03-02-2019, 04:44 PM
(This post was last modified: 03-02-2019, 04:49 PM by Steve Jones.)
The problem with just using a 5/16" bolt and modifying it is that A7 big end bolts are fitted bolts. That means they are of a very slightly larger diameter when compared with an ordinary 5/16" bolt and therefore the clearance between the bolt and the holes in the rod/cap is reduced. Try fitting a proper big end bolt and a normal 5/16" bolt through a rod & cap and compare the fit of the two.
However, the slightly increased diameter of a M8 bolt over a 5/16" bolt overcomes this and opens up a much larger range of bolts to choose from. In an ideal world, I'd hope you find a set of unused, correct, big end bolts, Colin, but I fear they might be a bit like trying to find the Holy Grail. If that does prove to be the case then a set of quality M8 cap heads of appropriate dimensions might be the best point to start from if you have to modify a standard bolt.
I appreciate the purists might shout and scream but my primary aim would always be that the engine holds together and anyway, the above suggestion was given to me by a certain Dr. Rob and if it's good enough for him, it's certainly good enough for me.
Steve
However, the slightly increased diameter of a M8 bolt over a 5/16" bolt overcomes this and opens up a much larger range of bolts to choose from. In an ideal world, I'd hope you find a set of unused, correct, big end bolts, Colin, but I fear they might be a bit like trying to find the Holy Grail. If that does prove to be the case then a set of quality M8 cap heads of appropriate dimensions might be the best point to start from if you have to modify a standard bolt.
I appreciate the purists might shout and scream but my primary aim would always be that the engine holds together and anyway, the above suggestion was given to me by a certain Dr. Rob and if it's good enough for him, it's certainly good enough for me.
Steve