On DOHC 2.5 liter interference engines.

 

Does anyone know if it would make valves collide.

 

The endwrench article on timing belt replacement actually suggests rotating crank counter clockwise 90 degrees and then rotating it 180 clockwise (step 23)

 

http://www.endwrench.com/pdf/engine/FtTimingBeltReplaceF00.pdf

EndWrench is a Subaru publication. no reason to doubt the techinical article.

If you think about it - the relationship between the crank and thus the pistons and the cam(s) and thus the valves is fixed by the timing belt (why is clled a timing belt) so moving them together in any direction would make no difference

Actually, there is cause to reflect on whether this might cause a problem. The "timing" relationship depends on the pull side of the belt; when you rotate the engine backwards, there is the chance that the tolerances on the slack side might cause the crank-to-valve relationship to be different. On a tight-tolerance design, this could cause problems.

 

I am NOT saying that this is a problem with this or any particular engine, just that it is good to think and ask first.

Seems like most manuals suggest don't rotate crank counter clockwise...I am not sure why...