what carb do you use
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Anonymous
Oh and BTW Dave for the record, you are absolutly right on the tuning deal, I just don't need to mess around, although one particular 750 speed caused a problem but there was NO WAY I was going to trash a perfectly good carb as the combo was wrong and no matter what was done it still wouldn't have cured the problem.
A holley is what ?100 secondhand a Demon is ?300 plus new depending on model, easier and cheaper to change the combo and bring it all into the parameters than butcher it and spend hours and hours doing it, thats not tuning it's stubborness
A holley is what ?100 secondhand a Demon is ?300 plus new depending on model, easier and cheaper to change the combo and bring it all into the parameters than butcher it and spend hours and hours doing it, thats not tuning it's stubborness
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Dave-R
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Neil. I am not calling anyone and you have no idea what I think of your buddy. I have never met the guy. you cannot form opinions on people from the internet. In my experience people are completely the opposite to what you imagine when you meet them.
In fact if you will find that how you perceive people to be is a reflection of your own attitude to that person and nothing to do with how that person actually is.
Just go put a bigger duration cam in a stock engine and see what happens to the mixture and idle. It will be too lean and starved of air at idle. The answer is not a new carb. It is in the calibration of that carb.
Start from there and forget these confused theories and sales pitches.
Oh and I would still like to see a Holley and Demon flow tested at the same pressures etc. My money is on the Demon flowing a lot more than the Holley which would make your comparisons useless.
In fact if you will find that how you perceive people to be is a reflection of your own attitude to that person and nothing to do with how that person actually is.
Just go put a bigger duration cam in a stock engine and see what happens to the mixture and idle. It will be too lean and starved of air at idle. The answer is not a new carb. It is in the calibration of that carb.
Start from there and forget these confused theories and sales pitches.
Oh and I would still like to see a Holley and Demon flow tested at the same pressures etc. My money is on the Demon flowing a lot more than the Holley which would make your comparisons useless.
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Dave-R
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Just to contadict myself. Actually if the duration is much bigger than stock the carb will suddenly go very rich. This is because the biger the duration of the cam, the lower manifold vacuum will be at idle. If the manifold vacuum drops below the rating of the fuel enrichment system (power valve in a Holley) the system will turn on and pour fuel in.Dave wrote:Just go put a bigger duration cam in a stock engine and see what happens to the mixture and idle. It will be too lean and starved of air at idle.
The cure for that is to fit springs or power valves that match the vacuum level. THEN you will find the idle system lean. In fact the car may not idle at all. You can easily prove it is lean by squirting fuel into the carb and you will instantly find it picks up.
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Anonymous
dave
how did you calculate the power and torque curves? very nice
are they accurate calculated figures and how close will they match real world dyno figures?
if its a computer program where can i get a copy
intake was the only one available when i decieded i wanted one NOW!!!
lokinh at it would be better with a torker 2 or mopar m1.
how did you calculate the power and torque curves? very nice
are they accurate calculated figures and how close will they match real world dyno figures?
if its a computer program where can i get a copy
intake was the only one available when i decieded i wanted one NOW!!!
lokinh at it would be better with a torker 2 or mopar m1.
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Anonymous
Why keep banging on about " if a bigger duration on the cam", I thought the debate was is the carb to big, it is too big for the cam end of.
As it is too big for the cam it would have been weak after idle, end of
This taken out of Don's tuning guide
"The idle circuit basically just dumps aerated or foamed fuel and relies on the air velocity flowing around the butterflies to further atomize the fuel so your engine can burn it efficiently. If you have too little velocity or the butterflies are open too far causing fuel to be pulled from the transition circuit, the fuel will not be atomized correctly and raw fuel will be sitting in your manifold and in extreme conditions on your piston. This causes a rich idle condition and very poor off idle throttle response."
"Too little Velocity" read carb too big.. end of...
And on a Demon it is a no no to open the secondaries to cure rich idle, speeds want 1 turn primaries 3/4 turn secondaries, Mightys need a little more but not much, always more on the primaries.
"Sales Pitch" No chance, I can only do that in the traders area, just a debate on the consequences of a carb that is too big
As it is too big for the cam it would have been weak after idle, end of
This taken out of Don's tuning guide
"The idle circuit basically just dumps aerated or foamed fuel and relies on the air velocity flowing around the butterflies to further atomize the fuel so your engine can burn it efficiently. If you have too little velocity or the butterflies are open too far causing fuel to be pulled from the transition circuit, the fuel will not be atomized correctly and raw fuel will be sitting in your manifold and in extreme conditions on your piston. This causes a rich idle condition and very poor off idle throttle response."
"Too little Velocity" read carb too big.. end of...
And on a Demon it is a no no to open the secondaries to cure rich idle, speeds want 1 turn primaries 3/4 turn secondaries, Mightys need a little more but not much, always more on the primaries.
