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First shake down on 72 cp


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Hi all

I have just taken my 72 out for its first shake down after buying it and doing all the jobs I could do,the car wasn’t drivable when bought but it did start,although it runs lumpy I was anticipating that.My question is gearbox related,the gears 1 2 3 are quite hard to engage,first is hard to get even when stopped at traffic lights, is this a normal thing (first TR6 I have owned) for this model car.I might add that this was quite a long test drive (given the miss fire) and the car was well warm,also what would be acceptable oil pressure at tick over when warm. Any thoughts/comments would be valued 

many thanks as always nige

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Might need to check how much throw you get from the clutch slave cylinder, to see if its fully disengaged the clutch, quite common with little bits of wear in clevis pins and peddle bushes etc. 

At a tick over of around 800 rpm, on an engine that's not been rebuilt probably 20 - 25, oil, oil filters, bearings and pump and the gauge itself can all affect what your seeing. 

Gareth

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Yep, probably a clutch issue. Might be as simple as a bleed, or more difficult a slave and/or master cylinder. All pretty straightforward and relatively inexpensive.

Oil pressure hot at idle as noted by Gareth. Above 2000 with the engine hot you should have over 50psi, preferably over 60 but 50-60 is OK. The book might say 40-60 but at 40 you are losing a lot of oil around the bearings etc.

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Hi Nigel,

Oil pressure warm as indicated above.

my reconditioned GB is also very stiff. Almost impossible to engage 2nd gear when cold. I hope it will improve with more use.

Waldi

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Well done!  In my experience of a couple of TRs, gears 1, 2 and 3 can be hard to engage when cold but improve once warmed up.

If the gears are still difficult after a few miles driving,  suspect clutch disengagement as above.

Nigel

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Gearbox can be a little notchy. Certainly don't expect modern standards of smoothness. Also, if you have it, the OD combine with the 6's torque mean you can keep changes to a minimum. For example my 6 will happily do 30 mph in 4th OD flipping to 4th when required. Same game can be played with 3rd and 3rdOD in slower traffic. 

Tim

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When you say difficult to engage, do you mean it grinds the gears, meaning the slave is not opening the clutch up enough to clear the plate, could be rust on the plate causing drag, could need bleeding, travel of the slave cylinder rusty, or perhaps broken pin on cross shaft.

Does the gear lever move easily into out of gear without the engine running or is it the same?, could be rusty selector rods perhaps,

John

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Hi John

have just raised the car back up on stands to re,bleed clutch,the master cylinder , slave cylinder and rods are all new (Moss).when cold 123 have to be really forced,(stationary).after ten or fifteen miles 123 still very clunky to get in even when on the move,double declutching was still hit and miss when going down and still hard to get 1 when waiting at lights.Slightly more success if I selected 2 and then tried 1 again??

nige

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Doesn't sound right. On mine 1 or 2 can be a little baulky initially but not like yours sound. 

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Is the slave cylinder bleed nipple at the top or bottom position, it doesn't bleed well if it's at the bottom.

Is it mounted the gearbox side of the plate it secures to?

Do you have a .70 or .75 clutch master cylinder?

Are your pedal bushes shot?

How far out does it throw the clutch release arm? 

 

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Make sure that you do not have GL5 oil in your gearbox- it plays hell with the synchros. I had it put in my gearbox by mistake once and it's operation  quickly turned to awful- needed to double de clutch etc. Two flushes with  GL4 and it was OK again.

There are a lot of opinions on gearbox oils in these pages- take your pick but don't use GL5.

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On 6/8/2021 at 11:48 PM, Tim D. said:

Gearbox can be a little notchy. Certainly don't expect modern standards of smoothness. Also, if you have it, the OD combine with the 6's torque mean you can keep changes to a minimum. For example my 6 will happily do 30 mph in 4th OD flipping to 4th when required. Same game can be played with 3rd and 3rdOD in slower traffic. 

Tim

I wish mine would do that. I have two TR2s, both potter around at 1000rpm in od, about 25mph. The TR6, 1970 PI, won't play smoothly below 1500rpm. On the flat with a gentle throttle I might get it down to 1450rpm. 

Bottom line, I have to keep the TR6 above 1500rpm. 

 

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42 minutes ago, John McCormack said:

I wish mine would do that. I have two TR2s, both potter around at 1000rpm in od, about 25mph. The TR6, 1970 PI, won't play smoothly below 1500rpm. On the flat with a gentle throttle I might get it down to 1450rpm. 

Bottom line, I have to keep the TR6 above 1500rpm. 

 

Sounds like your PI system needs the throttles balancing. A standard CP TR6 should be able to trickle along smoothly at 1,000 rpm.

Nigel

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53 minutes ago, John McCormack said:

I wish mine would do that. I have two TR2s, both potter around at 1000rpm in od, about 25mph. The TR6, 1970 PI, won't play smoothly below 1500rpm. On the flat with a gentle throttle I might get it down to 1450rpm. 

Bottom line, I have to keep the TR6 above 1500rpm. 

 

Interesting. My breakthrough was fitting an electronic ignition system that allowed me to add vacuum advance. Smoothed out performance at low revs.. guessing it gave more time to burn the lean mixture at low throttle openings. Most PIs run rich so perhaps not a problem.  I’m running a supercharger...

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On 6/8/2021 at 10:07 AM, nigelcurry said:

Hi all

I have just taken my 72 out for its first shake down after buying it and doing all the jobs I could do,the car wasn’t drivable when bought but it did start,although it runs lumpy I was anticipating that.My question is gearbox related,the gears 1 2 3 are quite hard to engage,first is hard to get even when stopped at traffic lights, is this a normal thing (first TR6 I have owned) for this model car.I might add that this was quite a long test drive (given the miss fire) and the car was well warm,also what would be acceptable oil pressure at tick over when warm. Any thoughts/comments would be valued 

many thanks as always nige

 

I would start by checking the throw on the clutch

Look at all the clutch pipework, just to ensure it's all neat and tidy.

Is the fluid clean?  Bleed some from the slave cylinder into a clean glass and check for contaminants

Fit a new slave cylinder . . Not expensive plus it's easy and quick and will do no harm

Be prepared to change the master cylinder

 

The gear change should not be that much heavier than you would find in a 5 - 10 yr old 'modern'

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On 6/10/2021 at 7:55 PM, Nigel Triumph said:

Sounds like your PI system needs the throttles balancing. A standard CP TR6 should be able to trickle along smoothly at 1,000 rpm.

Nigel

It idles smoothly at 70-800 rpm and will idle smoothly at 600rpm, pulls away smoothly, no flat spots and spins willingly to near 5,000 rpm. It is just in the higher gears it isn't smooth pulling away below 1450 rpm. It will pull away just not smoothly, probably more to do with my dodgy gearbox mount accentuating any engine vibration than the PI system.

There is an old saying with PI fuel injection. If it is working don't touch it.

Edited by John McCormack
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On 6/10/2021 at 8:06 PM, Tim D. said:

Interesting. My breakthrough was fitting an electronic ignition system that allowed me to add vacuum advance. Smoothed out performance at low revs.. guessing it gave more time to burn the lean mixture at low throttle openings. Most PIs run rich so perhaps not a problem.  I’m running a supercharger...

I have electronic ignition, no vacuum advance. Mine does run rich but only within specs.

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