What carb should i run?
Thread Starter
Instructor
Joined: Jun 2008
Posts: 173
Likes: 1
From: Central Iowa
What carb should i run?
So i'm really new to the world of carbs and idk what to look for. I was told to go w/ either a 750 holly or demon for my 454 rebuild. It will have a mild cam, re-worked heads, hopefully a dual plane intake if i can find one that'll clear a stock hood, and be running about 10.1 compression. Can anyone help me? 
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
What do you plan on using the car for? Just street use? Occasional drag racing? Or just racing all the time? What maximum rpm are you planning? What's the lowest rpm do you give wide open throttle it at?
Vacuum secondaries work great on the street. They are a lot more forgiving if you've picked one that is too big. I've gone from a 800 cfm double pumper (mechanical secondary) to a 600 cfm vacuum secondary and I like the 600 cfm the best.
Bigger isn't always better. Smaller will typically give better low rpm throttle response while bigger gives less pressure drop for a given air flow which means more power.
Use the equation: CFM = Engine Cubic Inches X Maximum RPM / 3456 to get you in the ballpark of carb sizes.
Vacuum secondaries work great on the street. They are a lot more forgiving if you've picked one that is too big. I've gone from a 800 cfm double pumper (mechanical secondary) to a 600 cfm vacuum secondary and I like the 600 cfm the best.
Bigger isn't always better. Smaller will typically give better low rpm throttle response while bigger gives less pressure drop for a given air flow which means more power.
Use the equation: CFM = Engine Cubic Inches X Maximum RPM / 3456 to get you in the ballpark of carb sizes.
Burning Brakes
Joined: Oct 2002
Posts: 914
Likes: 14
From: Aberdeen, Scotland
Stock hood?
If you are sticking with your hood you might need to use a GM Manifold. Then keeping your Q-Jet could be a decent solution. Just get an expert to help set up the carb. The problem is that there are not many Q-Jet experts. Call Lars; I did! And while you're at it I would send him your points distributor too. Great service!
Stock hood, GM intake and your old points Dist =
sleeper
carbster09
Stock hood, GM intake and your old points Dist =
sleepercarbster09
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Why not get the best of both and pick small primaries and large secondaries? There's one carb that does it best on both and that's the Quadrajet!Cheers,
Larry
12.10/114.4
http://youtube.com/watch?v=7FNC9tILoo0
Thread Starter
Instructor
Joined: Jun 2008
Posts: 173
Likes: 1
From: Central Iowa
I'm having the engine shop call comp cams and they are gonne make one for me. I'm also gonna go w/ an HEI set up. What kind of GM manifold? Is it a dual plane set up? I'd like to ditch the original one due to it being kinda ugly w/ all the emission stuff of there, and it being only a single plane design.
As for ppl knowing how to set them up, there aren't too many around this area. That's why i was told to go w/ the ones i mentioned cuz they are easy to set up. Unless you guys think otherwise?
As for ppl knowing how to set them up, there aren't too many around this area. That's why i was told to go w/ the ones i mentioned cuz they are easy to set up. Unless you guys think otherwise?
Last edited by 73 454; Jul 1, 2008 at 01:52 AM.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
I'm having the engine shop call comp cams and they are gonne make one for me. I'm also gonna go w/ an HEI set up. What kind of GM manifold? Is it a dual plane set up? I'd like to ditch the original one due to it being kinda ugly w/ all the emission stuff of there, and it being only a single plane design.
As for ppl knowing how to set them up, there aren't too many around this area. That's why i was told to go w/ the ones i mentioned cuz they are easy to set up. Unless you guys think otherwise?
As for ppl knowing how to set them up, there aren't too many around this area. That's why i was told to go w/ the ones i mentioned cuz they are easy to set up. Unless you guys think otherwise?
