Race engine/ timing chain replacement interval?
 

Anyone have any thoughts on how often timing chains should be replaced on a race engine?

There are different chains available from IWIS but both have long life expectations.
Some of the things to look at are sprocket wear and chain tensioner type. Solid tensioners often used for reliability in racing applications will add additional chain wear.
All things considered, you should get 100 to 200 hours safely.

Thank you Henry.

I've always assumed that chains were an automatic replacement item for every rebuild. For a race engine on, say, 40 hour rebuild intervals, would that suggest you could use the chains for 2 rebuild cycles? Probably not worth it, but had to ask.

Assumptions should be based in quantitative data. If the sprocket wear is minimal and solid tensioners are not employed, chains should last longer than most parts in a 911 race engine. I have never seen a broken chain and even with huge sprocket wear, the chains worked until the "stretch" hampered idler arm travel.