460 timing issues

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  #16  
Old 12-05-2009, 11:20 AM
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Originally Posted by Greywolf
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
So according to your little theory, when there is a vacuum advance unit there is no mechanical (AKA centrifugal advance) in the distributor which of course makes your theory not only WRONG but impossible. First off you will always have mechanical advance which is RPM related so at 3000 rpm you will never have less than initial plus mechanical advance. This of course assumes you aren't still running one of those idiotic duel vacuum advance units which were only used on the late 60s and early 70s emissions engines and anyone with a quarter of a brain would have replaced or at least disabled the retard function. Your theory also seems to assume that any throttle increase drops manifold vacuum to 0, which only happens at WOT and even at WOT you won't achieve zero vacuum or the engine will probably stumble, stall or die all together. As to you contention that there is at least one other vacuum port involved. This is a maybe and in the case of a lot of those system it does not effect the timing at upper engine RPM. Like my 1984 460 in my F250. True there is a second vacuum port to the manifold. However the vacuum advance unit can only "see" that port with it's higher vacuum (which of course advances the timing and not retards it per your darling theory again) when the engine is in a higher temperature state (usually higher than 230°) and then the temp switch advance the timing to increase idle RPM to help cool the engine down. But at higher RPM, such as driving down the road the two vacuum ports will "see" the same identical vacuum, hence making not one whit of difference to how much timing you vacuum unit will crank in.
 
  #17  
Old 12-06-2009, 05:32 PM
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Originally Posted by Bear 45/70
So according to your little theory, when there is a vacuum advance unit there is no mechanical (AKA centrifugal advance) in the distributor which of course makes your theory not only WRONG but impossible. First off you will always have mechanical advance which is RPM related so at 3000 rpm you will never have less than initial plus mechanical advance. This of course assumes you aren't still running one of those idiotic duel vacuum advance units which were only used on the late 60s and early 70s emissions engines and anyone with a quarter of a brain would have replaced or at least disabled the retard function. Your theory also seems to assume that any throttle increase drops manifold vacuum to 0, which only happens at WOT and even at WOT you won't achieve zero vacuum or the engine will probably stumble, stall or die all together. As to you contention that there is at least one other vacuum port involved. This is a maybe and in the case of a lot of those system it does not effect the timing at upper engine RPM. Like my 1984 460 in my F250. True there is a second vacuum port to the manifold. However the vacuum advance unit can only "see" that port with it's higher vacuum (which of course advances the timing and not retards it per your darling theory again) when the engine is in a higher temperature state (usually higher than 230°) and then the temp switch advance the timing to increase idle RPM to help cool the engine down. But at higher RPM, such as driving down the road the two vacuum ports will "see" the same identical vacuum, hence making not one whit of difference to how much timing you vacuum unit will crank in.
RE: Items in red highlight - You have assumed one hell of a lot that was neither said nor implied or is blatantly antagonistic - not to mention dead wrong.

Items highlighted in blue are somewhat if not totally contradictory.

The item in bold highight is not only completely the reverse of what I wrote above but therefore false and is an obvious personal dig.

You don't impress me. Far from it, you seem to want to confuse the issue and belittle anyone else that offers an opinion. If that's what it takes to float your boat good luck to you, I'm seriously considering dusting off the old tried and true "IGNORE LIST" function to see if IBI has updated that too.

I'll give you one shot at thinking over what you've tried to shovel on me and explain yourself, after which you can be non-existant for all I care.

First of all:

"So according to your little theory, when there is a vacuum advance unit there is no mechanical (AKA centrifugal advance) in the distributor which of course makes your theory not only WRONG but impossible."

YOU said that, not me bucko! It is dirty pool to try to make it look like added details of your own were someone elses. By attempting to put words in MY MOUTH you have stuck your foot in your own.

Mechanical advance is a seperate issue, so I never even mentioned it. Why would I?

But YOU mister seem to have an attitude. Vacuum advance is not "MY THEORY", "MY DARLING THEORY", or anything of the kind, it was invented before either of us was born. Why don't you study it, become certified as a technician, and then go belittle the original designer? Since he's dead you may have to go to hell to do that, but after reading all this I certainly don't mind if you do...

God knows after some of the nightmares I have had to sort out over the years I have a list of engineers of my own that I hope are down there too.
 
  #18  
Old 12-06-2009, 07:36 PM
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Originally Posted by Greywolf
RE: Items in red highlight - You have assumed one hell of a lot that was neither said nor implied or is blatantly antagonistic - not to mention dead wrong.

Items highlighted in blue are somewhat if not totally contradictory.

The item in bold highight is not only completely the reverse of what I wrote above but therefore false and is an obvious personal dig.

You don't impress me. Far from it, you seem to want to confuse the issue and belittle anyone else that offers an opinion. If that's what it takes to float your boat good luck to you, I'm seriously considering dusting off the old tried and true "IGNORE LIST" function to see if IBI has updated that too.

I'll give you one shot at thinking over what you've tried to shovel on me and explain yourself, after which you can be non-existant for all I care.

