finding tdc for cam change
Discussion
if you are worried the marks are out, although i cant see why check with a thin rod in number one cylinder and feel as it proceeds up the bore ,once at approx tdc make a suitable mark on the rod that you can reference and rotate the engine first clockwise to the mark and mark the pulley then anticlock to the mark i.e. slightly ahead of tdc and then slightly after tdc mark the pulley with chalk in both positions then exactly half way will be exactly tdc
john
john
Are your heads on or off?
If on, you need a dead stop and cycle it either side of TDC as said above... Not keen on this as you not sure where its hitting the piston ples your going the wrong way on one of the directions.
If your heads are off, use a DTI and rotating it clockwise half the angle between say 0.05mm before TDC and 0.05mm after
If on, you need a dead stop and cycle it either side of TDC as said above... Not keen on this as you not sure where its hitting the piston ples your going the wrong way on one of the directions.
If your heads are off, use a DTI and rotating it clockwise half the angle between say 0.05mm before TDC and 0.05mm after
The 'myth' about pulley marks stems from the old preserps where an adjustable pointer was bolted to the timing cover & had to be set. This wasn't too much of a problem as the little ends were in the middle of the piston so TDC was easy to derive with the dead stop & half the angle method (although piston canting in rings dictates the dead stop should be a point at the centre of the piston if you really want to be goemetrically accurate). However many folks shifted the pointer so it was out, or even forgot to set /reset it on re-assembly / maintenance work which is why that pointer earned the reputation of being unreliable.
However the later cars have it cast in to the casing so it is not adjustable, these also have pistons with offset gudgeon pins. With the offset pins the piston motion is not symmetrical about TDC, its effectively a slight crank so using the dead stop method will not result in TDC & those pedantics use that to criticise the std timing mark littl erealizing that their method & logic is flawed. Unless you really know what you are doing trust the cast in timing mark if you have it (all RV8s post 4.2 had offset wrist pins BTW).
However the later cars have it cast in to the casing so it is not adjustable, these also have pistons with offset gudgeon pins. With the offset pins the piston motion is not symmetrical about TDC, its effectively a slight crank so using the dead stop method will not result in TDC & those pedantics use that to criticise the std timing mark littl erealizing that their method & logic is flawed. Unless you really know what you are doing trust the cast in timing mark if you have it (all RV8s post 4.2 had offset wrist pins BTW).
I checked my 1997 Serp 4.0 with a dial gauge in number 1. I found that this correlated exactly with the 0 degree mark on the damper aligning with the ignition pointer. So I would agree with Spend in so much as the marks are accurate. Do not confuse the 0 degree marker with the slot milled in the damper though. You need to look closely at the damper to see the timing marks. I never did know what the the milled slot is for????
You need the dead stop as close to TDC as possible, no more than 6degs as the final split to minimize the odd path & dwell from offset pins.
The easiest tool Ive found is to smash up a spark plug then tap the centre, so you can fit a bolt (set screw) and lock nut to use as the dead stop.
The easiest tool Ive found is to smash up a spark plug then tap the centre, so you can fit a bolt (set screw) and lock nut to use as the dead stop.
My experience with setting up a dial gauge for TDC. (2/3 way down page). Setting the new cam location with variable timing sprocket did take some time to get spot on.
http://www.g33.co.uk/tuning.htm
http://www.g33.co.uk/tuning.htm
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