The Manhattan Project

[911hillclimber]

Good to read, and good to read about the gas tester too.
I've used the Gunson Colour-Tune for my carbs to good effect.

Always satisfying to get a result from your own handy work.

[AndrewSlater]

Now that the engine runs reasonably well, I wanted to adjust the clutch.

I'd spotted that if I engaged first gear even with the clutch depressed the car would pull forwards, so expect the clutch to need a tweak.

I tweaked the clutch arm adjustment a few times with no joy until I ran out of adjustment.

Now I know that when I originally fitted the clutch arm I had trouble understanding the settings in the manual.
However I thought I had finally understood it and set it right.

Thinking that the arm was possibly on the wrong spline, I took it off and moved it back a spline.
This gave me more adjustment on the clutch but still no matter how much adjustment I add the clutch still doesn't disengage correctly. The clutch pedal seems quite heavy ( it is definately not a light operation ).

I have also tried turning the engine by hand and then putting it in gear to confirm I can't turn it, and then depressing the clutch but it is definitely not disengaged.

So at this point I am running out of ideas to try ( other than a complete engine drop to check the clutch installation!! ).
It seems like another step backwards.

Any suggestions are more than welcome.

[911hillclimber]

Suggest you check if the clutch actuation fork (goes about the thrust bearing) is in the bearing slot and not outside of it?

Really hard to see with the engine in place as your only access is the cast hole on top of the box 'bell housing'.
It might be felt by disconnecting the cable totally. Move the arm (I assume it is the one piece arm) to check the play radially. If the fork is correctly in the bearing slot I think the free play will be about 6mm. If not the play could be zero as I think the fork will be jammed between the thrust bearing face and the inside of the bell housing, up against #10 in the diagram below.

Forgive me if you know all this already!

It has been a LONG time since I made this mistake, so I may be wrong, but it is very easy to 'miss' the fork into the bearing slot mounting the box onto the engine.

In this diagram, #3's fingers locate into #9's peripheral slot.

[Gary71]

I made the error Graham refers to putting my engine back in last time. So easy to do. Had to come back out...

I’d be surprised the clutch works at all though.

[AndrewSlater]

Thanks for the feedback gents.
The clutch arm does move through an arc but there doesn't seem to be any change in the grab on the clutch.
It seems to be in a position where it is slipping.

I've checked back through photos I took at the time but don't have any of the gearbox being mated.
Only this one that shows that I fitted the clutch plate the correct way around.

And another just before the gearbox was fitted.


I guess the next step is to get my endoscope out and see if I can view inside the bell housing.

I'm not sure I can contemplate the thought of an engine drop.

[911hillclimber]

Yes, an endoscope will quickly tell you a lot, but will be a tricky thing to get into the top inspection hole.
Getting the fork in the slot has to be done slowly, so easy to mis-engage it.
The engine tinware stops poking it down from he back of the engine unless you drop the engine bar off the mounts so giving a gap between seal and tinware.

Another thought is the travel of the clutch pedal. Is this impeded at all? I think you changed the shaft bearings etc so best check that lot before dropping the engine?
The fact that the pedal is very heavy and that some clutch release is found makes me wonder about the pedal travel.

On my 73T the pedal can travel a very long way with the cable off the arm at the box end, a good 150mm at the rubber foot pad from the 'up' position.

Also, is the cable free to move within the tunnel, ie is it's run straight or blocked? (esp at the hand brake/throttle lever areas.

Good luck, I know how this feels from personal experience, Gary too.

[AndrewSlater]

I can get the endoscope to the top inspection hole but I can only see the side view of the flywheel, impossible to manoeuvre it to see the clutch release bearing.

I have checked the pedal and the movement is full. I can pull the pedal up to the top where it stays. If I give it the slightest of nudges the helper spring pulls the pedal all the way until the pedal hits the bulkhead/floor. Pulling and pushing the pedal it is all smooth and this travel gives approximately 30mm of travel at the cable end.


I've currently run out of ideas so am starting to prepare for an engine drop.

[Gary71]

With the cable off at the gearbox end what does the lever do? Can you move it back and forth?

[911hillclimber]

As above, it should move about 6mm due to the clearances in the fork/bearing and the slight play in the arm/splined shaft combined, might be less.

So,
pedal is free
cable is free to move
if the play in the arm with nothing connected is about 6mm...
then it looks to be drive train out and check the fork in the bearing.
If that looks right, then box off and check the shaft in the box is free to spin and not partially seized/restricted. If the box has been rebuilt, then the shaft will move really easily as much as the fork will allow.

Just one other very remote thought.
The clutch cover has 3 tapped holes by the starter ring used to 'jack' the cover off the flywheel if it won't shift. I've never had cause to use them but are there any bolts in any of them from the strip-down? I expect you fitted a new clutch cover so this would be an irrelevant comment.

[AndrewSlater]

There was no free play in the arm.

I am on holiday this week so I took the plunge to try to drop the engine and correct the problem whilst I had a chink of time to throw at the problem.

I can't believe it was May 2017 that I was fitting the engine.

Despite the past experience I don't seem to have got any quicker at this, but after about 4 hours with help from my son, the car was back on axle stands with everything disconnected ready for the drop tomorrow.

The good news was that the oil looked very clean and free from any metal flakes - I even managed to catch some of it before it poured onto the floor. At least the floor won't rust now.



I expect it to be a busy day tomorrow.

[Gary71]

Really hope it’s something simple.
Best of luck

[911hillclimber]

Looking forward to the solution!
No play in the arm still has me thinking the fork has missed the bearing groove, or I will learn something new tomorrow.

[jjeffries]

On my 82 SC, the actuating arm and the clutch pivot shaft have matching reference marks (punched dots) to ensure correct alignment. My omega spring failed recently; the marks made the reassembly easier. I'm not sure if these are factory or were added by someone during the car's life before me. Hopefully your SC has them too. Best of luck, John

[911hillclimber]

I've assumed the arm on this errant car is a single piece arm, but could be the sprung arm?

On my 3.2/1985 box I have the spring assist multi=piece arm and no dots anywhere, but makes quite a difference to the pedal load.

[AndrewSlater]

Time to work on the car has been limited in the last few days, but we did find a couple more hours to drop the engine.

I'd made the mistake again of jacking the car high enough to give 33" of clearance at the rear to get the engine out, and then realising the engine was higher than my jack stand could reach.

Next time I must remember to jack the car up enough to drop the engine first and then further jack the car up to 33" to allow the engine to be manoeuvred from the shell.

As it was pretty late when the engine was dropped, it was left untouched until today.
After attending the BS Motorsports Autojumble we returned to recreate our photo from January 2015. It looks like the car has shrunk since then!

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The gearbox was split from the engine and found the clutch fork wasn't on the release bearing.
I also notice that the bottom prong seems to have a ripple and bend in it.
The damage is possibly from pushing the clutch pedal with too much force whilst trying to diagnose the problem.

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Having spoken to Johnny Hart at today's autojumble and hearing of his story of a failed clutch fork, I had already decided that I should probably change the fork. Now that I have seen the ripple in the fork I have a new one on order.

Just need to wait for the part to turn up now.