"Sales Pitch" No chance, I can only do that in the traders area, just a debate on the consequences of a carb that is too big
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Dave-R
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Desktop Dyno 2000. I will send you a copy when I get a chance. Too tired right now.Ford360Chap wrote:dave
how did you calculate the power and torque curves? very nice
are they accurate calculated figures and how close will they match real world dyno figures?
if its a computer program where can i get a copy
You can't trust the actual figures it gives. But they are a good rough guide and not a million miles off. What is more important is the shape of the curve. When I have compared the desktop Dyno curves to actual measured dyno curves the shape matches very well. The shape tells you things like where peak torque and HP will be in the rpm range. Very handy when working out shift points and gearing etc. In particular when used in conjunction with my gear/rpm calculator.
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Anonymous
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Dave-R
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- Location: Dave Robson lives in Geordieland
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Neil. Why keep banging on about Demons when they have no relationship with Holleys. Holleys don't have the fancy adjustments provided on Demons. Not everyone is trying to pee higher than everyone else with "look how much money I have spent on my car". So dumping a perfectly good Holley for a Demon just because it needs tuning is not an option open to everyone.
As for sizing. Yet again you quote refering to Demons. As far as I can tell by looking a Demon has the same size throttle blades as a Holley. BUT I am betting they flow a lot more. So if your 650 flows the same as a holley 750 your arguments are worthless. We need more data.
You have already said Don bases carb size on cam size. That is the same thing as saying what rpm does the engine rev to. Just a more flash way of asking a simple question really.
Use any carb sizing formula you like. A high revving 340 or 360 will need a bigger carb than a low rev 440 built for low rpm torque.
What you CANNOT say is a 340 is smaller than a 440 so the 340 MUST have a smaller carb.
Example. Take a 440 that revs to 5500rpm and has a volumetric efficiency of 85% (which would be about right for that engine because of the low rpms).
A simple calculation shows that it needs a 600cfm carb.
Now take a 360 that revs to 7500 rpm. It might have more than 100% volumetric efficiency because of the high air velocity with a good intake. But lets keep it to 95%.
Do the same calculation and you see it needs a 750cfm carb at least.
Now racers over the years have found that these calculated "ideal" carb sizes are in fact on the small side for racing. Mopars in particular respond to a bigger carb than the theory would suggest. Who are we to argue with what every racer in the last 40 years has found?
As for sizing. Yet again you quote refering to Demons. As far as I can tell by looking a Demon has the same size throttle blades as a Holley. BUT I am betting they flow a lot more. So if your 650 flows the same as a holley 750 your arguments are worthless. We need more data.
You have already said Don bases carb size on cam size. That is the same thing as saying what rpm does the engine rev to. Just a more flash way of asking a simple question really.
Use any carb sizing formula you like. A high revving 340 or 360 will need a bigger carb than a low rev 440 built for low rpm torque.
What you CANNOT say is a 340 is smaller than a 440 so the 340 MUST have a smaller carb.
Example. Take a 440 that revs to 5500rpm and has a volumetric efficiency of 85% (which would be about right for that engine because of the low rpms).
A simple calculation shows that it needs a 600cfm carb.
Now take a 360 that revs to 7500 rpm. It might have more than 100% volumetric efficiency because of the high air velocity with a good intake. But lets keep it to 95%.
Do the same calculation and you see it needs a 750cfm carb at least.
Now racers over the years have found that these calculated "ideal" carb sizes are in fact on the small side for racing. Mopars in particular respond to a bigger carb than the theory would suggest. Who are we to argue with what every racer in the last 40 years has found?
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Dave-R
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I just did the sums on a stock bore/stroke 440 that revs to 6500rpm with a Vol. Eff. of 91% which is about where a good street/strip engine should be operating at.
It works out as needing 745cfm. That is before adding the extra size that racers have always found they need. So a 750 is not going to cut it.
But I have no way of knowing if your "750" Demons actually flow more than that or not. If they flow more like 800cfm they could be ideal.
It works out as needing 745cfm. That is before adding the extra size that racers have always found they need. So a 750 is not going to cut it.
But I have no way of knowing if your "750" Demons actually flow more than that or not. If they flow more like 800cfm they could be ideal.
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Anonymous
Dave, lets quit insulting each other and purposely trying to wind each other up, we know we both can so there's no point.
I'm now going to have a family afternoon
got to do it sometimes, I am in the dog house already as I missed the family morning
I'll take a look at what you posted tomorrow and respond with the correct attitude
I'm now going to have a family afternoon
got to do it sometimes, I am in the dog house already as I missed the family morningI'll take a look at what you posted tomorrow and respond with the correct attitude
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Anonymous
My friend who has the black Riviera boat-tail with the 455 in it switched from a Holley to a Demon and picked up about 0.4 of a second, enough to Bananarama! into the 12s, not bad for a 2 and a half ton luxury car with mid 3 gears. He did find that the Demon was a bit 'tricky' at first, and on opening it up founda fair bit of aluminium machining swarf which was blocking some passageways. Disappointing but easily fixed (this was at the 2004 Mopar Nats) by disassembly and a clean/blow out.
