Supplied by Barry Ellis.
A Lotus TC article written by a mechanic from Vegantune who has now rebuilt over 5,000 twincams for road and race use. Approved for reprinting from Club Lotus UK Lotus News 1982, No 4 for Barry Ellis – a member of LCQ as well as Club Lotus UK.
Torque Talk
Your workshop manual tells you how to tighten down your cylinder head, but is the instruction correct or complete? I think not.
Set your torque wrench to just 30 lbs ft. Now having tightened all the head bolts down finger tight move around in the sequence shown in your manual cracking the wrench at the 30 lbs ft figure on every nut.
Now up the break figure to 50 lbs ft and go around again in the sequence. Finally, do it again at the 60 lbs ft figure.
After the car has been run for about 5 hours on the road, the time has come to torque the head down once again. So now you must drain out the water, crack all the nuts off their setting and go round again tightening again to 60 lbs ft in the right order again.
Why? Because several head bolts will have tightened up by up to 10% with heat and block/head distortion. Had you just taken a quick trip ‘round the head, cracking the wrench on each bolt you would not have detected one or two which were now at the 70 lbs ft level and ready to stretch or strip.
Now refill the engine with water, let it tick over for a while with the radiator cap off and watch the trapped air come out . Now you can get in another pint or two.
If you have to refill a Europa you need to spend quite a while purging the system of air.
Either park the car facing down a steep hill or jack the back high in the air. Now fill her up and start the engine with the heater valve set to full heat.
If the system has been totally drained of water you will need about 15 minutes to be sure that all the trapped air has bubbled out. On the Europa I recommend having BARSLEAK in the cooling water all the time as they are prone to leaks in the heater matrix and in the tubes that run from front to rear.
You must also remove the heater hose at the thermostat housing and then put your thumb over the end of the hose (or kink it closed) and wait until cooling water comes out of the thermostat casting without a lot of burps or trapped air. There is a vent on the nose mounted radiator. Open this from time to time as you fill the car to let the air hiss out.
WARNING: Don’t let the water temperature get too high before you start work on bleeding – it can be rather painful sticking your thumb over a pipe full of hot water!
Rocker Arm Pillars
WARNING: The rocker arm pillar torque setting is ONLY 15 – 20 lbs ft so don’t go making expensive mistakes! And who said your torque wrench was accurate? Rolls Royce check test all wrenches in “sensitive assembly areas” every day!