Cam timing - how am I doing?

[Cevan]

I’m at the point in my rebuild where I am timing the cams on my ‘86 3.2. First time doing this so just wanted a little feedback to confirm I’m doing this correctly. Per Webcam, I’m shooting for 1.9 - 2.2mm with .1mm lash with 20/21 cams. I am trying for 2.05mm, splitting the difference. I installed the #1 intake rocker, set the lash to .1mm while crank is at TDC. Installed my dial gauge, zeroed it out and spun the crank 360 degrees. I measured 1.25mm of lift.

I then continued to rotate the crank until at got to 2.05mm, removed the sprocket bolt and pulled the pin, at which time the cam rotated. Of course! I had read this may happen. I tried this a second time and same result.

So I started over, back to TDC, “930” mark pointing up, inserted the pin and rotated 360 degrees again. This time I was short again at 1.3mm. So I figured I would try and advance the cam when I was back at TDC so I rotated back around to TDC, gauge went back to zero, removed the bolt and pin. Then I used a small punch to gently rotate the cam relative to the sprocket maybe 1/2 a degree so I could move the pin one hole. Reinstalled the bolt and rotated again. This time I was closer to 2.05mm but not quite there. I repeated this maybe 3-4 more times and crept up on 2.05mm. Just prior to the last time, I tightened the cam bolt up to about 30 ft lbs as I felt this time would get me there. I then torqued to the 120 ft lbs and rechecked. Still at 2.05mm. I repeated this on the right side with #4 intake. I got to 2.07mm. Is this close enough?

I’m going to recheck the left side again to confirm my measurement, and then probably the right side again. Thanks for the feedback.

[Classic 911]

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[walt]

.02 mm variation is good that's less than .001 in. You can use your cam holder to rotate the cam back to the correct setting if it moves which it will with only one rocker in place. I found this video from Klassic that explains the procedure really well.

https://www.youtube.com/watch?v=u2HbSNdAB3A

[john walker's workshop]

Put all the rockers in next time and take up any slack. Then the cams won't move. Never understood the only one rocker approach.

[Cevan]

Originally Posted by walt

.02 mm variation is good that's less than .001 in. You can use your cam holder to rotate the cam back to the correct setting if it moves which it will with only one rocker in place. I found this video from Klassic that explains the procedure really well.

https://www.youtube.com/watch?v=u2HbSNdAB3A

My engine is 3.2 and there is no way that I'm aware of to rotate the cams CCW independent of the sprocket.

[HaroldMHedge]

Thanks for the great tip John.

[john walker's workshop]

Originally Posted by Cevan

My engine is 3.2 and there is no way that I'm aware of to rotate the cams CCW independent of the sprocket.

With bolt style cams, set the cam timing where you want it, then pull the pin and turn the crank to the Z1 position and put the pin in whatever hole will take it. Snug the bolt and recheck. The cam will stay put as the crank is turned ( if you have all the rockers in place).

[Cevan]

Originally Posted by john walker's workshop

With bolt style cams, set the cam timing where you want it, then pull the pin and turn the crank to the Z1 position and put the pin in whatever hole will take it. Snug the bolt and recheck. The cam will stay put as the crank is turned ( if you have all the rockers in place).

Thanks for the tip. Too late for me but hope it helps others. To be honest, I was a little hesitant to start spinning the crank with any more than one rocker in initially.

[David Inc.]

Originally Posted by john walker's workshop

Put all the rockers in next time and take up any slack. Then the cams won't move. Never understood the only one rocker approach.

Maybe it's idiot prevention so when you spin the crank 360 without moving the cam you're only chewing up one cylinder's worth of stuff than three.

[proporsche]

Originally Posted by john walker's workshop

Put all the rockers in next time and take up any slack. Then the cams won't move. Never understood the only one rocker approach.

yup... this^^^^

Ivan

[shoooo32]

Wayne's book recommended the one rocker approach. As a noob I had no reason to doubt it.

[Dripola]

Wayne’s book probably suggests one rocker approach for the first run, when your measuring valve to piston clearance. It’s easier with all rockers are installed.

Question though, what’s the issue with having both sides timed differently, the engine wouldn’t run as smoothly right?

[Classic 911]

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[unclebilly]

Why 2.05 vs 2.22? I think I set my race car up for max opening and got it bang on with DC40 cams.

[Cevan]

Originally Posted by unclebilly

Why 2.05 vs 2.22? I think I set my race car up for max opening and got it bang on with DC40 cams.

Per the information from Webcam, the instructions state to set the cam to 1.9 - 2.2mm. Splitting the difference gives 2.05mm.

Can you explain why you suggest 2.22mm? I do not race my car btw. Purely street driving.