Articles: Peugeot 505:
Installing valve lash caps (Turbo Injection)

Lash caps are inserted between the valve tip and the rocker arm. They are used to prevent the tips from mushrooming under the load of heavy valve spring pressure. Lash caps can also be used to correct minor rocker geometry problems by effectively lengthening the valve. In a stock 505 Turbo Injection engine you really don't need to use lash caps. But if you use a custom grinded race cam with more brutal profile, your engine might benefit from lash caps.

I bought some Bugpack Products' hardened lash caps (#4029) which are designed for 8 mm valve stems, a pack of 8 lash caps costs about 10 EUR or 10 USD. These lash caps should be quality products but I was really surprised to find out that only 7 of 16 brand new lash caps fitted perfectly. The inner diameter clearly varied between the lash caps when I test fitted them to the same valve stem. So, 7 fitted perfectly but the 8th needed some grinding to make it fit good enough. I measured that the effective thickness of these lash caps was 1,90 mm. That should be better than nothing but the optimum value for this Danielson profile cam is propably higher.

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Here you can see the valve tip without and with a lash cap.



The first picture shows how little there is room for adjustment left when using a custom grind cam (Danielson profile) which has a smaller basic circle than the stock cam. The second picture is taken after installing a lash cap.


After installing the lash caps I carefully adjusted valve clearances. The long-term effects of using lash caps are still unknown for me at the moment but the engine seems to work fine after some testing.