First of all:

"So according to your little theory, when there is a vacuum advance unit there is no mechanical (AKA centrifugal advance) in the distributor which of course makes your theory not only WRONG but impossible."

YOU said that, not me bucko! It is dirty pool to try to make it look like added details of your own were someone elses. By attempting to put words in MY MOUTH you have stuck your foot in your own.

Mechanical advance is a seperate issue, so I never even mentioned it. Why would I?

But YOU mister seem to have an attitude. Vacuum advance is not "MY THEORY", "MY DARLING THEORY", or anything of the kind, it was invented before either of us was born. Why don't you study it, become certified as a technician, and then go belittle the original designer? Since he's dead you may have to go to hell to do that, but after reading all this I certainly don't mind if you do...

God knows after some of the nightmares I have had to sort out over the years I have a list of engineers of my own that I hope are down there too.
You know, there is no point in trying to educate an emissions era know nothing because at least 70% of you missive and theories are just WRONG. But far be it for me to keep you from distributing pure BS like

"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."

and this

"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."

The only thing this says to someone that knowns how to tune an engine is you don't know squat about engine tuning. But I digress. Go ahead and spread your BS, I'm not gonna try stop the morons from taking over the world anymore.
 
  #19  
Old 12-06-2009, 08:01 PM
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THERE IS USEFUL INFORMATION FOR THE ORIGINAL GUY THAT BEGAN THIS THREAD HERE:

One thing you need to find real fast is the VACUUM DIAGRAM for that truck. It may be on the radiator support, firewall, or even on the underside of the hood. If worst comes to worst, an old manual or online archive may have that diagram. They were based on California, NON-California (or 49 states) models and engines, and there are many ways to get around the inefficient garbage in them.
I'm betting yours was a 49-state

It will show lines, vacuum devices, and where they are connected. It might take an act of God to figure them all out, and they may have to be run down in several manuals and other resources, but we should track it all down.

It's the only way we can figure out how that thing was supposed to work.

Emissions era machines were stupidly overcomplicated, but they can be restored with enough attention to detail.

Alternatively - they can be made to look like it's all in place but a system that really DOES make the engine efficient and make less smog can be run

SMOG techs are generally underpaid and not very knowlegeable...

Since you are from MT - we ought to focus on making it run like a raped ape, and leave a lot of rubber lines laying around to fool non-california dodoes into believing it's all an act of God...

Sometimes all it needs is a pair of BB'S stuffed into a vacuum line or two at the right places.

(I still have my old California Pollution Controls book from back then when I was at Grossmont Community College)


Most of the time what wrecks things is just plain old rubber lines that are cracked and leak like a sieve. Replace all of the rubber lines you can find, buy tubing at so many bucks per foot to do this....

Most of the time the "GIMMICKS" are still good, but rubber gets old and rots.

Look real close at the ENDS of all your rubber lines - if they look cracked, feel hard, and so on - they are not doing the job, they don't seal like they should. If that stuff is many years old it figures that it's aged and gone bad. The more of them there are, the weaker the vacuum in the whole system

*THESE DAYS I LIVE IN A COUNTY WHERE THEY DON'T INSPECT VEHICLES!!!!! I can run whatever I want to - even OPEN HEADERS....

That's why I like the place

* I have placed Bear 45/70 on my ignore list in my User CP because of his garbage posted in this thread. My original notion is the simplest way to handle a man that posts like an angry drunk - he should have named himself "Beer 24/7"!
 
  #20  
Old 12-07-2009, 05:22 PM
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Thanks you for the help and info Greywolf. That is my next step is redoing all vacume hoses and some electrical parts too see if this helps. The higher my timing the less of the bog issue i have. It will have to wait a few days tho its too cold in my garage to work on it and i want to take her out in the snow. Here are a few pics in the fresh snow. Hope to get this hesitation / bog fixed soon.......thanks



 
  #21  
Old 12-07-2009, 07:45 PM
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It occured to me that you might have an EGR valve stuck open too. I was just now thinking that over, if it was stuck - it would act just like a major vacuum leak that nobody could find (In other words, it would cause a flat-spot on accelleration)

The last ten vacuum advance problems I ran across, the vacuum can on the distributor was old and wouldn't hold vacuum. The diaphram inside is rubber and when they get old they can crack or get holes in them. Easy to test though - use a clean piece of vaccuum line and suck on the connection to it. If it's good, you can't pull a constant flow of air through it no matter how little. I usually suck on the line and cap it with my tongue - if it holds vacuum for ten seconds it doesn't leak. It sounds crude but beats spending thirty bucks for a test kit.
 
  #22  
Old 12-07-2009, 08:27 PM
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Yes the EGR has been in the back of my head also. I picked this truck up 1 month ago and have been wrenching on it ever since. The guy had the vacume advance dissconected along with the EGR system. I went thrue and hooked up things to their proper places. There is quite a mess of wires i am going to go replace and hoope to eliminate to clean up my engine compartment.

