Author Topic: '73 TCS camshaft timing  (Read 3621 times)

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Offline hey_kramer

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'73 TCS camshaft timing
« on: Thursday,March 06, 2014, 11:04:32 AM »
http://www.lotuseuropa.org/LotusForum/Smileys/default/newhere.gif

HELLO ALL and thanks for looking at my first post!

I recently inherited my father's '73 TCS and it hadn't been serviced...at all...in over 20 years. I disassembled the engine and gave everything a good workover, installed replacement parts/gaskets, etc., but in my EXCITEMENT to tinker, like a FOOL in a hurry I didn't mark any of the camshaft timing. I've never timed camshafts before so I have some rudimentary questions that I could not answer by looking in the workshop manual or in the forum.

To begin, I've reinstalled the camshafts but the sprockets are not installed yet. I've got the #1 piston at 5 degrees BTDC, as I have Zenith carbs.

1) Each camshaft sprocket has 3 circular holes through it, for what I call the camshaft's "nub" to fit into. I kept track of which sprocket goes with which cam, but which of the 3 holes do I use for the nub?

2) Once the sprockets are correctly situated, should I rotate each cam (NO timing chain installed yet) so that the sprocket timing marks are next to each other and horizontal with the cam cover mounting face, as according to the manual?

3) When timing, is 5 degrees BTDC best or do you guys who have Zeniths like to use something different than the factory setting?

BIG THANKS!

Offline Roger

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Re: '73 TCS camshaft timing
« Reply #1 on: Thursday,March 06, 2014, 12:39:05 PM »
Don't mix up camshaft timing with Ignition timing. Set the camshafts with No 1 at TDC.

Have you read the Workshop Manual? If you had, you'd know the "nub" is called a dowel. The dowels point outward, if I remember correctly, when the engine is at TDC. That will tell you which hole to use, though I can't remember being confused. There are three holes, but only one, the middle one, is the same size as the dowel.
The exhaust sprocket should have EX etched onto it.

If you don't have a workshop manual, look here: http://www.lotus-europa.com/manuals/tcwork/e/index.htm
« Last Edit: Thursday,March 06, 2014, 12:48:06 PM by Roger »

Offline hey_kramer

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Re: '73 TCS camshaft timing
« Reply #2 on: Thursday,March 06, 2014, 01:17:58 PM »
Thanks Roger! I own an original binder of the workshop manual, but I never put 2 and 2 together to realize those nubs were called dowels! Thanks for that. The camshaft/sprocket illustration has the dowels pointing outward but it was unclear if that illustration correlated to TDC. So, taking your advice into account I will:

1) Set #1 to exactly TDC,
2) Fit the camshaft dowels to their exact-size sprocket hole (probably middle), ensuring the EX sprocket is on the exhaust cam,
3) Like the manual says, rotate the shafts until the sprocket timing marks are next to each other and horizontal to the cover mounting face,
4) Connect timing chain and tighten,
5) Crank #1 to 5 degrees BTDC and install ignition components (distributor, plugs, etc),
6) Put cam cover on and hope it starts
7) Fine tune distributor timing

Anything else?
« Last Edit: Thursday,March 06, 2014, 01:19:59 PM by hey_kramer »

Offline Bainford

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Re: '73 TCS camshaft timing
« Reply #3 on: Thursday,March 06, 2014, 02:15:11 PM »
Thanks Roger! I own an original binder of the workshop manual, but I never put 2 and 2 together to realize those nubs were called dowels! Thanks for that. The camshaft/sprocket illustration has the dowels pointing outward but it was unclear if that illustration correlated to TDC. So, taking your advice into account I will:

1) Set #1 to exactly TDC,
2) Fit the camshaft dowels to their exact-size sprocket hole (probably middle), ensuring the EX sprocket is on the exhaust cam,
3) Like the manual says, rotate the shafts until the sprocket timing marks are next to each other and horizontal to the cover mounting face,
4) Connect timing chain and tighten,
5) Crank #1 to 5 degrees BTDC and install ignition components (distributor, plugs, etc),
6) Put cam cover on and hope it starts
7) Fine tune distributor timing

