3 replies to this topic

[Ferg 88]

I know this has been covered many times but can someone just lay down an idiots guide to cam timing please. Been struggling with it this afternoon.So far..... New timing gear on and aligned fine. Cam shaft installed Dot to dot fine, TDC found with DTI. Dial gauge on and zero-ed with pointer. Push rod in no.1 inlet and highest lift point found. Gives a reading of 104 on dial. (EV001cam Should be 107 setting.) Next  backed crank .025" then forward .005" and have come up at 86 on dial which seems a bit low to me.Anyway I think I was correct in the next procedure and finish with dial reading of 115. 86 and 115 gives 201 ,half that and its 100.5. Am I correct or  misguided !If correct do I need a offset woodruff of 6.5 ?? I am a bit unsure. Thanks in advance Ferg  

[jaydee]

The trick is, never turn the crank backwards.

I'm not very good at explaining..when you find the highest lift point, set dti to zero then keep turning..two cranks, you then get the timing at 0.005 before the zero then the timing at 0.005 and divide by two, so you have the max lift degrees

There are a few videos on youtube but most of them are misleading.

This can be quite hilarious but can give you an idea:

 

Forgot to say..repeat three times as its easy to get incorrect degrees, and would be better to add further two degrees advance to compensate chain wear.

Edited by jaydee, 07 December 2015 - 09:57 PM.

[dklawson]

If you do turn the engine backwards, turn about 20 to 30 degrees backwards, then slowly in the normal direction of rotation.  The idea is you turn in the normal direction of rotation so all the slack in the chain is taken up as it normally would be with the engine running.

 

Another point I will stress is that when you are finding TDC or the max lift point of the cam, zero the DTI at the point that appears to be the high point.  Turn the crank back 20 to 30 degrees and then slowly forward, stopping about 0.010" before the DTI reaches zero.  Record the angle on the degree wheel.  Then continue turning the crank, stopping when the piston has gone to zero and then dropped by 0.010".  Average the degree readings and then turn the crank to that angle.  Re-zero the degree wheel without moving the crank.  You will now have located true TDC.  Averaging the angle measurements 0.010" each side of TDC will allow you to account for the short period the piston dwells at TDC.  Do the same thing when measuring the max lift on intake 1.  

 

When locating the DTI over the piston, make sure it is on the center of the piston.  You want it to be right over the wrist pin so any teetering of the piston does not affect your measurements.

 

I encourage you to explore YouTube for videos on cam timing.

[Ferg 88]

Thank-you guys for your help. Had another go this afternoon and out of three goes got three consistent results.  The readings were,  inlet valve at highest point 104 degrees then 86. and 117 giving total of 203  ,halved gives a timing of 101.5 cam needs to be 107 so required an offset key of 6 ?? Does this all sound right. The tolerances on these engine timings seems to vary quite a lot. I thought my readings seemed a little low especially the 86 degree. Maybe I am just being paranoid. ! Ferg