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Stubborn con rod bolts

Started by steveale, 05 Jul 2015 at 20:20

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1913 2 3/4 engine dismantle.  Have the case apart and one connecting rod off but the other is being a stubborn mule.  the square heads on this one were a bit mushed sometime in the past.  Locking pliers have been futile.  I have penetrating oil doing work.  Was afraid to use heat but may have to as a last resort.  any other "tricks"?  don't want to break anything as my access to spares is very limited since I'm in the usa.


About the best way to move forward with a bolt or nut that is damaged and will need replacing anyway is to weld another one onto it and use the flats on that.
The heat of welding should break any seizing too.

In the meantime...
- have you removed one bolt ?
If not, and the eye has distorted, that may be pulling the stuck bolt, so removing one should make the other easier, or so I have found  :wink:
I have just recovered a big end that had ovalised by carefully squeezing in a vice, but that would be difficult with it in situ ! However it's worth checking.
- and have you squeezed shut the split end ?
That also helps a bit.

I'm just repairing a '3 2+2/4 myself !
Bronze for new shells is in the post.


quick update, got it out but had to get a machinist help.  Had to flush drill out the con rod bold head and remove the cap from the rod.  Then get on both sides of the remnants of the bolt and "coax" it out.  Rod is saved, threads are not damaged but will need to use one of my precious spare rod bolts. 

I am exploring having new rods & pistons built for my cannonball run, the challenge is finding someone who can make 0.375" wrist pins and also make the conrod/piston offsets required.  If I find a source I will post it up.


If you are getting new rods and pistons made, you could always make the gudgeon pin a bigger size and make the rods to suit


Smashing idea graeme...that's why I love this forum!  I did find a manufacture who thinks they can make pistons and rods to original spec but I'll keep this idea in the hip pocket.  I'm going to post again over in the parts wanted page, still need some spares although I have a bunch already.


          Wrist pins can be made from engineers dowel pins. They are good quality case hardened steel. If using them with alloy pistons, buy longer pins and cut the ends off - the softer centre can then be drilled to take bronze end pads. Also, if trying to re-use old pistons with worn wrist pin holes, you have the option to go up from .375" to 10mm.


I think this stuff is called "linear shafting" in Australia - hardened and ground on the outside but "soft" inside. At the recommendation of an engineer friend I have used this for gudgeon pins on some of my early engines. In a coincidence last night I came across someone on the web telling all who would listen that they had used "silver steel" to make a gudgeon pin. Now silver steel, I'm told, has rather poor core strength and is likely to shear more easily than some other steels. It's a no-no for spindles, and possibly no good for gudgeon pins either. The moral is to make sure you use appropriate steel for the components you make or have made. If in doubt ask (twice!), or look up "Radco".


Yes Leon,
               I'm in agreement - silver steel is a very poor material for making gudgeon pins. The main criteria for gudgeon pins is that they should have a hard, ground finish with a tough core. This is not normally obtainable with Silver Steel. Hardened Silver Steel is great for making punches etc. as it has a high compressive strength, but poor shear strength (a quality which is imperitive in items such as gudgeon pins). The damage resulting from a failed gudgeon pin has to be seen to be believed - one of our sprint lads had the pin fail on no.2 cylinder on a 1300 Suzuki - by the time he stopped, the flailing rod had completely taken out the barrel and crankcase (and the frame tube below it) - no1 cylinder was left attached to the rest of the engine by just the cylinderhead!!



I did once partially nip up a piston, but so far I've avoided any serious bangs, thank goodnees. Nothing I have goes fast enough or has enough power to blow up, touch wood.