black and brown chain guide rails

[Swallowtail]

Hi guys,

I'm rebuilding my 2.4t engine and I am wondering about the chain guides. In later engines (1974, 2.7 onward) you are supposed to one brown and 5 black rails. In my '73 the parts catalogue tells me to use six brown ones.

Can anybody explain the reasoning behind this?
Is it wise to use the later style rails in an early engine?

[Henry Schmidt]

Printing error.
All 911 engines from 65-89 (except 89 C2/C4) use the 5 black and 1 brown configuration.

[Dpmulvan]

Blacks are tall browns short, you only use brown where arrow is pointing.

[WMontald]

I had some bad luck with these chain guide rails years ago.
See comments on my post,
How a plastic Chain ramp can ruin your engine

[Swallowtail]

thanks for the replies!

I'm still wondering why (at least in Germany) multiple retailers explicitly state that you are supposed to use six brown rails in the older engines.
Here is an example (GERMAN): https://www.lager11.de/motor/gleitschiene-fur-steuerkette-fur-porsche-911-braun-65-89.html

For all engines built up to 1973 (2.4), six are used per engine.

One brown and five black slide rails are used for all engines built from 1974 onwards (2.7).

Für alle Motoren bis Baujahr 1973 (2.4) werden pro Motor sechs Stück verwendet.

Für alle Motoren ab Baujahr 1974 (2.7) wird eine braune sowie fünf schwarze Gleitschienen verwendet.

I asked them about it on the phone. They knew about the height difference between the black and brown but couldn’t really explain why not to use the newer setup in the older cars. Still, they insist that this is the correct way and it’s also how they do it in their workshop.

[AJKelly]

Sorry if this is sort of hijacking.

But has anyone used the non-genuine ramps, such as the 'ramp kit' available on this site, as the genuine Black ramps seem to be no longer available on this site?