Lotus Elan

ElanSprint Timing Chain

PostPost by: bloodknock » Thu Sep 14, 2017 7:37 pm

Regular readers will know that this restoration has been going on since circa 1973 more off than on!
Well, since retirement I'm getting more on with it!
The block has been assmbled for some considerable time and is now in the car. The time has come to fit the head, I dont have a problem with this except the following:
-It would appear that when I assembled the Block I used a linkless timing chain! Why?, I dont know! Is there any reason why I should not leave this in place other than the awkwardness in assembly? Does anyone know of any serious downsides?
-What sealant for the timing chain case to head cork gasket and cam cover?
-What sealant for the Oil vapour bypass hose head to block?
-What Oil should I use nowadays?, as I recall it was Duckhams Q20W-50 back in the day.
- Is there any reason not to use 4life coolant in this engine?

Thanks
Bob
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PostPost by: vincereynard » Fri Sep 15, 2017 10:01 am

If by linkless you mean a chain that is continuous and cannot be seperated then that is recommended. On the ground of the damage that would happen, in the admittedly unlikely case, of separating in use.

After a number of experiments with RTV and similar I used Wellseal. There is a permatex aviation stuff that is nigh on identical but is thicker and does not brush out as smoothly. Beware of a step at the top of the timing case. Mine was a Burton setup so the standard case may be better fit.

Quality high temp RTV seems the best solution for the breather tube.
I used - http://www.ebay.co.uk/itm/272815089137
because I was given it!

There is an opinion that special running in oil should be initially used. After that there as many opinions as oils! Just not modern, thin 10/40 synthetics. It's an old, oily engine without valve seals.

As for coolant, again there are many opinions. I have heard that the pink long life can attack the solder in the heater rad??
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PostPost by: bloodknock » Fri Sep 15, 2017 6:30 pm

Thanks for the info Vince
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PostPost by: billwill » Fri Sep 15, 2017 9:27 pm

It isn't difficult to get the chain on the sprockets and then the sprockets on the camshafts provided that the tensioner is slackened right off to the point of gently removing the adjusting plunger an spring on the right-hand side of the engine. Though it might take repeating the mounting of the sprockets a couple of times before you get the valve-timing right.

I remember writing out the entire procedure with checks, on this forum some time in the past, but I'm not sure where or when.

So yes indeed the chain with no removable link is the preferred option.


~~~
Edited to fix spelling mistrakes.. no change of meaning.
Last edited by billwill on Fri Sep 15, 2017 9:45 pm, edited 1 time in total.
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PostPost by: billwill » Fri Sep 15, 2017 9:38 pm

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PostPost by: bloodknock » Sat Sep 16, 2017 8:45 am

Thanks very much Bill, i'll print it out.
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PostPost by: MarkDa » Sun Sep 17, 2017 4:43 am

If you have any running in to do then you should use mineral oil until it's complete. This will avoid glazing and allow piston rings to seal properly for decent compression. There are special oils without friction modifiers to allow the right degree of contact. The engine should be worked reasonably hard to make the bedding in happen.
After initial rubbing in it's probably best to use a good quality 20/50 mineral oil for another 1000 miles after which "anything ' cane be used.
There's nothing wrong with 20/50 mineral oil changed annually.
Economically you may choose to keep synthetic oil in for years but if you do as said earlier don't go light, the engine won't thank you for it.
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PostPost by: billwill » Sun Sep 17, 2017 1:25 pm

bloodknock wrote:Thanks very much Bill, i'll print it out.


One thing that might not be clear from my posting referenced above is this line:
Pistons and cams are set at top dead centre.
I had started with the head on the engine and I had positioned the crankshaft at top-dead-centre TDC and had then prevented each cams from rotating (while the head was off) by removing one of the cam bearing caps and inserting a piece of cardboard (from a cereal box) across the bearing and tightening down so that the valve springs won't rotate the camshaft.

Since you are starting with the head-off, you will need to first have it on the bench (valves down) lifted off with some blocks so that the valves don't touch the bench, then putting the correct sprocket wheel on the cam rotate it until the timing mark is level with the horizontal edge of the top of the head (and facing the other sprocket position), then secure the camshaft in that position with a piece of cereal box cardboard on a cam bearing. Do this for both cams so that you start with the valves in their TDC position.

When you have the head in place and are fitting the chain you may need to slacken the card bolts to move the cam a little, but it is important to not move the cams much with the pistons at TDC, because the valve can hit the pistons and if any force it used they might get bent.
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PostPost by: bloodknock » Sun Sep 17, 2017 5:26 pm

Thanks for all that.
The head is supported off the valves by old necked inverted head bolts passed through old shocker rubbers - see Photo.
dsc04257.jpg and

I have built Twin cams in the distant past (Ex Lotus Cortina and Escort) Hence the necked bolts.. It was a long time ago and I just want to be sure taht I get it right.
As I understand what you are saying, make sure the inlet exhaust and TDC marks are lined up with the timing chain in tension from the exhaust sprocket to the crank sprocket and across the inlet and exhaust sprockets. Just to be clear see diagram.
fullsizeoutput_1ce6.jpeg and
dsc04253.jpg and
dsc04254.jpg and

I hope you are in agreement.
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PostPost by: billwill » Sun Sep 17, 2017 6:40 pm

Yes that's right.

Be aware that the timing marks on the sprockets may not align exactly once you have the tension in the top of the chain correct, the timing marks are only there really to make sure you get the chain onto the correct teeth on the sprocket wheels.
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PostPost by: vincereynard » Sun Sep 17, 2017 10:50 pm

First you have to find true TDC. Mine was about 5degrees out!

If you have had the head or block skimmed then the marks are even less likely to line up with the chain attached and adjusted. Hence the need for adjustable gears or offset dowels.

p1050322.jpg and
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PostPost by: bloodknock » Mon Sep 18, 2017 9:43 am

Thats a thought! Ive used a DTI and clocked TDC, and that is spot on. My head has been skimmed about 10 thou, I hadn't considered the effect of essentially shortening the timing chain between the crank sprocket and the exhaust sprocket. Interesting! Is there any data on this forum? Having said that, it should be simple enough to caculate the angle of rotation of the camshaft given the ~ known distance and the diameter of the sprockets. Is that what your diagram shows, I'm afraid I found it difficult to read. Where does one obtain adjustable sprockets? or offset dowels? if necessary.
You've sparked an interest!
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PostPost by: vincereynard » Mon Sep 18, 2017 5:21 pm

Just take the alignment marks on the sprockets as a guide.

Then check the final timing by measuring the MOP angle with your DTI. This should be unaffected by valve clearances / cam wear etc. Thats what the scribble was about.
screenhunter_197-sep.-18-18.32.jpg and

Remember the sprocket stays fixed by the chain, the camshaft is adjusted. So to advance the cam it turns anticlockwise. (The dowel can go in either way.)

Adjustable sprockets or offset dowels are available from the usual suspects. QED / Burton / S J Sportscars.
It's worth checking around as the prices vary.

Personally I'm not much of a fan of the adjustable things I've tried, I think they are a bit of a con. Others have a different opinion.
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PostPost by: billwill » Mon Sep 18, 2017 11:26 pm

If you study the pictures in the link I gave you to my Clay Test, you will see that mine are adjustable sprockets.

I've not fiddled with their setting though since Rob Morley put them in my engine back in about 1998, despite having a new head and new chain since then.

I suppose I ought to do a proper TDC measurement with dial gauge etc, but have not got around to it as the engine seems fine to me.
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