77 F150 w/ 460 not revving above 3400 rpm's
#31
01-16-2019, 08:25 PM
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#32
01-16-2019, 08:34 PM
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The good news is, peak torque is 342 at 2600 RPM's, which is the most important. I'm not gonna fret about it too much at this point, since it is running smooth and behaving incredibly well. My Holley 770 Street Avenger came today.....now do I send it back or slap it on and see what happens? 
#33
01-16-2019, 09:01 PM
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#34
01-16-2019, 09:10 PM
Lead Driver
A few observations.
One thing is that, yes the earlier engines did tend to have slightly more power due to higher compression and perhaps other things, much (most?) of the drop in power ratings between '70, '71 and finally '72, was due to the mandate that all vehicle manufacturers list "net" horsepower based on certain guidelines that kept things consistent between all the companies. This way they could not fudge the numbers, or use less than consistent methods like they did with "gross" horsepower ratings before that.
So if you see a drop of for example, 45 to 60 bhp between one year and the next with the same engine, much of that drop was the way the numbers were reached.
Which also means as a side note, engines that are making 450bhp now, are probably making as much as 100bhp more than a similarly rated engine from '70.
Are you running headers or cast manifolds? If headers, some of the ticking is natural from the exhaust pulses ringing on the thinner steel tubes. If cast, then yes you likely have a leak. But increasing the timing advance might have masked the problem, rather than actually fixing it permanently.
As was said already, when you changed from the vacuum port up higher up to the one below it, you changed from ported vacuum to full vacuum. That's why the idle speed increased immediately. The timing probably jumped at least 12 to 15° assuming the vacuum advance is fully functional. But at least you know it does work to a point, or you would not have had the increase. That's a very good sign, but that's also where a timing light comes in handy as a diagnostic tool. Lets you know just what it is doing and when, and by how much.
I'll have to look up the carburetor for more details, but at a glance it appears to have mechanical secondaries with a vacuum/load operated venturi valve. I did not see all the linkages, but usually when there is a big flapper valve blocking the secondary venturii, it's set up so that you can open up the secondaries all you want, but they only work fully when, under the right circumstances, the upper butterfly valve/plate/thingy opens up too. Should keep the engine from bogging down when the secondaries are opened suddenly by flooring the pedal.
Other carbs use vacuum totally, and only open up the secondary throttle plates down low with vacuum. Those have larger vacuum canisters that pull an arm that opens the throttle blades/plates. Similar in function to the vacuum advance, but in reverse. The higher the vacuum signal, the blades stay closed. As the signal drops from heavy acceleration, they open up depending on just how far the vacuum drops.
As to which vacuum port to run the vacuum advance from, I usually use the ported one for my Fords. This usually ends up with setting more initial advance with the distributor. But if yours is currently running better on full vacuum, that's fine too. Some engine and parts combinations just like that better.
But it also says to me that you could have gotten away with advancing your timing a little too. That's in effect what you just did by changing the hose. Now when the engine is idling your timing is set way more advanced, then starts to come back down as you open up the throttle and accelerate. Less vacuum, less timing...
Certainly still worth playing around with timing.
As to accelerating more quickly and having the engine rev up farther, you need to find out how to check and adjust your kick-down lever/rod and see if the transmission is otherwise functioning properly. After all, what you showed in your video is not the engine's inability to rev, but the transmissions inability to avoid shifting up. Nothing else.
Whether it's mechanical or vacuum/load in nature, that's what you need to find out.
Do the C6 transmissions in this case have a vacuum modulator? Or are they strictly mechanical? Seems to me they do use vacuum. And if so, maybe your modulator is not 100% anymore.
How far down were you pushing the pedal in that video? Like was said too, if you're not pushing the pedal it's not going to save the upshifts for the higher rpms.
And you did not maintain your throttle into third gear, so there's no way of knowing when your engine is going to stop revving.
