Anyone following my saga with the SU carb will know that I am having a hard time getting the HC emissions right on my petrol 2.25.
My local garage suggested that it might be the camshaft sprocket off by a tooth or night quite in line.

To add to the mix i am using a 123 electronic dizzy (16 curves that no one seems to understand or know which one i should use)
The end result of timing on the big test rig is the timing mark on the lower pulley shows around 20deg.
NOTE: the lower pulley is not the original (no dog for the hand crank) could this be wrongly marked.
If we static time it to 6deg with vacuum advance off She runs but a little rough, put the advance on and it picks up to 11 or so but runs smoother.
NOTE: it will also run at TDC 0deg but bloody rough.
I did however have to open the throttle stop a fair way to achieve tick over.

I am considering buying the Accuspark dizzy as the cost of a kit with an advance adjustable timing light is only a fraction more than the local cost of a decent timing light.

So before i rip off the front end to check the sprocket alignment, what reliable method could i use to measure TDC through the spark plug hole?

As we are trying to achieve more power beyond 1500 to 2000rpm, could this lack of push here be due to camshaft wear?

Sunday fun

Simon

Hi Simon,
It'd be odd if you had a pulley with a different timing mark. On both the pulleys I have (3MB and 5MB) the timing mark is around the 1 o'clock mark when the keyway is vertical. The keyway on the crankshaft is vertical when No 1 is at TDC, but you'd need to remove the pulley nut to see that, which is a major job in itself. In theory you can put a thin rod down the plug hole to detect when the piston is at TDC, but I've not done this myself.
If the timing chain has stretched, it would retard the timing a bit, but I doubt it would be enough to make it run badly. I think you could get some idea of the timing and cam wear with a DTI on the rockers (the valve timings and lift are in the green bible).

I found some reference data for the 25D4 distributor fitted to the older 2.25 petrol. It lists two different models for the 2.25 petrol, with advance as follows:
27 degrees at 2700 RPM (both)
12 deg at 1250 RPM and 17.5 deg at 1250 RPM
4 deg at 450 RPM and 7.5 deg at 450 RPM
I wouldn't take these as gospel, but they might give you a base setting. I've always set the timing by ear, starting around 6 deg BTDC and advancing for best idle (with vac advance off) and then fine tuning on the road, retarding a bit if needed to avoid pinking under load.

You can feel TDC using a thin wood dowl, pencil or kebab stick. You want something stiff that won't scratch. Its very hard to feel the top as the crank angle moves across TDC so the way to do it is feel for the top then go down (say) 6mm either side (ie BDTC and ATDC) and mark those on the gear then TDC will be in the middle. Its fiddely and you will find you have to do it several times and average out the answers.

You could remove the rocker cover, turn the engine by hand until the first two rockers are at their highest point meaning both valve are closed and piston 1 is at the top of its stroke. The valves stay closed for a couple of degrees either side of tdc so you need to judge the half way point. If you don't have the cranking handle dog, it makes turning the engine more difficult, I would get an assistant to rock it whilst in gear.

Col

If the cogs on wrong the valves will not be in correct position in relation to piston best check piston height as previous posts.
What Series is your engine from early version had timing marks on flywheel accessed by small plate on drivers side of bell housing.

My father used to time engines with timing marks missing, basically if setting to fire on number 1, the pistons 1 and 4 should be top dead centre and valves on number 4 should be rocking. Ie, as number 4 goes up exhaust valve open, going down the inlet opens, so if with something through plug hole the valves on 4 should be rocking at top dead centre, if not valve timing out