carb cfm

[Anonymous]

what is the smallest carb that got put on these engins and what was the cfm on them too

What was the biggest carb that was put on these engins and what was the cfm on them aswell

Thanks for the help 8)

 

[Anonymous]

good question.

I really wanna win the lotto and go to a tech school and learn all this...

most is over my head...but I am learning, THANKS TO FORD SIX!! Thanks guys for your wisdom...

 

[Anonymous]

ya I know I was thinking about dumpin the 250 for a 302 but this site saved me

 

[CZLN6]

Howdy:

Is this a trick question? all right , I'll bite.

The smallest carb was the Holley #1909 Used on the 144 engine in 1962 only. there was a 130 CFM Holley used on #1904 in '60 and #1908 used in '61 on 144 engines only.

The largest was the Carter RBS used on 250s from '70 to '73. It was rated at 215 cfm. A close second is the Autolite 1101 used on 1969 250s only. It was rated at 210 cfm.

Now, what's the catch?

Adios, David

 

[Rustang Racer]

just adding some numbers:

autolite 1100 used on a lot of 200's was about 150cfm.

the holley 5200 (never used but a good upgrade) 270cfm i think, and not at all too big for a stock 200.

I don't know why ford used such small carbs when they could have made them much bigger and still got good gas mileage like the holley 5200.

 

[Anonymous]

No tricks I was wondering because wouldn`t 2 auttolite 1100 s be nice on a log head ? or 2 1904 s ??

 

[CZLN6]

HowdyAgain:

Opps! I left out the cfm on the '62 Holley #1908. It was rated at 125 CFM.

FomoCo chose these carbs because they represented the best USA technology for MPG efficiency at that time. Remember, this was the era before automatic chokes were standard equipment, gas was $.29, and regular had an octane rating of about 95. Premium at 103 octane was avaiable everywhere.

Autolites 1100s were rated at 130 cfm on 144 engines, 156 on 170 engines and 185 on 200 engines with the biggest internal change being the removable venturi. They were also jetted and plumbed for each different application.

Three Holley's with their glass, side mounted fuel bowls, are my favorites on an Offy 3 x 1s conversion. Set up right and utilizing the progressive linkage they got great mileage too.

I think it's ironic that when FoMoCo finally woke up to two stage , two barrels they became standard on a 4 cylinder of about 140 cubic inches and never applied it to the venerable inline six. They would have gottem better mileage and better performance. Go figure!

Adios, David

2 H/W on a log manifold are something someone needs to explore.

Adios, David

 

[Anonymous]

thanks for all the help every one

 

[XFlow_Fairlane]

don't forget the 1908 carb had no venturi booster on the outlet. has very poor atomization. also the accelrator pump design is kinda poor on them. my 170 is choked real bad on the top end like it hit a wall. swapping in a 1100 this weekend

nick

 

[Anonymous]

I have quite an extensive book on different models of carbs and how they work etc. In the book it explains how engineers come up with the different characteristics for carbs etc. The engineers for Ford Chrysler and Gm used a formula for determining cfm. It is CID/2 XRPM/1728=CFM . This formula gives 100% volumetric efficiency so a 250cu@ 3000rpms would be 217.5cfms but due to the restrictions in manifold runners and logs, head ports, valve openings and so on STOCK engines(or as some people think them as an air pump} is restricted by 25% therefore the engineers take 75% of thevolumetric efficiency which in this case of the 250 would be163.125 cfms which would be the max amount of cfms the 250 could breath at 3000 rpm. So this being the case it would seem that Ford or Carter or Autolite or whoever knew what they were doing when they designed these carbs and actually designed them to flow more cfms than the engines could handle. With extensive manifold, head, valve, and exhaust work race engines can achieve volumetric efficiency in the top 80% so according to the book before spending money on larger cfm carbs for a stock motor get porting and grinding or your wasting your money--------------larry

 

[XFlow_Fairlane]

well my car has a 3.55 gear in back so a carb rated for 3000 rpm will blow since I spin more then that on the highway (90% of my driving)one needs tto pick a carb for what they intend to use it for. people liek me that do alot of highway miles would prob want a bigger carb so it isn't choked where as a city driver might want a smaller carb to help the lower rpm power out.


nick

 

[Anonymous]

well I have plans on a 79-83 head and port and polish with a 6 into 1 hedder so it should handle 300 CFM but I could still be wrong (I very ofen am ) but thanks for all the info every one

 

[Anonymous]

And, don't forget the Holley 1946 used from 1978-up. It was rated at 195 cfm.

 

[Anonymous]

62 Fairlane. that formula is a way of figuring out how many cfm an engine sucks at any rpm so manufacturers can put the right range carb on an engine just like you say. It has nothing to do with rear end ratios or city or highway driving. Put in your 170 and say you turn 2100 rpm (put in any rpm) at 70 miles an hour on the highway, 170 cubic inches divided by 2 equals 85. 2100rpm divided by 1728 equals 1.21, multiply 1.21 by 85 and you get 102.85 cfm this is 100% volumetric efficiency but because of restrictions your 170 will only suck 75% of that so multiply 102.85 by .75 and your 170 sucks 77.13 cfms at 2100 rpm. So the little Hollys and the autolites that come on the 170 suck more than enough cfms for a 170 engine to use. I guess thats why they put small single barrels on the low cubic inch inline sixes and 650 holley four barrels on the 400 cubic inch eights.

 

[Anonymous]

Just wondering if anyone knows the airflow rate on a Carter 1947?
(got it off e-bay a while back and im gonna stick it on my falcon soon. main reason for purchase is because its got a auto choke the one currently on my falcon doesn't, last owner cheaped out on the carb when the origonal died)

Just kinda curious, no harm either way, but if it can be answered it'll be appreciated