[YodaFan1138]

Hey fellas,

My 69 Mach I 351W FMX 3spd auto was not doing well on the 92 octane pump gasoline--it wouldn't handle the 6* btdc factory timing setting since the guy that had it before me put in a radical exhaust cam (not sure as to the layout of lobes, but idle is real lopey with the straight (no h or x crossover) pipes) and the bore of .060 over, so I added a bottle of Pennzoil Outlaw Octane Booster to my next tank of 92 octane--I noticed improvement in acceleration and elimination of all pinging, so I thought I might get greedy and advance it a little farther. I got the timing to 5* without any detonation whatsoever.

My question here is whether or not I can advance the spark timing too much. My understanding is that the farther I can advance it (to a point, of course, and as long as there's no detonation) the more power I can produce and the better MPG I can achieve (as of last tank, I was getting a whopping 7.87 mpg). Below is a diagram of my harmonic balancer

Passenger side of car

--10
-
-
-
-(where timing was before)
--5 (where timing is now)
-
-
-
-
-(Can't read what it says here-maybe tdc)

Driver's side of car


If I put the timing mark at the 5 above, is that BTDC or ATDC?

Thanks for the help--check out my post from a couple days ago as well. Thanks again!

[Vortex]

the 5 degrees is before top dead center.. that way the spark starts burning right when it compresses for more a even burn.

You can advance it as much as the engine will allow.. if you get detonation, back it down...

[NoSlow5oh]

Yodafan1138, from my understanding in your post you have the wrong idea on the timing. When you advance the timing, you would move to a higher number BTDC. So if you had 6* BTDC and you advanced it 1* then you would have 7* BTDC. If you had 6* BTDC and you retarded it 1* then you would have 5* BTDC. You are right though when you say that an engine will perform better with the highest number of timing BTDC right before it detonates. If it was pinging at 6 and at 5 it doesn't ping anymore then 5 would be your best bet.

[EZBNME]

Are you having spark knock at part throttle or full? Do you run a vacuum advance? Total timing is what you need to check with vacuum advanced unhooked. You can curve distributor to allow more intial timing without having to much total and change vacuum advance rate. Also, if ignition fires to late with increased cylinder pressure it will spark knock. Check the heat range on your plugs and make sure carb is not leaning out engine. It's not true that engines always make the most power advancing ignition until it quits knocking. Cylinder head design among other issues determine amount of advance. High swirl heads like TWs like say 32 degrees total timing where as a Dart would like 38 (examples).

[pjodea]

HELP! my new 302 can go beyond the balance limit. When I run the RPM up, the mechanical advance out runs the RPM. Does the vac nipple @ 5:00 vice 7:00 cause the non linear range difference between the two?