76 Cam Timing rebuild

[Nditiz1]

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

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
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?

[Flat6pac]

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

[Nditiz1]

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

[dannobee]

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.

[Flat6pac]

You were talking RSRseals so you remove the rockers anyway
Bruce

[gled49]

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

[Nditiz1]

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