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init. tim. + cent.adv.tim. = total timing.... max on initial? MSD bushing swap?

6

67resto-coupe

Member
so i was reading an old article in car craft (jan.'09) on a new boss 302 crate motor. most of their motor specs were pretty close to what i have....main differences were heads and carb. they're running turbo swirl alum heads and i have iron gt40p heads. the tester boss also has a 650 holley w/mech secondaries, jetted at 69/75...i have a 625 demon w/vac secondaries, jetted at 67/72.

from there, i read that they ran 37 degrees of total timing. seems like a lot. i'm running 16 deg initial and have the 18 degree black cent.advance stop bushing on my msd billet dizzy. so that should put me near 34 degrees of total timing, right?

QUESTION: is there a maximum amount of initial timing that you can run? can anyone tell me what bushing they're running in their msd? the instructions indicate that i can swap out the 18 degree BLACK bushing and swap it for a 21 degree BLUE bushing. that would get me to 37 total = 16 init + 21 degree cent.adv.

is there power left in those extra 3 degrees that i haven't tapped into? can i pull the bushing without pulling the dizzy? i hate to have to do that....should i swap the bushing?

thanks in advance.
 
A lot of timing is dependent upon the cam you're running. Other factors are compression ratio and whether you're running an auto or manual transmission.

16* is a lot of initial advance. I run ~13* initial with a lot of valve overlap. Your roller cam probably doesn't have nearly the valve overlap my cam does, so your low rpm cylinder pressures are going to be higher, necessitating less timing advance. I'd recommend somewhere around 10* as a good starting point.

37* does sound like a lot of total advance, especially on fast burn heads, but they can get away with a bit more on aluminum heads due to quench. They have the advantage of a dyno to test things though, where I imagine you don't. You have to guess, basically.

I'd shoot for 32-34* total. Yes, you can replace the bushing without pulling the distributor. You just have to have small fingers and be able to keep the nut and bushing from falling into the distributor when you take the nut off.
 
Not much help, but I found (through chassis dyno tests) that my engine ran best when I backed it down to 30* total. Started at 35* and went down to 28* to find the best setting.
 
doh! i forgot to mention in my initial post that among all of those similarities, both the "new" Boss 302 and my "new" roller 302 - are both running the same E303 cam. so back to starfury's post... i suppose alum heads could allow for timing that high, forgot about that.

i do have small fingers and while i can get the nut and washer off, i can't get the bushing out from it's recessed area.

....maybe i'll just leave well enough alone for now...but i'm still open to add'l opinions.
 
E303 likes a lot of initial timing - mine was up in the 14-16* range as well.
After reading the late-model boards, I found that's what many of them were running with that cam...
 
Weird. Maybe that E303 has more valve overlap than I thought. I'm not a roller cam expert by any means.

If you can't get the bushing out, stick your finger under it to catch it, then tap the top with a wrench. It should drop out.
 
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