Bottom line is that this is not about your engine's ability to rev like the title says it is. It's about the transmission shifting early, or you not pushing the throttle farther, and your unwillingness to rev it past a certain amount.
Remember earlier you said in low gear you could get it to 4000 rpm but shifted because YOU DID NOT WANT TO REV ANY HIGHER than that. Nothing wrong with the engine or trans at that point. You just didn't want to rev it any higher. So we're talking about different things here.
When someone earlier said they could get their engine to rev to 5000 rpm, that's because they didn't shift up when it hit 4000. They left it to go higher.
I can't guarantee you that hitting 5000 rpm is not going to hurt something in YOUR particular engine of course, but most normally constructed American V8 engines of this era can safely rev to 5500 and beyond without harm. Do you want to do that all the time? Certainly not, but if you need to, you can.
If you really want to see how high it will rev. let it rev to 5000 and stop because beyond that you don't need to know. If you want to know how high it will rev in any particular gear, push the throttle to the floor and hold it there.
If after doing that you find it still shifting at 3400 rpm, there is something wrong with your transmission or it's linkage. Otherwise I did not see anything out of the ordinary in the video, for light to mild acceleration characteristics.
I doubt that your engine is producing too much vacuum, but it would be still nice to know anyway in case that's pertinent to the discussion about any vacuum operation of the transmission. The recommendation of a vacuum gauge as a diagnostic tool was a good one too.
Good luck!
Paul
One thing is that, yes the earlier engines did tend to have slightly more power due to higher compression and perhaps other things, much (most?) of the drop in power ratings between '70, '71 and finally '72, was due to the mandate that all vehicle manufacturers list "net" horsepower based on certain guidelines that kept things consistent between all the companies. This way they could not fudge the numbers, or use less than consistent methods like they did with "gross" horsepower ratings before that.
So if you see a drop of for example, 45 to 60 bhp between one year and the next with the same engine, much of that drop was the way the numbers were reached.
Which also means as a side note, engines that are making 450bhp now, are probably making as much as 100bhp more than a similarly rated engine from '70.
Are you running headers or cast manifolds? If headers, some of the ticking is natural from the exhaust pulses ringing on the thinner steel tubes. If cast, then yes you likely have a leak. But increasing the timing advance might have masked the problem, rather than actually fixing it permanently.
As was said already, when you changed from the vacuum port up higher up to the one below it, you changed from ported vacuum to full vacuum. That's why the idle speed increased immediately. The timing probably jumped at least 12 to 15° assuming the vacuum advance is fully functional. But at least you know it does work to a point, or you would not have had the increase. That's a very good sign, but that's also where a timing light comes in handy as a diagnostic tool. Lets you know just what it is doing and when, and by how much.
I'll have to look up the carburetor for more details, but at a glance it appears to have mechanical secondaries with a vacuum/load operated venturi valve. I did not see all the linkages, but usually when there is a big flapper valve blocking the secondary venturii, it's set up so that you can open up the secondaries all you want, but they only work fully when, under the right circumstances, the upper butterfly valve/plate/thingy opens up too. Should keep the engine from bogging down when the secondaries are opened suddenly by flooring the pedal.
Other carbs use vacuum totally, and only open up the secondary throttle plates down low with vacuum. Those have larger vacuum canisters that pull an arm that opens the throttle blades/plates. Similar in function to the vacuum advance, but in reverse. The higher the vacuum signal, the blades stay closed. As the signal drops from heavy acceleration, they open up depending on just how far the vacuum drops.
As to which vacuum port to run the vacuum advance from, I usually use the ported one for my Fords. This usually ends up with setting more initial advance with the distributor. But if yours is currently running better on full vacuum, that's fine too. Some engine and parts combinations just like that better.
But it also says to me that you could have gotten away with advancing your timing a little too. That's in effect what you just did by changing the hose. Now when the engine is idling your timing is set way more advanced, then starts to come back down as you open up the throttle and accelerate. Less vacuum, less timing...
Certainly still worth playing around with timing.
