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MP, engine builders and the general consensus is that a 440 should be limited to 35 (+/-) degrees advance. I swapped my distributor last night due to a faulty pickup ,set the timing at 35 BTDC at 3,000 RPM and base timing is about 15 BTDC now at idle.

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I've run and still run, my timing at 37*. Full out @ 1100 rpm. 25* in the distributor, so that gives me 12* initial timing. I haven't used a vacuum advance in 35 years. 'Works for me!

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Well, for the past 15 years or so the consensus best dyno numbers for stock heads show 38 degrees total at 3000 rpm.

How an electronic ignition "knows" there is a vacuum advance is beyond me. That's one reason I am suspicious of the RNN.

When you are not at wide open throttle there is less in the chamber and it takes longer to light it all off. That's why the vacuum advance is there. It is not at all unusual to have 55 degrees advance at light cruise.

R.

BTW, there are very few times where I have found E-booger to mis-speak.

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As was stated vacum advance only works at cruise and part throttle where vacum is high. The vacum advance does not work at wide open throttle because there is no vacum at wide open throttle. Thats why race cars dont use vacum advance since they are at full throttle most of the time. As for how much total mech advance it depends on the combo. I have seen anywhere from 32 to 40 on NA bigblock Mopar engines. Right now I run about 37 total on my 63. Many combo's will have to try it at different settings to get the best power without eng knock if it uses pump. Also aluminum vs iron heads makes a difference as does comp and many other things to determine full mech advance. Ron

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Well, for the past 15 years or so the consensus best dyno numbers for stock heads show 38 degrees total at 3000 rpm.

How an electronic ignition "knows" there is a vacuum advance is beyond me. That's one reason I am suspicious of the RNN.

When you are not at wide open throttle there is less in the chamber and it takes longer to light it all off. That's why the vacuum advance is there. It is not at all unusual to have 55 degrees advance at light cruise.

R.

BTW, there are very few times where I have found E-booger to mis-speak.

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Hence my question, the RNN thought is that as the vacuum advance moves the breaker plate around there is the potential for some "chatter" or movement. I honestly dont understand the "electronic flywheel" concept either, other than it is supposed to give you more smooth and stable timing. I do know that out of the box a distributor's vacuum advance will need to be tuned. I just didnt understand the thought behind NOT running a vacuum advance.

X2 about Rick, I have been following him since the days of the first One Lap car - The Blue space Duster! and he is seldom wrong!!!!

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Different heads and compression along with the fuel
need the timing at different points.. use the MINIMUM
timing that gives you the best conditions... if you
had a near perfect set up your timing would be about
33* with load... in a cruise condition you have very
little load and can have the vac pull more timing
in so its more efficient at that load... remember
that if you are just off idle cruising along you are
getting a SMALL amount of air and fuel into the cyl
so it needs more time to get the full burn in the cyl
to get the max out of it... its not compressed like
if you fired it at 33*... the 33* is whats needed
to get the full burn so the piston is just coming over the
top when the fuel has the max power to push the piston
down... its all about using what power is in the fuel
and when to ignite it to get the most out of it
EDIT
Fuel that isnt compressed burns very slowly vs fuel
that is compressed hence the added timing

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It all depends on the efficiency of the chamber, quench and quality of the fuel. If you have tight quench and a very efficient chamber, it won't need a lot of spark lead to get the mixture burnt properly. Case in point, my 360 has .036" quench and MP R/T heads. So, tight quench and a fair to decent chamber with a material that won't absorb heat too fast. I ran it at first, with 38 degrees total timing, locked out. In a pickup truck, 4wd, 4800 lbs and the aerodynamics of a brick. Never detonated. Didn't tinker with the timing at all. Set the initial, found out it'd start fine locked, so I locked it in and then hooked up the vacuum advance after all the adjustments were made. Fast forward. Bored with the truck and my '72 challenger had no engine. Yanked the 360 out of the truck and stuffed it in the car. Had occasion to chassis dyno it and, lo and behold, dropping timing to 35 degrees picked up power. Left it alone until I pulled it again to freshen it and ran it on the engine dyno prior to teardown. Long story short, this little engine made 388 hp with a low 31 degrees of total timing. Perf RPM intake and a comp, hyd roller, 216/224 @.050, 114 lobe separation, installed at 110. I didn't keep testing, but it may have made more power with even less timing. No longer work at that shop and the engine isn't complete yet so I have no further information on it. But, my point being, there is no magic number. Start low on the timing and turn it up until it slows down. Watch out for detonation and keep an eye on those plugs. Keep in mind a lean mixture needs more advance to burn fully (hence the need for vacuum advance once people started worrying about fuel economy).

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I hear ya but generally smallblocks like less lead from my experience..................

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Course there is often a difference on what gives peak power on a dyno and what gives best 1/4 miles!

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True.........a stocker racer a few here know was racing w/38 degrees timing(smallblock)or there about and thaught that backing it off would slow him down so he set it at around 32 degrees and actually went faster. Same guy raced w/a good amount of ballast in the trunk to "fool" the other racers and thinking he had em way covered, removed the weight and went slower............