76 Cam Timing rebuild
 

UPDATE: Setting the correct lash has brought the numbers into spec. All good now.


So I am going through an unknown engine that was not finished being built. It was missing the final part of Al Kosmals EFI for ITBs. Since the engine is partial dismantled I wanted to check some items like RSR seals, lash, setting up the Carrera chain tensioners, ... Check Timing :rolleyes:

Anyway I put the Z block on with my dial gauge set it to the top of the retainer on number one with the engine at TDC (Z1). I rotated the engine 360 back to Z1. I see .0145" (.3683mm). Looked for overlap values and found .4 - .54mm. Went to the other side on #4. Got .0121" (.3073mm). So both sides are relatively matched with each other and if they were in the range I believe they would be acceptable. Is there any reason why these 911S 76 cams would be timed to what they are instead of .4 - .54?

Engine Specs
1976 - 911S 911/82 CIS
Heads drilled for twin plug
Cams are said to be 76 cams - I know what is the purpose of twin plug with stock cams :confused:
Induction will be Megasquirt running ITBs

I guess my next question is, am I to open the chain cases and reset the timing to be within the .4-54mm spec?

You have to pull the cam to actually know the grind. Or if any cam shop has modified the grind
See stamping on ends for regrind info.
Bruce

Ah Bruce, nothing can be simple. Is there any way that the lobes can be measured without pulling? Like measuring the total lift?

Yes. Measuring the valve lift on both the intake and exhaust can give you an idea of which cam grind it has. If you have a degree wheel, it'll narrow it down even further.

You were talking RSRseals so you remove the rockers anyway
Bruce

Looks like a used engine with a little chain stretch, which will retard the cam timing a little.

Thanks, I rechecked the lash and it was not set to .10 mm as I had originally thought. Things are now looking in spec.