As to accelerating more quickly and having the engine rev up farther, you need to find out how to check and adjust your kick-down lever/rod and see if the transmission is otherwise functioning properly. After all, what you showed in your video is not the engine's inability to rev, but the transmissions inability to avoid shifting up. Nothing else.
Whether it's mechanical or vacuum/load in nature, that's what you need to find out.
Do the C6 transmissions in this case have a vacuum modulator? Or are they strictly mechanical? Seems to me they do use vacuum. And if so, maybe your modulator is not 100% anymore.
How far down were you pushing the pedal in that video? Like was said too, if you're not pushing the pedal it's not going to save the upshifts for the higher rpms.
And you did not maintain your throttle into third gear, so there's no way of knowing when your engine is going to stop revving.
Bottom line is that this is not about your engine's ability to rev like the title says it is. It's about the transmission shifting early, or you not pushing the throttle farther, and your unwillingness to rev it past a certain amount.
Remember earlier you said in low gear you could get it to 4000 rpm but shifted because YOU DID NOT WANT TO REV ANY HIGHER than that. Nothing wrong with the engine or trans at that point. You just didn't want to rev it any higher. So we're talking about different things here.
When someone earlier said they could get their engine to rev to 5000 rpm, that's because they didn't shift up when it hit 4000. They left it to go higher.
I can't guarantee you that hitting 5000 rpm is not going to hurt something in YOUR particular engine of course, but most normally constructed American V8 engines of this era can safely rev to 5500 and beyond without harm. Do you want to do that all the time? Certainly not, but if you need to, you can.
If you really want to see how high it will rev. let it rev to 5000 and stop because beyond that you don't need to know. If you want to know how high it will rev in any particular gear, push the throttle to the floor and hold it there.
If after doing that you find it still shifting at 3400 rpm, there is something wrong with your transmission or it's linkage. Otherwise I did not see anything out of the ordinary in the video, for light to mild acceleration characteristics.
I doubt that your engine is producing too much vacuum, but it would be still nice to know anyway in case that's pertinent to the discussion about any vacuum operation of the transmission. The recommendation of a vacuum gauge as a diagnostic tool was a good one too.
Good luck!
Paul
#35
01-17-2019, 09:41 AM
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A few observations.
One thing is that, yes the earlier engines did tend to have slightly more power due to higher compression and perhaps other things, much (most?) of the drop in power ratings between '70, '71 and finally '72, was due to the mandate that all vehicle manufacturers list "net" horsepower based on certain guidelines that kept things consistent between all the companies. This way they could not fudge the numbers, or use less than consistent methods like they did with "gross" horsepower ratings before that.
So if you see a drop of for example, 45 to 60 bhp between one year and the next with the same engine, much of that drop was the way the numbers were reached.
Which also means as a side note, engines that are making 450bhp now, are probably making as much as 100bhp more than a similarly rated engine from '70.
Are you running headers or cast manifolds? If headers, some of the ticking is natural from the exhaust pulses ringing on the thinner steel tubes. If cast, then yes you likely have a leak. But increasing the timing advance might have masked the problem, rather than actually fixing it permanently.
As was said already, when you changed from the vacuum port up higher up to the one below it, you changed from ported vacuum to full vacuum. That's why the idle speed increased immediately. The timing probably jumped at least 12 to 15° assuming the vacuum advance is fully functional. But at least you know it does work to a point, or you would not have had the increase. That's a very good sign, but that's also where a timing light comes in handy as a diagnostic tool. Lets you know just what it is doing and when, and by how much.
I'll have to look up the carburetor for more details, but at a glance it appears to have mechanical secondaries with a vacuum/load operated venturi valve. I did not see all the linkages, but usually when there is a big flapper valve blocking the secondary venturii, it's set up so that you can open up the secondaries all you want, but they only work fully when, under the right circumstances, the upper butterfly valve/plate/thingy opens up too. Should keep the engine from bogging down when the secondaries are opened suddenly by flooring the pedal.
