600cfm not enough? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 05-11-2005, 05:46 AM
Technical Support Barry Grant
 
Last photo:
Join Date: Jul 2003
Location: Dahlonega, GA
Posts: 1,503
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
A 650 Vacuum Secondary carburetor would probably give you the best overall performance.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 05-11-2005, 03:49 PM
club327's Avatar
Member
 
Last photo:
Join Date: Nov 2003
Location: australia
Age: 50
Posts: 334
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I'd go the 750cfm route as I don't believe a it would be too big for your engine. The bottom RPM won't suffer as many are led to believe and the top end would be better off and the sound would be a lot better too.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 05-11-2005, 06:53 PM
Member
 

Last journal entry: Future Plans
Last photo:
Join Date: Sep 2004
Location: Port alberni, British Columbia
Age: 29
Posts: 118
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
well at the moment i have a 750 q-jet that is totally rebuilt and works perfect but in the future i would like to upgrade but im looking into the thunder avs 650 or the speed demon 650 and i cant decide
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 05-11-2005, 09:26 PM
stepside454's Avatar
Member
 
Last photo:
Join Date: Dec 2003
Location: St. louis area
Age: 47
Posts: 1,074
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
why not keep the Q-jet, properly tuned itll give you everything you want.
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 05-12-2005, 12:49 AM
club327's Avatar
Member
 
Last photo:
Join Date: Nov 2003
Location: australia
Age: 50
Posts: 334
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I agree. Going to a 650 from a 750QJET may be a step in the wrong direction. If you decide to go that way, then be prepared to be disapointed. Or better still, can you try a carb from one of your mates (buddies) before you commit?
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 05-12-2005, 01:15 AM
smallblocker2's Avatar
L79 327 5SPD S10 '65GTO
 
Last photo:
Join Date: Apr 2005
Location: Langley B.C.
Age: 35
Posts: 250
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I would keep the Q-jet as well. Mine gives me 21.5 mpg on the freeway, and crisp throttle response, and she pulls to 6700.
My 650 d/p didn't do any of that.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 05-12-2005, 05:18 AM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by 85Sierra
well at the moment i have a 750 q-jet that is totally rebuilt and works perfect but in the future i would like to upgrade but im looking into the thunder avs 650 or the speed demon 650 and i cant decide
Why didn't you tell us you had a Q-Jet in the first place? I wouldn't consider switching an "upgrade", get Doug Roe's book and spend some time on the Q-Jet, it probably works "OK" right now but you still have a way to go to be perfect. Once you get it "perfect" the only thing better on the street is EFI. It doesn't have the visual appeal of other carbs but it sure does work and once you've experienced one properly dialed in you'll start thinking it looks pretty good after all. Just my $.02 but from what I've seen in other posts there are quite a few experienced rodders here that feel the same way.
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 05-12-2005, 07:20 AM
Max Keith's Avatar
Member
 
Last photo:
Join Date: Jul 2003
Location: Fort Madison,Iowa
Age: 66
Posts: 2,391
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Carb Upgrade

I tend to agree with Hippie on this. Stick with the Q-jet and get to know how it works. Other than them not being the most eye appealing carb on the market, theres not a thing wrong with them, and they have just as much potential as any other carb out there. Save your bucks for something later on that will give you more bang for the buck, than another carburetor.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 05-12-2005, 08:04 AM
Member
 

Last journal entry: Future Plans
Last photo:
Join Date: Sep 2004
Location: Port alberni, British Columbia
Age: 29
Posts: 118
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
well i guess its time to start saving for the canfields or the Afr's
thanks for the input
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 05-12-2005, 10:18 AM
King of my Man-cave.
 
Last photo:
Join Date: Nov 2003
Location: Michigan
Age: 55
Posts: 2,899
Wiki Edits: 0

Thanks: 3
Thanked 15 Times in 12 Posts
Quote:
Originally Posted by 85Sierra
well i guess its time to start saving for the canfields or the Afr's
thanks for the input
Personally I think you would be happiest with a 750 vac. sec, Holley. It will pull a LOT harder than the 600 or 670.

tom
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 05-12-2005, 11:38 AM
smallblocker2's Avatar
L79 327 5SPD S10 '65GTO
 
Last photo:
Join Date: Apr 2005
Location: Langley B.C.
Age: 35
Posts: 250
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
If you do stick with a Q-jet, get a 75-later model. They have an adjustable part throttle feature that can be adjusted with a screwdriver while the engine's running, You just need a 1/8th" pipe thread tap and plug and a phillips screw.
Awesome fuel mileage.
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 05-12-2005, 11:49 AM
packratwrecker's Avatar
Too many hobbies!
 
