• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Carburetor Love Triangle.....

74Beeper

74Beeper

Well-Known Member
Local time
12:20 PM
Joined
Aug 15, 2015
Messages
227
Reaction score
142
Location
Fargo, ND
I can't make up my damn mind as to which CFM carburetor to choose for my Roadrunner.

I DO know it will be a Quick Fuel Race Q. What I don't know is which CFM.....

I have a 1974 Roadrunner..... 440ci R3 small block (yes small block) with 7000rpm shift points, 11.5 to 1 comp, INDY 360-1 rectangle port aluminum heads fully CNC ported, with 2.15 intake valves and 1.625 exhaust. These heads have been totally worked over by Ryan J. at Shady Dell Speed Shop. Intake is an INDY 360-R3 single plane. Cam is a custom Bullet roller with 262 & .680 @ .050. Rockers are T&D 1.5 rollers. Full MSD ignition, and an Areomotive Stealth 340 fuel pump. Exhaust is TTI 1-7/8 long tube headers and full TTI 3" X-pipe exhaust with Super 10 Flowmaster ear muffs and the whole works is ceramic coated.
Transmission is a TKO 600 and rear is a Dana 60 with 4.10's.

This car will be street/strip with more street than strip.

Ryan J. said if it was a strip only car I would need a 1050 and he recommended running a 950 for better street throttle response. BUT...... Don at FBO (4secondsflat.com) where I'm buying this carb, swears up and down and even sideways a little, that I shouldn't have anything bigger than an 850.

I want the throttle response but don't want to choke it down when I tach it up.

any insight on this would be greatly appreciated.
 
I talked with the guys at Quick fuel about my setup couple weeks ago at a show they talked me into an 880cfm for my car I would imagine you could use more cfm like that 950 with those kind rpm's.
 
The 850 will be super snappy, more than enough flow too spin the motor into the happy zone... Personally the 1050 would make for lazy bottom end even with the manual trans and steep gear, do you really want that or willing too chance it with a heavier car?
 
Phil McGrath said:
The 850 will be super snappy, more than enough flow too spin the motor into the happy zone... Personally the 1050 would make for lazy bottom end even with the manual trans and steep gear, do you really want that or willing too chance it with a heavier car?
Click to expand...

I'm not considering the 1050 because i will be street/strip. But i guess i can't decide between the 950 and the 850. My engine guy says 950 and my carb guy says 850......
 
I ran several different carbs on my 360 stock stroke bracket car. Ended up with an 850. You have way. More cubes.. I wouldn't hesitate to put the 950 on it.
 
My 2 cents, you just said the majic word---------- throttle response, the 850 will due just fine and tune just fine. I would not even be afraid of steping back from the Q-series to a vac secondary. back in the day of multiple carbs in the 60's and over carburation was a tough gig to get out of doing and many learned that long and hard lesson trying to run them on the street. I suggest you look at the factory CFM rated carbs and the CID with the RPM they were running and go up from there. Oh and I'm with Don. Good luck, it sounds like an awesome build. 850 CFM will run a well developed 500 ci. street driven car. Just my opinion only.
 
if the quick fuel 950 is like the holley 950 then it's a 750 with a countoured body with 850 throttle bores (1 3/8" venturiis and 1 3/4" throttle bores) and doesn't flow anywhere near 950. an 850 will have 1 9/16" venturiis and 1 3/4" throttle bores. the "950" will have better throttle response on a single plane intake. cfm ratings are just for marketing; lot of times not real.
 
lewtot184 said:
if the quick fuel 950 is like the holley 950 then it's a 750 with a countoured body with 850 throttle bores (1 3/8" venturiis and 1 3/4" throttle bores) and doesn't flow anywhere near 950. an 850 will have 1 9/16" venturiis and 1 3/4" throttle bores. the "950" will have better throttle response on a single plane intake. cfm ratings are just for marketing; lot of times not real.
Click to expand...

That's the plus side of carbs from Quick Fuel and Proform...... They're CFM ratings are true unlike Holley
 
74Beeper said:
That's the plus side of carbs from Quick Fuel and Proform...... They're CFM ratings are true unlike Holley
Click to expand...
really? call quick fuel and ask them about the venturii and throttle bore sizes between the two carbs then you will know for sure what your buying.
 
For the reasons of discussion I think I would call them Modular carbs. they have different applications for use and the boosters vary widely in physical dimension and are used for conventional use with straight and downleg boosters and then the larger looking annular discharge boosters for basically race use with large cams and poor velocity but they have to have a bigger or smaller change in venturi sleeve size and shape for CFM regulation. I would suggest calling the tech line of carb supplier. good luck
 
lewtot184 said:
so what are the venturii and throttle bore differences?
Click to expand...

1.400 Venturi and 1.75 throttle plates for the 850. The thing that makes them true CFM carbs are the way they've contoured and rounded several small things to get the flow. This is what they told me. How true it is I don't know but I do know a QFT 850 will outflow a Holley 850.
 
Just went through the same dilemma for a carb choice on my 451. I ended up going with Don @ FBO also and his recommendation of a Quick Fuel Q750 for my setup. I was thinking a 850, but Don did the up, down, and sideways thing with me too lol. Decided to trust him as he knows way more about this kind of thing than me. Ordered yesterday and will ship by the end of this week.
 
hunt2elk said:
Just went through the same dilemma for a carb choice on my 451. I ended up going with Don @ FBO also and his recommendation of a Quick Fuel Q750 for my setup. I was thinking a 850, but Don did the up, down, and sideways thing with me too lol. Decided to trust him as he knows way more about this kind of thing than me. Ordered yesterday and will ship by the end of this week.
Click to expand...

Haha..... That's funny. I just got off the phone with him and told him i wanted the 950..... He wasn't happy! I just don't want to loose that extra HP on the top end. Ryan J, my engine guy says my engine combo will lose at least 30hp with an 850 due to the massive amount of air my heads will flow. Don said i can run a 4 hole spacer under the carb to get more bottom end. I'm gonna see how this goes and if i hate it that much on the street i will save my pennies and get an 850 as well. Then i'll have one for street and track.

One thing is for sure..... Ol' Don sure is passionate about his carbs!!!

Good luck and let me know how you like it!
 
I use the standard 850 Holley DP on my 440/493 street car. I can tell you it wants fuel as the more jet I gave it the faster it went. But where it is now gives good throttle responce and great drieability. I feel very sure I would go fatser at the track with a Dominator but I like how well the 850 works on the street. Its not a trick 850 as its the basic one with no jets in air bleeds or anywhere other then main jets. Any tuning on it I have to drill things to do but I have it where it works nice on the street and ok at the track. Ron
 
You must log in or register to reply here.

Similar threads

2quick
Got the 572 back, Now lets find some power
2 3
Replies
44
Views
4K
2quick
2quick
ozzymaxwedge
What Heads ?
2
Replies
24
Views
2K
dvw
dvw
Tex013
Race weekend this weekend .
Replies
12
Views
804
Tex013
Tex013
J
Rear suspension suggestions needed
2
Replies
22
Views
2K
weedburner
W
E
505 short block
2
Replies
22
Views
2K
33 IMP
33 IMP
Auto Transport Service
Back
Top