68 F-100 with a mutt of a 390. Engine seems to be a combination of several FE engines based on casting numbers, but all factory parts. Truck was originally a 360, but 390 was swapped in by my step grandfather. Unfortunately no one knows what it came from and he is no longer around to ask. Based on the C7ME-A it was a late 60 FE, and the short block should be matching factory components. The heads and intake were installed by my father in the 80s, he said they all came from the same 63 Thunderbird that he thought had a 390. Well the heads are casting C3AE-6090-G which matches a 63 427 low riser, but the intake is casting C8OE-9425-C which seems to be from a 68-70 427 Cobra Jet. Just wanted to give this info in case it affects following questions.

PCV Question:

I'm replacing the factory ported carburetor spacer that the PCV valve is currently connected to with a 1" phenolic spacer. The intent is reroute the PCV into the Manifold Vacuum port on the carburetor base plate. PCV valve (correct valve for 68 390) has 1/2" hose barb while the base plate has a 3/8" hose barb. Would there be any problem with swapping the 68 PCV valve with one from say a 76 that has a 3/8" hose barb? It would make for an easier and cleaner connection to the base plate.

Timing Question:

In 68 this truck would have been equipped with a points style ignition. Somewhere along the way it was converted to a Duraspark II ignition with a blur grommet module. Valve cover has a label saying that timing should be set to 6° BTDC, which sounds about right for points. The Duraspark II blue module should have a several degree crank timing retard function when wired correctly, and this one does appear to be wired correctly. Setting initial at 6° would put crank timing pretty close to 0° and from what I've read 6° is probably a little low for initial timing if the engine is capable of more. About what should I be setting initial timing too?

FWIW I've currently for a stock style starter, but intend to go to a high torque mini starter soon in preparation for headers and exhaust. Don't know how that might affect timing, but I'm guessing that the better stater could handle more advance crank/initial timing.


Hope that's understandable, second time I typed it. Computer crashed the first time and I'm in a rush.

 

For PCV valve, I don't believe it matters much what size valve you have so long as it's "tuned" to your engine. Now that you have a somewhat custom engine might want to verify your PCV valve is working correctly. I have custom built FE and tried many things to keep the PCV valve from sucking too much oil. I ended up getting an expensive Wagner adjustable PCV valve. That way it open/closed at the right time to sweep my crankcase but not suck oil. Three years ago I replaced the PCV valve with valve cover breathers and I run a 180 thermostat to make sure the oil gets hot enough to drive off any moisture or vapors. The problem you can get into with an incorrectly tuned PCV valve is too much oil in the combustion chambers leading to stuck rings, blow by, and even detonation or run on. In other words, a wrong PCV valve does more harm than good. So pull your plugs and take a look for a while until you're satisfied it's the right PCV valve.

For timing, you'll probably want to experiment and see what you like. When I had a stock 390 I liked it with the initial bumped up to around 10 but can't remember what the total time was....probably around 36 or 38 since it had iron heads. My method for dialing in my timing curve is to make sure it has enough advance for a strong idle yet not too much to make it hard to start. Then get a stop watch and time how fast it goes from say 40mph to 60mph while watching out for spark knock. I use this info to adjust the rate of timing advance. This way I get not only the right amount of advance but also have it come in at the right time. Made a noticeable improvement in pulling power in my stock 390. Dialing in a timing curve is partly what the engine likes and partly how you drive it. For instance, I like full vacuum advance for tow/hauling on the freeway. If I was drag racing, I probably wouldn't use vacuum advance. Also, my aluminum heads make no more power past 31 total advance but iron heads seem to like around 37 total time.

 

You can do whatever you want with a PCV, really, just as long as it is set up to flow properly. What you are doing won't change the flow. Some people struggle with this.

Regarding the phenolic spacer: Why do you want to do this? I would be concerned about it melting with a stock-type manifold that has a heat-crossover. IIRC, these spacers are not recommended for this application. Are you looking to cool your carburetor? They make insulated spacers/heat shields that would possibly be more suited to your application. An air cleaner base that stands up off the carburetor and isn't reflecting heat back down would theoretically help here as well, and you should have room for it.

How is your vacuum advance routed, assuming you have one? You shouldn't have any issues going up to 10* to start. Make sure you unhook your vacuum advance when setting mechanical timings. Rev the engine up while checking timing and note the max advance. Note degrees at 500 RPM intervals if you have a tach to do this. Keep in mind that the marks on the balancer may be off from what is reality due to it slipping on the hub over time. In an ideal world, you really want to worry about your final timing first and work back from there...it's not super practical and is probably a little more in depth than what you are looking for.

It works well for me to leave the vacuum advance out of the picture to get some initial driveability tuning done. Once you are stumble free, hook it back up to MANIFOLD NOT PORTED and use it as a tool to smooth out idle/increase vacuum/decrease fuel consumption.