Last photo:
Join Date: Dec 2003
Location: Kansas
Age: 41
Posts: 240
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by machine shop tom
Personally I think you would be happiest with a 750 vac. sec, Holley. It will pull a LOT harder than the 600 or 670.

tom

Had one on a 402 big block. Had half the power, and less than half the mileage of my worn out Q-Jet. I won't own an Ede, or a drooling Holley, until I can no longer get Q-Jets.

I'd say, stick with the Q-Jet. It will do everything you want, and probably get you decent mileage, if you keep your foot out of the ****** ports.
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 05-12-2005, 11:37 PM
lluciano77's Avatar
Short changed on common sense
 
Last photo:
Join Date: Jun 2003
Location: california
Age: 37
Posts: 3,548
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Hippie
You must have plugged in 100% volumetric efficiency, 80% for a street motor will probably be more like it and that's optimistic. Using 80% it comes out to a 517 cfm.
Here the formula, and 517 CFMs are okay?
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 05-12-2005, 11:39 PM
lluciano77's Avatar
Short changed on common sense
 
Last photo:
Join Date: Jun 2003
Location: california
Age: 37
Posts: 3,548
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Hippie
Why didn't you tell us you had a Q-Jet in the first place? I wouldn't consider switching an "upgrade", get Doug Roe's book and spend some time on the Q-Jet, it probably works "OK" right now but you still have a way to go to be perfect. Once you get it "perfect" the only thing better on the street is EFI. It doesn't have the visual appeal of other carbs but it sure does work and once you've experienced one properly dialed in you'll start thinking it looks pretty good after all. Just my $.02 but from what I've seen in other posts there are quite a few experienced rodders here that feel the same way.
But now a 750 CFM carb is okay?

If 750 is okay, that means the formula doesn't work. Didn't I just get an A S S chewing for doubting the carb formula the other day???
Reply With Quote Quick reply to this message
  #30 (permalink)  
Old 05-13-2005, 06:56 AM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by lluciano77
Here the formula, and 517 CFMs are okay?
Quote:
Originally Posted by lluciano77
But now a 750 CFM carb is okay?

If 750 is okay, that means the formula doesn't work. Didn't I just get an A S S chewing for doubting the carb formula the other day???
What is your problem? I'm not the one that argued with you about the formula, we disagreed about Holley 4010's being a "new" design vs. other carbs but I put it behind me, obviously you can't. The original question here was whether or not a 600 Holley was big enough for a 400 SBC, he didn't ask if a Q-Jet would be better or if a 750 was too big, he asked if the 600 was ENOUGH. From my personal experience it is. As far as a 750 being OK a vacuum secondary carb will only flow at WOT what the motor will pull, using the dreaded "formula" his 406 will probably only flow around 517 cfm assuming a volumetric efficiency of 80% at WOT, very few street motors exceed 80% . Could it be more, yes, but with the combination he eventually listed probably not much more and realistically how much time does a street motor spend at WOT, a few seconds a month at best? A 750 Q-Jet would be better choice over a 750 square bore carb due to it's smaller primaries. A 750 square bore would kill his gas mileage and throttle response because of it's large primaries and idle circuits, if he was racing? Hell yeah go for a 750 Holley, Demon, etc. but he's not. The Q-Jet is capable of excellent throttle response, mileage, etc. and my experience with Holley spreadbores has been that they can't hold a candle to a Q-Jet for those attributes regardless of what Holley claims. That didn't come from a formula, chart or some magazine article, that comes from real world experience. Even as much as you hate "formulas" they provide a pretty good baseline to use to start making comparisons, thousands of people use them with great success. They were developed over many years by people with a lot more education and experience than just about anybody on this board. As for your "A S S" chewing the other day that didn't come from me in fact even though I felt you were out of line I felt kind of bad for you, I thought the guy over reacted. I've changed my mind.

Last edited by Hippie; 05-13-2005 at 12:02 PM.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Holley 600cfm problems fulton Engine 5 03-27-2005 06:57 PM
600cfm carb too big? montea Engine 6 09-09-2004 03:22 PM
600cfm Carb question calimstng66 Engine 12 04-19-2004 08:34 PM
750 cfm carb - tuning - smaller jets or 600cfm? 65truck Engine 8 01-20-2004 06:13 PM
Is a 650cfm carb noticeably better than a 600cfm Stinky Engine 1 06-18-2003 09:00 PM


All times are GMT -6. The time now is 04:17 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.