cam timing marks - where should they be?

[JJDraper]

more info here..

lotus-twincam-f39/camshaft-sprockets-t26924.html#p179852

Jeremy

[billwill]

Simplest way to correct?

I would assume it is to mark up the sprockets and chain with something like tippex, then loosen of the cam chain tensioner.

Then if there is enough slack in the chain, move it one sprocket across and re-tension then check it all again.

Woah, don't do anything until you find out why it is presently seems to be off by one tooth. Do you have any engine history from the previous owner. that placing might be deliberate not just a mistake. It may already have an offset dowel in there.


As I said above if you are not certain what is going on, measure it up properly.


~~~

Both sprockets are marked both IN and EC, because they are made to identical spec and can fit on either camshaft. You then use whichever mark corresponds to whichever camshaft.

[billwill]

Hi
Standard Ford Sprocket is used of Exhaust (I think ) and a special used for Inlet ( I Think ) the sprocket you have can be used as the Exhaust or Inlet as they are one tooth different. Sorry I can?t remember which way round it is but it could explain the 10 deg error.
For what it?s worth Ron.

It can't be a count of one tooth different, that would end up with one camshaft rotating slowly relative to the other followed fairly rapidly by disaster. But I don't think you meant that.

So I guess you meant the mark was one tooth different place than the other sprocket. I guess that's the reason for having two marks on those sprockets, one for when it is used on the inlet camshaft and the other mark for when it is used on the exhaust camshaft. They look about a half to one tooth different in placement.

[twincamman]

OK here is the trick to make your TC run sharp and strong ------line the cam sprocket markings as close as possible with the intakeand exhaust sprockets in place --and the crank timing mark at correct setting ---then remove the exhaust cam sprocket and place said sprocket in the chain in position opposite the intake sprocket -----the clamp some vice grips on the exhaust cam and turn the cam back until the sprocket aligns with mounting bolt hole and replace the bolt ---the sprocket will fal lin place nicely-----about 1 /8 th of an inch or so shoild do it - setthe distributor close to number one tdc spark a spare plug on number one by turning the distributor ----start it up set the timing with a timeing light ---no stress ---no bent valves just HAPPY HAPPY HAPPY ----ed

[ricarbo]

If you do make any changes, don't start the engine before you have turned it over by hand to make sure there are no clashing parts!
regards
Richard

[twincamman]

Hate to break this to you but ....Any contact of piston to valve bends the valve

[billwill]

OK here is the trick to make your TC run sharp and strong ------line the cam sprocket markings as close as possible with the intakeand exhaust sprockets in place --and the crank timing mark at correct setting ---then remove the exhaust cam sprocket and place said sprocket in the chain in position opposite the intake sprocket -----the clamp some vice grips on the exhaust cam and turn the cam back until the sprocket aligns with mounting bolt hole and replace the bolt ---the sprocket will fal lin place nicely-----about 1 /8 th of an inch or so shoild do it - setthe distributor close to number one tdc spark a spare plug on number one by turning the distributor ----start it up set the timing with a timeing light ---no stress ---no bent valves just HAPPY HAPPY HAPPY ----ed

It is not clear what you are suggesting? It appears to be a suggestion that you move the exhaust cam out of standard position by one tooth position (approx 10.6 degrees). Is that really what you meant?

[rgh0]

Hi Bill
I think Ed is suggesting setting the timing based on the inlet first and not worrying about getting the exhaust right precisely then fitting the exhaust sprocket to the chain in the correct position and then rotating the exhaust cam until it fits on the sprocket. I do it the same way but I start with the exhaust sprocket set right and then set the inlet sprocket, this way you are working back down the tension side of the drive chain from the crank drive sprocket

cheers
Rohan

[billwill]

OH, I see.

Personally I do it like you, I always put the head on with the cams in approx the right position, so that the valves won't immediately hit the pistons, then slacken off the chain tensioner, then get the exhaust sprocket on first and ensure that with the chain taut from crankshaft to exhaust sprocket the sprocket timing mark is as near as possible to horizontal and in line with the top of the timing case,

Then with the chain NOT on the inlet sprocket I use the leverage of the sprocket wheel to rotate the inlet cam the little bit to get the marks lined up, then take the sprocket off the inlet cam, poke it into the chain in the correct links, checking it by holding it just in front of the camshaft and observing if the marks line up, with the top of the chain also taut, then as Ed says it slips onto the camshaft dowel and I can put its securing washer & bolt on loosely, then tighten the chain tensioner and check that everything is in the right place before tightening the sprocket retaining bolts.

Always remembering that the marks may not line up exactly anyway, because they can only move by one tooth position.