Patrick, Can you show us a photo of the Cam and the followers, There are some funny ones around, I have a set with big round lumps on the followers !!. Sometimes there is a number stamped on the inner end of the cam, 1, or 2. Cheers Bill.
E: Engine Series ‘C’ Comet Camshafts
- Thread starter aciera
- Start date
You're right there Bill. The timing diagram in "Richardson" for the Single is wrong. Slot pointing between pushrods at 4 degrees B.T.D.C. is right as long as the cam is original or has been ground to the same profiles using the original slot as the datum. There are, of course, cases where this is not so!
You better not rely on any marks on camshafts or cam gears . How can you know if these are still exactly as designed ? It has been written numerous times that the ONLY safe way to find a correct timing is to set even valve lift at overlap and 4 to zero degrees before TDC. So why mess around with questionable numbers of valve timings from old books or records from factory findings like those noted down after assembling Lightnings - which have quite some variations, not because they were in a plan but because they were found when measuring up later.
Vic
Vic
Do yourself a favor and DO NOT order a Mk 2 camshaft as they have lots of lift which means you need to make many modifications to the cases and the head to accommodate that extra travel and also they are down on power at moderate revs though they are great for race track work where the revs are much higher. For road work a Mk1 or Mk3 cam is the way to go.
As Bill advised - ignore ALL timing marks and set the valve timing so you have equal lift at 4 degrees BTDC - if you cant get 4 then go towards TDC not away from it, such as 3 BTDC.
Martyn
I should have remembered to tell people to shorten the top of the lower valve guide, With Mk2 cams,
But after all these years, I forget !!, I always use race cams.
Cheers Bill.
But after all these years, I forget !!, I always use race cams.
Cheers Bill.
Hello, a photo of the camshaft, and followers. On the cam shaft, I did not find any number,
On the followers the part number ET 29 and C 3.
I bought this bike in 1987 from a man who was racing,
He talked a lot, he told me that on his bike he was riding pistons of FIAT and other editing a little weird.
Patrick
On the followers the part number ET 29 and C 3.
I bought this bike in 1987 from a man who was racing,
He talked a lot, he told me that on his bike he was riding pistons of FIAT and other editing a little weird.
Patrick
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Patrick, the picture of the cam is very useful and it certainly is not the Mk II racing cam. However, despite what some of the others have written do not just use this cam and set it up so that there is equal lift at 4 deg BTDC. This is not getting at the experts, it is because you have no idea what this cam is. It could be a perfectly formed Mk I or it could be a total mess. Once you know whether the cam is a normal cam then you can use the equal lift method. Before that you need to find out what the lift profile is. This sounds tedious but in fact can be done quite quickly provided that you can set up a good test system. The ideas is that you should measure the lift on both cams every ten degrees of engine rotation and at least check that the base circle is round. I have seen base circles with a 20 thou dip in them. When you have the measurement plot them on a graph. If you use Excel, or some other spread sheet, then this is very easy. If not then if you send me the measurement by private message (seek instructions on how to do this via the forum or use my email address enw07@btinternet.com if you wish) and I will do it for you and put the resulting graph on the forum here. This way you can find out whether the cam is properly formed and from then on you can use whatever method you find most convenient to do the final timing.
Yes Patrick, They are standard followers, And Cams look like Mk1 or Mk3, I have never seen a Mk3 !.
I get the Piston at TDC, Not on the firing stroke, Or the mag will be timed wrong !!. On the other side of the Camshaft There is a slot, Have that slot upper most, Pointing in between the push rod tubes, Pop the pushrods in, With no adjusters, And turn the Cam by hand, Forwards and backwards, Just by looking, Find the spot where the pushrods are sticking out the most at the same time,
ie the overlap, Then check with your degree plate what the numbers are, The inlet opening number should be a little higher that the exhaust closing number, For best performance !.
Good Luck, Bill.
I get the Piston at TDC, Not on the firing stroke, Or the mag will be timed wrong !!. On the other side of the Camshaft There is a slot, Have that slot upper most, Pointing in between the push rod tubes, Pop the pushrods in, With no adjusters, And turn the Cam by hand, Forwards and backwards, Just by looking, Find the spot where the pushrods are sticking out the most at the same time,
ie the overlap, Then check with your degree plate what the numbers are, The inlet opening number should be a little higher that the exhaust closing number, For best performance !.
Good Luck, Bill.
Just thinking, Don't worry about inlet closing and ex opening, You can't do anything about it because they are welded together, Just think about Inlet opening and ex closing, And as I said the first number should be a small bit more than ex closing.
For a Comet with Mk1 cam, Inlet open 40 ish and ex closing 33 ish.
You can be a lot out with a Vin' and it will still run OK, And as Timetraveller says there are a lot of badly made cams sold, Another reason to do it the overlap way ??.
The Mk3 has ramps to help it run more quiet, But I don't know those numbers.
Cheers Bill.
For a Comet with Mk1 cam, Inlet open 40 ish and ex closing 33 ish.
You can be a lot out with a Vin' and it will still run OK, And as Timetraveller says there are a lot of badly made cams sold, Another reason to do it the overlap way ??.
The Mk3 has ramps to help it run more quiet, But I don't know those numbers.
Cheers Bill.