But as of now i have that bog problem. I am a novice when it comes to the egr system as i am not even sure what port it connects to on my Holley Carb. Anyways im going to tear it apart in the next few days and see what i can find out. I was thinking of blocking it off but have heard not to do so. I use my veichle as a daily driver so i would like strong performance with decent gas for a 460.....10mpg would be great!!
 
  #23  
Old 12-07-2009, 09:56 PM
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If the EGR has been dis-conned for a while, the EGR valve is probably shot and the check valve too. Exhaust gas makes them rust up real bad. But hopefully if the vac line to it was taken off, it rusted shut instead of open.

I'm not 100% sure on 460's, but on windsors and 302's there is an EGR tube at the back of the engine (firewall end) that bolts to a pair of ports, one on each cylinder head. That tube has the EGR Check Valve on it, screwed into a welded on fitting.

Around my part of the country when we build a rod or race engine what we do is leave off the EGR tube, and cap the ports in the heads with either brass or steel caps that look a lot like engine block "Freeze Plugs" (or more correctly "Core Plugs"). You can do that, and still bolt on the EGR tube & plumbing to make it look like all of it is there - but blocking those two head ports make the system non-functional and there is no way to prove it was done without a complete teardown. (FACT!)

*NOTE: The purpose of the EGR (Exhaust Gas Recirculation) system was:

"To reduce oxides of nitrogen in the exhaust by lowering combustion chamber temperatures. The EGR system dilutes the air-fuel mixture in the intake manifold with a small amount of exhaust gas. The exhaust gas does not contribute oxygen or burn during combustion, but it does absorb some of the combustion heat. This reduces the cylinder combustion temperature and reduces nitrous oxide levels."

~Glenn E. Ireland
"Automotive Fuel, Ignition, and Emission Control Systems" 1981

~whatever~

(Most of THAT became out-moded with the further development of catalytic convertors)

Since we seldom use stock intake manifolds, we don't have to do much else. The rest of the EGR hardware goes to the dump...
(I'm lucky, I live in a place where we can do that)

On a stock intake manifold, the EGR valve itself is usually at the back of the manifold. I think one way around it is to bolt a plate right over the top of it, but the best answer is to install a non-EGR manifold and forget about it. End result? EGR problems solved for all time - unless a smog inspection is possible. If you capped the head ports as above, all of your EGR stuff will remain in pristine condition forever even though it does nothing, nada, 100% of ZERO.... (No exhaust gasses to ruin anything) But all of the hardware is in place if someone really feels conscientious about their job, and even in California they wouldn't notice anything wrong since they could test every bit of it and prove that it's working.

Where I live, we either don't have inspections or the techs that can be bought are well known by the hotrod underground...

The last time I got heavy into researching a smog system and vacuum line diagram I was trying to get a 1973 two door Gran Torino past the smog ****'s in San Diego California. On top of all the other problems it was a non-california car AND heavily modified.

351C factory four barrel, four on the floor, side pipes, NO cat convertors, NO A.I.R. pump - it was doomed, but I made it work! I wish I still had that thing, but it cost me a lisence not long after I finished it (TRUTH). It was a fun car....

BIG question here is what kind of shape the distributor you have on it and the vacuum can on it are in.

You probably have the DURASPARK-II ignition module system, or a good old fashioned distributor with points in it. If so, you're ahead of the game. I found on a 1982 F100 project I did a few years ago that a complete ignition system INCLUDING THE DISTRIBUTOR for a stock DURASPARK-II system was only about a hundred bucks - IN A BOX from a local parts store, everything brand new, including the plugs and wires...

The thing that makes that worth doing is that by going with a later and much cheaper to install system, it LOWERS the cost of the ignition system, AND SIMPLIFIES IT!

Under California law - I noticed right away that if you install older engine systems in a newer truck it is illegal. If on the other hand you install a NEWER system in an older truck, they love you for it - and so does your bank account. The bottom line is better performance without a lot of bullcrap (DS-II ignition modules are less than $20 at any parts store. Mine was fourteen bucks at the time in Norfolk Virginia...)

With that and an Edelbrock 650 double-pumper it ran like a tyranosaurus rex with meat in front of it!!!

The only thing I spent extra bucks on was the wires themselves. I'm a die-hard believer in thick silicon suppressed ignition wires with copper cores.

It will **** off people with cell-phones, but I don't have one, so whoopee...

(I later bought resistor-wires, because I got a C/B stack and the RPM BUZZ was an issue)


PS: I gotta admit, it's a lot easier to read this thread now that in several places all I see is:

This message is hidden because Bear 45/70 is on your ignore list.

Like I have time in my day to concern myself with someone who has obvious socially self-destructive issues...
PFAH!!!

A lot of what I am telling you is illegal in California, but a lot of it also helps your engine to be more efficient and last longer.

"Breaking the law! Breaking the law!"

Proving it is another matter...

An engine that runs like crap pollutes worse than one that makes efficient use of fuel. YOU BE THE JUDGE

How many machines have you seen chugging down the road that burn more oil than gas? SLAP WORE OUT....

I rest my case

A well made hotrod is better than a worn out "on it's last legs" piece of junk

And most of those wore out cars and trucks are late models that never had a hope of being thought classic
 
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