Couple 390 FE questions, PCV system and Timing
#16
12-15-2018, 08:24 AM
There's no debate, just a clarification. I always suggest people should actually try it, to familiarize oneself with how both mechanical and vacuum advance actually works, and how they work together. A vacuum gauge plumbed into the dash goes a long way towards this. A fulltime manifold connection will pull in lots more advance at idle. What does this mean? Well, it will run smoother, and cooler. Won't it cause engine knock? Since there's no load on an engine at idle it doesn't matter, "ping" or engine knock is not a factor, though many people become agitated when they see the high levels of ignition timing at idle RPM using a timing light.
The key thing to keep in mind is a manifold distributor connection won't affect the total ignition advance at high RPM or, under low load cruise conditions. Simply because there's 30° at idle does not mean there will be say, 60° of lead at the far end. It doesn't work that way. I think this is probably the most common mistake a lot of people make.
For all that, unless one is running a highly modified street motor a ported connection is the way to go, what's important though, is that both the mechanical advance and the vacuum advance is setup properly. Because it is not often well understood neither mechanism is generally setup correctly regardless of the hose connection. See this all the time.
The key thing to keep in mind is a manifold distributor connection won't affect the total ignition advance at high RPM or, under low load cruise conditions. Simply because there's 30° at idle does not mean there will be say, 60° of lead at the far end. It doesn't work that way. I think this is probably the most common mistake a lot of people make.
For all that, unless one is running a highly modified street motor a ported connection is the way to go, what's important though, is that both the mechanical advance and the vacuum advance is setup properly. Because it is not often well understood neither mechanism is generally setup correctly regardless of the hose connection. See this all the time.
#17
12-15-2018, 11:09 AM
For what it's worth: On a Ford, manifold vacuum will advance the timing at idle, and then RETARD it as you lay into the go-pedal (vacuum drops), exactly opposite of what you want for a stock or mild motor.
The only reason I ever found for manifold vacuum for vacuum advance (and did it on my built 390) was because the cam is so big that idle vacuum is not enough. So advance the idle timing way up, get more vacuum which helps the idle. Lay into the go-pedal, timing retards, reducing pinging, etc, but then you need to lighten up the springs on the mechanical advance to keep the advance up as the engine revs.
In a typical stock configuration, mild cam, stock distributor, use PORTED vacuum as Ford intended.
The only reason I ever found for manifold vacuum for vacuum advance (and did it on my built 390) was because the cam is so big that idle vacuum is not enough. So advance the idle timing way up, get more vacuum which helps the idle. Lay into the go-pedal, timing retards, reducing pinging, etc, but then you need to lighten up the springs on the mechanical advance to keep the advance up as the engine revs.
In a typical stock configuration, mild cam, stock distributor, use PORTED vacuum as Ford intended.
#18
12-15-2018, 09:00 PM
Wow, wasn't intending to start a debate on manifold vs ported vacuum. Just trying to figure out what initial timing should be set to with Duraspark II since I figured it would be higher than with points.
Same Baddad on TRS? That's kinda what I was thinking. 6° setting might be appropriate for a straight vacuum advance distributor running off manifold vacuum. That would give a low cranking advance, and bump it up probably 6-10 degrees at idle when the full manifold vacuum is present. Since the Duraspark II has crank timing retard feature, initial timing (no mechanical or vacuum) can be set higher. My initial timing is already setting at about 12°, so I probably just need to see what the current timing gives me at crank and total advance. Can use those as a base for the sniper tuning since I know they do work, and play with tuning from there within the Sniper software.
Thanks for the replies and input, y'all have definitely given me a bit to think about.
Same Baddad on TRS? That's kinda what I was thinking. 6° setting might be appropriate for a straight vacuum advance distributor running off manifold vacuum. That would give a low cranking advance, and bump it up probably 6-10 degrees at idle when the full manifold vacuum is present. Since the Duraspark II has crank timing retard feature, initial timing (no mechanical or vacuum) can be set higher. My initial timing is already setting at about 12°, so I probably just need to see what the current timing gives me at crank and total advance. Can use those as a base for the sniper tuning since I know they do work, and play with tuning from there within the Sniper software.
Thanks for the replies and input, y'all have definitely given me a bit to think about.
