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Re-building engine

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Gooday all you helpful guys,

I'm about to order shells, gaskets and want to include everything I should replace like for example nuts for big ends, there seems loads of parts I could replace but could anyone list the vital parts I should replace? Many thanks jim

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I suggest proper new tab washers for crank. New crank bolts in case you torque them to the wrong setting. At least one version of the Haynes Dommie manual has an extra 10lb.ft.

Locking wire for tappet retainers. I thought the books recommend big end bolts should be changed, not just the nuts.

Also if you are really keen,  some of those plastic mesh pipe sleeves to protect the edges of your con rods against Nick's from the edges of the cases.

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in the Commando service notes (I believe from John Hudson) which suggests filing off the sharp edge on new big end bolts as it can raise a sliver of alloy on the conrod leading to failure.

I would put new crankshaft bolts & nuts and the same for big ends. Failure is expensive.....

My Haynes says 15 ft/lb 500s/600s, 25ft/lb 650/750s - but I snapped a big end bolt once relying an earlier Haynes edition.

Lucky it did snap, the ones that hadn't snapped were seriously overstressed.

I did research this and there is no metallurgical reason not to re-use old bolts that I could find.

 

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It's the crankshaft bolts that Haynes have wrong in my 1974 edition. They say 35 lbs.ft and it should be 25.

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I’m just about to rebuild my crankshaft, so just to be sure, what is the correct torque figure for the crankshaft nuts on a 600cc engine? is the torque value 15 foot pounds or 25 foot pounds?

Thanks

Regards

Tony

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Crankshaft nuts 25 lbs.ft.

Big end nuts, 15 lbs.ft for 500 and 600

And 25 lbs.ft for 650 and 750 (which have bigger journals than the 88 and 99 engines)

( Haynes had wrong values for crankshaft)

 

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One reason for not reusing the crank bolts is the threads may become galled during disassembly due to the nuts having been staked originally.

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and as it's the "springiness" of the steel that keeps them done up another reason to fit new. Assuming of course you can get the genuine article - I'd go for Andover Norton for these if they have them.

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I worked on a modern Astra engine, where you tighten bolts up to a certain torque, then another 120 degrees. Feels horrible as they start to permanently stretch, as they were designed to do. Single use bolts.

No classic engine design worked like that, they spring back to exactly their original length. I doubt there is any change to the crystalline structure over time either. I couldn't find any source that suggested it anyway. 

If they cycled like a valve spring, that would be a different story.

I used new ones of course!

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New gudgeon pin circlips, valve springs, spring washers. Do not use Ebay stainless engine bolts, most are made from free cutting stainless S316. They stretch and have no real tensile strength. I always try to find bolts that are old stock Landrover, or Jaguar XJ6/XJS. I have a lot of high tensile S98 material in my odd box originally used for helicopter bolts. Good for making any new bits I cannot find easily. I have 50metres of 16mm high tensile studding which is good to turn down for smaller studs/ and or bolts. I also buy gasket material by the roll to cut out new gaskets. Try Les Emery at Cannock for flywheel bolt sets, he usually has everything, and is very helpful. Using non standard flywheel parts will alter the balance factor to some extent. The vibration might be better, or worse. I once ground a BSA A10 crankshaft all over as it was not straight, it vibrated worse than ever, but the fuel consumption was really good, over 60mpg with a sidecar on a 4500 mile trip around Scandinavia. I got the same mpg out of a N15cs on a 4000 mile trip around France and Spain solo. Check the valve heads are square to the shaft too, and the seats are not pocketed.

 

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