Other carbs use vacuum totally, and only open up the secondary throttle plates down low with vacuum. Those have larger vacuum canisters that pull an arm that opens the throttle blades/plates. Similar in function to the vacuum advance, but in reverse. The higher the vacuum signal, the blades stay closed. As the signal drops from heavy acceleration, they open up depending on just how far the vacuum drops.
As to which vacuum port to run the vacuum advance from, I usually use the ported one for my Fords. This usually ends up with setting more initial advance with the distributor. But if yours is currently running better on full vacuum, that's fine too. Some engine and parts combinations just like that better.
But it also says to me that you could have gotten away with advancing your timing a little too. That's in effect what you just did by changing the hose. Now when the engine is idling your timing is set way more advanced, then starts to come back down as you open up the throttle and accelerate. Less vacuum, less timing...
Certainly still worth playing around with timing.
As to accelerating more quickly and having the engine rev up farther, you need to find out how to check and adjust your kick-down lever/rod and see if the transmission is otherwise functioning properly. After all, what you showed in your video is not the engine's inability to rev, but the transmissions inability to avoid shifting up. Nothing else.
Whether it's mechanical or vacuum/load in nature, that's what you need to find out.
Do the C6 transmissions in this case have a vacuum modulator? Or are they strictly mechanical? Seems to me they do use vacuum. And if so, maybe your modulator is not 100% anymore.
How far down were you pushing the pedal in that video? Like was said too, if you're not pushing the pedal it's not going to save the upshifts for the higher rpms.
And you did not maintain your throttle into third gear, so there's no way of knowing when your engine is going to stop revving.
Bottom line is that this is not about your engine's ability to rev like the title says it is. It's about the transmission shifting early, or you not pushing the throttle farther, and your unwillingness to rev it past a certain amount.
Remember earlier you said in low gear you could get it to 4000 rpm but shifted because YOU DID NOT WANT TO REV ANY HIGHER than that. Nothing wrong with the engine or trans at that point. You just didn't want to rev it any higher. So we're talking about different things here.
When someone earlier said they could get their engine to rev to 5000 rpm, that's because they didn't shift up when it hit 4000. They left it to go higher.
I can't guarantee you that hitting 5000 rpm is not going to hurt something in YOUR particular engine of course, but most normally constructed American V8 engines of this era can safely rev to 5500 and beyond without harm. Do you want to do that all the time? Certainly not, but if you need to, you can.
If you really want to see how high it will rev. let it rev to 5000 and stop because beyond that you don't need to know. If you want to know how high it will rev in any particular gear, push the throttle to the floor and hold it there.
If after doing that you find it still shifting at 3400 rpm, there is something wrong with your transmission or it's linkage. Otherwise I did not see anything out of the ordinary in the video, for light to mild acceleration characteristics.
I doubt that your engine is producing too much vacuum, but it would be still nice to know anyway in case that's pertinent to the discussion about any vacuum operation of the transmission. The recommendation of a vacuum gauge as a diagnostic tool was a good one too.
Good luck!
Paul
One thing is that, yes the earlier engines did tend to have slightly more power due to higher compression and perhaps other things, much (most?) of the drop in power ratings between '70, '71 and finally '72, was due to the mandate that all vehicle manufacturers list "net" horsepower based on certain guidelines that kept things consistent between all the companies. This way they could not fudge the numbers, or use less than consistent methods like they did with "gross" horsepower ratings before that.
So if you see a drop of for example, 45 to 60 bhp between one year and the next with the same engine, much of that drop was the way the numbers were reached.
Which also means as a side note, engines that are making 450bhp now, are probably making as much as 100bhp more than a similarly rated engine from '70.
Are you running headers or cast manifolds? If headers, some of the ticking is natural from the exhaust pulses ringing on the thinner steel tubes. If cast, then yes you likely have a leak. But increasing the timing advance might have masked the problem, rather than actually fixing it permanently.
