yea, i think the 750 is a tad bit too big also, but i got it so when i build my 360 into a 390. Although it works pretty good. it works awsome actually but then again i dont know what a 650 would feel like or drive like. And on friday I will crank my truck with the fuel line off of the carb and put it into a cup and see if there is fuel immediatley present. So if there is not does that mean that the pump is bad even thought it works fine?
A little? To need a 750 he would need to twist that 360 to 7200 RPM. For a basically stock 360 revving to 5000 RPM he only needs a 520 CFM carb. And the stock came is good to 4600 max.
Yeah Im putting a 2100 1.33v on mine and expect to get the max streetable carb combo with my 360. 424cfm. At that I expect some performance as it will match up with the whole package from intake to tailpipe. I have carefully measured it out. You can really open them up but loose performance, gas mileage, etc. as their breathing range is limited. But will go for a good 300k plus.
"edel intake , headers, msd ignition. other than that its stock 360." Untill you get that 390 I am with Bear, 520 4v. Save the 750 for ass kickin.
I was wondering if the gas cap was loosed would the vac break on the gas line? Geese I might as well add this. When I first got mine it did the same thing but it was all in the choke set up. I admit I didn't understand it very well but the guys on this forum gave me a lesson and bing bang boom it starts with just one push to set and one turn of the key.
Last edited by Kennewick; 10-27-2009 at 12:44 AM.
Reason: Blah Blah Blah
Yeah Im putting a 2100 1.33v on mine and expect to get the max streetable carb combo with my 360. 424cfm. At that I expect some performance as it will match up with the whole package from intake to tailpipe. I have carefully measured it out. You can really open them up but loose performance, gas mileage, etc. as their breathing range is limited. But will go for a good 300k plus.
"edel intake , headers, msd ignition. other than that its stock 360." Untill you get that 390 I am with Bear, 520 4v. Save the 750 for ass kickin.
I was wondering if the gas cap was loosed would the vac break on the gas line? Geese I might as well add this. When I first got mine it did the same thing but it was all in the choke set up. I admit I didn't understand it very well but the guys on this forum gave me a lesson and bing bang boom it starts with just one push to set and one turn of the key.
You are aware that a 2V - 424cfm is not the same cfm as a 424 cfm 4V, aren't you? Different rating systems.
so you guys are saying that my 750 cfm will be good for a stock 390 as well as a hopped up 390? and that my 360 should have a carb in the 600 -650 range ? and i will gain M.p.g. and performance with the smaller ????
also since we are talking about gas caps I leave mine open somewhat to let air in because I have not vented my tank yet . otherwise it dies of course when the air all sucks out ...
You are aware that a 2V - 424cfm is not the same cfm as a 424 cfm 4V, aren't you? Different rating systems.
Well here is what I think. Street applications not race.
One thing to keep in mind is that these numbers do not take into consideration a tuned exhaust. A tuned exhaust can scavenge (act like a vacuum cleaner) the whole system increasing the net CFM rating for the motor. If a system is flow balanced or as close as one can come to it, it should perform better than a system that is just opened up wide. Even too big of pipes causes the exhaust gases to loose velocity and cool off too soon. It takes a lot of pressure just to push a high volume of sub cooled air out a long big pipe. Of course one can make it too small also which is a direct restriction.
Another consideration is that most motors are less than 80% efficient by some degree. So the net air flow rates could be multiplied by .75 say and the carbs have an additional 25% less load on them. [b]This is also taking into effect the scavenge effect. It is easy to pick a carb that is too big.
It is my OPINNION that it is better to err on being too small then to err on being too big for street use. My 2 cents.>>
PS a 2 into one system will prolly flow better than a dual exhaust when considering the entire benefit and not just dumping exhaust. Weird science behind that. Anyway here are some numbers to mull around in the noggin.>>
With the #’s below one has to remember that a 2v only flows less as compared to a 4v if you are at WOT. How often do you drive at WOT? This is why a lot of large motors were fitted with 2 barrels. >>
Convert 2 to 4 or 4 to 2 barrel cfm ratings.>>
To convert: multiply 2 bbl. rating by 70.71% to get flow at the 1.5" (lower) vacuum 4 bbl. rating. Multiply the 4 bbl. rating by 141.4% to get the 3" 2 bbl. rating. The formula is simple: New flow rate = (new vacuum level ÷ old vacuum level) /.5 X old flow rate
Example: 500 cfm 2v flows 353.55 CFM at the 1.5" (4v) vacuum level. >> >>
My 360 FE @ 4000 rpm = 312 cfm (adjusted) Now lets make some more comparisons. Remember adjusted is a best guess at efficiency vs good scavanging vs vac level @ wot.
