Guy Croft Racing Engines Lincoln UK 01522 705222

Delahaye 6cyl reproduction head prep

by Guy Croft » Fri Jul 23, 2010 2:28 pm

Gasflowing a nicely excuted 6cyl Delahaye 'repro' alloy head very nicely reproduced, at least so I understand, by the respected Delahaye Club (based in France). Owner Ross Keeling.

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GC

Attachments

: doing the port entry section after careful marking out. The inlets are siamesed.; IMG_0528.JPG (598.23 KiB) Viewed 424 times

: roughing out the ports, first all the port floor out sections, then the sides, then the roof, very laborious; IMG_0529.JPG (121.56 KiB) Viewed 424 times

: matching and porting one of the three inlet manifolds; IMG_0531.JPG (117.57 KiB) Viewed 424 times

: the whole thing, a lot of it........; IMG_0532.JPG (121.53 KiB) Viewed 424 times

: the head on end so I can do the sides of the ports near the guides - they were already fitted which makes the job twice as long; IMG_0541.JPG (578.78 KiB) Viewed 424 times

: smoothing at 80 grit; IMG_0542.JPG (115.74 KiB) Viewed 424 times

: manifold at 80 grit ready for final dressing, the amount of debris in the port will give you some idea of just how much work is actually involved here; IMG_0544.JPG (100.04 KiB) Viewed 424 times

: view of seat inserts as received, some copper alloy and quite right too. Very nicely machined I have to say.; IMG_0545.JPG (116.19 KiB) Viewed 424 times

: roughing-out with an alucut burr, high mass removal but leaves the region pretty rough, a finer burr will be needed next. You have to split port into 4 quadrants to do this, front-back and sides so you can imagine that during the course of the prep you will move this head about 50,000 times to reposition it.; IMG_0546.JPG (112.37 KiB) Viewed 424 times

: tons coming off here...; IMG_0547.JPG (115.46 KiB) Viewed 424 times

: see what I mean about re-positioning? If you don't bother you are just not going to do it properly and this area, the short side radius, needs a heck of a lot of reshaping and extreme care. I have no idea how thick the casting is, I guess 4-5mm maybe less here.; IMG_0548.JPG (114.49 KiB) Viewed 424 times

: this is the 'short side' prior to my prep. My heart sinks sometimes when I confront the work ahead of me. If I were doing the remanufacture of these heads no way would I leave any part of them in this state. Easy life eh?; IMG_0523.JPG (485.03 KiB) Viewed 424 times

: fully flowed now; IMG_0557.JPG (911.95 KiB) Viewed 421 times

: from a functionality point of view this is plenty good enough around the guides although it never looks as pretty as a full 'cosmetic' job but if you try to be too ambitious (with guides in) you're going to knock them to bits.; IMG_0560.JPG (484.33 KiB) Viewed 421 times

Guy Croft: Site Admin; Posts: 2913; Joined: Sun Jun 18, 2006 9:31 am; Location: Lincoln, UK

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Delahaye 6cyl reproduction head prep

Delahaye 6cyl reproduction head prep

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