pistons and valves contact

[Europa88]

With respect, if you don’t understand that the cams should not be rotated independently… you really need to seek professional advice from an engine builder. Many knowledgeable people, as HCA and others have indicated have said ‘Do not rotate the cams independently’ I don’t really understand why you would want to try this. Anyway good luck!
BTW you do realise that swapping existing shims to get clearance is madness.. it will never work. Check the gap with a feeler gauge and THEN calculate the correct shim clearance.
I’m beginning to wonder if this post is a wind up!

[checkrail]

With reference to Brian Buckland's book page 366 he infers that if the first cam has all valves closed it is safe to turn the second cam, with the head on the bench

John

[HCA]

He is correct. His defining words are ‘on the bench’.

Your wording indicates your head is on the block. Two things here: how sure are you that all valves on one bank are shut, and what is the position of the crankshaft? There is only a brief moment where all valves are shut - a small rotation is enough to have one valve open enough for a clash. If the crankshaft is N-S, then you will have valves hitting the pistons…

Again, align everything and connect the chain. But maybe a good idea to remove the head and check you do not have any damage to the valves…

[Europa88]

If the head isn’t on the block, it should be easy to flip the head when the cam binds and look at the valves to see if they are touching! I am sure they will be. Otherwise… all advice as HCA says

[2cams70]

Just set the clearances with one cam installed at a time. Simple. Don't bother with that rubbish about rotating one of the cams so all the valves are closed on that side and then setting the clearances for the other. All too hard. Keep things simple.

[checkrail]

Perhaps I should explain that because of my age and lack of height and weight I cannot lift/move the head with the cams in place.
So when I remove the head from the car I lay old cushions etc on the wing and do it in two stages, replacing it is worse because of lifting it over the studs. A block and tackle is the answer but I haven't a suitable girder to use.

John

[elanman999]

John,
Yes I have the same problem, those bits of the engine just keep getting heavier.

I use my engine hoist to remove and replace the head.
Cheers
JohnE.

[checkrail]

Thanks to 2cams70 I followed his advice and sorted the shims, I rotated the engine but the Inlet cam needs adjusting its too far out, I don't expect it to be spot on

John

[checkrail]

Back to square one, I can only rotate the engine approx. half a revolution before it jams, so it's head off again. There must be a valve/piston contact this time.

John

[rgh0]

It is still not clear that you understand that you cant rotate the cams independently if both cams are installed. They must be timed correctly and being turned by the engine timing chain so their valve opening and closing is syncronised with each other and the pistons

You also cannot rotate the engine if the cams are installed and they have not been timed and the engne is also turning the cams.

If a cam is installed it always holds at least one valve open and this will interfere with the other cam's valves and the pistons if the timing chain has not been set correctly. There is no postion of a cam where all of that cams valves are closed.

If the engine turns freely when the head is not on and the individual cams can be installed one at a time in the head and turned to operate that cams valves when the head is off the engine. Then it is likely you do not have the cam timed correctly if it jams when the head is assembled.

Posting photos of what you are doing and showing the cams and timing chain setup and how you have timed the cams would make it clearer what is going on.

The only other way the engine can jam when the head is installed is that you have insufficient clearance between the piston and the head.

cheers
Rohan

[Europa88]

Rohan is spot on with all his advice!

I would check that after removing the head, you have full rotation of the engine before doing anything else to rule that out.

"If the engine turns freely when the head is not on"

As alluded to by Rohan.

Cheers
Neil

[checkrail]

When the head was off a few days ago I had full rotation of the pistons.
I am unable to post photos, sorry.

John

[promotor]

When the head was off a few days ago I had full rotation of the pistons.
I am unable to post photos, sorry.

John

John,

Perhaps there is someone nearby who may be willing to visit you and to offer help / advice and get you back on track.
It's really difficult to diagnose what's happening and help you over the internet!

[Hawksfield]

John
You could try and locate lotus owners near you. Especially club lotus
There is quite a selection of groups for lotus listed for Lincolnshire
Hope you get help.

John

[alanr]

John,
Firstly some basics.
Head on bench, with only one camshaft at a time fitted, with a spanner on the sprocket do the camshafts/valve etc do all valves rotate freely and appear to open/close/seal all ok?
Note:-You must have only one camshaft fitted when you do the above!
Now without the cylnder head on and a spannner on the crankshaft sprocket check the pistons all go up and down freely?
If all the above is all ok then it should prove that nothing is bent or broken and that the problem is one of the way you are timing the camshafts on assembly.
So..
Fit the cylinder head with no camshafts installed.
Ensure crankshaft is on TDC.
Ensure chain tensioner is fully slackened off.
Without rotating anything fit the exhaust camshaft with No4 cam lobe pointing lobe inwards, correct Ex marked sprocket fitted and pointing to the centre in line with timing chest and then fit the chain over that sprocket.
Now, again without rotating anything, fit the inlet camshaft with No4 cam lobe pointing inwards and with chain over sprocket and aligned to centre and lined up with the exhaust sprocket.
Then roughly take the slack out of the chain tensioner and check that the camshaft sprocket marks are still in line with each other, they will in all probability be a tooth out, so slacken tensioner off again and move cam and sprocket ever so slightly and carefully as appropriate and then roughly at this point again re-tension the timing chain.
Double check everything again before trying to rotate/turn anything.....Check that you are on TDC and have both No4 lobes inwards, both camshaft sprocket marks pointing to each other in alignment with each other and top of timing chest and with the chain roughly tensioned correctly.
If all the above is good you should by now be ok to turn engine over with a spanner on the crankshaft. Do a full rotation and double check again that all marks..TDC and camshaft marks are all lined up as they should be.
Do a final tension of the chain and check all once again.
Fingers crossed, all should now be good.

Alan.