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Esprit Turbo project car - part3 - the further continuation


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In Lotusfabs defense, there does seem to be some black magic (or unaccounted variable)  in the valve clearances. The engineering view would be once the clearance  and the existing shim are well measured, do the maths, swap the shim and job done!  But-  it often seems to take even experienced builders several cycles for each cam carrier.  

(Or perhaps generally we won't accept less than the exact clearance? Another issue entirely)

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A set of these is being made for me with the straight side reduced by 1/2 inch to aid fitting.

http://axminsterspecialistpanels.com/fuel-petrol-gas-tanks/lotus-esprit-tanks/

 

IMG_6547.PNG.f5ef6b2e1ca4e8d5a6f8e18527cf2696.PNGThese arn't the exact Turbo tanks. I have taken the originals down so they can be copied exactly.

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17 hours ago, snowrx said:

 

(Or perhaps generally we won't accept less than the exact clearance? Another issue entirely)

The Lotus service notes specify a range of 3 thou. Specifying a tolerance is good engineering practice and they were good engineers :)

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I'm hoping to get the shims sorted over the next few days the the camshaft holders back on and it should be fairly quick after that to finish the engine. It's then onto the gearbox. There are signs of new sealant so it looks like it has already had work. When I drove the car 2. 1/2 years ago it seems to work fine apart from the gearchange was very poorly adjusted. I have upgraded the entire gear linkage. It has all new pivot bolts and bushes. The bolt pivot that links the two arms has now been replaced with a bearing. I hoping it will operate really smoothly.

I just intend to inspect the gear wheels for chips, check the bearings and seals then change the oil and reseal.  Have a new Nylatron washer and circlip waiting to go back on. The clutch looks like the pressure plate is new and the release bearing has been replaced. I've been lucky with some parts of this car. There had been a significant amount of money spent on it. Hopefully it will be pretty tip top at the end. Looking back through this thread I think I have replaced just about everything that can wear! Should outlast me! 

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Here's a pic of the Internet if the gearchange selector.IMG_6529.thumb.PNG.e9fe6c8248097b18f3a5fbc791991a2f.PNGIMG_6531.thumb.PNG.1b26de252871df315516b99ab35f1b23.PNGI the bottom picture you can see where fatigue causes the original thin lever to snap, through the spiro pin hole.  My one now has the new thickened design welded to the thinner upper part. The spring and clip are very difficult to get off so I had the stud pressed out. It took a really heavy duty shop press to budge it. The circlip is 1/4 inch imperial. I am hoping I can reassemble it with the stud back in. The pivot at 30 in the lower diagram has now been replaced with a bearing, using Andys idea. Hopefully it will be much smoother and offer less resistance in operation. I won't be assembling the gear tunnel until it's all adjusted. I have fallen into that trap before! 

IMG_6553.PNG.ed8b93c3c22d010fc3f6c8f805300f57.PNGa

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Having taken it apart and understanding how it works you probably could get the arm out without pressing out the stud. Like all these things without detailed info you have to experiment!

It's not that obvious which way round part 21 fits. I hope I have got it correct! 

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Wait until you do the final tower assembly with sealant and they go out of whack again!    🤨  (Hopefully not!) 

 Gear selector -  I also modified 12 & 15 to use a 5mm rose joint, this removed a fair bit of side to side play and made the 1st gear/5th gear adjustment paradox more forgiving...   

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Yes a rose joint there makes so much sense. They used 4 of them on the headlights so why they didnt use one more there is a mystery to me.

The 29 lever I fitted a ball race to the pivot and bolted the inner of the race firmly to the engine leg. Took out all rubber in the linkage except for the one at the bottom of the lever. The rubber in this linkage seems to have no purpose, there is no additional noise/vibration without it.

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52 minutes ago, 910Esprit said:

Wait until you do the final tower assembly with sealant and they go out of whack again!    🤨  (Hopefully not!) 

 Gear selector -  I also modified 12 & 15 to use a 5mm rose joint, this removed a fair bit of side to side play and made the 1st gear/5th gear adjustment paradox more forgiving...   

I hope they don't go out of whack, will be needing therapy if they do! 😀😀😀😀Yep I forgot to mention that. I have done that mod also. I really hope this project gets some momentum soon. I seem to have been spending more time travelling all over in my car gettting things sorted than actually building it! 

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58 minutes ago, Andyww said:

Yes a rose joint there makes so much sense. They used 4 of them on the headlights so why they didnt use one more there is a mystery to me.

The 29 lever I fitted a ball race to the pivot and bolted the inner of the race firmly to the engine leg. Took out all rubber in the linkage except for the one at the bottom of the lever. The rubber in this linkage seems to have no purpose, there is no additional noise/vibration without it.

Thanks Andy, your good idea is now on my car! 

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Reference valve clearance, I am a automotive manufacturing engineer and have specified, signed off the design, and carried out final acceptance and handover to production of 2 tappet selection machines, both cost over £1m and are still in production today.

The machines measure the cams before they are assembled into the head ( base circle diameter, cam journal diameter and centre to centre distance) and the head ( cam journal diameter and distance from valve tip to cam journal centre) and probably some stuff I have forgotten. The machine then calculates the correct size bucket tappet for each position and walks the operator through a process of filling a mask with the correct tappets, these are then all measured to ensure they are correct before the operator puts the mask on the head and presses the tappets into the head. 

