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Race VW Jetta 1800cc 16v shimming on Piper BP285 cams

Posted: July 3rd, 2012, 10:00 am
by Guy Croft
Here building up a 16v VW head, StII race spec. Head is fully flowed on standard valves, race spec seats, OE bronze guides. The only springs that will take the lift from the BP285 without machining the spring platforms are by Ferrea. Caps are also from them. The guides have flanges which will not accept the Ferrea spring bases so the OE ones have been used.

The cam base circle is a long way from the cams and even with Piper long-nose buckets there is a big clearance. I shall be using top hat shims designed for 8mm valve stems and inverting them to fit on the nose of the bucket which is the same diameter. This is far safer - and easier - than locating them on the valve tips which would give me barely 0.5mm engagement.

To get the dimensions of the top hats required the cams are offered up with two only top hats in place and the clearance on each valve pair measured in turn. I have created a table of measurements in Excel which you can download and use yourself.