rgh0 wrote:For the bolts to fail like shown in the photo it implies the flywheel was not properly clamped to the end of the crank. This in turn implies the bolts were not originally torqued correctly or came loose in service or were to long and bottomed out in the crank thread before properly clamping the flywheel ( seen that one a couple of times). I have never seen a properly torqued flywheel bolt come loose. The fact that the cast iron flywheel shows signs of extended hammering around the bolt holes also says the flywheel was loose for some time and the over rev was just the last straw that broke the already loose flywheel free.
Regardless of the cause of the failure - get good bolts and genuine ARP ones are guarranteed quality. Lots of problems with counterfeit bolts on the market so you need to be careful where you buy stardard high tensile bolts from to be sure they are truely up to specification. The you need to make sure all the threads are clean and check the bolt length to ensure it does not bottom out in the crank. Apply high strength loctite just to be sure and torque the bolts to the required specification in a criss cross patter nad over a few steps of increasing toque with a calibrated good quality torque wrench ensuring the flywheel is fitted snug on the flywheel and clamping correctly . You need to clamp the crank or flywheel some how to stop it turning when tightening the bolts, this is why the bolts do not get tightened correctly often as you cant easily hold the flywheel by hand when tightening the bolts
cheers
Rohan
That's very interesting to know Rohan, thanks. I probably will be doing all jobs like this myself so I can't get enough advice like that. I'm getting a guy called Trevor Addison (Some of you GRRC members might know his name, he mostly rebuilds vintage motorcycle engines) to fit new valves and springs to my head and he's also going to look at the block this weekend. I could do everything myself but I don't have all the tools, knowledge and the confidence yet to do the important/more difficult tasks. I got a very good Teng torque wrench for my last birthday which will get some serious use soon. I'm going to stick a copy of the torque settings page from the Lotus workshop manual inside my toolbox lid as someone on here very cleverly suggested. Once the head comes back and I get the bottom end rebuilt with the crack tested (or new!) crankshaft and con rods, I'm going to refit the engine myself. There are lots of other jobs which need doing before/during refitting the engine. I'm planning to;
Clean up and, in part, respray the engine bay in matt black.
Replace all hoses that are looking slightly tired with Samco classic black ones.
Fit new choke cable (the last one was only connected to one Weber!)
Fit rev limiting rotor arm to optical distributor
Fit blanking plate to mechanical fuel pump mount (The pump was left on even though it has electric fuel pump in boot now)
Fit new Tudor washer bottle and tubing (I think the one in there was original by the looks of it, dark brown!)
Remount ignition coil to sensible place, not directly under intake trumpets of Webers.
Repaint Anti-Roll Bar in Red Hammerite
Repaint Block and head in correct Battleship Grey
Respray Cam Cover in Crackle Black
Grind millimetre or so from bottom of accelerator pedal so it's not touching the Spyder footwell anti-intrusion bar.
There's lots of other bits to do but that'll keep me busy.