Ok i have a 1975 4x4 with a 460 dropped in it. I just got this truck about a month ago and love the thing..I do have some issues tho. First of all (i am fairly mecanically inclined) The timing sticker on the valve cover says the timing should be at 18* This is my first 460 so im not sure of all the ins and outs but it just seemed quite high as my 1974 390 runs smooth at 8-10*....

Although the sticker says run it at 18* i have timed it with my vacume guage and timing light (i set it according to my higest vacume reading) and it is set at 25* as we speak and i get the best results by far at the higher setting. Also my timing marks only go up to 30* I do have a fear that the setting is way too high for my engine. It does have a tick that seems to appear when the engine is under load and at certin differnt spots thrue the throttle range. This tick does sound more like a lifter rather than a pinging sound but i do not know for sure yet. I do not know what the previous owner may have done to this engine as far as upgrades and what not....the engine appears to be in VERY stock form.

So why does my timing have to be so high in order for my engine to run its best? The previous guy also had the vacume advance dissconected and who knows what else. I have reconected the vacuum advance back up and i do believe that it is working but honestly i am not sure as i am somewhat of a rookie when it comes to this.

Also what are others running their timing set at with a stock 460 and or what should my timing be near? One more question i know its hard to describe problems and sounds over the net but what would this ticking sound be coming from? just tired or stuck lifters? Or a loose timing chain? Thanks for any help!!

 

First off you shouldn't setting timing by the highest vacuum reading. The best way to set timing is by determining your max total mechanical advance, your advance curve and set your initial so that you get no more than 38° max mechanical advance (34° to 36° is safer). You adjust your carb so you get the max vacuum possible. Oh and with 25° initial, I am sure you have a pinging issue.

 

I don't think it would even want to start after it was warmed up at 18* initial timing. I think I run mine around 12* initial.

 

Actually I ran 24° initial in my race 428CJ with 11.5 to 1 compression and never encounted any start problems.

 

On the 460, do you disconnect and plug the vacuum line to the distributor to set the timing with the timing light?

 

There is no vacuum to the distributor at idle.
The vacuum line at the base of the carb goes to an opening ABOVE the throttle valve
Is the vacuum line to the distributor supposed to be connected somewhere else? This is a 73 Lincoln 460

 

On any engine with a vacuum advance you are suppose to do that. However, I have found that if you are not being stupid and using manifold vacuum and your carb is set up properly, there is no vacuum at the ported vacuum port at idle, so there is no reason to disconnect and plug it. Just disconnecting it will suffice.

 

On some 460s there is a temp operated vacuum switch that feeds ported vacuum normally to the advance unit (my '84 F250 is this way). But if the engine gets hot idling in traffic the switch feeds manifold vacuum to the advance to jack up the idle speed so the fan will pull more air thru the radiator and cool things down. The only people running manifold vacuum to the advance unit full time are those with poor builds that won't idle properly and they cheat and pull the timing around with the extra vacuum. But no factory engines ever came that way.

 

Thank you.
It confused me because the timing is the same with or without the vacuum line connected to the distributor

 

That's as it should be. Because until you open the throttle plates the ported vacuum port is cut off from the manifold vacuum. Connecting the hose at idle and having the idle speed increase means the carb is set up with the throttle plates to far open, which is wrong.

 

Bear, Why do you think manifold vacuum is stupid?

Here what a GM Engineer has to say about ported vacuum and emissions in the early 70s


by Lars Grimsrud
SVE Automotive Restoration
Musclecar, Collector & Exotic Auto Repair & Restoration
Broomfield, CO Rev. B 8-19-02

Part 1 - TIMING AND VACUUM ADVANCE 101


Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.

For More go to the 460 forum here


Timing & Vacuum Advance 101 -good article by GM engineer - 460 Ford Forum

 

well i backed the timeing down to 10*, 8*, and 6* test drove it at each setting. It seems any setting below 22* has a hesitation and bog at quarter throttle. I can stomp on it and it wont bog at all or i can gently accelerate and it will make it with no bog. But normal driving it has that hesitation/bog. I dont understand why it needs such a high timeing setting to get rid of this bog problem. I have it set at 10* now and i still feel unhappy with my results. It seems like i may have another problem as well because the timing should not be at 22* to make it run good.....back to the drawing boards for awhile

 

Emissions is NOT about making an engine run right or well. It is about meeting a bunch of BS requirements that have never been proven to help anything, just hurt fuel economy, which if you are hurting fuel economy you are not helping emissions because you are making the engine inefficient. But you will never hear anyone tell you that manifold vacuum should be used for vacuum advance, mainly because it was originally designed as a mileage improvement system, ONLY. The emissions ***** have stolen it to screw up engines in the name of political power. Emissions is the only reason EFI now exists, because they could not make engines run right with emissions control requirements and carburetors. Oh and your little quoted missive is engineers justifing what they have done, in the name of emissions and not in making engines run right.

 

Hey Bear, Thank you for your explanation.

yeahbuddy, I hope you get it running better

 

Personally - I'd ditch that ported spark vacuum connection in a red hot split second, depending on how the distributor is set up. Vacuum advance as it was originally designed modifies ignition timing based on engine load as sensed by how much vacuum is lost.

A loaded down engine has lower intake manifold vacuum, therefore it is the presence of vacuum that signals the system to return spark timing to 'no-load' conditions, which are far enough in advance of top dead center to allow air and fuel in the cylinders to burn completely yet without causing ignition so early that the piston doesn't pass top dead center before the increasing 'flame front' is producing back pressure (pre-ignition).

When the engine is under load and the vacuum drops, the vacuum advance moved spark timing closer to but not quite past top dead center so that ignition occurs after the piston is moving down in the cylinder. This changes the point of maximum cylinder pressure to a time when the crank angle has maximum mechanical advantage, but this also leads to incomplete combustion in the cylinders beyond a certain point...

To have no vacuum applied at idle at all seems to me totally ridiculous, because without a truckload of additional vacuum plumbing and hardware the engine would be running under full-load conditions at idle.

This is where some vacuum diagrams become hair-pulling-out nightmares. There was a ton of vacuum dingusses developed in the era of BIG POLLUTION CONTROLS to try to make the tree hugger ideas actually work while using an honest to pete carbuerettor to mix fuel and air. 99% of it all turned out to be incomprehensible garbage...

The purpose of vacuum advance is to maximise fuel burning in the engine, while at the same time allowing the engine to compensate for WOT operation.

About eight to ten degrees before top dead center is reasonable with NO VACUUM APPLIED. Run like that, most engines will lope and the throttle plate usually has to be held open a tad.

When the vacuum line is reattached to the distributor and full vacuum is on it, the timing should roll back far enough in advance (BEFORE) top dead center that the engine smooths back out and runs normally for what is called the "Low-Speed, No-Load" operating range.

I guarantee ya that if you have a ported vacuum system there is at least one other vacuum port involved and the diagram for the vacuum circuit FOR THAT YEAR looks like a bowl of spaghetti even to an electronics technician...

Early Turbo-charged systems were even worse