Timing chain parallelism, how long a strait edge?

[sam_james30]

Hi

Very quick question, I’m up to needing to check my Timing chain parallelism and was wondering how long a strait edge I need?

I’m rebuilding a 964 engine and I can easily get a 60cm (just less than 2 foot) straight edge. In the book it says you need a 3 foot straight edge, but as far as I can see I can get for the intimidate shaft to the timing sprocket with ease with 60cm?

Thanks

Sam

[Flat6pac]

I use a 3 ft aluminum ruler thats been in the box for 30+ years, I guess what ever works for you.
Bruce

[BoxxerSix]

More about how straight it is vs how long. 2ft can work. I use a 3' machinist parallel that's probably older than I am(drilled and ground cast iron). A wide flat surface makes it more stable, thus any decent straight level from a hardware store can work as well if the length is required.

[prschmn]

Always found it curious methodology. One is assuming the area that the straightedge rests on is perfectly square to the longitudinal axis. Think about it-if that surface is out by even a couple
thou the deviation at the cam end is multiplied more that ten-fold. I;ve tried checking using a good square and referencing from the case half surface to the straightedge and it isnt always pretty but probably the simplest way to get some idea of alignment. Maybe I'm picking nits.