2 barrel carbs converted to 4v specs @1.5” @ wot>>
1. Autolite 424cfm @ 3.0” @ 1.5” = 300 cfm
2. Holly 500 cfm @ 3.0” @ 1.5” = 354 cfm
3. Holley 4v 750 cfm @3"1075 this is at the 2v level this means off the charts crazy flow from 1/2 throttle up to wot. @ 1.5 = 750 cfm >>
>What will my motor flow compared to flow rate of 2v carbs?>
Motor CFM = CID X max RPM / 3456>>
360 (CID) X 4500 (RPM) / 3456 (constant) = 469 cfm X .75 (efficiency factor) = 351 cfm.
I wouldn’t run a 360 past 4500 RPM at this point you will just be floating the valves.
360 X 4000 / 3456 = 416 cfm X .75 = 312 cfm
360 X 3500 / 3456 = 364 cfm X .75 = 273 cfm
360 X 3000 / 3456 = 312 **
360 X 2500 / 3456 = 260 **
** not at wot so it is hard to judge the carbs by the 4v formula so the 2 barrel would be flowing higher. Very economical.
In my case with a fairly good running mostly stock with improvements 360, a Autolite 2100 1.33 carb is a excellent choice and I should see good MPG and decent performance. I would think that if I had very open exhaust and a 750 Holley I would loose power and drink gas like Dean Martin.
so you guys are saying that my 750 cfm will be good for a stock 390 as well as a hopped up 390? and that my 360 should have a carb in the 600 -650 range ? and i will gain M.p.g. and performance with the smaller ????
also since we are talking about gas caps I leave mine open somewhat to let air in because I have not vented my tank yet . otherwise it dies of course when the air all sucks out ...
Well I am not saying that. Look at the last post for my idea on that. There are some formulas that would lead me to a smaller carb and controlled exhaust system. But I aint that smart so you may want to consider that too
Well here is what I think. Street applications not race.
One thing to keep in mind is that these numbers do not take into consideration a tuned exhaust. A tuned exhaust can scavenge (act like a vacuum cleaner) the whole system increasing the net CFM rating for the motor. If a system is flow balanced or as close as one can come to it, it should perform better than a system that is just opened up wide. Even too big of pipes causes the exhaust gases to loose velocity and cool off too soon. It takes a lot of pressure just to push a high volume of sub cooled air out a long big pipe. Of course one can make it too small also which is a direct restriction.
Another consideration is that most motors are less than 80% efficient by some degree. So the net air flow rates could be multiplied by .75 say and the carbs have an additional 25% less load on them. [b]This is also taking into effect the scavenge effect. It is easy to pick a carb that is too big.
It is my OPINNION that it is better to err on being too small then to err on being too big for street use. My 2 cents.>>
PS a 2 into one system will prolly flow better than a dual exhaust when considering the entire benefit and not just dumping exhaust. Weird science behind that. Anyway here are some numbers to mull around in the noggin.>>
With the #s below one has to remember that a 2v only flows less as compared to a 4v if you are at WOT. How often do you drive at WOT? This is why a lot of large motors were fitted with 2 barrels. >>
Convert 2 to 4 or 4 to 2 barrel cfm ratings.>>
To convert: multiply 2 bbl. rating by 70.71% to get flow at the 1.5" (lower) vacuum 4 bbl. rating. Multiply the 4 bbl. rating by 141.4% to get the 3" 2 bbl. rating. The formula is simple: New flow rate = (new vacuum level ÷ old vacuum level) /.5 X old flow rate
Example: 500 cfm 2v flows 353.55 CFM at the 1.5" (4v) vacuum level. >> >>
My 360 FE @ 4000 rpm = 312 cfm (adjusted) Now lets make some more comparisons. Remember adjusted is a best guess at efficiency vs good scavanging vs vac level @ wot.
