Base timing for TBI-HEI with .060 spark plugs

With my tune, I never drop below 20* spark advance. Would it make sense to rotate my dizzy to, say, 10-15* base timing in order to align the cap&rotor more closely when PCM fires the coil?

What say ye, regarding startup cranking and whatnot? Any reason not to use 20* base, or even 25*??

My plugs are glazed and I've had awful misfire problems lately (not a major concern 'til it recurs). I happen to have a new set of delco iridium vortec plugs factory set at .060, which is a way bigger gap than stock TBI speification (HEI). I was previously using the copper vortec plugs gapped to .035 or so.

The .060 plugs work, but I worry the larger gap could spell trouble for other ignition components down the road.

considering that the module itself determines timing below whatever RPM(assuming i'm remembering this correctly), i wouldn't change it... if you drop into limp-home mode(or the EST line for some reason breaks), you're going to have a LOT more advance than what it was intending.

you could try it as a test and maybe change the EST enable RPM to something really low to minimize the amount of time that the EST module is controlling timing/dwell, but unless you see a significant improvement from it, i would change it back.

I've run lots of advance and always at 0 base timing. The small cap HEI distributor is set to run as much as 41 degrees in the bin. Look into the cap and you'll see a tube, look at the rotor and a channel. They are made right to prevent cross fire, unlike large cap HEI or just old cap and rotors.

I don't have a TBI small cap distributor here but IIRC they are phased a few degrees anyway, star points line up and rotor is still a few degrees away from firing to plug on cap. This is where we got the idea to phase Duraspark distributor conversions years ago...

I thought bigger gaps were proven a myth years ago? They went up then back down, more a marketing scam. Bigger gaps blow out in high compression...

it really depends on a lot of things... speaking from my 60V6 experience:

the LH0 engines run 8.8:1 compression and a .045 gap
the L82 engines run 9.6:1 compression and a .060 gap

the ignition system between the two is identical. i've run .050 on the LH0 before, not sure if there was any noticable change though. i've seen the 60V6 DIS setup still fire a plug with a .125 gap with 9.6:1 compression.... though it did misfire sometimes under full load(which actually registered as knock retard).

I hope you're right about the gap issue being a myth, but I think I'll start carrying spare ignition parts =). I'm up to 39* advance with EGR, hitting 41* yielded sporatic pinging (engine felt good and sounded awesome when there was no pinging).

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if you drop into limp-home mode(or the EST line for some reason breaks), you're going to have a LOT more advance than what it was intending.

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Funny, I see base timing advance as a side benefit for me in limp mode.. I've hit limp mode before (neglected to solder a wire when I remote-mounted my ICM). It was awful, not enough advance for vortec's. IIRC, I think limp mode gives you fixed 15*, I'd much prefer it to be 25*. You're right, though, going overboard would be unwise.

It's a bit cold outside to enjoy playing the timing light game this week, but I may go to 10* when I get to it.

i'm not that familiar with vortecs... but if i ran a fixed 25* on a LH0, it would be it's end. 19* is the highest SA at WOT that the factory calibration shows. the L82 would probably handle it though... runs 23* at 2000RPM, up to 25* at 3600.

considering only the change in compression(8.8 vs 9.6), that's backwards of what i would have expected.