engine crunching sound with more timing?

this one is a wierd one, since I've put the heads/cam/intake/headers/lifters, etc in the stock bottom end, with the tweecer if I essentially run anymore than 28* total timing at lower rpm's the motor makes a really loud crunching sound.. you know how a motor kinda shakes, its almost like something is hitting something, but it sounds internal to the motor? what could this be? as soon as it starts to rev it smooths itself out..

is this time for a better damper?? or is this a distributor problem? or motor mounts? anyone ever had this? I know its timing cause I went into my tweecer and dropped total timing under 1500 all across the board to 24* and instantly it went away (and idled smoother too)...

another worry is what sound would your motor make if your valve train geometry (or, if your pedestal mount lifters weren't set at the proper tightness?)... would the above be the result?

thanks !!

Michael Yount said:

Is it detonating - sounds sort of like marbles rattling around in a can? Too much timing can cause detonation. Not sure if that's what you're experiencing or not, I guess it could be described as a crunching sound.

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that's exactly what it is... wierd that its detonating at lower rpm's, is it not getting enough fuel or something? as soon as it gets over 1000 rpm's it doesn't make that sound... I have a tweecer, wonder what I should do to fix this (I've lowered the timing for now)...

Michael Yount said:

First thing I'd do is pull the codes and see if something obvious is amiss -- like a malfunctioning egr; those often cause detonation.

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I only pulled a 512 KAM error... this is the wierd one, who knows what this could affect.. this timing pull at the low rpm low loads is working, stock program has 43* timing at these low loads.. that seems crazy...