Stop in for a cup of coffee

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Seen on Facebook just now, Tony Fields isn't doing very well and has now sold his Cuda :(
 
straightlinespeed said:
3:23 and that was changed from 3:73. I've never gotten good gas mileage and Im stumped why? I was thinking the large (750) carb was the issue, hence why I swapped to the 600. But swapping to the smaller carb slightly improved it. Thinking about it if Im really easy on the throttle I can get maybe 120miles and that leaves me with a quarter tank of gas, but I dont know how accurate my gauge is so I dont push it. At 60mph, Im turning 2800rpm, at 70mph Im turning 3500rpm. I only have a 26.4" tire on the rear. So if I could get a taller tire that might help some also.
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The engine is an air pump so at a fixed A/F ratio, carb size doesn't matter for fuel used. A/F ratio determines the amount of fuel used per each revolution. If you are using more fuel than normal A/F ratio can provide to maintain a certain RPM, the rest of the drive train is providing resistance making more fuel necessary to maintain that RPM...or you aren't using the fuel efficiently (low MPG)

A 42 RH with a 0.69 OD gear will increase MPG only if you don't need to pour in the extra fuel to maintain the drive power to maintain speed. The risk is that the OD will actually be less efficient than a standard 1.0 top gear if it needs all that extra fuel.

I suspect your timing curve is way off so that you aren't using the fuel you are delivering efficiently...and just blowing it out the tail pipe instead of turning it into power.
 
Ddaddy said:
The engine is an air pump so at a fixed A/F ratio, carb size doesn't matter for fuel used. A/F ratio determines the amount of fuel used per each revolution. If you are using more fuel than normal A/F ratio can provide to maintain a certain RPM, the rest of the drive train is providing resistance making more fuel necessary to maintain that RPM...or you aren't using the fuel efficiently (low MPG)

A 42 RH with a 0.69 OD gear will increase MPG only if you don't need to pour in the extra fuel to maintain the drive power to maintain speed. The risk is that the OD will actually be less efficient than a standard 1.0 top gear if it needs all that extra fuel.

I suspect your timing curve is way off so that you aren't using the fuel you are delivering efficiently...and just blowing it out the tail pipe instead of turning it into power.
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I understand what your saying. See this is where Im young and dumb, I understand how to tune the carb and set timing etc... But I dont know how to find the optimal timing.
 
straightlinespeed said:
I understand what your saying. See this is where Im young and dumb, I understand how to tune the carb and set timing etc... But I dont know how to find the optimal timing.
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Do you know what your current timing curve is? 18° initial plus what for vacuum and mechanical...and at what RPM?
 
Ddaddy said:
Do you know what your current timing curve is? 18° initial plus what for vacuum and mechanical...and at what RPM?
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I was not taking my vacuum into consideration with my total so Im running 16* mechanical, which gets me my 34* total. My vacuum I honestly cant tell you as I've never really paid attention and when I do run my RPM's up my marks on my crank run out, but Im guessing Im somewhere in the 50's when my vacuum is being used.
 
For example, my advance curve is 22° initial with mechanical advance coming on at 1200 rpm with 23° more all in at a 3200 rpm (45° total). My vacuum advance adds 5-7° at 15" vacuum...but I only use the vacuum advance when temps are below 70° F or it can pull lean and cause detonation at part throttle.
 
straightlinespeed said:
I was not taking my vacuum into consideration with my total so Im running 16* mechanical, which gets me my 34* total. My vacuum I honestly cant tell you as I've never really paid attention and when I do run my RPM's up my marks on my crank run out, but Im guessing Im somewhere in the 50's when my vacuum is being used.
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34° total makes you light and not using the fuel like you should. Vacuum advance falls out under heavy throttle (vacuum drops) which makes you even lighter. You need a better advance curve to get the power and fuel efficiency you should have.

What RPM does your mechanical advance start and then go all in?
 
Ddaddy said:
For example, my advance curve is 22° initial with mechanical advance coming on at 1200 rpm with 23° more all in at a 3200 rpm (45° total). My vacuum advance adds 5-7° at 15" vacuum...but I only use the vacuum advance when temps are below 70° F or it can pull lean and cause detonation at part throttle.
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Sorry I forgot the curve. Right now my mechanical starts @ 1200 and ends at 3200. I just picked up the curve kit from Summit for my MP distributor, so I would like to mess with it to fine tune it more. My vacuum can I have no idea what it adds.

My distributor was set up for racing originally and mechanical started @ 900 and was all in by 1400. So I slowed it down, to what I mentioned above.
 
straightlinespeed said:
3:23 and that was changed from 3:73. I've never gotten good gas mileage and Im stumped why? I was thinking the large (750) carb was the issue, hence why I swapped to the 600. But swapping to the smaller carb slightly improved it. Thinking about it if Im really easy on the throttle I can get maybe 120miles and that leaves me with a quarter tank of gas, but I dont know how accurate my gauge is so I dont push it. At 60mph, Im turning 2800rpm, at 70mph Im turning 3500rpm. I only have a 26.4" tire on the rear. So if I could get a taller tire that might help some also.
Click to expand...
I think I would figure out the miles on a trip or something and check the accuracy of your odo meter
 
I've also been told and read many times on here that you want your total somewhere from 32-36*. So Im not following you with adding more, because that can cause pinging correct?
 
dartnabout said:
I think I would figure out the miles on a trip or something and check the accuracy of your odo meter
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I have done that. Nice and easy on the throttle the entire trip and my MPG was 11.4ish. That was also driving 55-60mph. Im running aftermarket gauges which has a calibration procedure. I've also compared my gauges with GPS and its right on.
 
straightlinespeed said:
Exactly, Its made me think, but I have no idea



How do you know? I've asked that question many times and no one has been able to tell me? Other than starter kick back
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I think you use a vacuum gauge to sweep the advance and see where it gets max vacuum... Then leave it there or back off a degree or two...

Maybe sweep the RPM range and see at what advance you get highest vacuum, then recurve the dizzy to match....
 
krazykuda said:
I think you use a vacuum gauge to sweep the advance and see where it gets max vacuum... Then leave it there or back off a degree or two...

Maybe sweep the RPM range and see at what advance you get highest vacuum, then recurve the dizzy to match....
Click to expand...

See you totally lost me. LOL

So others with my combo get higher vacuum readings and I can only pull about 13.5-14 while tuning the carb. Now if I twist the distributor to increase my initial I'll get a higher reading around 15 + which is what others are getting. But I think that Im at about 24-26* initial at that point. Timing I get but obviously I dont get it at all.
 
Ddaddy said:
Practice make perfect. And there is nothing as admirable as a perfect ***.
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I hear you....

I just love the way her legs make an *** out of themselves.... :p :p :p

Giggity, giggity... :D

tightass.jpg
 
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