Anything else?
That pretty much sums it up, Mr Kramer. In step 2 it is indeed the middle hole you are looking for. I wouldn't get too hung up on step 5. 5 degrees is easily covered with distributor rotation once installed. Just be sure you have some rotational freedom in the distributor to the advance direction. Are you running Stromberg carbs? You will likely find that the engine wants more than 5 degrees advance. You will probably be in the 10 degree range to make the engine happy, perhaps more. When my engine is timed at 5 degrees it is quite lazy. The Miles Wilkins book also recommends more then 5 degrees. By the way, if you are going to be playing with a Twin Cam, I recommend the Miles Wilkins book. Lots of good information there and it has recently been reissued in soft cover. Good luck.
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline jbcollier

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Re: '73 TCS camshaft timing
« Reply #4 on: Thursday,March 06, 2014, 03:46:08 PM »
YOU NEED TO GET THE CAMS IN THE RIGHT POSITION EITHER BEFORE THE HEAD GOES ON, OR, BEFORE YOU FULLY TIGHTEN THE CAM BEARING CAPS !!

It is very easy to bend a valve otherwise.

I set piston #1 to TDC then I turn the crank back 90° so that NO piston is TDC, then I place the head on with the cams in the proper position for #1 TDC. Finally I turn the crank ahead 90° to bring piston #1 back to TDC.

Offline EuropaTC

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Re: '73 TCS camshaft timing
« Reply #5 on: Thursday,March 06, 2014, 10:46:23 PM »
 :I-agree:

Excellent advice.  I also managed to break a camshaft many years ago during a rebuild (my only brain cell was on holiday) so be very careful. It's not a difficult task, but there are places where a lapse of attention will make it very upsetting.

Also the recommendation for Miles Wilkins book is a good one. It has more detail than the workshop manual and has been written later, thus benefiting from knowledge gained after these engines had been in service for a long time.  In some areas he disagrees with the OEM manual (timing IIRC ?) so it's good to have background info from other sources if you find problems after setting up as per the Lotus manual.

Brian

Offline hey_kramer

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Re: '73 TCS camshaft timing
« Reply #6 on: Friday,March 07, 2014, 07:14:49 AM »
Everything is back together and cranking smoothly...but now I have extremely weak spark / no spark. That really put a damper on my mood at 2:30AM when I turned the key.  >:( It wouldn't fire up and I diagnosed it as the plugs not getting any juice. I suspect my Ignitor II air gap is too big again. Will further investigate after work.

Offline Bainford

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Re: '73 TCS camshaft timing
« Reply #7 on: Friday,March 07, 2014, 04:25:32 PM »
YOU NEED TO GET THE CAMS IN THE RIGHT POSITION EITHER BEFORE THE HEAD GOES ON, OR, BEFORE YOU FULLY TIGHTEN THE CAM BEARING CAPS !!

It is very easy to bend a valve otherwise.

I set piston #1 to TDC then I turn the crank back 90° so that NO piston is TDC, then I place the head on with the cams in the proper position for #1 TDC. Finally I turn the crank ahead 90° to bring piston #1 back to TDC.
Yes indeed. Excellent catch Mr Collier. This is most critical information.

Also, Brian's mention of cam breakage is something to keep in mind. Cam bearing caps should be tightened carefully and incrementally. Don't just wing one down all the way then move on to the next, but ease them all down a bit at a time whilst being wary of anything 'not right'.

Though perhaps too late now, I should have mentioned that it may be prudent to apply cam lube to the lobes. This may not be necessary for existing parts that are already worked in to each other, but it's a prudent step nonetheless, and one I always observe whenever I have a cam out of an engine.
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline 3929R

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Re: '73 TCS camshaft timing
« Reply #8 on: Friday,March 07, 2014, 07:43:27 PM »
Hello,  Welcome!  I also inherited my father's TCS.  He bought it new in 1973, when I was 5 years old.  As yours, mine had been stored for about 20 years when I towed it home and started sorting it. 

I can't offer any help on your cam, but you've already sorted it anyway.

Cheers,
Mark
Mark
Salt Lake City, Utah, USA

Offline hey_kramer

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Re: '73 TCS camshaft timing
« Reply #9 on: Sunday,March 09, 2014, 05:00:58 PM »
Thanks everyone for all the cautionary tips. I'm DELIGHTED to report that the engine runs! Weak spark was from the IGNITOR II ignition module air gap being too wide.  :headbanger: BUT frustrated to say that the timing is quite terrible. It won't run faster than about 400 rpm with full throttle, and dies as soon as I stop giving it gas. I timed it just as we agreed to in the earlier posts:

