Timing chain woes.... :(

[mazfg]

Ok, so went to do my chain today. Undid the cam sprocket, temporarily marked it and the backplate. Refitted no problem. Now the thing is when I move it round to line up as it should, with No.1 cylinder at TDC, the marks are out? I have just put the chain on as before, nothing moved, but the setting points don't tie up. I have a dot with a line on the cam sprocket, one on the plate and a dot on the crank pulley...but they don't ever line up together?? At TDC, the crank sprocket dot lines up with the dot with the line on the backplate, but the camsprocket dot & line is out??
I attach a pic,, although had trouble getting a decent shot.

[piman]

Hello Mazfg,

If the crank is at TDC and the camshaft hasn't moved your lines should line up. Does your camwheel have four holes, if so are you using the same two? You may just have to give it another try, but be sure your camshaft is still in the right position. Make sure the drive side of the chain is taut, that is the side that is pulling the camwheel round.
From your picture the crankshaft sprocket looks quite worn?

Alec

[mazfg]

Hi Piman, camwheel only has 2 holes. As I said, didn't  move anything..? Drive side is taught too

Is their any advice for setting up the camshaft position/ timing  in relation to sprocket position....can't find anything in haynes. Am a little concerned as to why it wasn't right to start with....car did run ok...? Only seems to be a little out...? When No.1 is at TDC the dot on the crankshaft lines up with the dot on the plate....so I presume this is correct....it's just a case of moving the cam sprocket?, so long as the cam is going to be correct too in relation to the rest....?

All help gratefully received... :)

[piman]

Hello Mazfg,

Yes the dots should line up.

For peace of mind, before bolting the timing cover on, do a check on the camshaft timing. The easiest way is with the head on, set the rocker clearance on 7 and 8 rockers to 40 thou. Turn the engine until those rockers are rocking. (This is when if you move the crank back and to about TDC one valve is closing and the other opening). Now turn the crank to TDC and measure the rocker clearances on 7 and 8. If the timing is correct then those clearances will be very similar. If there's a big discrepancy the timing is wrong.

Alec

[mazfg]

Head is off and out at the moment, having new guides n valves in...... Will try that trick once I get it back.....will leave cover off then for the moment.

Out of interest, looking at my current cam position....what affect does that have on the whole running.....It's only out by a bit and as I said the engine was running ok, with the out splutter. One thing I did find before, was i couldn't get the engine to pink when advancing the timing by more than 12 deg...but that might not have any bearing on anything....

Thanks again :)

[GT6 M]

It seems as though youve move the cam, its very easy to doo with no load onit.
it looks like ye  2 teeth oot,  so slacken cam bolts off, and tuen chain over the teeth, to re set.

regarding if it will make a difference, depending on which way its out, then the power band will be higher or lower in the rev range.
on a wee engine like this, and the cam, I doubt it make a bigg diff at all,
thats the idea behint adjustable cam gear wheels.
but re set it back to factory figs, its a simple job, as its already in bits.

M

[JohnD]

Don't know if this is true for four cylinder cars but it is for the sixes.
Triumph cunningly offset the four holes in that cam sprocket, so that you could gain or lose fractions of a tooth to optimise timing.  You only have two holes, but if your sprocket is marked on the back, have you inadvertently turned it back to front?

John

[JensH]

John: Same with 4 cylinder engines.

[Pete Lewis]

question  where did the 2 hole cam sprocket come from , its not ( as said) normal  they should have 4  holes which gives you increments of 1/4 tooth per hole set.  maybe a new gear would be advisable,
our 1600 had cam timing errors of about 1/2 tooth and it was always like a thruppenny bit , very unsmooth.

pays to get it spot on, then you need a cheap  timing protactor ( print one off the net)  make a simple piston stop to arrest the piston eitherside of tdc and half the angle between, for accurate TDC

use a dial indicator on the followers to and mark any equal lift either side of the  cam lobe tdc and half it to get the Lobe TDC

then fit the chain to align the best set of holes

sorry needs a picture  tells a load of words .

Pete

[mazfg]

JohnD wrote:

Don't know if this is true for four cylinder cars but it is for the sixes.
Triumph cunningly offset the four holes in that cam sprocket, so that you could gain or lose fractions of a tooth to optimise timing.  You only have two holes, but if your sprocket is marked on the back, have you inadvertently turned it back to front?

John

It's on the right way, the other side has the mark that lines up with the front of the cam face....I guess what I should have done was, check it was lined up on the dots before I removed it in the first place!!! Very frustrating......I think I'll wait till head n rocker gear is back on and do as Piman suggested....
Thanks for the help guys.


Mmmm, not sure about the cam sprocket.....it's what I had, don't know why it only has the 2 holes?

Is it worth changing both cam and crank sprockets?

[GT6 M]

Pete, its got 4 holes init,
LooK closely at the pic.

cams moved thats all, nowt to worry aboot

M

[mazfg]

So it does......that was my fault...

So as long as the cam face that goes against my sprocket, lines up(as in that marking on the unseen face of the sprocket) and the holes line up, I should really just need to turn the cam a little more clockwise to line up all the holes...then check as Piman mentioned/

[mazfg]

piman wrote:

Hello Mazfg,

If the crank is at TDC and the camshaft hasn't moved your lines should line up. Does your camwheel have four holes, if so are you using the same two? You may just have to give it another try, but be sure your camshaft is still in the right position. Make sure the drive side of the chain is taut, that is the side that is pulling the camwheel round.
From your picture the crankshaft sprocket looks quite worn?

Alec

So, worth me getting a new one then?

[mazfg]

piman wrote:

Hello Mazfg,

If the crank is at TDC and the camshaft hasn't moved your lines should line up. Does your camwheel have four holes, if so are you using the same two? You may just have to give it another try, but be sure your camshaft is still in the right position. Make sure the drive side of the chain is taut, that is the side that is pulling the camwheel round.
From your picture the crankshaft sprocket looks quite worn?

Alec

So, worth me getting a new one then?

[mazfg]

piman wrote:

Hello Mazfg,

If the crank is at TDC and the camshaft hasn't moved your lines should line up. Does your camwheel have four holes, if so are you using the same two? You may just have to give it another try, but be sure your camshaft is still in the right position. Make sure the drive side of the chain is taut, that is the side that is pulling the camwheel round.
From your picture the crankshaft sprocket looks quite worn?

Alec

So, worth me getting a new one then?

[mazfg]

piman wrote:

Hello Mazfg,

If the crank is at TDC and the camshaft hasn't moved your lines should line up. Does your camwheel have four holes, if so are you using the same two? You may just have to give it another try, but be sure your camshaft is still in the right position. Make sure the drive side of the chain is taut, that is the side that is pulling the camwheel round.
From your picture the crankshaft sprocket looks quite worn?

Alec

So, worth me getting a new one then?

[Pete Lewis]

maybe yes, chains dont stretch they get longer as the links and pivots wear, this  with the  driven load wears a hooked tooth form.

so new gear with a new chain makes for a happier solution,  I would suggest you make a protractor dial and and borrow a dial indicator
with this you can mark  a positon on the dial at the same lift each side of the cam lobe you half the marks and thats the cam lobe bolt upright (TDC)   you can do the same with the pistons  make a plate to block the piston 10mm from the top , mark the protractor disc
for this in both directions , then half the maks for piston TDC #
then fit the chain wheel as said taut on the drive side and keep twiddling the gear to get the best line up of the 4 hole positons
and once together recheck all lines up ..  

sounds a lot harder than it really is  

Pete