Valve Timing Theory

[SilentUnicorn]

I have a couple of questions on timing theory. Hope someone can set me straight. I do not need to know how to time them, there are lots of threads on that. I would like to discuss valve events and the results of (mis-timing)moving the timing one way or the other.

Lets suppose i have a kent cam (th2), the intake timing at full lift is 108° ATDC.

what would the effects to performance and the engine be if say it was set at about 90° ATDC? Obviously performance would be lost- but what other effects would be seen? such as would it run rich- or lean? would it run at all? Would ignition timing have to be advanced to compensate? Other thoughts?



mark

 

[texas_bugeye]

You need to talk to Charlie Tolman In Mpls. You can find him at sprite spot He can tell you all you need to know about cams and timming.

 

[lesingepsycho]

My Desktop Dyno says HP/Tq would go from about 80/87 to 67/71. That's a 15% loss in power. Granted, this is just a computer program and obviously it can't say anything about rich/lean, timing or runability. The program always "assumes" ideal A/F ratio and ideal ignition timing.

I can say from my personal experience however that when you install a timing chain set and you get off by ONE TOOTH, the car is still driveable, even some pep, but none of the dig-down-deep, get-up-and-go. I drove my car for months with the timing off by one tooth. I want to say that I had to really richen up the mixture to compensate. I never changed the timing however.

JACK

 

[jvandyke]

The PO had my Opel's 2,0 cam off by one tooth too (or it slipped). I managed to massage it back to good. Hard to tune that way.