locking idler gear bolt

Doing the head on 2004 zd30
After many hours of manual turning engine over to align gears I now need to secure the gears so that I dont loose the timing if I need to do more work than just the head.
Problem
The manual says locking/securing bolt is a 20mm long 6Mx1 thread which is just a standard size bolt but manual says to only use a Nissan bolt for this as otherwise damage may occur to idler gear.
Has anyone used a standard bolt, the only thing that I can see where there might be a problem is when I look through the hole (with mirror and light) is that the far outer hole is only about 4mm.
I am currently 100km from nearest Nissan dealer so any help would be appreciated

any bolt of the right size will do the job. its only to hold the gears from moving so no strain is placed on anything. Nissan will tell you to also use there shifting spanner for a particular job, ha ha.

Thanks

jonney said:

any bolt of the right size will do the job. its only to hold the gears from moving so no strain is placed on anything. Nissan will tell you to also use there shifting spanner for a particular job, ha ha.

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Thanks for that it was as I suspected but best to check