As was said already, when you changed from the vacuum port up higher up to the one below it, you changed from ported vacuum to full vacuum. That's why the idle speed increased immediately. The timing probably jumped at least 12 to 15° assuming the vacuum advance is fully functional. But at least you know it does work to a point, or you would not have had the increase. That's a very good sign, but that's also where a timing light comes in handy as a diagnostic tool. Lets you know just what it is doing and when, and by how much.
I'll have to look up the carburetor for more details, but at a glance it appears to have mechanical secondaries with a vacuum/load operated venturi valve. I did not see all the linkages, but usually when there is a big flapper valve blocking the secondary venturii, it's set up so that you can open up the secondaries all you want, but they only work fully when, under the right circumstances, the upper butterfly valve/plate/thingy opens up too. Should keep the engine from bogging down when the secondaries are opened suddenly by flooring the pedal.
Other carbs use vacuum totally, and only open up the secondary throttle plates down low with vacuum. Those have larger vacuum canisters that pull an arm that opens the throttle blades/plates. Similar in function to the vacuum advance, but in reverse. The higher the vacuum signal, the blades stay closed. As the signal drops from heavy acceleration, they open up depending on just how far the vacuum drops.
As to which vacuum port to run the vacuum advance from, I usually use the ported one for my Fords. This usually ends up with setting more initial advance with the distributor. But if yours is currently running better on full vacuum, that's fine too. Some engine and parts combinations just like that better.
But it also says to me that you could have gotten away with advancing your timing a little too. That's in effect what you just did by changing the hose. Now when the engine is idling your timing is set way more advanced, then starts to come back down as you open up the throttle and accelerate. Less vacuum, less timing...
Certainly still worth playing around with timing.
As to accelerating more quickly and having the engine rev up farther, you need to find out how to check and adjust your kick-down lever/rod and see if the transmission is otherwise functioning properly. After all, what you showed in your video is not the engine's inability to rev, but the transmissions inability to avoid shifting up. Nothing else.
Whether it's mechanical or vacuum/load in nature, that's what you need to find out.
Do the C6 transmissions in this case have a vacuum modulator? Or are they strictly mechanical? Seems to me they do use vacuum. And if so, maybe your modulator is not 100% anymore.
How far down were you pushing the pedal in that video? Like was said too, if you're not pushing the pedal it's not going to save the upshifts for the higher rpms.
And you did not maintain your throttle into third gear, so there's no way of knowing when your engine is going to stop revving.
Bottom line is that this is not about your engine's ability to rev like the title says it is. It's about the transmission shifting early, or you not pushing the throttle farther, and your unwillingness to rev it past a certain amount.
Remember earlier you said in low gear you could get it to 4000 rpm but shifted because YOU DID NOT WANT TO REV ANY HIGHER than that. Nothing wrong with the engine or trans at that point. You just didn't want to rev it any higher. So we're talking about different things here.
When someone earlier said they could get their engine to rev to 5000 rpm, that's because they didn't shift up when it hit 4000. They left it to go higher.
I can't guarantee you that hitting 5000 rpm is not going to hurt something in YOUR particular engine of course, but most normally constructed American V8 engines of this era can safely rev to 5500 and beyond without harm. Do you want to do that all the time? Certainly not, but if you need to, you can.
If you really want to see how high it will rev. let it rev to 5000 and stop because beyond that you don't need to know. If you want to know how high it will rev in any particular gear, push the throttle to the floor and hold it there.
If after doing that you find it still shifting at 3400 rpm, there is something wrong with your transmission or it's linkage. Otherwise I did not see anything out of the ordinary in the video, for light to mild acceleration characteristics.
I doubt that your engine is producing too much vacuum, but it would be still nice to know anyway in case that's pertinent to the discussion about any vacuum operation of the transmission. The recommendation of a vacuum gauge as a diagnostic tool was a good one too.
Good luck!
