shortnose crank update

[K10]

A question for all the mechanically minded out there:

If the pulley is locked (using your custom tool) and you tighten the bolt, you are twisting the crank clockwise and by reaction, the pulley anticlockwise, putting your repair under pressure.

Whereas if you leave the pulley free, and tighten the bolt against the (almost) immobile crank, then you are possibly putting the repair under less pressure (the key is not necessarily taking all the strain of the tightening effort).

Does this make sense? The torque setting should still be reliable, since the crank can move a little but the torque is being applied actoss the bolt-crank joint still.

[Geese]

Ssssshhhh K10

[Steve]

That sounds right ... put the car in 5th gear to torque it (I remember we had an issue with Robin's auto for this reason.. ).

[ger]

here is the crank pulley in place with the bolt locked down to 95 foot pounds, the factory spec is 87 foot pounds but from reading discussions on this topic 95 seems to be the agreed best torque to use without damaging the key.



I am following Harry Sue's right up on this one and he used the crank tool and got 30k out of his repair. His crank shaft oil seal gave way and dissolved the loctite 242 he used. 243 is now the preferred compound for this repair as its oil resistant.
30k to me is 5 years driving as its not a daily driver. I'd be happy with that.

[K10]

Looking good Ger - you've got the hard part of the job done. Did you replace the crank seal also?

[Steve]

Class job! Be sure to hang on to that crank tool, all those with Autos doing a cambelt change will buy you pints for it

[ger]

If the pulley is locked (using your custom tool) and you tighten the bolt, you are twisting the crank clockwise and by reaction, the pulley anticlockwise, putting your repair under pressure.

It's a quite a while since I have tried my hand at applied maths but assigning only two forces to this complex system is a little simplistic.

Your right that there is a rotational force imparted on the crank by the bolt turning in the crank but there is also a counter force, the friction or clamping load between the back of the pulley and the crank shaft. Remember when you pulling 7000rpm this is what stops the pulley turning not the key. Think of tightening a nut onto a bolt normally the turning force on the bolt can be seen at lower torque, as the back of the bolt clamps you no longer need additional counter force to hold it in place.

So as the clamping load or friction overrides the turning force imparted on the crank the tool serves to lock out the crank also.

there are many other forces at play here. Some oblivious ones are the back lash of the crank a small force working in an anticlockwise direction (car was in fifth just in case the tool gave way), the clockwise force of the bolt shoulder which is cancelled out by the locking of the pulley, right down to the friction of the bolt and inner crank threads, this will effect the final torque of the bolt.

Although it maybe better to give each method a go as a guide to the next victims.

ger

[K10]

So, did you get the job done this weekend? Itching to know how it went, so I can get stuck into mine next weekend.

[Geese]

good too see the crank tool fitted ok.

I see that you had to modify the alternator part of it.

If you get a chance return it to me so i can make a final drawing of it and have it ready for the machines to make should anyone else need one.

[ger]

So, did you get the job done this weekend? Itching to know how it went, so I can get stuck into mine next weekend.

Its still as in the pic. The loctite 660 takes 24hrs to dry. I couldn't get anything done on sunday or today. Hopfully i can get a few hours to rebuild on tues or wed.

I see that you had to modify the alternator part of it.
If you get a chance return it to me so i can make a final drawing of it and have it ready for the machines to make should anyone else need one.

Yeah had to cut it quite a lot really, but got it to fit in the end.
I will drop it up to you with a spare pulley later in the week. Handy for all those auto's, you could make some money selling them across the forums.

Thanks again for your help, hope to see you soon.

ger

[ger]

Eureka!

Put on the outer pulley with the crank at TDC for piston 1.
Here is how the timing marks lined up. Its was at 12 degrees before the repair.



Now its just a matter of the crank bolt staying where it is.

[Steve]

You should frame that!

[ger]

I might just do that, still smiling, what a relief.

I put the 2.5" SS cat back on while I was waiting on the repair to dry, cant wait to get the timing belt back on and give it a lash.

Question, at what point during the timing belt re-assembly can I start the car to check the belt alignment. Do I have to have the rad back in or the alternator belt on?

I did it with kamen the last time, well he did most of the tricky stuff and we still managed to get it a tooth off the first time around.

Don't want to have to put it back together twice.

Ger

[Steve]

unfortunately you'll need to reassemble.. (incl intake tube + the airflow meter wiring)

[ger]

Sorted.

Cam belt on, power back, vacuum 22hg at tickover and a sweet burble from the exhaust.

Just getting a chance to try out the hard dog too, really stiffens up the car, feels like it has a hartop with the roof down.

Now onto ditching the AC…

Many thanks for the help and advice.

K10 what do you want to do about the crank tool and the loctite?
If you want to give me a call, I can go through the set up before the fix.

ger