Anything and everything Herald. Talk about anything from the first 948s to the last 13/60s.

Engine, cooling system, fuel system, exhaust system.

I have recently rebuilt a 1300 engine but am having trouble getting it running right. The problem seems to be getting the ignition corrrect, it's not as if I'm a novice at setting the ignition timimg as I've done it may times so I'm confident it should be okay. Whatever I do it either won't start very well, won't tick over properly, if I get it right when it's cold it's a problem when hot and vice versa, if I get it right at tick over it misfires when accelearting or if I get it right when accelearating it won't tick over properly, etc etc. I've even tried a different carb and distributor.

I've now come to the conclusuion I must have the valve timing one notch out but before I start stripping it down does anyone have good suggestions on how I can accurately confirm if the valve timing is correct? I know with the notches aligined and no 1 at TDC the valve clearances can be checked but this seems a bit vague. Any suggestions welcome.

To set the valve timing properly (or check it) you'll need to use a Dial gauge, degreeing wheel and a magnetic stand.... the head has to come off and a 'dummy' pushrod needs to be made up. This is the only way I'd trust.

...unless someone else has a better plan...

Steve,
You can check that your timing is correct, without any dismantling apart from removing the rocker cover, by using the "lift on overlap" method. "Overlap" because the two valves are both open, overlapping each other, as one four stroke cylce ends and the next begins. This method relies on the fact that Triumph camshafts are symmetrical - the lobes are equally set about the TDC position, and measures the 'shaft position on No.4 cylinder, not No.1, with the crank at TDC for the No.1 firing stroke.

If No.4 valves are equally 'on the rock' when the crank is at TDC, No.1 valves both closed. then the cam shaft is correctly timed. With a dial gauge, this is easier to measure than estimating TDC, as the cam is moving the valve quickly, unlike at full lift, when of course the valve slows down and stops moving. Easier still if you can borrow a second dial gauge!

John

Assuming you have a standard cam, John is quite right. The other good news is that you can adjust the cam timing without taking the engine out. You need to remove the radiator and front timing case.
The crankshaft pulley timing marks should be an accurate enough indication of TDC to find out if you are a whole tooth out or not. (Removing the timing case may also highlight the original timing "assembly" marks, if there are any. and immediately confirm if your idea is correct).
I think the Haynes manual gives a good enough indication of how to set the timing correctly, if not the factory manual certainly does. You have quite a scope for adjusting, as the camshaft wheel can be positioned in at least two different positions to the four mounting bolts, and turning the wheel "front to back" gives another variation.
If I recall correctly, to check the timing you set 7&8 rockers to 40thou (?) clearance in the normal matter (ie 7 with 2 valve fully open, 8 with 1 valve fully open) and then set no 1 cylinder to TDC. At this point 7&8 rockers will have EQUAL clearances. It doesn't say WHAT that clearance is, just that both rockers will be the same.

Thanks for the advice. I was able to take a look today and decided the valve timing is correct after all. I then spent some time tweaking the carb and ignition timimg and eventually got it running pretty much okay - until I took it for a longer run. After about 5 miles at 70+ mph it was running really well but when I checked the plugs they were a bit dark so I weakened the mixture a fraction and now I'm back to square one. I now think that maybe a tappet or two could be too tight (despite taking care during the rebuild) and thereby explaining why it was okay until I ran it hard.

Anyone got any other ideas?

Steve, I'm with NiG, you need to accurately measure the crankshaft rotation and the cam lift.

the way I do this when building engines is to use the ring gear as a protractor, counting gear teeth (I'm a sad b*****d) and then using a dial gauge indicator on a dummy pushrod in a tappet (is it no1 inlet?) to indicate max cam lift.

you need to know the number of degrees crankshaft rotation to maximum cam lift for the camshaft profile you have got, I suppose that also requires you to know which camshaft you have...

it is quite easy to get the camshaft timing one tooth out, even half a tooth out by reversing the sprocket on the camshaft

before you strip the engine again, you might want to exhaust ('scuse pun) every other possibility

bin

Section : Engine

Valve timing

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