Paul
I wholeheartedly agree with you on the carb as far as the secondaries. I just don't know what actuates them, without some accurate documentation. I don't see any linkage that would appear to open them up, so that's why I have always assumed that they were vacuum controlled. I'll continue to dig around the internet for something concrete.
I've verified that the kickdown is moving like it should, at least without or without it connected to the carb. Whether it is binding down below, I don't know. But if I disconnect it from the carb and push it back, it travels the same distance when connected to the carb. I was told that my transmission does have the vacuum modulator, so I will try to climb under it this weekend to see if I can successfully adjust it. Someone sent me a video from Youtube that shows how to simply do it with a small flat head screwdriver, a little at a time. We'll see if that makes a difference in the shift points.
In the video, that is with the foot to the floor. I don't let off on that run until I get to almost 70 mph, and that's because I was in a 55 mph zone. And I agree, it does sound like more of a transmission issue since I can put it in 1st manually and get it up to 4000 with no problem. The reason I'm hesitant to go higher was that I haven't had it that high before and I didn't want to press my luck. Just because someone else said they have done it up to 5000, doesn't mean that I'm ready to break something to find out for myself.
When I'm able to tweak that vacuum modulator on the transmission, I'll check back and let you know how it goes. Seems very simple to do and undo in case it doesn't go as planned.
#36
01-17-2019, 12:06 PM
Lead Driver
Sounds good. Very interested in your findings.
If that was floored, then I'd agree with you that, either the tune is still not right, the timing is not sufficiently advancing, OR as suspected, the secondaries are not opening up. Or if they are, at least not fully.
Doesn't sound floored at all. Maybe it's the video, because we can't always hear things the way the person taking the video does, but I don't detect any of that "whoomping" or "whooshing" sound you'd expect to hear when a 4bbl carb opens up.
Hmm, have you checked the air cleaner lately? I'm guessing you have since you've had the whole thing off to mess with the carb, but still wondering if it's restricting at all. Check the inlet tube (snorkel) to the air cleaner housing as well. Maybe the heat stove inlet valve is stuck closed and you're not getting the full blast of cool air into the air cleaner.
Was trying to diagnose a bogging once on a neighbor's '68 Grand Marquis. Wasn't running quite right, but taking the air cleaner off made it worse. Would just bog down and fall on it's face when you floored it. Turned out that the engine was sucking the hood insulator right down on top of the carb and choking it off! You just never know about this stuff...
When you're messing about with the modulator, make sure that the hose itself is getting vacuum. At the very least this means finding the hose up at the back of the intake manifold, likely on one port of a multi-port thingy called a "vacuum tree" and make sure it's getting vacuum signal and is free flowing down to the modulator.
Both the modulator and the hose may have failed over time. However, if the hose failed I would think it would make the transmission take longer to shift. Whereas yours is shifting early no matter what the pedal position. So I would suspect it's more likely the modulator itself.
Not sure if the mechanism inside where the kickdown lever is, has anything to do with upshifts at high loads, or if it's just for downshifting when pushing on the throttle.
Anyone know how that works on a C6? Do they work separately, or in conjunction with one another?
Paul
If that was floored, then I'd agree with you that, either the tune is still not right, the timing is not sufficiently advancing, OR as suspected, the secondaries are not opening up. Or if they are, at least not fully.
Doesn't sound floored at all. Maybe it's the video, because we can't always hear things the way the person taking the video does, but I don't detect any of that "whoomping" or "whooshing" sound you'd expect to hear when a 4bbl carb opens up.
Hmm, have you checked the air cleaner lately? I'm guessing you have since you've had the whole thing off to mess with the carb, but still wondering if it's restricting at all. Check the inlet tube (snorkel) to the air cleaner housing as well. Maybe the heat stove inlet valve is stuck closed and you're not getting the full blast of cool air into the air cleaner.
Was trying to diagnose a bogging once on a neighbor's '68 Grand Marquis. Wasn't running quite right, but taking the air cleaner off made it worse. Would just bog down and fall on it's face when you floored it. Turned out that the engine was sucking the hood insulator right down on top of the carb and choking it off! You just never know about this stuff...
