two? I've reclaimed a couple of heads with welding but only in very specific areas. I'll dig out photos when I get time.Richard
Mabel is a white 1972 Mk1½, TV8, Mo/d.Comment
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Here's a poorly sick LH head, there\s a lot of corrosion but only a couple of places that matter:
Sick LH head face copy.jpg
It was welded where the corrosion was close to the fire rings and then skimmed, here's the result. The welded places are highlighted in red:
Left head gasket face copy.jpg
This head went on to do some 5,000 miles including competition work before I took the engine out during a bodyshell rebuild.Richard
Mabel is a white 1972 Mk1½, TV8, Mo/d.Comment
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wow, mine look like new compared to that. thats taken a real weight off my mind. thanks for all your help, happy motoring.You do not have permission to view this gallery.
This gallery has 4 photos.Comment
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That looks as though a very light skim will bring it back to good condition. Check LDPart website for the measurement details (https://ldpart.co.uk/shop/shop.php?s...&c=ex&page=145) to make sure which thickness gasket you'll need. That one of mine needed a thick gasket and a saver shim!Richard
Mabel is a white 1972 Mk1½, TV8, Mo/d.Comment
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No harm in leaving previous corrosion pits so long as they don’t breach…. No harm In careful welding up either.Originally posted by marshman View Post
The development chaps at the time used tea leaves to watch coolant flow…. I’m not joking….still a valid technique even if it’s smiled at.
The coolant flow was (actually) developed, hence dead ends & restrictions via gasket stamping.
Interestingly, Steve Hill I believe uses the core plug holes as coolant outlets from the head ….
Nowadays, if you trust it , we can use infra red / laser thermometers to measure spot temperatures though , although the measurements seem to be dependent on surface type & type of finish.
Coolant flow & heat transfer can also be predicted now with cad analysis techniques…. But the proof of the pudding is still dyno runs with temperature monitoring.
The stag heads need flow at the rear of the heads to feed the heater….. the pump isn’t at the rear though.
A full cylinder head temperature survey would be a great thing to see imho, if just to put to bed the myriad of hypotheses & snake oil offerings out there.
I have the basic beginnings of a geometrical stag engine coolant model, but with quite a few items left still to model.
Only ever encountered a cooling issue when head gaskets were breached, or a system leak occurred or with hot fuel handling.There are 2 secrets to staying on top :- 1. Don't give everything away.
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