650 or 750 cfm. carb??

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74scamp360

74scamp360

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Hey guys and gals, i've been doing some carb. reaserch and am looking for opinions on what you guys think i should buy. I've narrowed it down to an edelbrock and a performer series but i'm not sure if the 750 cfm will be too much for my application. I'll be running a stock 360 but here's the catch, this motor will be seeing some performance upgrades in the near future such as a head job, heavier cam, aftermarket intake etc. What i was thinking is buy a 750 and then lean it out until i get some more power and then re-adjust it instead of having to go out and buy another new one. I'm open to opinions so please let me know what you guys think. Thanks!!
 
I would go for a Speed Demon 750 with annular boosters. That way you get the low end response of a 650 and the top end of a 750. I've got an 850 annular Demon on my 440. A lot of people said it was too much carb but with the annular boosters it runs great all the way through the RPMs.
 
hmm interesting anyone else?? like i said above i'd kind of like to get into a 750 cause then it gives me room to "expand" if you know what i mean and a 650 seems a little small.
 
Do the 750. It'll be fine since it will see some of the work you made mention off.
 
you guys seem to going towards holleys??? i've had some bad experiences with holleys which is why i didn't really want to buy one. O and by the way i'll be getting it in electric choke as well. it gets cool sometimes here in the great white north even in the summer.
 
74scamp360 said:
you guys seem to going towards holleys??? i've had some bad experiences with holleys which is why i didn't really want to buy one. O and by the way i'll be getting it in electric choke as well. it gets cool sometimes here in the great white north even in the summer.
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Eveyrone's had bad experiences with Holley's lol but once you've got them sorted out they seem to offer much better performance than an edelbrock. I've got a 750 vac on my very stock 360 and it works good, I've had 750DP's on it before as well as 650DP's(it hated the 650) I think I'm going to put a 750DP back on it and go to the track for the last time this year. Good luck with it.
 
Quick fuel 750 should get the job done now and when you upgrade..Demons are a pain to deal with,i will never buy one again..
 
I have quite a stout 360 (~370HP) and have had 600, 670, 725 and 750 cfm carbs on. There is absolutely no difference in top end performance between the 670, 725 or 750 but the 600 and 670 have it all over the 725 and 750 in low/ mid range throttle response. I would recommend the 650 if the car is primarily a street car.

For a street car smaller is better when it comes to cams and carbs.
 
stroked 340 said:
Quick fuel 750 should get the job done now and when you upgrade..Demons are a pain to deal with,i will never buy one again..
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I'm curious as to why you think Demons are a pain to deal with? They are almost the same carb as a Holley or a Quick Fuel. 4 corner idle, power valve, double pumper, seems the same at least. Never had a pain dealing with mine.
 
All these carbs are fine as far as a model goes, it is yor expertise on working with them.

The AFB design is easy to make quick metering rod changes etc.
 
When selecting a carb for a street motor Ive always used a volumetric efficiency formula which is (cubic inches x max rpm)divided by 3,456 = carb cfm. Its always worked very well for me. Once you do the math, round up to the nearest size carb.
 
wish4hemi said:
I'm curious as to why you think Demons are a pain to deal with? They are almost the same carb as a Holley or a Quick Fuel. 4 corner idle, power valve, double pumper, seems the same at least. Never had a pain dealing with mine.
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I found my Demon to be quite finiky,make an adjustment take it for a ride everything goes out of wack,make a few more adjustments same problems finally gave up on it..Quick fuel right from the get go best carb, i've ever bought not one issue with it going on 3 seasons of racing..And Demons are not the same as a Holley Holleys are much easier to deal with..glad your having good luck with your Demon but i'll never buy one again...
 
wish4hemi said:
I'm curious as to why you think Demons are a pain to deal with? They are almost the same carb as a Holley or a Quick Fuel. 4 corner idle, power valve, double pumper, seems the same at least. Never had a pain dealing with mine.
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They really are the same ..... just maybe a little hear and there but the over all operation is the same. Now a AVS, Carter, Performer, now that's a different carb.
 
well i would like performance but from my experience the edelbrock also has great performance. My dad put one on his very healthy 440 in his 69' charger and he loves it way more then the holley he used to have. mind you it's an 800 thunderseries (or 850 whichever they are??) but i don't know how much difference that there can really be. you say holley is the a certain line that i should be looking at?? Thanks for the info. guys
 
JoseyWales said:
When selecting a carb for a street motor Ive always used a volumetric efficiency formula which is (cubic inches x max rpm)divided by 3,456 = carb cfm. Its always worked very well for me. Once you do the math, round up to the nearest size carb.
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You will see a lean condition everytime with a built motor. Now if the motor is bone stock then you will can get away with that formula.
 
mine is bone stock for now but will see some performance improvements soon like i said above. From what i'm hearing from you guys i'm thinking a 750 will do just fine. am i wrong?
 
The 750 will work but it will require more tuning to get it right than a smaller carb and will provide little or no more power and will not have as good response in the rpm range where you will be driving the car. Something in the 650 to 700 range is a much better choice even for a modified motor. The only time you would really be able to use the capacity of a 750 is when you exceed 6000 rpm.

FWIW, if you check the adds in the Mopar rags for the 5.7/6.1 hemi motors that are rated for well over 400 HP they are supplied with 600 CFM carbs.
 
dgc333 thanks for the tip, that's what i really wanted to see is some numbers and this motor will never be turning 6000 or more so you think something like a 650 to 700 would be a better range??
 
mullinax95 said:
What CFM is a Thermoquad carb which came stock on a lot of mopar motors such as 318s?
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800's-930cfm, good mention, and it really depends on the tune and transition circuit on weather it'll work 'better' or not.

If you tune for, the bigger carb will make more power before 6000 rpm at any point from full advance. jmo
 
1wild&crazyguy said:
800's-930cfm, good mention, and it really depends on the tune and transition circuit on weather it'll work 'better' or not.

If you tune for, the bigger carb will make more power before 6000 rpm at ant point from full advance. jmo
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Exactly.
 
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