Engine mount box section query

[brainbug007]

If you're making the custom engine mounts described in the book for non-pinto engines, personally i'd go for the bigger stuff as by the time you drill the hole for the bolt and then put the lock nut on, it doesn't leave that much space to get a spanner/socket in there to tighten it up. I'd also go for 3mm personally as I would think 2mm could end up bending under the weight & twist of the engine?