Just picked up a small cap HEI distributor for my sons 66 Wildcat w/ 401. I remember seeing somewhere that mentioned the nailhead typically likes less timing advance than most motors. This distributer does not have a ton of adjustment, but i wanted to get it as close as i can. What initial timing does a stk motor typically like? What total mechanical advance does a stk motor typically like? All in by what rpm? What about vac advance? Any help would be most appreciated! -Mark
Well, i believe i found most of the info i was looking for. Looks like 12 deg initial and total of 32-34 all in by 2500-2700rpm. Anyone know how much vac advance i should have? I assume it should be ported vac, correct?
The car, weight and gearing, avg cruise speed might ultimately determine how much you can add. 10* would be reasonable, with the ability to road test using a vacuum gauge being quite helpful.
I have an Electra 65' with the 401".. I run pertronix conversion, with pertronix coil, full 12v and 8.8 wires. I have the lightest springs in from the springkit and manifold vacuum at 32-34' at 2600-2800rpm ( guesstimate, no tach ) I picked up a lot of smoother power and more mpg.. At 60-65mph it goes close to 20mpg.. it's a different story when you keep you foot in it at every opportunity..
Tommy set my distributor up, I've got 24 in the distributor at 3k, run either 10-12 initial. I used the method described on Larry's power timing thread to limit my advance to 10 (20) degrees.
I have a question.. I am setting my vacuum advance and I see mentioned a lot 10deg which is 20 at the crank ... What does this mean ? I only look at my timing light atthe timing pulley... Why the 2x difference ? On the pulley do I look for +10° or +20° vacuum advance ?
Distributor is 1/2 of engine. So 10* dist. =20* at engine. Normally I like to limit set-up vacuum at 4*-8* at dist. which = 8*-16* at crank.
Thanks. I have a vacuum advance with aB1 stamped on it. I found this on the net: The B1 was used on numerous GM applications, including some high perf, but I like the VC 1810 (B28) better. They both provide the same 16º of advance but the B28 is all in by 8" of vacuum while the BI doesn't reach max until 16-18". --> So is this saying that it advances 16° at the distributor or the crank ? Should I find a way to limit the adavcne or am I fine ? Here is my set up: 1960 401 nailhead: I am at 8 initial advance at 700RPM I am at 12° with mechanical at 1000RPM I am at 20° at 2000RPM I am at 30° at 3000PRM... all this is with vaccum disconnected. With vaccum connected at 2800-3000RPM I am above 40°... Is this too much ? What should be my maximum ? I am over heating a bit during sitting traffic and I would like to lower the temp. I should set it to 12° initial advance but I am scared that will then bump my 40°+ to 50° .... is this good or bad ?
Here is my distributor.. I have a thick grey spring and a light silver one... I did this 15 years ago (was an non skilled amateur then)... Dont remember my thinking then...
8*-12* initial. 30*-34* total all in by 2400-2800 RPM's. Complete total incl. vacuum 42*-46*. Listen for any pinging & back off as nec.
http://v8buick.com/index.php?threads/power-timing-your-buick-v8.63475/ The above thread applies to any engine. As far as distributor degrees vs. degrees at the crank, nobody talks about distributor degrees unless you are modifying a distributor. 1 distributor degree = 2 degrees at the crank. 30-34* total at the crank, without vacuum advance is what most Buick engines want for best WOT power. Bringing it in quicker boosts low end performance. As far as vacuum advance goes, most engines can easily tolerate 40-45* at light load cruise for best economy. Most stock vacuum canisters delivered 14-18* at the crank. That was fine with stock distributor springs that didn't allow full mechanical advance until 4600 RPM or thereabouts. At cruise RPM, only part of the mechanical advance was in, so the 14-18* of vacuum advance put you at about low 40's, about right. Speed up the mechanical advance so ALL of it is in at cruise RPM, and now you have to limit the vacuum advance canister to again make it mid 40* timing. It isn't like you have a choice of what initial timing and what total timing to run, UNLESS, you can adjust the mechanical advance, not easily done on stock point or HEI big cap distributors. Some of them have a lot of mechanical advance built in which restricts how much initial advance you can run. If your initial advance is low, the engine will run hot at idle just from that. In that case, you don't want ported vacuum to the vacuum advance, you want manifold vacuum to boost your closed throttle timing. Bigger cams will like more initial timing. Again, unless you can adjust mechanical and vacuum advance amounts, your choices are limited to the distributor you are using and it's specs.
Tom, Thank you for all your help. I often follow your posts ..... but I am not sure I have ever heard pinging. What does it sound like or what should I look for ? Larry, I printed your post on power timing and reread it several times. Very easy to understand. Thanks.
Glad you found it easy to understand, that was my aim, not all understand it though. Pinging is a rattling noise some describe it as sounding like marbles in a can.
Just for information purposes here is my ignition info. It is a 401 nailhead (1960) with a carter carb: RPM 500 1000 1500 2000 + Adv (all w/o vacuum) 12° 17° 20° 24° With Vacuum 12° 19° 36° 42° 45° (40° at 1700 RPM) At standstill the engine had a tendency to overheat slightly.... Here at idle and revving a bit it stayed at 180° although with a IR heatgun I could measure different areas on the engine that were higher (I guess that makes sense) from 177° to 230°. Most areas were avrg 195°. Exhaust was at 400°.
Try connecting your vacuum advance to manifold vacuum. That will give you added timing at idle. Most pre pollution device engines had the VA connected to manifold vacuum.
Are you implying that I could use more advance at low RPM ? Isn't that enough already (I have no idea) ? I have 40° at 1700RPM.. Are you saying I need more ? How much advance can an engine usually take at low RPM ? I could also put a softer spring on the mechanical advance to make it come earlier.....
No, I am saying that the more advance you have at idle speed, the cooler your engine will run in stop and go traffic. An engine can take plenty of advance at low RPM, especially one with a bigger cam. I have my advance locked out at 34*, so it runs at constant timing. I also have 10* of vacuum advance. So at low RPM, at idle and slow traffic, I have up to 44* of timing. Between that, my aluminum heads, intake, and radiator, the temperature never goes above 185 with a 180 stat. You can hook your VA to ported or manifold vacuum. At part throttle, the VA will be exactly the same. At WOT, the VA will drop out completely. At WOT, vacuum will be at or near 0. In order for the VA to add timing, engine vacuum must overcome a spring in the canister. At WOT, when vacuum goes to 0, that same spring pulls whatever VA timing there was out. You have nothing to lose by switching to manifold vacuum for the VA except cooler temperatures when idling and stop and go. Try it and note the difference.