After all this measuring the machine still has a 'fudge factor" built in so each tappet position can be tweaked up or down until the selected tappet gives the correct clearance, although once set over a number of heads the fudge factor remains stable. 

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Thank Steven, very impressive and interesting. Reminds me of mathematical proofs in Physics where a constant(fudge factor) is introduced to make the sums work. When you ask the professor what itvphysically means means they can't explain it, but it makes it all work! 

Despite the earlier discussion in my opinion it's not an exact science, but it is possible to achieve inspec with a bit of effort. When it comes to setting these I have found reducing the shim or increasing it by 1 thou doesn't always translate into the same change in the valve clearance. I think there are many factors at play. But it has been possible with effort to set the inlet clearances to spec within the 5-7 thou range. Now just need to sort the exhaust valves.

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17 hours ago, Lotusfab said:

Despite the earlier discussion in my opinion it's not an exact science, but it is possible to achieve inspec with a bit of effort. When it comes to setting these I have found reducing the shim or increasing it by 1 thou doesn't always translate into the same change in the valve clearance. I think there are many factors at play. But it has been possible with effort to set the inlet clearances to spec within the 5-7 thou range. Now just need to sort the exhaust valves.

This statement runs very true and most of us have had the situation when its needs a thou more then goes too tight..   However 3 thou tolerance is very wide and more for ware allowance than room for error in initial setting..  Yes there are many factors in play , but as the assembler you should be taking these into account.    Setting up the shimming on an outer limit is defiantly going to give you a ticking cam noise, especially on start up..  Not the sort of thing you want to hear on a new donkey..  Different engine builders will have different thoughts where they would set the clearances for any given engine which they will then achieve..   What it really comes down to is the individual and experience / capability / understanding.  As i said before it ain't Lego...   The truth is most of the members who do this have achieved the exact clearance they desire, maybe not straight away , but with persistence they are able to understand how it is done , become more capable at doing it , then repeat the results easier each time through experience..  Some may have employed the help of others to better understand the little things that are so important that sometimes get over looked... :secret: For eg..  On each attempt, mating faces get wiped with tack cloth , each thread on each bolt is oiled and torqued in same order ,and the cam position for each check is consistent with before..  Simple, long winded , very effective but easily overlooked..   Oh and you should be prepared to grind the odd shim to the half thou if needed..     I am sure you will find the exhaust side a lot easier as you develop a method..   

PS if you think its fiddly now ,,  wait till you do it when the engine is fitted in the car. .      :thumbsup:   

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 I have targeted 5 or just above on the inlet, lower end of the tolerance and 12 on the exhaust the higher end. I have accepted 5/6 on the inlet and will accept 11/12 on the exhaust. The reason being I expect the inlet clearances to increase with wear and the exhaust to reduce. For those that have never used feeler gauges before there are lots of good videos on you tube. The resistance felt when you have got the correct guage and pull it out of the gap is equivalent to pulling a sheet of paper from between two magazines, this s what the guage manufacturers say. Also the joint will have to be grease free as this will affect the resistance. You can see why there might be discrepancies. Anyhow I have achieved the clearances I have targeted for the inlets and will repeat them for the exhaust. 

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IMG_6560.thumb.JPG.d5208466691ac7a1c8604f950ce3c4c7.JPGEngine now shimmed and  all inspec, just need to final fix the cam towers.  Much more time consuming than I had anticipated, but now spot on. Here you can see I amin the process of replacing all of the exhaust studs. Slowly coming on.

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Like all the things you leave and come back to I'm having trouble assembling the gear leaver. Should there be two washers(picture above) One in the inside sitting on a rebate, then the spring then the second washer and circlip? Looks like something has been lost from my one! 

Or does the washer go on the top and the circlip hold the spring without a washer? On mine the circlip got lost! 

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Gear lever

To echo Rolls advice do not separate this unless you have no choice. It's near impossible to get the clip back on  without pressing the gear lever holder out of the mechanism. This needs a seriously heavy duty press! To complicate matters do not loose the clip! There are two washers and a clip .One washer inside the holder sitting on a rebate then the spring and then the second washer and the clip. The second washer and clip must be thin enough to move inside the holder. That's my problem. The clip is 1/4 inch imperial. It's C clip. I lost the original and now can't seem to source a C clip that's 1/4 witha small enough diameter to fit the mechanism. May have to make one!

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2 hours ago, Lotusfab said:

Gear lever

That's my problem. The clip is 1/4 inch imperial. It's C clip. I lost the original and now can't seem to source a C clip that's 1/4 witha small enough diameter to fit the mechanism. May have to make one!

You can find this here:

https://www.mscdirect.com/products/clips

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Apart from the normal service items. I'd change the tensioner springs (inner & outer) as a matter of course - not expensive.  I found my old ones were 'tired' and effectively coil bound before they could acheive the correct tension, which then meant that when the engine was hot the belt ran at very tight - solved with new springs

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Another Complecation!

reading the manual it seems a shim may be required between the clutch housing and the engine. Since the lower engine is a replacement I need to check whether a shim is required. In order to do this the sump can't be fixed! So it's seems I will have to get bthe engine off the stand, support it. Bolt the bellhousing on, measure for a shim and then stamp this size on the underside.. then put back in the stand and secure the sump! 

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