how to find top dead centre on a 4ac

[Wedged'86]

this has probably been answered on here somewhere before but i can't search for it cause top, dead and centre are too short.

as previously stated i wanna know how to find top dead centre.

was i right in thinking i just line up the groove in the crank pulley to zero on the timing belt case??

thanks.

[WDE_BDY]

Depends on engine, the pulleys can often be wrong so be aware of that. If its got central sparkplugs you can drop a plastic (or any other) rod down the no 1 plug hole then wind the motor over to find where it sits highest. this will be TDC on No 1, will need to check cam for valve opening and closing to confirm if on compression or exhaust stroke.

Callum

[WiLo]

when searching for multiple words that are short use + in between the words.
this should help

[styler]

in short i have seen 2 methods:

1. use a plug stop and turn one way until it stops, mark, turn the other way until it stops, mark and then its in the middle of the two.

2. use a dial gauge and base, put the tip in the hole, turn, reading goes up then down, get it to its highest point and mark.

with all the wear a system gets its always advisable to measure the
actual item not the other parts connected to it as the play in the linkage will give a false reading and it may take a different amount of movement from a part down the track to move the original item, which grows with wear.

thats all i can think of at the moment

[Wedged'86]

wow i didn't even think about the exhaust stroke. thanks heaps. my mate's comming round with a spark plug socket so i'll check it then too just to be sure

thanks again +rep

[Roundy]

1. use a plug stop and turn one way until it stops, mark, turn the other way until it stops, mark and then its in the middle of the two.

this is the best option, when a piston gets to TDC (or BDC for that matter) there will be a small period where the movement is absolutely tiny, so using a rod through the spark-plug hole or a dial gauge isn't totally accurate.

Cheers
Nathan

[jimmmayyy]

4ac has a dizzy?? if it does you'll know tdc when the rotor is pointing at the no 1 electrode.

-jimmy

[Aust162]

4ac has a dizzy?? if it does you'll know tdc when the rotor is pointing at the no 1 electrode.

-jimmy

That method works assuming everything else is lined up properly. if the timing belt is off or if the dizzy has been put in wrong then it wont help you.

Edit: what is a Plug stop? can someone explain this method better?

[Roundy]

a plug stop (if it is what i am thinking of) is a plastic bung that screws into the sparkplug hole and protrudes enough to stop the piston before TDC

[Wedged'86]

haha wish i had one of them.
i had to make do with a screwdriver and feel it out.
i got it to start first key and idle (roughly) but it still backfires down low and stuff

need to hit it with a timing light