No idea if he changed carb sizes going from the Holley to the Demon, my memory would like to say 850, but that isn't too big a jump considering the stock carb on a stock 71 Riv is an 800cfm Quadrajet. He did consider the Demon to be pretty good though, and worth the money.
Regarding cam/carb theory, my understanding has always been that while duration is interesting, it is overlap that can be critical in controlling idle circuitry in a carb.
Oh, and with regard to WOT fuelling, my old GN ran an injector duty cycle at WOT of 110%, and that was never revving over 5000rpm. No carb in the world will deliver 110% of fuel.
No idea if he changed carb sizes going from the Holley to the Demon, my memory would like to say 850, but that isn't too big a jump considering the stock carb on a stock 71 Riv is an 800cfm Quadrajet. He did consider the Demon to be pretty good though, and worth the money.
Regarding cam/carb theory, my understanding has always been that while duration is interesting, it is overlap that can be critical in controlling idle circuitry in a carb.
Oh, and with regard to WOT fuelling, my old GN ran an injector duty cycle at WOT of 110%, and that was never revving over 5000rpm. No carb in the world will deliver 110% of fuel.
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Anonymous
Sandy, some Demons out of the box do have quality control problems which is a shame, this is one reason why FBO do the inspection, and setup service, swarf is easily sorted as you say, although as you also say damn annoying and really not good enough.
What Demon did your buddy fit? was it a speed or a mighty.
Dave to answer your question about venturi sizes, Speeds and Mightys of the more common sizes are 650 1.280.. 750 1.400.. 850 1.562.. Roads,Race and Kings are different as for one they are not in those sizes.... butterfly sizes are 1 11/16 up to 825/850 depending on series and application after that it's 1 3/4 up to around 950 then 2.00 for the bigger Kings, and 2.100 for the big RS models
All Demons are flow tested wet, How does Holley flow test??
Between the 8 series there are at least 28 different application carbs and at least 20 different sizes, this is not counting the possibilities of the RS Race and Kings, and no doubt there is more.
Also Dave, (bearing in mind we are not arguing here) As far as Demons are concerned an increase in duration @ 50 does not automatically mean an increase in CFM, or at least a huge increase, for instance if you had a 440 with duration from say 220 to 240, dual plane or a small single and a stall under 3000 the series would be a speed vac sec and the cfm would be 750 ( just assume the entire deal is ideal for now).
If then a cam with a duration from 240 to 260 and everything else to work right with this cam was fitted then a 750 mighty would work so would a 825, an 850 with annular boosters would but thats quite close to the lower CI ideal, an 850 without annular boosters would be too big. Mightys will work on a smaller CI motor than speeds though
None of it is ever black and white there is just too many variables
Having said all that there is such an overlap in series and applications, there are 4 different speeds, mightys are a little easier, 14 different race demons and 6 kings, this is just applications not sizes, the BG catalogue has 47 pages just for carbs, this is without even considering the 16 pages of tuning and repair parts, you're right Dave I have not got the time or the need to figure it out to the last detail.
There could well be a difference in flow numbers and if so then the figures don't work
What Demon did your buddy fit? was it a speed or a mighty.
Dave to answer your question about venturi sizes, Speeds and Mightys of the more common sizes are 650 1.280.. 750 1.400.. 850 1.562.. Roads,Race and Kings are different as for one they are not in those sizes.... butterfly sizes are 1 11/16 up to 825/850 depending on series and application after that it's 1 3/4 up to around 950 then 2.00 for the bigger Kings, and 2.100 for the big RS models
All Demons are flow tested wet, How does Holley flow test??
Between the 8 series there are at least 28 different application carbs and at least 20 different sizes, this is not counting the possibilities of the RS Race and Kings, and no doubt there is more.
Also Dave, (bearing in mind we are not arguing here) As far as Demons are concerned an increase in duration @ 50 does not automatically mean an increase in CFM, or at least a huge increase, for instance if you had a 440 with duration from say 220 to 240, dual plane or a small single and a stall under 3000 the series would be a speed vac sec and the cfm would be 750 ( just assume the entire deal is ideal for now).
If then a cam with a duration from 240 to 260 and everything else to work right with this cam was fitted then a 750 mighty would work so would a 825, an 850 with annular boosters would but thats quite close to the lower CI ideal, an 850 without annular boosters would be too big. Mightys will work on a smaller CI motor than speeds though
None of it is ever black and white there is just too many variables
Having said all that there is such an overlap in series and applications, there are 4 different speeds, mightys are a little easier, 14 different race demons and 6 kings, this is just applications not sizes, the BG catalogue has 47 pages just for carbs, this is without even considering the 16 pages of tuning and repair parts, you're right Dave I have not got the time or the need to figure it out to the last detail.
There could well be a difference in flow numbers and if so then the figures don't work