timing light

[tone]

Either I'm pretty thick or there is way too much information out there as to the type of timing light required for my XPAG engine Tc
I have a TD cam and supercharger but it is running too hot to the point of nearly boiling in the hot weather the UK has at the moment

So I thought of buying a timing light and trying to check it myself
Working out what it is and how to check and adjust it is another mystery to me at the moment!

So any advice very welcome
Many thanks

[Steve Simmons]

Any standard timing light will work, but my preference is for an analog dial-back timing light. A standard light fires the strobe once every time the #1 spark plug fires. So if you want the timing at the factory setting of TDC (0-degrees BTDC), you aim it at the timing mark on the front of the engine (right above the crank pulley) with the engine at low idle, pull the trigger, and adjust the timing until the mark on the pulley lines up with the pointer. But, if you want 10-degrees BTDC to run better on modern fuels then you need to adjust the timing until the mark is in a different position, and there are no marks for it. So you either need to make your own timing marks for various settings, or measure how far from the pointer 10-degrees is and mark that.

With an adjustable timing light, you have a knob on the rear that you turn to any degree setting. As you turn it while the light is pointed at the timing mark, you can see the timing mark on the pulley "move" back and forth. So if you want to set your timing to 10-degrees, just set the timing light to 10-degrees and adjust the timing until the mark lines up with the pointer. Or, if you want to see what timing you're currently at, you just idle the engine and adjust the knob until the marks line up, then look at where the knob is set. You can also use this to check the advance curve, checking the setting at various RPMs. Very handy. Digital lights work also but sometimes are affected by interference from the generator.

The timing adjustment is done at the distributor, either by turning the micro-adjuster (small adjustments) or by rotating the distributor itself (large adjustments). Be careful not to lift the distributor away from the block while rotating.

[tone]

Crikey, a brilliant and quick response
Learnt more in your one reply than ever I did spending too long on google!
I read somewhere that 10 degrees btdc is where I should be going for?
Thank you for the info Monday tomorrow off to the motor factors

[Steve Simmons]

In my opinion, and based on modern US fuels, timing should be somewhere between 7-14 BTDC at idle. I know that's a wide range, but every engine is different in its specification. With a supercharger, I would start on the low side. Pinging is bad on a normally aspirated engine but can be catastrophic on a supercharged engine!

My TC is happy at 7 degrees at idle, and around 32-34 at 3500 RPM. My dad's XPEG-powered TC is happier at around 12 and 34. The advance curve is a bit different also. The XPEG seems to like the advance to come on a bit slower, ramping up as RPMs increase.

[Tom Lange, MGT Repair]

Since the various different distributors used in T-types have mechanical weights that start to advance as low as a few hundred RPM's, it is most accurate to check total advance at the other end with the timing light Steve notes above - no more than 32 degrees at full advance, 3,500 RPM.

A worn distributor is a sure way to cause an engine to overheat - having it rebuilt has resulted in engine-overhaul-like improvements in running!.

Tom Lange
MGT Repair

[Duncan M]

OP did ask about a supercharged XPAG. I thought there were some different timing numbers people have come up with over the years? NA vs SC.

In most engines with a supercharger you go for total advance sooner (lower RPM) than the NA version. Not doing that advance spring adjustment on the centrifugal advance will result in a retarded situation. ie less advanced than desirable. Any sort of retarded (not advanced enough) timing in the XPAG (supercharged or not) will generally result in overheating.

[Duncan M]