#19
12-15-2018, 10:27 PM
IMO, the best advice anyone can give another driver about setting up a timing curve is guidelines. There are too many variables in play to say do it the way Ford did...especially after all these years. Variables like tire size, intakes, heads, cams, personal preference and on and on not to mention variables between the many choices of distributors make it impossible to give specifics on timing curve strategies. What one person considers mildly modified another person might consider heavily modified. In fact, you might look at two identical trucks with different distributors...you may want stiffer springs in one but weaker springs in the other. You may want ported or you may want manifold but with the vacuum canister adjusted.
My advice to anyone setting up a timing curve is to play with the variables. Might want to graph the current curve in 500 rpm increments, drive it, modify the curve, drive it some more and see what happens. Took me a couple summers to get to where my curve is today.
My advice to anyone setting up a timing curve is to play with the variables. Might want to graph the current curve in 500 rpm increments, drive it, modify the curve, drive it some more and see what happens. Took me a couple summers to get to where my curve is today.
#20
12-16-2018, 06:00 AM
#21
12-16-2018, 08:17 AM
Now we've got a debate. The vacuum always goes bye-bye or retards the timing as you lay into the go pedal regardless of connection point, either under throttle plate or above. Under throttle, under load, the vacuum quickly goes to zero or near enough. At that moment in time the ignition advance is limited to whatever the mechanical + initial is. This is one reason drag racers don't even bother installing vacuum advance. Then the load starts to level off, vacuum comes back up, and the unit starts adding more timing. This all happens in a split second, the breaker plate really gets a workout!
Some generalizations can be made that cant really be argued:
1. as rpm increases we want advance to increase (up to a certain point)
2. as load increases we want advance to decrease (down to a certain point)
3. basically you can say that at ANY given rpm, there is an appropriate maximum and minimum advance which depends on load.
Like you said, drag racers don't mess with vacuum advance at all due to the fact that it is mechanical advance which affects power. The mechanical advance should be no different between ported and manifold, if it is optimized.
Thus we are left with looking at vacuum advance as an economizer and something to make a nicer idle. Using ported vacuum as the source does not fit the generalizations above, but manifold vacuum does perfectly.
The OP might be able to echo my comment regarding efi behaving more like a manifold vacuum source when it is used to control spark. I haven't seen the Holley software, but the one that I have played with in the past was pretty insightful on this debate when I studied how the ignition maps actually played out. This absolutely put the nail in the coffin for ported spark advance in my practices.
Seems like any other time I've seen this debate, some guy comes along saying that manifold vacuum gives too much advance at idle and causes pinging, so that's why he uses ported. The problem here is that this means vacuum is adding too much, period, and needs limited. In theory, the basis of this argument says that at 750 RPM idle, it's too much timing, but at 900 RPM slow cruise, before mechanical is kicking in measurably and load has increased to be slightly more than that at idle, the ported source somehow isn't too much advance...pretty fallacious stuff if you ask me.
edit: regarding the park-in gear truck I mentioned above early on... The idea here was that the distributor would be on ported in park/neutral but a vacuum switch would move it to manifold when in gear. Not a bad theory. Also not really an argument in favor of ported vacuum...since the ported vacuum pull never actually sees any action outside of revving your engine in your driveway. I suppose it might be good if you have a hydraulic pump or the like that would pull a light load in park at some point. It's a good argument in favor of vacuum switches and such though. Just thinking out loud on this particular point, if ya couldn't tell...
#22
12-17-2018, 10:25 AM
The best way I've found to get the max usable timing is to set it as advanced as reasonable. I then go to a freeway on ramp that has an incline to put a load on it. I floor it going up the incline. If I have pinging I'll slightly back off the timing till it's gone. If no ping I'll slowly advance the timing. In doing it this way it also takes into consideration the octane and quality of the gas that you're using.
#23
12-17-2018, 11:54 AM
The best way I've found to get the max usable timing is to set it as advanced as reasonable. I then go to a freeway on ramp that has an incline to put a load on it. I floor it going up the incline. If I have pinging I'll slightly back off the timing till it's gone. If no ping I'll slowly advance the timing. In doing it this way it also takes into consideration the octane and quality of the gas that you're using.
#24
12-17-2018, 02:12 PM
Very true. My method is the poor mans dyno. Keeps the Mustang running close enough to perfect for street use. I don't race it. Original owner and drive train. I'd like to keep it that way.
#25
12-17-2018, 02:29 PM
It's a beautiful machine....makes me wish I lived out where you do. Everything dies a painful, rusty death here.
