Bugga bugga chugga bugga cruise
- Thread starter Namehtnad
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I appreciate all the help, last night at the gas station (I tinker everywhere) I adjusted the accelerator pump linkage and it took care of any bogging on hell giving time. I think I'll go to get the .101 jets and the 73/47 metering rods, I'll swap the lil uns ( .095 for the .098) I'll see where that leads me on the cruise issue and continue to tinker accordingly.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Can you feel the miss tugging on the chassis, or are you just hearing a popping in the exhaust?Or is it both together?.
Here's how I ballpark my cruise mixture.
On a fully warmed up engine.
With the T-port sync previously set;
I set the fast idle cam up to get me about 2200rpm. Then I set the mixture screws in the center of their range,usually 1.5 to 2.5 turns. Then with the vacuum advance hooked up, I adjust the timing for the highest rpm; I just tug on the dizzy without regard for the numbers at this point. Then I gently start to close those primaries with a rag; NOT with the choke.. The secondaries should be fully closed, with a small cam. If the rpm goes up, then she's getting too much air and wants fuel to go with that air. If the rpm goes down, she wants more air.
Then I fix the dizzy,to try and give her the timing she is craving.Usually the biggest Vcan I can find.
Then I fix the cruise AFR.
Them I fix the idle quality, and T-port sync.
Then a roadtest to see how close we are.
Then another AFR adjustment as may be required.
Followed by a roadtest.
Finally, I fix the power-timing, if I messed with the initial.
Here's how I ballpark my cruise mixture.
On a fully warmed up engine.
With the T-port sync previously set;
I set the fast idle cam up to get me about 2200rpm. Then I set the mixture screws in the center of their range,usually 1.5 to 2.5 turns. Then with the vacuum advance hooked up, I adjust the timing for the highest rpm; I just tug on the dizzy without regard for the numbers at this point. Then I gently start to close those primaries with a rag; NOT with the choke.. The secondaries should be fully closed, with a small cam. If the rpm goes up, then she's getting too much air and wants fuel to go with that air. If the rpm goes down, she wants more air.
Then I fix the dizzy,to try and give her the timing she is craving.Usually the biggest Vcan I can find.
Then I fix the cruise AFR.
Them I fix the idle quality, and T-port sync.
Then a roadtest to see how close we are.
Then another AFR adjustment as may be required.
Followed by a roadtest.
Finally, I fix the power-timing, if I messed with the initial.
It's a tugging on the chassis. The pop was a an issue I quickly corrected. It's a bogging, chugging sensation as if it's starving for fuel. Literally is a bugga bugga chugga bugga the chugga is the miss. Doesn't do it when hammer is down, doesn't do it at idle. Just cruise and slow acceleration. Maybe it's the lack of a fuel sending unit as the fuel line is just run into a gas can, (the tank was clogging filters faster than I could replace them), but it's never been an issue before with previous old vehicles. 72 f-100 76 valore both shitty tanks, both I ran a temp gas tank till getting a new one. I have no idea what a t-port sync is.
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I read the manual and now understanding the functionality of the various circuits, I believe my problem will be solved with a stronger stepup spring, and a smaller metering rod. She runs cherry through all the other circuits, it's the off idle, cruising circuit. Rectified by the metering rod and stepup spring
Saying there's not much difference between the 1405 and 1406 is showing that you don't really know. There are a lot of differences. There's a thread around here somewhere that details all the differences and there are many. Jets, rods and even the boosters are completely different. It's safe to call them two completely different carburetors, because they are.
Here is the link to the thread where Zwap shows all the differences between the two. There are many.
Another 1405 vs 1406 thread
Another 1405 vs 1406 thread
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
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The step-up spring is fully collapsed at steady-state cruising, to keep the rods fully down.At low speeds you want to be cruising on the transfers. The springs begins to lift the rods as the engine vacuum falls, due to increased load. You can time the lifting process to coincide with the mainjet fuel becoming insufficient, to improve driveability. The changeover is usually at about 10 inches of vacuum, where the mains run out.If your mains run out before that, they may be too small. If below that, then they may be too big.
You the tuner kindof get to fine tune the changeover point, to customize the fuel delivery for your application.If you are an aggressive driver you may wish an earlier changeover. If the vehicle was a low speed,low rpm car with lots of cubes, and had enough power on the mains, then the changeover could be quite late.
During steady-state cruising,If you feel the tugging in the chassis, you could try more timing. The engine can run quite lean if you manage to start the fire early enough.A multi-strike can be a big help. By starting the fire early,it will have more time to find all the gasoline atoms to react with,and it will be done burning when the exhaust valve opens. If it wasn't finished, and if the still burning charge found oxygen in that pipe, on it's way to the muffler, that creates a popping.
This is also where hi-compression and tightQ can help.By agitating the charge prior to the ignition event,the small number of fuel atoms, stand a better chance of finding oxygen atoms to react with.