A better starter certainly will handle more timing. The DSII has a retard in it for starting, so it shouldn't be a concern.

 

Lot of good points made by the hetz. To clarify, I believe the hetz is saying to reconnect the vacuum advance to "Manifold" and do not use "Ported". Your FE is close enough to stock that you may prefer full manifold vacuum advance (I do).

The hetz made a good point that I forgot...always measure timing with vacuum disconnected and plugged. You can measure advance with the vacuum connected but that's more or less for fun because vacuum varies depending on your driving situation (up/down hill, heavy/part/light throttle etc) And don't get too concerned if you're a couple degrees different than someone else because there will be a little error in reading your timing and possible error in your timing marks or damper pulley location, etc.

 

Yep, I always recommend to connect to manifold and not ported. Lots of arguments both ways...I've not seen a great one in favor of ported, IMO, and they seem to revolve around "well {some manufacturer} did it that way for years and it worked."

I think "It worked" and "They MADE IT work due to x,y,z requirements" are 2 wildly different things.

The only decent argument I've seen in favor of ported vacuum is that you can use it with a vacuum switch and make it so that your idle in neutral is approximately the same as your idle in gear (vacuum activated when in gear)...you can do the same thing with other methods...

 

Pretty much in agreement for timing strategy here, especially for factory engines. Once guys start customizing (e.g. changing cams, heads, etc) then I recommend experimenting to see what the engine and driver likes.

 

Not drag racing, not racing at all. Original post (lost in computer crash) had more info about truck. It's a 68 F-100 4x4. Manual transmission, a NP435 w/ Dana 21 transfer case. Gear ratio is 3.50:1 and tire size is 265/75R16 or about 32" diameter. Main usage is driving to work on occasion, camping and hunting. Will see occasional towing/hauling duties, but I was using my 99 Ranger 4.0L 4x4 for about the same duties, so it's not really working the truck at all.

Clearance Clarence, clearance...

I've actually installed a Sniper EFI on the engine, and it's running fairly well with it. When installing the EFI system I had to use extra base gaskets (what I could get quickly) to raise the throttle body so that throttle shaft would clear intake manifold. I never liked that solution and purchased a spacer to replace it with, just haven't installed it yet. Going to be working in the area to track down a potential vacuum leak and want to install the spacer while I'm in there.

FWIW the current spacer with vacuum port is phenolic and it's been on there for 30+ years and hasn't melted. Not like I ran this thing out on my 3D printer, it's a composite and not going to melt that easily.

90% positive it's currently connected to ported vacuum. I know it is connected to the same type of vacuum it was running prior to my getting the truck. Dad ran it that same way from the mid-late 80s up until he parked the truck in 2006/7. I removed the carburetor, noted where the advance hose was connected, and connected a new hose to same type of source on throttle body. That was 3-4 months ago, at this point I can't say with 100% certainty if that was ported or manifold.

Already checked the balancer accuracy and it still seems to be spot on. Current timing is sitting at about 12 degrees. Need to get the balancer marking colored so I can see them better with the engine spinning, but it's been raining every chance I've had to work on it (no shop to work in).

Full disclosure, I'm not going to be running the Duraspark system for much longer. I've got a Holley Dual Sync distributor sitting by the desk to install for full electronic timing control through the sniper EFI system. It's been recommended to use the timing from the existing distributor as a base line for settings in the EFI tuning software. Trying to make sure that the Duraspark distributor is still right before I start trying to record the current timing settings. Once I have it set up and running with the dual sync distributor the timing won't be limited by mechanical or vacuum advances. Basic timing settings I'm trying to start out with are:
Though with the Duraspark I suppose that I can actually get a better crank timing reading by reading what the module is doing while cranking the engine over.

Off to work now. I'll be able to read replies, but may not be able to reply until the AM.

 

Sounds like it will be a nice setup!

 

Ported vacuum will be located above the throttle blades. Manifold below it. I've always run my vacuum advance on ported. Never saw the need to do otherwise. Your intake is a 428CJ unit if iron. The 428PI intakes were identical but in aluminum.. The factory 6* setting is retarded, literally. Every Ford I've had just plain runs better set at 10-16*BTC. I set them with the vacuum connected. If it's ported, no need to pull it at idle..

 

 

Beginning in the late 60's Ford went to an advance/retard vacuum system on their distributors. These had two nipples, the one farthest from the body was advance, the one nearest retard. These two were switched by a temperature switch. A straight one nipple distributor does not retard and did not have a switch to control it. The factory ignition timing setting of 6*BTC performed this. So bumping the initial to 10-14* has a double benefit here. Much like using straight manifold vacuum. As for the location of the ported vacuum, it is always above the throttle blades. There is no in between. Ported is ported, full manifold is full manifold. Or is on Holleys and Autolite/Motorcraft carbs. Maybe on some off the wall brand carbs that may not be true, but I've never run these.

 

 

 

 

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.