#26
12-17-2018, 02:39 PM
#27
12-18-2018, 02:35 AM
Thought so. Still visit semi regularly, but not near as much as I used to since giving up on the 99 Ranger (atleast for now). Remembered the baddad handle, but couldn't remember the numbers that went with it.
Unfortunately I can't "echo that comment" that at this point. Prior to June I'd only fixed factory EFI systems in my own vehicles. This is my first time playing with an aftermarket EFI, just got it in June and just got the truck registered and out of the shop in late October / early November. I haven't really even thought about trying to tune anything yet. Once I get the bugs ironed out and finish getting the truck mechanically sound, I'll start trying to figure out how to tune.
I do understand and agree with using minimum timing advance required for best torque, just not sure how to find that without a Dyno or spending time on a strip. Running on a drag strip is pretty much out of the question, and spending the money on Dyno time is questionable. If I get a good pic of the truck in its current state, I'm sure you'll understand why. Down the road, once I've got the truck in much better shape and ready to build an engine, dyno time will definitely be worth the investment. Right now I'm just going for getting running well and reliable. If I can squeeze out a few more HP or a couple of MPG with a good tune, well it's not what I'm looking for, but it wouldn't hurt my feelings either.
That's probably what I'll end up doing with this thing for now. Unfortunately I got more work to do before I cen even attempt that. I hate to admit, but as it stands the truck would be pinging its hart out and I wouldn't be able to hear it. One of the manifolds is cracked on two bolts tabs (but still sealing for now) and the pipes are rotten. I think more exhaust gasses are escaping through pinholes than whats actually passing through the mufflers. The other day the exhaust fell apart in front of the passenger side muffler (just inboard of bedside tool box) and I thought the truck was about to blow up. Limped it home, saw pipe hanging there open, then realized I should have just thrown in ear plugs and drove on to work. 
Don't think my neighbors would have liked me pulling back into the yard at 2am with open exhaust though. 
Next "big" purchases for the truck are a High Torque Mini Starter to clear headers, a set of SS headers off eBay (Sandersen FF427 copies), and full 2-1/2" dual exhaust.
The OP might be able to echo my comment regarding efi behaving more like a manifold vacuum source when it is used to control spark. I haven't seen the Holley software, but the one that I have played with in the past was pretty insightful on this debate when I studied how the ignition maps actually played out. This absolutely put the nail in the coffin for ported spark advance in my practices.
The best way I've found to get the max usable timing is to set it as advanced as reasonable. I then go to a freeway on ramp that has an incline to put a load on it. I floor it going up the incline. If I have pinging I'll slightly back off the timing till it's gone. If no ping I'll slowly advance the timing. In doing it this way it also takes into consideration the octane and quality of the gas that you're using.
Don't think my neighbors would have liked me pulling back into the yard at 2am with open exhaust though. Next "big" purchases for the truck are a High Torque Mini Starter to clear headers, a set of SS headers off eBay (Sandersen FF427 copies), and full 2-1/2" dual exhaust.
#28
12-18-2018, 11:04 AM
Yea, I sold my 89 several years ago. I still wander over to both Ranger sites occasionally. The 331 I built for the Ranger is in my 77 Comet now, along with the Toploader 4 speed from the Ranger as well. Still wouldn't mind doing another Ranger but don't have the time or cash now since buying a second house and acreage to retire on.
#29
12-18-2018, 12:27 PM
You don't particularly need a chassis dyno or a drag strip. A freeway onramp with an incline will do nicely since it ensures no pedestrian or cross traffic...especially early Saturday mornings. . No need to go over 70mph or past 3500 rpms. Time it at wide open throttle from around 1800 rpm to 3500 rpm. That's the range where your timing advance curve is more important. You won't (shouldn't) get any pinging past 3500 even if you're drag racing because your advance should already be "all in" by then.
Figuring out how much and what type of advance you have at initial can be determined in your driveway so no need for dyno or drag strip.
Figuring out how much and what type of advance you have at initial can be determined in your driveway so no need for dyno or drag strip.
Thread
Thread Starter
Forum
Replies
Last Post
irishredcoat
1967 - 1972 F-100 & Larger F-Series Trucks
43
02-22-2016 01:40 PM
73ragnar
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
3
11-15-2010 08:41 PM
tractoman
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
3
03-15-2006 02:32 PM
albcasummit
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
1
07-26-2005 04:44 PM