1986 460 Smog Pump Delete

[Bullnose Gator]

Got it, thanks.  I've also seen others say they only had to adjust or replace the stock carb and not touch their timing.  Should I address the carb first and then see if the timing is an issue, or do they both need to be done in tandem in my case?

[ArdWrknTrk]

Ignition timing and advance always has to be confirmed before any carb adjustments are made. (ignition timing can effect carburetion, but carburetor adjustments can't effect timing)

[ArdWrknTrk]

Im sorry if my replies are sporatic.
I've managed to lock myself out of Google so I'm not receiving any Gmail notifications or new posts. .  

[viven44]

If you decide to do the timing chain, this thread might be worth looking at

https://forum.garysgaragemahal.com/460-Straight-up-Timing-Chain-upgrade-tp147525.html

The only thing I wish I did was add some blue thread locker to the cam bolt. I followed the factory instructions completely so didn't add blue thread locker. I did check the torque like 4 times though. There is only 1 bolt holding the cam and we are counting only on friction! There is a locating dowel but it isn't structural much from what I understand.

[Bullnose Gator]

Thanks for that.

I got back in the garage today to start decided which direction I'm going to head with it.  I hooked up a vacuum gauge to the carb manifold port (where I moved the vacuum advance) and it reads zero at idle. Few questions:

1) Do I need to hook it up to one of the stems on the manifold tree that i capped and leave the vacuum advance hooked up to the carb manifold port to see what it's at with where the idle mixture screws are currently set?

2) the idle doesn't change whether the advance vacuum is hooked up or not, should it? I didn't think so, but an old guy I saw today said it should, so now I'm confused.

3) If I adjust the vac advance clockwise all the way, any idea how many turns counterclockwise I should make as a baseline starting point?

[ArdWrknTrk]

1) You have a manual gearbox. There's really no advantage to Ported vacuum for advance, and if you look at the vacuum routing diagram you'll see the distributor connected to red (Manifold) vacuum, through the thermal Vacuum Control Valve.
If you have a stock carburetor, and a stock distributor, the system -as a whole- is set up to perform best like that.

2)edit: yes, it should, but the idle certainly won't change if the distributor doesn't see any vacuum with the throttle closed because you hooked it to the E port on the carb.
Vacuum advance is supposed to be highest with the throttle closed and go away as engine rpms (and mechanical advance) increase.
This is why the routing sticker says to clamp/cap the vacuum line,, make the adjustments then reconnect the vacuum line and readjust your curb idle to 650-700 with the gearbox In neutral

3) You need a timing light to determine the amount and limits of your vacuum advance can.
Mine was rusted so bad inside I couldn't even get a 3/32 Allen wrench to turn. So I bought the Crane can and a MrGasket spring kit and followed the instructions, after bushing my advance plate stop pins so I didn't get so much mechanical advance that I had to limit my vacuum to a few degrees.
As Scott says mechanical advance is twice the number stamped on the plate.
This is why he needs to know tire size, gearing, max rpm's, etc...

With that and a straight up timing set my truck runs well and pulls hard

[viven44]

ArdWrknTrk wrote

1) You have a manual gearbox. There's really no advantage to Ported vacuum for advance

Could you explain this a bit more? Why would there be a benefit in running ported vacuum for advance with an automatic?

Reason I’m asking is the 460 truck with auto transmission still wants manifold vac for advance … and it seems like the trans shift characteristics might depend on that choice based on your comment (just a inference/ guess)

[ArdWrknTrk]

Ford set them all up with manifold vacuum, but with an auto tranny you have a tendency to creep or stall when the revs drop and there's no dashpot on the carb, like every aftermarket carb I've ever seen.

[viven44]

It’s a very rare occurrence… happened once on the bronco when the transmission was still coming out of the woods.

My understanding has been that running manifold vacuum would be better for idle cooling characteristics …… recall Bill or you mentioning that

[Gary Lewis]

I don't like manifold vacuum with an automatic transmission.  The reason is that I've seen an unstable idle with it.  If something drops the idle just a bit, like the A/C coming on or the idle dropping as you come to a stop, the load on the engine drops and the RPM will increase.  With increasing RPM the vacuum goes up which increases the vacuum advance which raises the idle RPM.  But that increases the load on the engine via the torque converter and the RPM drops, which reduces the vacuum and that reduces the advance which reduces the RPM, which decreases the load on the transmission, which...

So I prefer ported vacuum for automatics.  You get no vacuum advance at idle so the idle is stable.  And you get a good bump of advance as you tip into the throttle so you get a good surge of power.

[Gary Lewis]

viven44 wrote

My understanding has been that running manifold vacuum would be better for idle cooling characteristics …… recall Bill or you mentioning that

The vacuum source won't change cooling if it is the same every time - assuming the same idle RPM.  The beneficial cooling comes when you have ported vacuum with the temp below a certain point and manifold vacuum if the temp goes over that point.  When you hit that temp the added vacuum will raise the idle RPM and, therefore, help cooling.  But unless you firmly have your foot on the brake you may start creeping forward as well.

[viven44]

Yes that makes a lot of sense... the stock vacuum diagrams for a 460 are configured purely for manifold vacuum though. The only difference between hot/cold is the presence of a V REST while cold and straight manifold vacuum when hot...

[Gary Lewis]

Right.  There's something about the VREST that I don't understand.

[ArdWrknTrk]

Neither one of you are looking at the dashpot (throttle positioner) that comes on trucks with AC or automatics.

[viven44]

VREST is supposed to keep the distributor from leaking vacuum, remember ?  Just kidding.. I am still embarrassed

[viven44]

I have grabbed just about every Holley 4180 I found on one of these 351W/460 and tossed it into a storage bin and dropped in a Edelbrock so I have no idea how these were configured or supposed to work stock  Nothing against those Holley, I am sure they are wonderful. I don't intend to learn all carburetors.. or at least there isn't a need yet.

[ArdWrknTrk]

Vrest keeps the distributor from advancing or retarding too suddenly/abruptly.
It provides hysteresis in the loop, where the VCV pulls in full manifold vacuum instantly (and -in my truck- increases idle speed)

[viven44]

Yes its amazing what a little orifice can do.

It allows vacuum to get through from the main reservoir to the destination (intake to the distributor) but the micro fluctuations are "too big" of a signal to get through that orifice

[ArdWrknTrk]

So call Vrest a damper....

[ArdWrknTrk]

The 4180 is technically a Motorcraft carb.
It was never offered by Holley, and doesn't wear a 14 or 15 series number, but you can read that on the front bowl of every one...