As you have shown it is not a simple or quick solution to make this
repair but I believe it can be achieved with the aid of a number of
considerations mentioned below:
1: Quality of head material - in this case unknown I guess but lets hope
it is good ie not something like die cast, if it is die cast or similar
forget welding for the amount you have to do.
2: Preparation for welding must be meticulous - you must guarantee
complete removal of all residual oil, water, cleaning fluid etc trapped
in the existing defects to be welded. It may/would be worth drilling
out each hole so that it's surface is clean and sound. Degrease the
hole's internal surface so there is no danger of contamination (even oil
fumes entrained into the shielding gas stream). Degrease the whole head
as well and remove all cleaning residue.
3: Depending on the depth to width ratio of the prepared hole it may not
be necessary to fill completely ie a plug weld may be sufficient - this
will help to reduce total weld heat input and localized shrinkage, you
will have to decide what minimum depth of weld will be fit for purpose.
If this method is adopted do not short cut in preparation, holes must be
fully prepared and cleaned even if only partially filled.
4: Check there are no cracks running from the inside of the prepared
holes as they will contain contamination - if there are cracks they must
be prepared and cleaned as above.
5: You could preheat the whole head to about 200 deg C but I would
suggest first trying to weld one hole at a time and allow cooling each
time.
6: You need to consider the possibility of the formation of condensation
at commencement of welding (depending on the ambient and head
temperature), this can be prevented by a gentle overall warm up before
welding starts.
7: I would bolt the head to a solid work bench throughout the welding
operation, don't release until it is back at ambient temperature.
8: Get the best welder to do the welding and explain the
procedure/importance. Do not let him rush the job - will cost more time
but rushing could cause a failure and be more costly in the long run.
9: All other usual welding controls will be necessary, cleanliness of
filler, condition of equipment and environment etc.
10: The final skim to ensure flatness will most probably increase the
compression ratio but this can be minimized by close process control.
Hope this helps a bit
Regards
R Taylor
-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of
donboscomarine@vsnl.net
Sent: 11 November 2010 05:07
To: materials-welding@googlegroups.com
Subject: [MW:8198] Repairs to the Aluminium Cylinderhead of a Vintage
Car
November 11, 2010
Dear Friends,
The attached is a report of the repairs carried out on a Vintage Car's
Engine's cylinderhead and the continuing problems of the same. The
material is cast Aluminium and being a vintage car, replacements are not
available. Cutting the present cylinderhead for making moulds for
casting not acceptable to owner due to the risk of losing the
cylinderhead for good ! We have described the problem and seek advice
about Probable Solutions.
Thanks in advance & B. Rgds.
G. A. Soman
Principal
DON BOSCO MARITIME ACADEMY
Premier Automobiles Road,
Kurla West, Mumbai 400070
Tel: (022) 2504 1585 / 2018; 25036344. Fax: (022) 2504 0682
Email: donboscomarine@vsnl.net
Website: www.dbma.in
Mobile No: 9819451277
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