When you're messing about with the modulator, make sure that the hose itself is getting vacuum. At the very least this means finding the hose up at the back of the intake manifold, likely on one port of a multi-port thingy called a "vacuum tree" and make sure it's getting vacuum signal and is free flowing down to the modulator.
Both the modulator and the hose may have failed over time. However, if the hose failed I would think it would make the transmission take longer to shift. Whereas yours is shifting early no matter what the pedal position. So I would suspect it's more likely the modulator itself.
Not sure if the mechanism inside where the kickdown lever is, has anything to do with upshifts at high loads, or if it's just for downshifting when pushing on the throttle.
Anyone know how that works on a C6? Do they work separately, or in conjunction with one another?
Paul
#37
01-17-2019, 12:52 PM
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#38
01-17-2019, 09:08 PM
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I think I found the issue with the shift points.... ;)
Here's what I found when I check the vacuum modulator on my C6 today. 
I'll hopefully be following up on this by the weekend. Unless online prices are that much better. Then I'll have to wait for one to ship.
I did dabble with the carburetor some more this afternoon. I decided to see if I could adjust the metering rods to get a richer mixture. It did not like that at all and immediately shut the truck off. When I went back, it started right back up. I did some fine tweaking with the vacuum gauge hooked up and I'm almost dead nuts at 20 psi, which I think is fantastic. When I said this carb was running as good as it ever has, I wasn't lying. When I first got this truck road-worthy, I was lucky to get 15. I did two more things while I was at it. I climbed under the hood so I could look down through the top of the carb. I actuated the arm that makes the accelerator pump go. I could see healthy shots of fuel shooting out, so that was good. The next thing I wanted to do is see if the secondaries were opening under heavy throttle. I pushed the air valve open over the secondaries, gave the throttle a healthy push and the secondary throttle plates are not opening. From what I've read, the "air valve damper piston and rod" keeps the plate closed, because of the attached spring. But under load, the air valve plate should open as well as the throttle plates. So this still remains a mystery. I've read posts where guys say it part vacuum, part mechanical. It's just different enough than the Motorcraft 4300, which has much more documentation, that I am still befuddled on how it actually works. I will continue to dig!
I'll hopefully be following up on this by the weekend. Unless online prices are that much better. Then I'll have to wait for one to ship.
I did dabble with the carburetor some more this afternoon. I decided to see if I could adjust the metering rods to get a richer mixture. It did not like that at all and immediately shut the truck off. When I went back, it started right back up. I did some fine tweaking with the vacuum gauge hooked up and I'm almost dead nuts at 20 psi, which I think is fantastic. When I said this carb was running as good as it ever has, I wasn't lying. When I first got this truck road-worthy, I was lucky to get 15. I did two more things while I was at it. I climbed under the hood so I could look down through the top of the carb. I actuated the arm that makes the accelerator pump go. I could see healthy shots of fuel shooting out, so that was good. The next thing I wanted to do is see if the secondaries were opening under heavy throttle. I pushed the air valve open over the secondaries, gave the throttle a healthy push and the secondary throttle plates are not opening. From what I've read, the "air valve damper piston and rod" keeps the plate closed, because of the attached spring. But under load, the air valve plate should open as well as the throttle plates. So this still remains a mystery. I've read posts where guys say it part vacuum, part mechanical. It's just different enough than the Motorcraft 4300, which has much more documentation, that I am still befuddled on how it actually works. I will continue to dig!
#39
01-18-2019, 08:38 AM
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Are you able to open the secondary plates manually with out the engine running?
Have you seen this thread for vacuum routing?
https://www.ford-trucks.com/forums/8...-needed-3.html
Have you seen this thread for vacuum routing?
https://www.ford-trucks.com/forums/8...-needed-3.html
#40
01-18-2019, 09:29 AM
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Are you able to open the secondary plates manually with out the engine running?
