Need tuning help on 340

midnight340 said

I've just go a relatively inexpensive timing light (non-dialback, which is recommended with MSD) Could be it is off.

And I'm not very experienced with reading plugs. I'd like opinions on the plug heat range, and any info as to timing that can be seen by you guys with more experience.

I could see no evidence of grey or tan at the base of the porcelain (with otoscope) in spite of what I'm told is a fairly fat A/F of about 11.5-12:1. (most sites say 12.5-13 it seems)

Click to expand...

do you have a friend with a timing light?
also, are you sure you're getting all the way to the end of the advance curve when you are checking total timing? maybe there is a stiff second spring in the dist. that is extending the curve further up in the rpm range...

anyways, if i were you i would try to bump timing down a little lower even, maybe 2* more and see if it still detonates.

the plugs to look really clean too, but for full throttle you should be looking way down into the porcelain to see if you can see any color down there after a full throttle blast like you did...

once you get some color on the plug then maybe try adding a little more timing back in...