1986 460 Smog Pump Delete

[ArdWrknTrk]

22" hg is very good, but the timing marks bouncing around is not.

I'm going to suggest you check for chain slack in two ways.

1) with the timing light on and the vacuum advance capped or clamped with hemostats, rev the engine up slowly to see how much total mechanical advance you have (this is probably 3,000- 3,500rpm) then -while watching the timing marks let the throttle slam shut. Do the timing marks retreat smoothly? Or do they flail around while returning to your static mark of 10°?

2) get a 15/16 deep socket and a breaker bar or long ratchet. Remove the distributor cap so you can see the rotor.
Turn the crank counter clockwise so the rotor moves and the wrench is directly at 12 o'clock.
Then move the wrench clockwise until the rotor begins to change direction.
Where is the handle? 3 minutes? 5 minutes?  8 minutes???
This is going to give you a good idea how much wear or slacks you have.

Maybe Vivek can explain it better than me. 🤷‍♂️

[Bullnose Gator]

It stabilized at 20 in the end, but I'll need to look up some videos to see what "stable" truly looks like since I've never used a timing gun before.

Also, to clarify, I adjusted the CURB idle screw, not the idle mixture screws.

[viven44]

I like Jim's suggestions

When I attempted 2) in the past, I would turn the crank counter clockwise until the distributor rotor would start moving barely... read the degrees on the harmonic balancer... then turn the crank clockwise until the rotor starts moving the other way barely... and see how many degrees on the harmonic balancer that resulted in... I have seen that if that is <5 degrees, the timing chain is OK. <10 degrees might be OK near-term. >10 degrees = new timing set.

And don't forget to remove the wrench off the crank. I can't tell you how many times I left the damn thing on, and got lucky

Jeremy, your adjustment of the vacuum advance via the allen wrench all the way clockwise should result in more advance per the guide below that Jim sent, but listen for potential pinging. You don't want to overdo it for sure. Not sure why your distributor needed that adjustment.....

https://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide

[ArdWrknTrk]

Right.
We are talking about two different things.
Idle mixture to achieve highest vacuum (then I usually open up 1/8-1/4 more. Better safe than sorry!)

Then you use the throttle stop (curb idle screw to adjust the engine speed.
Then you adjust the ignition timing (and back and forth if you need to reset the idle rpm)
Then you reconnect the vacuum advance and set the curb idle again.

Now we're where the compliance sticker tells us.

[Bullnose Gator]

So is 20 OK, even though the emissions set up originally called for 8? Seems like a big jump. It also seems to have a little more "chuggalug" to it than before as well.

[ArdWrknTrk]

20° BTDC is your static timing?

That seems WAY  too much, and I'd expect the starter to labour, if it could spin the engine at all.

10 is fine, and 12° BTDC should be okay if the timing retard or your DS-II module is functioning .

[Bullnose Gator]

Static...BTDC....more terminology for me to look up. Lol

[viven44]

Yes that is too much timing. It might cold start without problems most of the time but re-starting when hot on a hot day might be impossible. I had that problem recently... even just running 10 BTC initial timing. I upped the battery size (With double the CCAs) and that seemed to have helped me deal with that. My old battery was probably junk too. The cheap load tester probably overstated its capabilities.

Jim, a local guy and I thought of an idea to deal with this problem... the starter can turn all day when this happens as long as there is no power to the DS-II/coil... how about a "spark switch" in the dash. The idea is to get the starter going, and when it is really going, you turn on the "spark switch" which finally sends power to the DS-II module. Also be a nice theft deterrent...

I think modern cars/trucks must have some spark-delay in place to deal with heat soak.... and why you crank for a few hundred milli seconds before the engine fires.

[Bullnose Gator]

So I need to adjust the distributor, or is this part of the recurving rebuild process to bring it back down?

[viven44]

Should be able to just loosen the 9/16th or 1/2 inch nut and turn the shaft of the distributor (I think counter clockwise) to bring back initial timing to 10 BTC.... you can make adjustments on the fly with a timing light before finding the sweet spot.

A set of these would be nice
https://www.autozone.com/wrenches-pliers-and-cutters/wrench-set/p/duralast-1-2in-and-9-16in-distributor-clamp-wrench-set-2-piece/914110_0_0?cmpid=LIA:US:EN:AD:NL:1000000:TLS:19489353547&&CATARGETID=120054150001289970&CADevice=c&gad_source=1&gclid=Cj0KCQjwwae1BhC_ARIsAK4Jfrx59Xvwja22YdtuPlKm_yWlHuweFFJMp7lNvXxkbrnpO5nC8npaDDkaAhANEALw_wcB&gclsrc=aw.ds

[ArdWrknTrk]

I would first determine that the outer ring of the harmonic damper hasn't slipped, and your timing marks are off.
If you're really seeing 20° Before Top Dead Center as your static timing, I can't imagine where you are at full advance.  🤯
How on earth are you adjusting the ignition timing now?
The vacuum advance shouldn't do anything if the engine isn't running.

Remove the #1 spark plug (the one closest to your left when you're standing there in front of the truck)
Find yourself a plastic straw or something else that is stiff, but can't break off or damage the piston when you stick it in the spark plug hole.
Take the breaker bar and slowly turn the engine over.
When the straw comes out as far as it can, stop and look to see if the timing mark is at 0, or OT, or whatever your damper is marked as TDC #1.

