Vac System Removals, 1984 F250

[Starliner]

Today I bypassed the thermal switch and opted to go directly off the carb for Vac Advance.  I seems to rum much better.  You guys OK with that?  I was thinking of doing the same for the throttle kicker if I am able.  I just don't trust those things.

[Gary Lewis]

I find the extra complication of the thermal switch unneeded.  I like the vacuum advance connected to ported vacuum.  Simple, and it works.

[Starliner]

Thanks Gary.

[Rusty_S85]

My 302 in my truck loves manifold vacuum for the advance.  I tried ported vacuum but couldn't get the engine to run as smooth.

Im going to try ported on the timed ignition port on my Sniper for my 306 since its self adjusting and should give me a smooth idle regardless.

[ArdWrknTrk]

I think you're going to run into driveability issues with manifold vacuum and no EGR.
Seriously consider having your distributor recurved before you hole a piston or shatter your compression rings driving it like that.

At the very least install a vacuum restriction in the advance line.
But that won't fix how much advance you get at light throttle on the highway.
While you may be a luddite, all these things were installed as a system to improve mileage and driveability.

If you think the truck was thirsty before, wait til you get the fueling and distributor curve set right after crippling all the engine management.

Bill Vose needs to weigh in here.
He ran a carburetor and tune-up shop for years.

[Rembrant]

Rusty_S85 wrote

My 302 in my truck loves manifold vacuum for the advance.  I tried ported vacuum but couldn't get the engine to run as smooth.

I've never really understood that. So you're running base timing plus full vacuum advance at idle? What are your base and advance settings? I don't think I could get my 302 to run right like that.

[ArdWrknTrk]

Cory,
How is your new Parkland Performance recurved distributor?
I've been meaning to ask...

[Rembrant]

ArdWrknTrk wrote

Cory,
How is your new Parkland Performance recurved distributor?
I've been meaning to ask...

Great so far Jim. I'm really happy with it, and Scott was a treat to work with on it. I dropped it in the engine, set the base timing exactly where he said to set it, and it's been working great ever since. Just like a Ronco Rotisserie....set it, and forget it!

I'm still having a hard start issue sometimes, but I haven't dug into it yet. I'm hoping it isn't the base timing because the thing is working so well I don't want to touch the distributor...lol.

[ArdWrknTrk]

Be sure to check that your ignition box is actually retarding while cranking.
I can't imagine you have insane compression.

Maybe it's time for a PMGR starter???

[Rembrant]

ArdWrknTrk wrote

Be sure to check that your ignition box is actually retarding while cranking.
I can't imagine you have insane compression.

Maybe it's time for a PMGR starter???

Yes, I'm going to check the ignition box first. I installed a new Ford box, but not sure if it is the same as the original or not, so I'll swap the stock box back in for a test.

Compression is nothing special, but a little higher than the stock 302 was. From the factory it was 8.3:1 compression and 150 psi per cylinder as I tested it. Now it is 9:1 compression and 175-180 psi per cylinder. Basically the same as any of the later 80's or 90's EFI 5.0L compression afaik.

And yes, possibly the starter...the original 1984 starter is still in the truck, so it might be time;).

[Gary Lewis]

Rusty - Jim is right.  You need the dizzy recurved to take out the expectation that EGR is there - assuming you are removing it.  I'm sure you know, but with exhaust gas in the mix the burn time is quite long so they have to give a lot more advance.  And a dizzy set for that but no EGR gives way too much advance, causing pinging if not detonation.

Or, does the Sniper control ignition timing?

Cory - Don't forget that it is easy to test the box.  Pull the red/light blue wire off the starter relay and connect it to the battery's positive terminal.  With a timing light on it you should see a noticeable retard.

[Rembrant]

Gary Lewis wrote

Cory - Don't forget that it is easy to test the box.  Pull the red/light blue wire off the starter relay and connect it to the battery's positive terminal.  With a timing light on it you should see a noticeable retard.

So if I do that while it is running, you're putting power on the start circuit to trick the DSII box into thinking it is cranking while it is actually running? I might try that.

It doesn't take long to swap the whole box either, so I was going to stick the original on and just run it that way a few days to make sure.

[ArdWrknTrk]

You're energizing the retard function.
You don't need to bring it to the battery either, the hot side of that relay -is- battery power.

[Gary Lewis]

Yes, it is the retard function.  And yes, the hot side of the relay will work.

But if you swap the box then all you have is how it seems to work.  If you do the test you'll know for sure as you'll see a retard in the timing and hear the engine slow a bit.

In my case the box I was using didn't always retard.  The "seems" had it cranking well one time and kicking back another.  And I couldn't figure out a rhyme nor reason.  But when I did the test it worked some of the time and didn't others.  Swapped boxes and the "new" one retarded 100% of the time.

[Rembrant]

Gary Lewis wrote

But if you swap the box then all you have is how it seems to work.  If you do the test you'll know for sure as you'll see a retard in the timing and hear the engine slow a bit.

I already swapped the box, so if the issue stops, then I'll swap the other box back in and test it. That's no big deal...it only takes a few minutes to do.

[Starliner]

I just cut and plugged the hose coming from the EGR.  But I see cover plates to fully remove the EGR.  Is there a performance difference between the two or is it just an issue of getting the junk out of there?

[grumpin]

My truck had the EGR disconnected when I got it.

I used a blank off plate just to clean it up and to preserve the EGR Valve, if that’s possible.

I tried a couple of times to set up my EGR to work and was not successful. It runs really good without it so I’m not sure I’ll worry about it.

[Gary Lewis]

Yes, all the block-off plate does is to let you remove the valve.  But most valves are tight enough that they don't leak when you remove the vacuum, like you've done, so if you are happy with what you have there's no need for the plate.