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

porting, development, valve and seat work, combustion chambers, cams, head construction, etc
Guy Croft
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Race VW Jetta 1800cc 16v shimming on Piper BP285 cams

Post by Guy Croft » July 3rd, 2012, 10:00 am

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.
NH VW FR 16v_dry-run shimming...JPG
cam on and caps secured with two buckets only fitted and two indentical top-hats fitted. Doing it this way is simpler than measuring all 16 top hats and marking them. The buckets have of course been marked by valve ie: E1/E2, I1/I2 etc.
NH VW FR 16v_dry-run shimming...JPG (149.99 KiB) Viewed 7440 times
NH VW FR 16v_Ferrea caps and springs fitting.JPG
NH VW FR 16v_Ferrea caps and springs fitting.JPG (134.08 KiB) Viewed 7439 times
Shimming table_master.xlsx
the figures in this table are mine from Neal Humphries VW - but you can use this to record your own..
(12.04 KiB) Downloaded 637 times
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