Judging Top dead centre

[bob_rich]

Hi Folks

I think this has been asked B 4 but it is nice to get a reply just 2 B sure I have got it correct

For top dead centre on cylinder 1 on its compresion stroke can this be determined by looking at the valves moving on cylinder 4 through the oil filling hole?? and what exactly does one look for??

thanks

Bob

[bcmc33]

Quite simple really - with both cams on #4 cylinder 'rocking', #1 is on the compression stroke. When looking into the filler hole the exhaust cam should be at about 7 o'clock, and although you can't see it, the inlet cam should be a about 5 o'clock.

[bob_rich]

Thanks very much Brian

Cheers

Bob

[Baggy2]

Here are some pictures that may help. I always remember the correct cam lobe position as pointing toward the inlets - the left on this picture. I've also attached pictures of using a dial guage to find tdc fairly accurately. I used a very clean 3/8" socket extension bar that was a reasonable fit in the plug hole. The small ali plate with the hole in stopped everything wobbling and the precision engineering mole grips were used the clamp the dial guage to one of the cam cover stud nuts. Why do all this - I hear you ask - when all you have to do is look at the indicator on the crank shaft pulley against the timing marks on the front cover. The reason is that for some reason new crank pulleys seem to be sold without the tdc indicator. I've put a dob of paint on now but this was the method used to find where to put the dob of paint.
Hope its helpful.
Baggy

[Jeff@Jae]

Finding true top dead center is a good thing to do along with actually timing the cams. The notch in the pulley is not very accurate and it's nice to know when using a timing light whether your using the top or bottom edge of the notch at any point on the front cover marks. The width of that notch is several degrees. Timing the cams is also important because they can be off by quite a bit and using offset dowels to make them spot on can make a huge difference on how well a Twin Cam runs.