2 barrel carbs converted to 4v specs @1.5 @ wot>>
1. Autolite 424cfm @ 3.0 @ 1.5 = 300 cfm
2. Holly 500 cfm @ 3.0 @ 1.5 = 354 cfm
3. Holley 4v 750 cfm @3"1075 this is at the 2v level this means off the charts crazy flow from 1/2 throttle up to wot. @ 1.5 = 750 cfm >>
>What will my motor flow compared to flow rate of 2v carbs?>
Motor CFM = CID X max RPM / 3456>>
360 (CID) X 4500 (RPM) / 3456 (constant) = 469 cfm X .75 (efficiency factor) = 351 cfm.
I wouldnt run a 360 past 4500 RPM at this point you will just be floating the valves.
360 X 4000 / 3456 = 416 cfm X .75 = 312 cfm
360 X 3500 / 3456 = 364 cfm X .75 = 273 cfm
360 X 3000 / 3456 = 312 **
360 X 2500 / 3456 = 260 **
** not at wot so it is hard to judge the carbs by the 4v formula so the 2 barrel would be flowing higher. Very economical.
In my case with a fairly good running mostly stock with improvements 360, a Autolite 2100 1.33 carb is a excellent choice and I should see good MPG and decent performance. I would think that if I had very open exhaust and a 750 Holley I would loose power and drink gas like Dean Martin.
Just my opinion!>>
The question is, did you know this before (I learned it in the late 60's) or did you just look it up and find out now?
The question is, did you know this before (I learned it in the late 60's) or did you just look it up and find out now?
Not sure what your getting at Bear. But I have been doing my home work for the last 6 months.
I studied evrything that i have been working on. If you had been following any of my posts you could see a pattern of that. I studied exhaust mainfolds, mufflers, headers 360 vs 390 differences, air flow scavenging vs open exhaust, intake manifolds, cams rocker assemblies and yes carburators.
I was looking at replacing the iron mani with a aluminum one and a 4v but as I studied the air flow ratings which led me to the little lesson you refer to about 4v vs 2v cfm ratings. I found that I would be wasting my money to throw a bunch of gadgets at my motor and neglect the real science behind the issues. I teach a college course on air flow so I took it serious.
But rather than just give you a bull **** answer to "do you know the difference" I thought some folks might find some benefit to what I found out. If not then turn me off. Heck I don't care.
Short of taking a lie detector for you I guess you will have to just take my word for it.
Here are a few of my posts but there are gobs more that show to a resonable person that I have been working on it. I also have references to where I have picked up most of my information. I am a technical teacher and save all that stuff for future use. (I have a gigantic technical library of media) I don't say I'm right I just say this is what I found and I am open to learning more.
By the way My intake is off right now. It will be tanked and cleaned then EGR plugged, reinstalled, custom spacer installed along with a 2100 1.33v carb. All this has cost me some cash and at this point if I wanted to drown my 360 with a Edlebrock and 750 4v I could. But I ran the numbers and decided against it.
PS My question is do you agree with my findings? Or am I wasting my time?
Kennewick, I wouldn't worry too much about it, you obviously have some (modern) knowledge in this area and have done your homework- nothing wrong with that, and you don't have to "prove" anything to anyone. I don't know much, but one thing I do know is that technology is constantly changing, evolving, and improving, and many of the things that were accepted as gospel in the "old days" (which can be 40 years or last week ) have proven inaccurate or have been improved upon or superceded. Remember when a .500 lift cam was considered huge? When polishing intake ports was considered a good thing? There's something new to be learned every day, and if you don't keep up, you get left behind
Methinks your students are very lucky that you research your material to that extent
Not sure what your getting at Bear. But I have been doing my home work for the last 6 months.
I studied evrything that i have been working on. If you had been following any of my posts you could see a pattern of that. I studied exhaust mainfolds, mufflers, headers 360 vs 390 differences, air flow scavenging vs open exhaust, intake manifolds, cams rocker assemblies and yes carburators.
I was looking at replacing the iron mani with a aluminum one and a 4v but as I studied the air flow ratings which led me to the little lesson you refer to about 4v vs 2v cfm ratings. I found that I would be wasting my money to throw a bunch of gadgets at my motor and neglect the real science behind the issues. I teach a college course on air flow so I took it serious.
