Carb selection help

[Mr Roadrunner]

Just looking for a little advice. .030 over 440. 10.5 to 1 cnc ported edelbrock heads. Hughes engines solid lift 239/245 at .050 .582/.597. 68 road runner. 4.11 and 4 speed. What size/ brand carb should I try. Been looking at a Holley hp or a mighty Demon, but I understand Demon carbs is not out of business. They are still availably, but a little scared to drop the cash on one. Thanks in advance.

 

[Meep-Meep]

You should be fine with about 750-770 CFM. I would expect the Holley street version will work well.

 

[67 B-body]

I would first want to know what your application is going to be. If I were running that combination and wanted to spend a fair amount of time with my foot to the floor... I would think 800 or 850 CFM. Those heads can realy flow with good CNC work. That Hughes cam is a real breather too! I would stick to 750 for street but at the strip,, I would have at least an 850 Holley on it! I can point you to an engine build and dyno test with similar combination that gave horespower gains into the 1000+ carb CFM ratings. Look up the history of the "440 Mauler" engine build. It's easy to over carb for light to light driving, but if your out for serious performance, that rule doesn't apply as much. It sounds like a more than a healthy street application by the components you've listed.

 

[Mr Roadrunner]

The car is going to be mainly ran on the street with some track time (I can't resist). I was thinking 850 cfm would be more suited to this build for the street but you guys seem to think 750 is enough. This is why I asked. I forgot to mention that the heads have 2.19 intake valves and were cnc ported by Hughes engines. Can't wait to see how it feels in the car. If you don't mind me asking, why not 850. What would I loose in going with a bigger carb for the street. Not trying to argue and I hope you don't take it that way. I screwed together a really healthy 340 for my brother a few years ago (big solid cam, ported iron heads, etc) and I runs great with a 750 holley street avenger on it. Educate me please. Thanks again.

 

[the wall]

750-850 750 would be mild and very responsive a good choice but i like the 850 and it looks like this build will have no problem using it, as far as the demon they got a bad rap in my opinion but i like them i think there a very precise holley basically. they use the same jets gaskets power valves as a holley so i see no problems with them. if you do the math on a 440 to 6000 rpms the recommendation comes out to 750 so i think that one of the reasons people suggest the 750 but i say for that build i like 850

 

[Meep-Meep]

I think the answer will be to try a few different carbs and see what the engine likes best. You need a certain velocity passing by the venturies to pick up fuel and picking the right size carb is part of the equation.

 

[Mr Roadrunner]

Thanks guys. This motor should have no problem turning 6500 to 7000. Holleys carb selector reccomended a 1050 dominator at 7000. I think this is too much for me. I am looking at getting a vacuum sec. and havent decided whether or not to run a choke. I live in western nc, and we see some pretty cold weather, but the car will probably be inside during winter months. Guess I was asking too much for the "perfect" carb for my combo. Trial and error makes sense, just not from a pocket book stand point. I don't have a 850 to borrow but several different 750's. Someone may find a deal on a nearly new 850 before long. Thanks again for the help.

 

[1badgtx]

1050 is way too much...I,m runnin a 800 edelbrock on my car and it,s setup pretty much like yours...You just have to play with it to get it tuned in...If street use is most of what you do then go with a tune friendly carb...If your going to the track then the mighty demon would be my next choice...
Petty Blue 67 gTx

 

[daredevil]

Thanks guys. This motor should have no problem turning 6500 to 7000. Holleys carb selector reccomended a 1050 dominator at 7000. I think this is too much for me. I am looking at getting a vacuum sec. and havent decided whether or not to run a choke. I live in western nc, and we see some pretty cold weather, but the car will probably be inside during winter months. Guess I was asking too much for the "perfect" carb for my combo. Trial and error makes sense, just not from a pocket book stand point. I don't have a 850 to borrow but several different 750's. Someone may find a deal on a nearly new 850 before long. Thanks again for the help.

Did someone say 1050 dominator? hehe. Pain in the a&& to tune a 3 circuit for the street but when you stomp it it opens the gates of hell.