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Camshaft impossible to turn also with a wrench....please help - Engine/Ancilliaries - The Lotus Forums Jump to content
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giorgio67

Camshaft impossible to turn also with a wrench....please help

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Hi gents,

another problem here.

I have installed the EX cam and carrier on the head to check the shim but once mnounted and lightly torqued down the bolts the cam is impossible to turn by hand and also with a wrench, it's completely blocked.

The head is on the bench, lifted up on the two side so no probs about valves touching anything.

The valves on the cylindeer N. 1 and 3 are a little open (the N.3 more) but it seems to me that something is wrong.

I have no idea, what could be?

What I need to check?

I don't think a very tigh oil seal can cause this.

Thanks for your help.

Giorgio

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Undo the cam carrier, check all the cam followers move and see if the cam turns OK when off the head. Have a very good look around the cam lobes...it is quite possible that a shim or a washer can fall in and stop the cam rotating by jamming between a cam lobe and the carrier casting. If there is no obstruction and the cam rotates "off the head", check all the valves move....also check that the mating faces of the cam carrier and head are both flat. Then reassemble the cam, carrier and followers to the head and see if it rotates this time.....What else? Have a look at the end float and the screw holding the thrust washer at the front end of the camshaft. Can't think of anything else....work your way through it logically and have a very good look at everything....and you'll find out what it is!! Good luck, chum!!

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Ciao John, thanks for your inputs but:

I've just removed the new oil seal to see if it was the problem, I've fitted the old one in good conditions and the camshaft turns easy and free by hand.

No issue with the thrust washer, and no shims out of position on the valve steam.

So, I've reassembled the carrier on the bench, torqued down the bolt and again the camshaft is completely blocked, no way to turn it.

Buckets are new and are free in the bore, spring and valves can be compressed by hand with a lot of force so I can't understand what the problem can be.

Some pics of the head-carrier, you can see the cam lobes and the opened valves, any ideas?

It seems to me that when I torque the carrier bolts over the opened valves (putting the carrier in contact with the head) the camshaft being blocked.

That's really strange...

I'm stupid? :help: :help: :help:

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post-3419-0-81753800-1365357295.jpg

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What happens if you rotate the camshaft to a different position before securing the carrier down, will it rotate and then become stuck at a certain point?

Will it rotate in the reverse direction (I appreciate the bolt will come undone so you'd have to do it with the holes in the sprocket)?

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Hi Andy,

I can rotate the camshaft in any direction before bolting down the carrier on the head, once torqued it is totally blocked, I'm being mad....

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Giorgio - make sure the shims are not too large - start with your thinnest.  Are the valves genuine lotus or pattern.  Have you had the valve seats cut to excess - I'm just thinking of things that may cause your valve springs or collets to bottom out.  Maybe the guides are fitted too high?

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Did you have the head machined? If so thats the reason I think they should NOT be skimmed. Even if warped.

 

Buddsy

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Oh my god guys!!

Yes, head skimmed a little, new recutted seats, new aftermarket bigger valves from Garry Kemp, new valves, new guides I think correctly fitted.... :realmad:

how can I check all these things..?

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I now believe if a head looks warped it will pull flat when done up on the head bolts. When the heads were machined by Lotus the cam mating surfaces were machined at the same time as the main face so when the cam carriers are bolted on the cams are perpendicular to the main face and the bores in which the cams run are in line. If the head looks to be bent and you machine it flat then when the head is bolted down the cam carriers can no longer in line. If you don't machine a warped head Im sure all will be ok when clamped up as it will pull flat. That's what I think now anyway.

 

Buddsy 



If you remove the cam carriers and put a flat edge along the face to see if they are all level when the head is bolted down?

 

Buddsy

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I would go back to basics - All valves out.  Check fitted heights of valve guides.   I would then test fit valve 1 and see what happens when you bolt up.  What Buddsy says is the next step to worry about when you torque the head down ;-)  

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Just a thought,

the new cam followers are different from the old ones, they had a protusion inside where the shim touches so,

supposing a wrong guides height maybe I can check the part with the old buckets to see if I have more gap?

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Giorgio As Steve says start at the beginning and check every thing. Hope fully it will be something silly and easy to put right.