Is it lined up exactly?
If yes, then you need to turn the whole distributor by loosening the bolt and clamp at its base.
A distributor wrench is handy, as Vivek says.
Sometimes the O-ring inside is stuck and you need to get hold of the 'neck' of the distributor and work it back and forth until it turns freely.

[Bullnose Gator]

Alright, guys.  I didn't have much time to get back under the hood the last few days, but I did spend some more time here researching and over at youtube university.

I've got the day cleared to get back to it, so I'm going to start with finding/marking TDC and re-checking time.  I'm going to take Jim's advice that I saw in another thread and go ahead and replace the spark plugs and wires while I'm at it.  I did replace the dist cap/rotor a couple of years ago, but I might start fresh there too.  

If you have any recommendations for plugs, wires, dist cap/rotor that would be in stock at the big chain auto parts stores here, definitely let me know, thanks.

I'll let yall know how the timing looks after finding TDC first...stay 'tuned'...

[ArdWrknTrk]

Do you have a NAPA in your area?

I like the NAPA Belden Premium wires.
The fit right and last at least a decade.

My plug recommendation would be NGK V-power copper core plugs.
I use UR-4 (I think these cross to their modern 6610, but please check to be sure)

[Bullnose Gator]

Yes Sir, 5 mins away.  They have those plugs in stock. 8, to be exact.

https://www.napaonline.com/en/p/NGK6630

These wires are available at another Napa a little further away:

https://www.napaonline.com/en/p/BEL700233

[ArdWrknTrk]

Can they transfer the wires to your local store?
It would be a lot easier than chasing all over the county.
Maybe you can to buy online and set the purchase for local pickup?

[Bullnose Gator]

They can't transfer those today in time. I wanted to put them in today while I set the timing, but I agree, ordering and putting them in when they get here is preferred over going out of my way just because I'm impatient.

[Bullnose Gator]

I used a straw, and eyeballed when it stopped getting pushed out as closely as I could while holding it with one hand and cranking the engine with the other. Unfortunately, I'm a one man show, and the pup below is no help, smh. Here's where it reads at that point:

[ArdWrknTrk]

Okay, it seems close enough that we can assume the outer ring hasn't slipped.

What a cutie! So affectionate.
I had a rednose, that was my constant companion.
She was the most attentive and easy going dog I've ever had..

[Bullnose Gator]

After my last post, it wouldn't start. Thankfully, I didn't waste hours before I realized it could be out of gas, and sure enough, it was! Lol

So after I went and got 2 gal of super premium (93), and made a couple of store runs, I started testing timing, bit by bit. It read the same as last time to start, aprox 22 degrees.

First, per the factory instructions on the radiator support, once up to temp I pulled the dist vac adv and plugged it. This made it run rough, and the timing dropped to a wobbly 12-15 degrees, and vac dropped as well:





From there, the only adjustments I made were to the dist vac advance, which I learned is fully open (counterclockwise, if I don't have that backwards) at 10 full turns. I made 2 full turns at a time, all the way up to 10, and then all the way back down again. The results below were the same on the way up as they were on the way back down.

Dist Vac Adv positions/readings (all turns counterclockwise):

1) Closed (turned full clockwise) = 22 deg and vac 21-22 in.

2) 2 full turns = no noticeable change.

3) 4 full turns = timing dropped to a wobbly 14-16 deg, vac 19-20in.

4) 6 full turns = timing dropped to a wobbly 13-15 deg, vac 17-18in.

5) 8 full turns = timing dropped to a steady 12/13ish deg, vac went back up to approx 20-21in.

6) 10 full turns = timing MIGHT have dropped a smidge, still 12ish deg and steady, vac MIGHT have gone up slightly, but not sure since the vac was a little jumpy at every point by about 0.5-1in. Here's timing/vac at 10 full turns:





Questions:
1) Is the engine supposed to run rough when I disconnect the vac adv?
2) Yhe timing instructions say "800 rpm max" but I doubt it's at 500 with the vac adv hose off, am I supposed to have someone give it throttle up to 800 to see the timing at that point?



3) I want to take it around the block and see how it does. Which of the above dist adv settings looks like the best to set it at for that test drive?

Lastly, these pups are some of the best around, Jim. We fostered this guy back in March after he was found after being left in a house for over a month by tenants that got evicted, he nearly starved to death. We knew from the first day he was never leaving us. Here's him when they found him, and now, doing what he loves the most - keeping me company while he waits for a chance to sit in the truck lol





Thanks again for all the help!

[viven44]

Now it makes sense why your "initial timing" was close to 20 degrees.. thats because the vacuum advance was connected to manifold vacuum... initial timing reading should be obtained with the vaccuum advance disconnected...

12-13 degrees initial timing is also on the high side... maybe that adjustment was necessary previously as the chain may be stretched.

Yes, the engine will have better vaccuum with the vacuum advanced hooked up to manifold vacuum. RPM will also increase.

On my 460 with a brand new timing set, if I don't hook up vaccum advance. I'm around 19-20".. If vacuum advance is hooked up I am at 21-22"... of course the RPM difference is also a good reason why the vacuum is different.

If your chain is old and stretched, you will find that the cam timing and distributor (as distributor is cam-driven) is retarded. To compensate for this, I have heard that you advance the initial timing (by rotating the distributor). Makes sense... if distributor timing is retarded, you make up by advancing it so things are relatively where they need to be.

Below is a good watch. Go to 6:15 where he starts explaining this
https://www.youtube.com/watch?v=kAgsMzAxaac