8 replies to this topic

[amsgw]

Appealing to those more experienced before I tear my hair out
Timing in the new Evo01 cam on a fresh rebuild. Reusing sprockets with replaced chain and tensioner. Original crank (ground).
** Method: bring crank to TDC with DTI, set up chain and sprockets dot to dot, install. Reconfirm TDC, set this on the cam timing wheel. Inlet valve (2nd from rad) to max with DTI, then measure at 10 degrees (reading from the DTI) before and after the max. Average the values. **

Dry build with a new standard woodruff key gave me a reading of 124.5 + 81 = 102.75 so purchased a 4 degree woodruff to get to 107
Installed woodruff. Per advice as it wouldn't sit flush in the cam, lightly filed down the hemisphere side until it would.
Now with the 4deg key installed I'm getting:
112 + 69 = 90.5 (offset edge to the right)
122 + 80 = 101 (offset to the left)
In despair I tried one tooth over from the dot to dot starting point, which gave me
142 + 100 = 121 (offset left)

Neither sprockets have been free sliding, they require fair force to either pull off or put on. From memory they were also like this when I took them off in the original tear down.

This truly doesn't make sense to me. Any clues as to where I'm going wrong? Any advice welcome at this stage. Thanks all

[timmy850]

Where have you got your DTI set up on the valve side? Is it on the pushrod or are you using the valve?

[Ethel]

Are you also turning the engine in the running direction to get to your reading points?

[amsgw]

DTI is set up on the pushrod as if it's a rocker arm. I'm turning the crank over clockwise when facing the radiator to reach peak height, then measuring 10° past peak height going clockwise and then anticlockwise

[KTS]

it may be accidental, but you've mentioned taking measurements 10 degrees before and after peak lift twice now.  I would assume you've taken measurements at 10thou before and after peak lift ?

 

if so try repeating the measurements at 20thou before and after peak lift, and as Ethel advises,  both measurements need to be taken with the crank being rotated clockwise

[amsgw]

Sorry yes, I'm taking the measurements at 10 thou to then read off the degree wheel. Doh!
I'll give 20thou a try

[imack]

DTI is set up on the pushrod as if it's a rocker arm. I'm turning the crank over clockwise when facing the radiator to reach peak height, then measuring 10° past peak height going clockwise and then anticlockwise

Never take a reading after rotating the engine anti clockwise, you'll get a false reading due to slack int the timing chain.
I note peak lift value on the dial gauge for no. 1 intake valve, then rotate the crank about 90° anti clock, then slowly rotate the crank clockwise until 3 thou short of peak lift and not the crank degrees. Then continue rotating the crank clockwise until 3 thou past max lift and note the crank degrees. Then you have the two figures to add together and divide by two.

[Spider]

You should check for engine TDC in a similar way to how you check for your cam peak left, only instead of checking in the same direction of rotation, check with piston rising for both numbers for your average calculations. Or you can use a Piston Stop and average it from that.

I note on your opening post you are measuring 10⁰ before and after peak lift - instead of that try 5 or 10 thousands of lift rather than trying to use the angle, ie establish what your peak left number is then measure the angles at 0.010" before that and after that, as imack has suggested, in the direction of rotation.

[amsgw]

Ah that makes a lot of sense, thank you imack. My brain couldn't make sense of the numbers not making mathematical sense but the slack could definitely explain it.

I'll double check my TDC as you suggest Spider, that could also be why such a random difference in measures.

Thanks all for saving my sanity