Ensured the EX sprocket was on the exhaust cam;
Used the middle hole on each cam sprocket;
Put #1 to TDC (Double-checked by actually making SURE that it was TDC, not just assuming it was by only looking at the flywheel timing mark);
Rotated each camshaft so that the sprocket timing marks were exactly next to each other and horizontal with the cover mounting surface;
Installed the timing chain and tightened, checking that the sprocket timing marks were still aligned afterwards;
Rotated to 10 degrees BTDC and installed distributor (10 degrees because it seems to be the modern suggestion instead of 5);

I played with the distributor timing by rotating it but it has no noticeable effect. The car ran REALLY well 2 months ago (before the teardown) with it at 5 BTDC, so I put it back to that, but same sputtering and dying results as it did at 10.

The owner of the car, before my father, raced it professionally. Perhaps he installed some altered engine components which require timing that is quite different from stock, which are preventing it from running smoothly. I still suspect the camshafts/sprockets are to blame. Perhaps it is not the middle holes on the sprockets? It's not the carbs either. They were recently rebuilt and were working fine before the teardown.

Offline jbcollier

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Re: '73 TCS camshaft timing
« Reply #10 on: Sunday,March 09, 2014, 08:22:45 PM »
How far did you have to rotate the cams to line them up?

Do a compression test.

Offline EuropaTC

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Re: '73 TCS camshaft timing
« Reply #11 on: Sunday,March 09, 2014, 11:39:59 PM »
It sounds as if you've got the cams right, IIRC the two marks on mine don't line up exactly but it's a while since I last did that job so memory is hazy.

I think I'd look at the distributor again, mainly because it's the easiest thing to check and cross off the list. 

I set the flywheel to TDC to install the distributor. Position the pigtail connector towards the block with the rotor arm pointing towards the rear distributor clip such that it rotates towards #1 as the screw meshes. Then I turn the flywheel to the timing mark and adjust the distributor/ignition timing roughly by using a bulb across the distributor/coil connection and earth. Once it's about right I start up and put a timing light on it to get a better setting.

In the past I've managed quite successfully to get this wrong by not having the rotor in exactly the right position before installation and although the engine will run, it's not what you'd call good.  ::)

For some reason I can't find the section in my Europa Manual (and it's a proper, paid for, genuine Lotus one ! ) so I have copied the relevant page from the Elan manual into a JPG and attached it to this post just in case you have the same issue.

Brian

Offline hey_kramer

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Re: '73 TCS camshaft timing
« Reply #12 on: Tuesday,March 11, 2014, 03:44:33 PM »
Are the cams in the TCS (Federal) supposed to have any overlap in timing? By overlap I mean the exhaust valve and intake valve on any given chamber are partially open at the same time. My coworker who races professionally suggested I find that out. THANKS!

***Update***
So upon further research I see that under the factory specs there is a 132 degree overlap of the valves. This cannot be right, can it? Surely I've calculated something wrong here:
Exhaust opens @ 66 BBDC (114 degrees clockwise after TDC)
Inlet closes @ 66 ABDC (246 degrees clockwise after TDC)
246 - 114 = 132 degrees of everlap.  :blowup: Really that much????
« Last Edit: Tuesday,March 11, 2014, 10:34:35 PM by hey_kramer »

Offline EuropaTC

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Re: '73 TCS camshaft timing
« Reply #13 on: Wednesday,March 12, 2014, 12:31:48 AM »
There's a page here with a diagram very similar to the one in Miles Wilkins' book that tends to support a similar overlap theory. The text is about any engine, but the diagram at the bottom of the page is from the TC motor, and a picture/sketch makes it much easier for me to visualise what's happening with the valves  rather than working with a list of numbers.

http://gglotus.org/ggtech/907camdial/body-907cams.htm

If the cam timing interests you, then I'd suggest you grab a copy of Mile's book before it goes out of print again. There are sections on setting up standard cams and also how to approach timing with non-standard cams and cylinder head thicknesses, plus what you can expect from them.

But does it matter? You can't change the profile, only the cam and ignition timing so it doesn't really make any difference what the overlap is, does it ?  I guess I'm saying "don't get hung up on it"   ;)

Brian

Offline Roger

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Re: '73 TCS camshaft timing
« Reply #14 on: Wednesday,March 12, 2014, 03:28:22 AM »
Kramer, it's a 4-cycle engine. Suck, squeeze, bang, blow. 2 TDCs per combustion.
In the cycle you're imagining, ask yourself when the inlet opens.