But rather than just give you a bull **** answer to "do you know the difference" I thought some folks might find some benefit to what I found out. If not then turn me off. Heck I don't care.
Short of taking a lie detector for you I guess you will have to just take my word for it.
Here are a few of my posts but there are gobs more that show to a resonable person that I have been working on it. I also have references to where I have picked up most of my information. I am a technical teacher and save all that stuff for future use. (I have a gigantic technical library of media) I don't say I'm right I just say this is what I found and I am open to learning more.
By the way My intake is off right now. It will be tanked and cleaned then EGR plugged, reinstalled, custom spacer installed along with a 2100 1.33v carb. All this has cost me some cash and at this point if I wanted to drown my 360 with a Edlebrock and 750 4v I could. But I ran the numbers and decided against it.
PS My question is do you agree with my findings? Or am I wasting my time?
I'm not disagreeing with you info. But new, this stuff it isn't. All this stuff was known and available (though the net has made it alot easier) 40+ years ago. I even have most of it copied into my racing info book from back in the early 1970's.
Kennewick, I wouldn't worry too much about it, you obviously have some (modern) knowledge in this area and have done your homework- nothing wrong with that, and you don't have to "prove" anything to anyone. I don't know much, but one thing I do know is that technology is constantly changing, evolving, and improving, and many of the things that were accepted as gospel in the "old days" (which can be 40 years or last week ) have proven inaccurate or have been improved upon or superceded. Remember when a .500 lift cam was considered huge? When polishing intake ports was considered a good thing? There's something new to be learned every day, and if you don't keep up, you get left behind
Methinks your students are very lucky that you research your material to that extent
Must be really nice being omnipotent like you and think you know everything.
Kennewick, I wouldn't worry too much about it, you obviously have some (modern) knowledge in this area and have done your homework- nothing wrong with that, and you don't have to "prove" anything to anyone. I don't know much, but one thing I do know is that technology is constantly changing, evolving, and improving, and many of the things that were accepted as gospel in the "old days" (which can be 40 years or last week ) have proven inaccurate or have been improved upon or superceded. Remember when a .500 lift cam was considered huge? When polishing intake ports was considered a good thing? There's something new to be learned every day, and if you don't keep up, you get left behind
Methinks your students are very lucky that you research your material to that extent
Thanks, By the way My students are in the largest prison in Wa State.
Right now they are taking a test. I just love my Ford!
Well I don't think I know much. But I figured most people look at numbers from monster, big HP motors whith race spec's up the ying yang. I am kinda practical and like to look at where I use the system everyday. My truck rarely runs at WOT and if it does not for long. The rest of the time it's every day kind of driving. From that aspect I want it to perform good and get the best gas mileage I can for a 40 year old truck. So my #'s may not jive with some of the stuff folks may read out there cause I adjust my findings to the conditions if I can. Some guys race and some guys have monster big HP motors. A guy might want to adjust the #s towards his conditions. We were talking about a mostly stock 360 with a rather large carb on it.
Here is another typical link but keep in mind it has race applications and wouldn't do me much good except to educate me.
I'm not disagreeing with you info. But new, this stuff it isn't. All this stuff was known and available (though the net has made it alot easier) 40+ years ago. I even have most of it copied into my racing info book from back in the early 1970's.
You asked if I knew. I did.
It is new information to someone who hasn't heard it before.
Whats new is that old info adjusted to everybodys different application.
No biggie just thought the 750 CFM carb was a tad big. The man was questioning why. I just gave him my 2 cents since I brought it up.
I could be wrong also.
Why did you send rain my way
You asked if I knew. I did.
It is new information to someone who hasn't heard it before.
Whats new is that old info adjusted to everybodys different application.
No biggie just thought the 750 CFM carb was a tad big. The man was questioning why. I just gave him my 2 cents since I brought it up.
I could be wrong also.
Why did you send rain my way
I don't think you are wrong about the carb, I agree 100%.
I sent you the rain because I got tired of it over here. Unfortunately for me and you, more is on the way.
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For a basically stock 360 revving to 5000 RPM he only needs a 520 CFM carb. And the stock came is good to 4600 max.
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) have proven inaccurate or have been improved upon or superceded. Remember when a .500 lift cam was considered huge? When polishing intake ports was considered a good thing? There's something new to be learned every day, and if you don't keep up, you get left behind 
