Autolite 2100 1.21 2bbl carb - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-04-2006, 07:57 AM
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Autolite 2100 1.21 2bbl carb

I have a cougar gt, 351c w/a autolite 2100 w/ 1.21 casting on the side and am trying to determine the cfm, I think it's a 351cfm but am not sure.
I am also having problems with it idling. I've re-built/cleaned the carb 2 times now and the fuel to air mixture screws don't seem to do anything! I blew air through them and they seem to be clean. It runs fine at higher rpm but when I come to a stop it starts surging and dies. I checked the vacuum and have 20 in, and can't find any vacuum leaks. When I start it up it idles ok till I rev it up or drive it and then it wants to die when the rpm's drop.

It's driving me nuts! I'm about ready to buy a whole new carb if I can't figure this out soon! If I do I'd like to know what would be the best way to go as far as 2bbl or 4 bbl and a new intake/ and what cfm the 351c will handle without over carbureting it. (as far as performance goes) I know I'm asking alot, your patience is appriciated!!
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Old 02-04-2006, 03:31 PM
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I have to leave the house with she who must be obeyed in 10 minutes, so I can't google the links, but there are a couple motorcraft carb references out there and you should be able to make it work good.

The 1.21 is one of the bigger bodies, and would be good for a mild street build and good economy. You would have to go 4 bbl with attendant expense for manifold etc..... that would be the way to go for big hp but you can have a nice car with what you already have. Motorcraft is carb of choice for many performance oriented jeepers that want good low end and tunability.

I will return tomorrow with links if no one else has the info quickly.
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Old 02-04-2006, 03:39 PM
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The following I.D. Nos. (found on the side of the float bowl behind the accelerator pump rod) will give you the individual CFM ratings.

Stamped No + CFM

.98=190
1.01=240
1.02=245
1.08=287
1.14=300
1.21=351
1.23=356
1.33=424
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Old 02-04-2006, 05:27 PM
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Where did you find these?

Quote:
Originally Posted by KULTULZ
The following I.D. Nos. (found on the side of the float bowl behind the accelerator pump rod) will give you the individual CFM ratings.

Stamped No + CFM

.98=190
1.01=240
1.02=245
1.08=287
1.14=300
1.21=351
1.23=356
1.33=424

I was wondering where you found these cfm ratings, I've seen quite a few differences in these on the net.
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Old 02-04-2006, 05:39 PM
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Worked on it some more

Ok, I've been tinkering and got the fuel to air screws cause some reaction...but the engine is still surging at idle and I have to keep it idled up to 900 to 1000 rpm to keep it running, especially when it gets warmed up good. It will crank right up but when I rev it up & let off it drops down & dies or almost dies, then it surges back & forth and idles back up after awhile but still surges up & down some. I checked my vacuum lines again too. Seems to me it's not getting a steady supply of fuel at idle................................... but I might be wrong
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Old 02-05-2006, 12:41 AM
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Quote:
Originally Posted by Manic Mechanic

I was wondering where you found these cfm ratings, I've seen quite a few differences in these on the net.
Sheesh...I am not quite sure where I found these ratings but they are sourced from FORD. I have so much data here that I cannot remember where I drew it from (my filing system sucks).
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Old 02-05-2006, 12:49 AM
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What model year of COUGAR and is it the origional intake and carb? The carb should be a 2150 SERIES MOTORCRAFT. Was the 20" reading steady?
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Old 02-05-2006, 03:04 AM
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Not Steady

It's a '71 cougar gt 351c, (only 787 gt's were made that year). I believe it is the original 2 bbl 2100 autolite carb. & intake w/1.21 venturi (351 cfm). And no the vacuum isn't steady, it surges with the rpm. I was wondering if this may indicate a vacuum leak somewhere or something stopped up . It ran fine w/ this carb then sat up in the garage 4 or 5 yrs. and got gummed up. I soaked it in carb cleaner & blew it out pretty well (I think)
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Old 02-05-2006, 03:22 AM
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Quote:
Originally Posted by KULTULZ
Sheesh...I am not quite sure where I found these ratings but they are sourced from FORD. I have so much data here that I cannot remember where I drew it from (my filing system sucks).
Thanks, I've found quite a variation on the net, (eg 1.08 = 450cfm,1.14 =520cfm, 1.21=575 cfm) but I had my doubts, that seems a bit much for a 2bbl!
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Old 02-05-2006, 06:10 AM
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Quote:
Originally Posted by Manic Mechanic

It's a '71 cougar gt 351c
Well, that shoots down my EGR theory I was going to impress everyone with...

Quote:
And no the vacuum isn't steady, it surges with the rpm. I was wondering if this may indicate a vacuum leak somewhere or something stopped up . It ran fine w/ this carb then sat up in the garage 4 or 5 yrs. and got gummed up. I soaked it in carb cleaner & blew it out pretty well (I think)
The vacuum gauge should hold steady at idle.

-INTERPRETING VACUUM GAUGE READINGS-


-FINDING AND FIXING VACUUM LEAKS-

Does your carburetor appear as this?



Gasoline gels and turns to varnish after sitting. Check for gumming in PN 32.

Also look at the bottom of this thread and you will see a list of previous similiar posts.
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Old 02-05-2006, 07:33 AM
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http://home.earthlink.net/~bubbaf250/2150carb/carb02.html

Try this link, he has lots of good info. From what you say I am guessing vacuum leak but that is just a guess.

Also, here is another link:

http://www.ifsja.org/tech/fuel/2150.shtml
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Old 02-05-2006, 06:44 PM
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Much Better!

Ok I soaked the Venturi Cluster and got some gunk out of it, put it back together and she cranked right up & ran smooth! The vacuum steadied out and is right at 19in. Still tweaking the fuel to air mixtures but the idle problem is gone, took it out for a spin and it didn't die once, steady as a rock!
Thanks for all the help, you guys are great! And I'll know what to check for next time I have a problem like this! If not I know who to turn to!
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Old 02-05-2006, 06:53 PM
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It's an Autolite 2100

Quote:
Originally Posted by KULTULZ
What model year of COUGAR and is it the origional intake and carb? The carb should be a 2150 SERIES MOTORCRAFT. Was the 20" reading steady?
It's definitley a n Autolite 2100, it has "D1ZF UA" on the tag.

The 2150 was used in later year models, when the pollution laws started stiffening up around '74 to '76.

Thanks for all the help though !
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