>Some combos just have to be richer than necessary, to ensure that the fire does not go out, as the fire jumps from one gas-atom to another in the chamber.This is why low compression,no-Q chambers are such gas hogs., compared to the same engine with hi-compression and very tight-Q.It is also why low-compression engines like more Part-Throttle timing. It's all about having enough time to burn ALL the fuel that's in there.
>Keep in mind that it only takes maybe 48hp to cruise 60 mph. On a V8 this is about 6 hp per cylinder. If one dies and contributes nothing, that is 6 hp lost. Now the crank sees that power loss, and for 1/4 turn there is no power delivery, so it slows down just a tiny bit. Then the next one speeds the crank back up.
>But if one cylinder fires too early, then its power will/may FORCE the crankshaft to slow down more than a dead cylinder.And then it may take several next-firing cylinders to bring the crankspeed back up. So not only did the engine lose 6 hp, but perhaps 3 or 4 more were subtracted by the after-affects.
If the a cylinder fired late,and only half the fuel burned, then only 3 hp gets lost.
So in these examples,a "missfire" could be a 3 hp loss, a 6hp loss or a 9 hp loss
>Now if multiple cylinders are doing something wrong, then the gas pedal has to be pushed down further to make the 48 total horsepower. Then when a couple of them work right, while 6 are only making 5 hp, these two are suddenly making 8 each. So the total 48 is still there, and the car continues at 60 ok, but the crank is getting hammered, and you sure feel it. In this example, a "missfire" could be a 12 hp loss.
>Of course any missfire is pumping raw gasoline right out the tailpipe. A 3hp loss is 6% at 60mph. a 12hp loss is a 25% loss.
So if there are any teeners reading this with 268cams in your sub 8/1 engines with open chambers.....I feel sorry for you.......
Been there, done that, never again,lol
You the tuner kindof get to fine tune the changeover point, to customize the fuel delivery for your application.If you are an aggressive driver you may wish an earlier changeover. If the vehicle was a low speed,low rpm car with lots of cubes, and had enough power on the mains, then the changeover could be quite late.
During steady-state cruising,If you feel the tugging in the chassis, you could try more timing. The engine can run quite lean if you manage to start the fire early enough.A multi-strike can be a big help. By starting the fire early,it will have more time to find all the gasoline atoms to react with,and it will be done burning when the exhaust valve opens. If it wasn't finished, and if the still burning charge found oxygen in that pipe, on it's way to the muffler, that creates a popping.
This is also where hi-compression and tightQ can help.By agitating the charge prior to the ignition event,the small number of fuel atoms, stand a better chance of finding oxygen atoms to react with.
>Some combos just have to be richer than necessary, to ensure that the fire does not go out, as the fire jumps from one gas-atom to another in the chamber.This is why low compression,no-Q chambers are such gas hogs., compared to the same engine with hi-compression and very tight-Q.It is also why low-compression engines like more Part-Throttle timing. It's all about having enough time to burn ALL the fuel that's in there.
>Keep in mind that it only takes maybe 48hp to cruise 60 mph. On a V8 this is about 6 hp per cylinder. If one dies and contributes nothing, that is 6 hp lost. Now the crank sees that power loss, and for 1/4 turn there is no power delivery, so it slows down just a tiny bit. Then the next one speeds the crank back up.
>But if one cylinder fires too early, then its power will/may FORCE the crankshaft to slow down more than a dead cylinder.And then it may take several next-firing cylinders to bring the crankspeed back up. So not only did the engine lose 6 hp, but perhaps 3 or 4 more were subtracted by the after-affects.
If the a cylinder fired late,and only half the fuel burned, then only 3 hp gets lost.
So in these examples,a "missfire" could be a 3 hp loss, a 6hp loss or a 9 hp loss
>Now if multiple cylinders are doing something wrong, then the gas pedal has to be pushed down further to make the 48 total horsepower. Then when a couple of them work right, while 6 are only making 5 hp, these two are suddenly making 8 each. So the total 48 is still there, and the car continues at 60 ok, but the crank is getting hammered, and you sure feel it. In this example, a "missfire" could be a 12 hp loss.
>Of course any missfire is pumping raw gasoline right out the tailpipe. A 3hp loss is 6% at 60mph. a 12hp loss is a 25% loss.
So if there are any teeners reading this with 268cams in your sub 8/1 engines with open chambers.....I feel sorry for you.......
Been there, done that, never again,lol
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Found the culprit. Cleaned it out and Rejetted it anyhow, put the orange springs in it...And oh what a beast (ish) no more bugga bugga chugga bugga. Now it's bugga bugga bugga bugga. I may want to change back to normal size primary jets with a different metering rod and maybe the pink spring...Put in the .101 primary .098 secondary and the orange springs. Drove it and it flooded real quick on takeoff so I moved the accelerator pump actuating rod down a notch.
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