Help: 3 Specific Cam Timing Questions...

[Dauner]

Hi,

Attempting to Time the Camshafts on my 1989 Carrera 3.2. I have the engine removed, and have replaced the timing chains due to stretch.

I have adjusted the #1 intake valve to 0.004" to the best of my knowledge, although it is my first time. I have slight drag, and using the backside method, 0.0025" slips thru and 0.003" does not.

I am using a P204 Chain Sprocket Holder to tension the timing chain.

I am using a new dial indicator, and have pretty good confidence that my Z-block setup is correct per "the books".

My engine calls for 1.1mm to 1.4mm valve lift at TDC, with nominal at 1.25mm. Converting using 1mm = 0.03937", the english equivalent would be approximately 0.043" to 0.055" with nominal at 0.049"

My problem is I can't seem to get close to nominal. The two neighboring sprocket hole options (equal preload/backlash on pin) put me either at 0.045" or 0.055". Stated differently, when I rotate crank to achieve 0.049", my TDC mark on pulley either slightly overlaps case split to the left, or slightly overlaps case split to the right, never ending up perfectly aligned.

Questions:

1. Does the range of 0.010" sound right between two adjacent sprocket holes? I don't see how it could be less, given consistent preload and the design of the mechanism.
2. Assuming answer to question 1 is "yes", then should I err toward high side (actually out of spec), low side, or try adjusting my valve gap?
3. If answer to 2 is yes, adjust your valves to bring one of the sprocket holes in closer to nominal, then am I correct in assuming I should increase my valve gap slightly, which will put the hole that ends up at 0.055" closer to nominal?
4. Am I thinking about this too much, and should I just go with the 0.045" which is technically in spec?

Of Course, I am assuming I am doing the entire process correctly. I've read the chapters, and watched the Peter Morgan Youtube video many times over...

Thank You in advance for your thoughts and advice,

Mark

[Eagledriver]

Do not change your valve clearance to get the correct number, you would just be fooling yourself. Either setting you have will work. For street driving I'd use the .055 setting for a little more torque. The reason the spec has a range is for just the reason you've found. There is some slop in the pin holes, so you can try turning the sproket against the pin to get it a little closer to ideal.

-Andy

[docrodg]

After you set it be sure to turn the crank at least 2 revolutions to properly load the pin then use that reading as your final, it can move a little. Also, remeber to check valve clearance if you changed anything.

[Dauner]

Thanks Guys!

Followup question: Am I correct in assuming that I should target as close to the 0.055" for the right side as well? --> Which is more important, being closer to the left side cam, or not going officially out of tolerance?

[docrodg]

In general you should try to get them as close as possible, but not go out of specification as that can cause clearance issues sometimes.