True Tdc From Engine To Engine

[skinner2k3 3]

Can the crank woodruff key slot and therefore TDC vary from engine to engine?

 

Basically I need to swap my cylinder head onto another block having spun a big end. I want to ensure my cylinder head is refitted in exactly the same position relative to the crank. I figure if I lock the current bottom end with a 10mm dowel through the alternator pulley and mark the position of the cam against the cylinder head casting, then fit the same alternator pulley to the replacement bottom end and lock it via the dowel, then fit the head ensuring the cam/cylinder head marks line up I should be back where I was. Assumptions being the woodruff key slots are identical as are the dowel slots in the block casting.

 

The reason being I spent 2 hours on a rolling road setting up the cam timing not two weeks ago and would like to get as close as possible to the exact same cam position relative to the centre of the dwell at TDC as possible.

 

Or do I need to get the DTI out find TDC of both blocks and refit head/adjust cam pulley according?

 

Cheers

[pug_ham 245 3 Cars]

It shouldn't be any different imo.

 

Petert's topic Fining TDC might help speed things up for you.

 

Graham.

[welshpug 1,666]

I take it that your cam pulley doesn't have the locking pin hole in it?

 

a paint mark on the top cover and the cam pulley would be sufficient, you could mark the belt top and bottom too to make sure it goes on in the same place.

[skinner2k3 3]

Thanks Graham, I will have a read.

 

Its a modified XUD pulley, so no locking hole.

[skinner2k3 3]

The current block had a TDC bracket on but I assumed it was out as the cam was designed for a certain lift at TDC. At TDC I have much more lift than specified, this was set for best power on the RR.

 

I will have another look. I think finding the center dwell at TDC shouldnt be too bad as I can measure from inside the sump on the piston skirt rather than trying to get a dti extension through the spark plug hole. The new block can be checked with the head off.

 

Then again going by some marks on the belt top and bottom should be full proof unless the crank and cam centers can change, ie deck hight. But thats not going to be much. More likely to have a slight variation in HG thickness.

 

Cheers.

[DrSarty 90 1 Cars]

TDC is TDC. It's related to the bottom end only.

 

Cam timing can be set in relation to TDC (e.g. lift at TDC), but TDC is a bottom end thing only.

[luggy 13]

Basically I need to swap my cylinder head onto another block having spun a big end.

 

Slightly off topic but related to your predicament, make sure the little filter in the head is clean of any shell derbis before you transplant it.

[skinner2k3 3]

TDC is TDC. It's related to the bottom end only.

 

Cam timing can be set in relation to TDC (e.g. lift at TDC), but TDC is a bottom end thing only.

 

I know, I wanted to know how accurate the position of the woodruff key was to avoid the need to check TDC when swapping bottoms ends.

 

Cheers Luggy, although I have to admit I dont know where that is!