Choosing my carb

[68_sixpeashooter]

As my engine finally nears completion I need to choose what carb I want for it. I'm getting the 2v conversion on my 78 late model head. I already bought the adaptor for the head and its a autolite/ holley adaptor. At first I wanted to get the holley 2300 with 350 ccm, but I used the cfm calculator and it says my engine is at 290 cfm. Right now I'm stuck in choosing the Autolite 2100 with 1.08 venturi @287 cfm or the autolite 2100 with the 1.14 venturi @300 cfm. What carb should I purchase? Also I want to make sure I'm using the calculator right. I put that my engine max's out at 5000 rpm it was just a wild guess but I'm not exactly sure what its max rpm is.

 

[kenny170]

Check out my post which holly is better got one heck of an answer from xctasy.

 

[68_sixpeashooter]

my short block is finally done!

 

[ludwig]

I am not the authority here but I was working on the same problem a few years back. The guys here helped me think about what I wanted to do.

The point is, you want to size the carbie to its max efficiency where it will be most useful. That means, do you want to use it at peak rpm for a drag car or will you want to use it for a cruiser and get max power/efficiency at highway speed. This affects where the power tops out. If the power tops out at 5000, it will be over-carbed for most daily use. And vice versa. So you need to look at that too. You can calc the rpm from the differential gear ratio and the transmission. I don't have the numbers but you want to look at the rpm at a given speed in a particular gear (e.g. 4 speed stick or 3 speed auto)

Sorry, no answers. Just observations. When I did it, I think I came up with something around 300 cfm/ 320 max. That neighborhood. You have to do your own calcs for the new block and stuff. But that is a nice looking piece of machinery right there. Have fun.

 

[68_sixpeashooter]

I am going to need something that's not too much because my car is going to be my daily driver. I'm definitely going to get an Autolite or holly mainly because I already purchased the adaptor.

 

[ludwig]

Do you have the Ford Six Handbook? If not, you should get it. The Schjeldal brothers here on this site have assembled almost everything you should need to know to get a killer engine working. They also help you calc the compression ratio and I believe the carb sizes. You can order it at Ford Six Performance, the sponsors of this site. It is a must read if you are serious about your build up.

 

[68_sixpeashooter]

I actually do have the handbook. I've been using it for my whole build but I lost it about 2 weeks ago. I must have just misplaced it. I need to look for it asap

 

[ludwig]

Then you are definitely on the right track.

 

[ludwig]

Here is the string from 2004 where I was playing with the rpm/cfm issue:

viewtopic.php?f=1&t=12063&p=84610&hilit=cfm#p84610

Here is a follow up on the same idea after I saw a cool Demon 2bbl in Hot Rod:

viewtopic.php?f=1&t=28080&p=200965&hilit=cfm#p200965

 

[68_sixpeashooter]

Thanks for your help and links ludwig! I ended purchasing the autolite 2v carb with 300cfm. I also purchased a throttle cable. Wish me luck with my setup!

 

[ludwig]

You won't need any luck at all with that. You'll do just fine. If you get in trouble with the cable linkage, use the 'search' function. You will find pics of four or five very snazzy setups with cable anchors at the carb. Just use the terms "cable throttle" and/or "2v" together or individually.

 

[68_sixpeashooter]

I bought the lokar hi-tech throttle cable and carb bracket. I've heard you have to change the pedal as well. Would I have to change my pedal to make this setup work?

 

[CZLN6]

Howdy:

Been gone. The differences between the 1.08 and the 1.14 is minimal. The 1.14 is a little richer in the idle circuit and transition that the 1.08. I don't recall your cam and CR, but, I'd be inclined to go with the 1.08 knowing it could be enriched a little, if needed. I used one on my 250 a while back and I think I'm going back to it. I'll give up a little top end, but it ran cleaner. that's my two cents, for what it's worth

Adios, David