TDC on new crank pulley

joe27979 · Jun 3, 2014

chaps.
Fitted a new crank pulley and the new pulley came without a notch in it for TDC!

its a 3mb 2.25 petrol, am I right in assuming that as valve 7 (cyl 4 inlet) is fully open then I am at 6DBTDC?

Just trying to work out the best way to mark up pulley, or should I stic a screwdriver in number one piston and mark pulley when screwdriver is at top of its stroke?

Or should I watch the lobes...

Old wives tricks welcomed please. :whoosh:

Dr_evil · Jun 3, 2014

mark at tdc one way and then in reverse and split the distance

joe27979 · Jun 3, 2014

Dr_evil said:
mark at tdc one way and then in reverse and split the distance

cum agen say what Doc?

Dr_evil · Jun 3, 2014

screwdriver in bore, rotate clockwise, mark tdc, rotate anti, mark tdc, take the distance on a piece of paper and split then mark on pulley, thats tdc, there'll probably only be a cm or so gap

mrchurchill109 · Jun 3, 2014

Use a piece of key stock to hold old and new pulleys face to face and transfer the mark from old to new. Of course, that prob'ly would have worked better before you installed it...

ajr

dominicbeesley · Jun 4, 2014

What Dr Evil says, don't do it from the tappets as you don't know if someone else has set the cam wrong. Borrow a Dial test indicator you'll struggle to see/measure TDC accurately.

It's actually better to stick a DTI down the hole and mark off when it's about 1/10" down on either side and split the difference and 2/10" again and 3/10"...as much as you can be arsed. That will reduce errors due to the little end bearing being out.

joe27979 · Jun 4, 2014

cheers Dr and Dom,
I have a DTI that I can attach, its possibly not long enough reach to hit the piston face down the spark plug hole so I will have to attach something to it first.

Joe

joe27979 · Jun 4, 2014

ps why rotate anticlockwise? I thought it was a no no on these engines?
Is it to take up any slack in bearings etc?

Dr_evil · Jun 4, 2014

No it's to get tdc at both ends of the revolution as there's obviously an error percentage so you then split the difference for true tdc between them

dominicbeesley · Jun 4, 2014

They go backwards fine. You don't want to run em arseways but I've turned mine back and forth with a big spannerer on the crank nut.

jamesmartin · Jun 4, 2014

joe27979 said:
ps why rotate anticlockwise? I thought it was a no no on these engines?
Is it to take up any slack in bearings etc?

just turning clock wise takes up slack in chain so its as it will be when running, should be done when checking tappets or timing etc ,but if its just tdc you can rock crank back and forth, theres a couple of degrees were piston it at tdc going from up to down

joe27979 · Jun 4, 2014

muchos gracias.
so I stick my dial gauge in no1 plug, rotate on compression stroke and mark pulley when dial stops moving..then rotate it back the other way and marke when dial is fully up/stopped moving-and midway is TDC

cheers fellas

TDC on new crank pulley

joe27979

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