TO ALL WITH ENGINEERING BACK GROUNDS

[Andy Rundell]

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Mpower738 wrote:

alan_thomas wrote:

Mike, Thanks for the informative post on the new heads. I would love to read more in the magazine as I am sure there were many hurdles on the way and I for one would be interested to know what they were and how the team overcome them.

One point I would like to know is if the aspect of siezed studs was considered by the obvious experts on the project. This problem is not due to the wrong type of coolant but due mainly to the galvanic reaction between dissimilar metals. Has any thought been applied to different head studs or coatings or increasing the hole dia to obviate this problem?

- Alan

In the marine industry Duralac compound is used on Aluminium masts to prevent pop rivets andstainless screws causing corrosion. I am planning to use it next time I remove the heads on my stag.

http://secure.silmid.com/ENG/product...50ML%20DTD369B

Personally I think increasing the hole size is asking for trouble, as there are no dowels to positively locate the head. If the holes are madelarger then there is more scope for the head to move about as it expands and contracts.

In TR7 circles it is common practice to open the stud holes out by 0.5mm to help avoid future siezure. The bolts rarely ever sieze, their holes are not eased, the thought being that they will act in a dowel-like way for head location.

I like Mikes comment about waiting the studs - again the unmodified bolts will perform dowl job of location and no sweating over removing too much head-metal !

.........Andy

[MB]

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Interesting article on repairing Heads by a company in the US. There's comment about they would like to look into adding a water port to the centre cylinders! No mention of cost though.

http://www.aronline.co.uk/index.htm?stagheadsf.htm

[al-stag]

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"there are probably other surface treatments which will be prevent corrosion all together"

Cadmium plating gives the lowest emf of all adjacent to aluminium. Extensively used on aircraft parts. The idea to waist the studs is a good one as long as it is very little, leaving a short collar of material where the stud meets the block leaves the necessary location intact. Otherwise tightening torques will have to be modified to get the correct clamping force. http://www.roymech.co.uk/Useful_Tabl...reloading.html

I'd be interested to know a bit more about the castings? Were the originals Sterling Metals jobs? What was the original casting method, gravity dies, shell mouldings? Was any impregnation used and do you have to do any now? How many newcastings have been made from the new pattern equipment, and have they all been good?

Regards

Al