Have you seen this thread for vacuum routing?
https://www.ford-trucks.com/forums/8...-needed-3.html
Have you seen this thread for vacuum routing?
https://www.ford-trucks.com/forums/8...-needed-3.html
I got on a 460 Facebook page last night and a guy told me that there is a screw on the passenger side by the choke and that if I remove that screw it will allow the secondaries to open. I pulled up a picture and sure enough there is a flat head screw. This is what he posted: "back passenger side there is a linkage that stops the sec. it's controlled by the choke it has a big flat srew on it remove that and the sec. will open when you floor it". So I'll check that when I get home and see if it works.
Yes, I actually did come across that post with the vacuum diagrams, that's why I decided to move my vacuum advance hose to the front right instead of the front left where it says "Manifold vacuum - plug this one".
#41
01-18-2019, 03:54 PM
#42
01-18-2019, 06:08 PM
Join Date: Oct 2004
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Niko20, either you and I have the same problem, or we in the minority. I just had a guy tell me on another site last night that said he's owned 15 460's over the years and they'll do 6000 RPM's. Clearly there's something wrong with mine. LOL
#43
01-18-2019, 08:31 PM
Lead Driver
It would be a rare C6 I think that would shift at 6000 rpm even when floored, so perhaps he meant he could rev his engines that high. Whereas you simply have not wanted to rev yours that high yet, as you have stated before, but yet may actually be able to if you let it ride.
Just wanting to point out the possibility, so you don't go thinking something is wrong with your engine's internals, when it still could be your transmission and the fact that maybe your secondaries are not opening (yet to be determined, but still certainly in question), or opening all the way at least.
Your engine sounds like it might actually rev to 6000 too, like the other guy's have done, but you cut it off at 4000 because you weren't sure you wanted to rev it any higher.
Most of my engines will easily rev to their traditional 5500 rpm redlines, but my Bronco with it's stock engine configuration used to practically fall on it's face when it reached about 4500 and would barely pull beyond that. Not in danger of breaking, it just ran out of breath.
Paul
#44
01-18-2019, 08:33 PM
#45
01-18-2019, 09:07 PM
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Are you sure you two were comparing apples to apples? Did he know you meant it would not "shift" above 3500 when accelerating? Or did he think you meant would not rev up at all.
It would be a rare C6 I think that would shift at 6000 rpm even when floored, so perhaps he meant he could rev his engines that high. Whereas you simply have not wanted to rev yours that high yet, as you have stated before, but yet may actually be able to if you let it ride.
Just wanting to point out the possibility, so you don't go thinking something is wrong with your engine's internals, when it still could be your transmission and the fact that maybe your secondaries are not opening (yet to be determined, but still certainly in question), or opening all the way at least.
Your engine sounds like it might actually rev to 6000 too, like the other guy's have done, but you cut it off at 4000 because you weren't sure you wanted to rev it any higher.
Most of my engines will easily rev to their traditional 5500 rpm redlines, but my Bronco with it's stock engine configuration used to practically fall on it's face when it reached about 4500 and would barely pull beyond that. Not in danger of breaking, it just ran out of breath.
Paul
It would be a rare C6 I think that would shift at 6000 rpm even when floored, so perhaps he meant he could rev his engines that high. Whereas you simply have not wanted to rev yours that high yet, as you have stated before, but yet may actually be able to if you let it ride.
Just wanting to point out the possibility, so you don't go thinking something is wrong with your engine's internals, when it still could be your transmission and the fact that maybe your secondaries are not opening (yet to be determined, but still certainly in question), or opening all the way at least.
Your engine sounds like it might actually rev to 6000 too, like the other guy's have done, but you cut it off at 4000 because you weren't sure you wanted to rev it any higher.
Most of my engines will easily rev to their traditional 5500 rpm redlines, but my Bronco with it's stock engine configuration used to practically fall on it's face when it reached about 4500 and would barely pull beyond that. Not in danger of breaking, it just ran out of breath.
Paul