 

Buddsy

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Giorgio,

 

Skimming the cyclinder face makes no difference, to the shim size,  if it was just a light skimming. I'd say your shims are too big. This happened to me after getting my head re done by getting the valve reground into their seats. The valves sit  deeper in the head so your won't need as big a shim as before. The protrussion on the the tappet is bigger than the depth of the valve head below the spring retainer, so remove all the shims and tighen down the cam carrier again and the try and rotate the cam. it should now turn with only the resistance on the valve springs. you can now measure the gap between the cam and tappet to work out your shim size.

 

The height of the tappet protrussion is around 1.125" and the distance from the Spring retainer to the top of the tappet is .600".

 

Cheers

Dave

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Hi Dave,

already tried without ANY shims and the camshaft is still blocked, I do not want to force it as it needs tons of torque to be rotated....

Desperation....

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Just a thought,

the new cam followers are different from the old ones, they had a protusion inside where the shim touches so,

supposing a wrong guides height maybe I can check the part with the old buckets to see if I have more gap?

 

If you bought the newer steel followers, then they do require a different thickness of shims.  I had to make a bunch of dummy shims in order to get proper measurements when I replaced my old cast iron followers with the new steel nitrided version.

 

I'm guessing you have the head of one of the bolts, for the cam tower to head, is interfering with one of the cams ability to rotate...

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Giorgio - are you accustomed to turning a camshaft against valve pressure?  It does require quite a bit of torque...

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If you have fitted new steel followers it is worth checking the skirt length.

they are longer than standard on some and can cause this problem.

simple check..

next check is the guide length...

Anything that has been  changed or altered will need a compatibility check .

including overlap timing when running large valves.. 

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Looking at the photos, I can see no sign of any lubrication? Not sure, but with the loads exerted by the valve train it may well be very difficult to turn the cams without bags of oil everywhere. I've always used a spot of gear oil on the followers and camshaft and the cams will rotate on their own as you bolt the carriers down, until they reach an equilibrium position. Otherwise, it does sound like the camshaft is being pulled out of line somehow, distorted head face or cam carrier face imposing bending loads on the cam.

Edited by molemot

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Hi John hi guys,

today I have visited my head machinist, he's an engine builder too with 35 years of knowledge so..

he has been able to solve the problem in about 3 minutes.... :fun:  great man!

Now just seen the John post:

.....and camshaft and the cams will rotate on their own as you bolt the carriers down, until they reach an equilibrium position. Otherwise, it does sound like the camshaft is being pulled out of line somehow, distorted head face or cam carrier face imposing bending loads on the cam.

That's exactly the issue, he told me that the alloy carriers ,even if not warped, are always a little bit out of flat so you need to torques down the bolts while turning the camshaft and with a precise procedure starting from the centre versus side.

He carefully torqued down the carrier on the head checking the rotation and the bolts, two minutes job and after all the bolts have been torqued down the camshaft turns free and easily in the carrier.

No probs about guides, spring or other head components just an experienced men and a great skill.

Thanks for your advices and help, now I can continue to shim my buckets!!!

Giorgio

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Glad you sorted that out, Giorgio....I quote the service manual..."Tighten the fasteners to the specified torque, loading diagonally outwards from the centre".....

Don't you have the manual??

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Indeed, that's v important. Cam covers will distort badly if not tightened to the correct torque in sequence. Bearing in mind that you'd probably fit and remove the carriers several times in the course of shim setting, it'll pay to look after them.

But also tighten them gradually in stages - rather than tighten the centre nuts fully before moving onto the next ones.

 

If you set the cams so that cam lobes on cylinder #1 are 'on the rock', as you place them onto the head, it seems to give the carriers a more level starting point.

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I had the benfit of a Rolls Royce factory trained Grandfather who would look at me desparingly, roll his eyes and suck on his pipe if I didn't tighten EVERYTHING diagonally....also such things as lining up screwheads....a useful apprenticeship, but hard going when you're 9!

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Hi guys,

so, finally fitted the new camshaft seals (thanks Garry...), fitted the shims on the EX valves to check gap and found that

I have only two valves with 0.35 and 0.40 mm clearance, all the others have 0 clearance (the 0.05 gauge does not fit).

Is it normal after an head rebuild,new cams parts etc... or it's symptomatic of something wrong?

I need very thinner shim, under 2 mm to adjust them.

Thanks

Giorgio

 

PS: some pics of my shims set.....I'm totally nut..... :fun:

 

 

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