Gudgeon pin

[12jslater]

I'm about to undertake replacing my cars Gudgeon pin clamping bolts (all four as a matter of caution as ones failed) do torque settings matter or is "good'n tight" fine? Also when I'm having them out is there anything in particular to look out for on the little ends?

[David Stepney]

Being unfamiliar with the Big Seven engine, I can only give general advice, but I suspect that the clamping arrangements are similar to that found on the more 'normal' Seven engines.

1. Ensure that there is  no 'rock' between the gudgeon pin and the piston and that the pin is a good fit.
2.  Check the little end of the rod for any signs of damage or cracking. Any small burrs can be dressed with a file, but make sure that the pin is a snug fit in the rod eye and that it clamps up tight.
3. Make sure that the thread in the end of the rod is in good condition and that the clamping bolt screws in easily. I chase them out with a suitable tap (probably 1/4in BSF)
4. Ensure that the cutout in the pin is perfectly aligned with the bolt hole. Failure to do this by a previous person caused failure of a little end on my own car.
5. Use some threadlock (I use Loctite 222)and do the bolts up ,as my first boss would say, conveniently tight. Remember that they are (probably) 1/4 in BSF so 'murder tight' is not an option! If you pull the thread, or even worse, snap the head off the bolt, the remains are difficult to get out again.


Hope this helps

[Bob Culver]

The tightened pin must move easily in the piston.
Many report cracks extending down from the machined cut. The hole would normally be correspondingly worn but if not it would seem for moderate use a waste to scrap an otherwise good rod. A hole could be drilled just beyong the true end of any crack.The pinch bolt is supposed to be of special stuff. Ordinary 45 ton HT were labelled R and S was grade higher. I dunno what is avialable now. Allen key screws are genrally of tough stuff. Any bolt which has run not tight is at risk of fatigue failure.