I have read a lot of articles on here trying to understand the effects of advancing or retarding Cam. How does this effect timing marks , does it increase / decrees vacuum and change carb adjustments.
gjaprops
The effect on timing marks will be nil, as you'll still use them the way you'd always use them, the thing that changes is the cam's position in relation to those marks....and you'll need to degree in the cam to ensure that it's correct, whether you advance or retard the cam....however, it will affect cranking compression, dynamic compression, vacuum, peak power rpm, and may require additional tuning to fuel system.
Advancing the cam will generally move the peak power lower in the rpm range, and there will generally be a gain in lower rpm torque. Cranking compression may increase.
Retarding the cam will move the peak power higher in the rpm range, and generally reduce lower rpm output. Cranking compression may decrease.
However, the only way to accurately tell will be to degree in the cam to the desired location and put it on a dyno. Then move it around until you find the sweet spot for that cam/combo. You can guess all day long at what you need to do but without actual data telling you what is happening, it's a crap shoot at best. Different combos will respond differently when a cam is advanced or retarded.
Advancing the cam will generally move the peak power lower in the rpm range, and there will generally be a gain in lower rpm torque. Cranking compression may increase.
Retarding the cam will move the peak power higher in the rpm range, and generally reduce lower rpm output. Cranking compression may decrease.
However, the only way to accurately tell will be to degree in the cam to the desired location and put it on a dyno. Then move it around until you find the sweet spot for that cam/combo. You can guess all day long at what you need to do but without actual data telling you what is happening, it's a crap shoot at best. Different combos will respond differently when a cam is advanced or retarded.
Also changing the cam timing, so you have to reset the ignition timing. I've played with 1/2 tooth (4.75 degrees cam) +/- on a dyno.
Different deck heights changed the cam indexing. 207mm vs 212mm. That was over 25 years ago.
Different deck heights changed the cam indexing. 207mm vs 212mm. That was over 25 years ago.
Alaskaracer covered it pretty well. But I'll state this: The dyno will show you the changes but most racers experiment with the performance change in cam timing by making passes at the track. Just like changing transmission gear ratios, rear gear ratios and torque converter(s), the car's performance will tell you if it's good/bad. Most (if not all) of those that do this have a cam drive that can be adjusted "externally" in a few minutes without disassembly of the engine.
With 2 posts in this thread, and join date 2 days ago, probably not helping anyone who really wants to move a cam. 
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