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Intermediate
Joined: Feb 2008
Posts: 29
Likes: 1
From: Indian Trail NC
The Q-Jet will pay for itself quickly in fuel economy and the performance on a properly set up Q-Jet is as good as anything out there. Several carb companies can help. Don't like Jet, but Carb Shop or some others can help and it will be worth the money!!!
Intake depends on your hood.........
Intake depends on your hood.........
Thread Starter
Instructor
Joined: Jun 2008
Posts: 173
Likes: 1
From: Central Iowa
Damn now i don't know what to do
I need a combo that will work w/ the stock hood, unless i can find a nice 427 hood for cheap? lol but that being outta the question, i'm between a rock and a hard place. Cuz that motor will be done in 2 weeks and i need to get him a intake manifold, carb, and a distributor.
He told me to go w/ nothing more than a 750 cuz you can always tune a carb up and not down. As for the intake he recommended finding another replacement to get rid of the emission stuff and better flow over stock.
Thanks
I need a combo that will work w/ the stock hood, unless i can find a nice 427 hood for cheap? lol but that being outta the question, i'm between a rock and a hard place. Cuz that motor will be done in 2 weeks and i need to get him a intake manifold, carb, and a distributor. He told me to go w/ nothing more than a 750 cuz you can always tune a carb up and not down. As for the intake he recommended finding another replacement to get rid of the emission stuff and better flow over stock.
Thanks
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
For the mild build that you say that you are having done, the stock
intake and Quadrajet will most likely work very well.
The intake wont be optimal, but with the increased compression ratio
and the larger cam you are getting, I bet you will be happy with the performance.
If your original carb has problems, then seek out Lars here on the forum.
I have never used his services, but everyone that has speaks very highly of his work.
intake and Quadrajet will most likely work very well.
The intake wont be optimal, but with the increased compression ratio
and the larger cam you are getting, I bet you will be happy with the performance.
If your original carb has problems, then seek out Lars here on the forum.
I have never used his services, but everyone that has speaks very highly of his work.
Last edited by DRIVESHAFT; Jul 1, 2008 at 03:31 PM.
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
Holley has even admitted that they don't produce a good "spreadbore" carb.
If you can look into an Edelbrock 750 cfm with an Edelbrock Performer intake, you'll have a good streetable set up. I've got a 71 454/365, and I get 12.7 mpg around town with a bit of tire spinning, playing and not so calm driving. Take it for what it's worth. Tank
Thread Starter
Instructor
Joined: Jun 2008
Posts: 173
Likes: 1
From: Central Iowa
Oh boys, now you guys got me all messed up. lol I was told to stay away from edelbrock carbs, but to use their intakes if i could find one that fits. lol My engine shop recommended to use a holly or demon under 750 cfm. So idk what to do. I may just have to use the stock intake and have the stock rochester rebuilt or something. That will help w/ the budget and probably work for the time being just so i can cruise my car. 
Does anyone have any picts of there BB they can post up w/ what they're running? Hoods open and closed?
Does anyone have any picts of there BB they can post up w/ what they're running? Hoods open and closed?
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
If you cant find another intake that will fit under your hood, then you will have to run a spread bore carb.
So its either the Q-jet or a spread bore Holley . Edelbrock carbs are all square bore.
Tank runs the Performer intake, but he also has an L88 hood.
So its either the Q-jet or a spread bore Holley . Edelbrock carbs are all square bore.
Tank runs the Performer intake, but he also has an L88 hood.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 173
Likes: 1
From: Central Iowa
I found this in the forsale section...Would this be something i may be interested in?
http://forums.corvetteforum.com/show....php?t=2065491
http://forums.corvetteforum.com/show....php?t=2065491
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI
Yes, its part number 6772. My book says "Direct street replacement for all Quadra-Jet carbs on 1972 350, 402, 454 C.I.D. engs., emission carb." If you have never had a double pumper before you are in for a real treat - neck snapping response.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
cc
Ok, I admit that was 35 years ago and no one cared about gas mileage.
Last edited by CCrane65; Jul 2, 2008 at 10:25 PM. Reason: add time reference