Quadrajet float level: Carb year or CAR year? - 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
  #1 (permalink)  
Old 02-26-2008, 05:00 PM
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Maryland
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quadrajet float level: Carb year or CAR year?

I've got it cleaned and now reassembling (NAPA kit).
The current float setting is 9/16!
Bought it rebuilt had been having trouble starting it almost from the start.
At that float level, very little fuel would be able to get into the bowl before closing off the fuel inlet. Also, the new seat for the inlet needle has "windows" near the bottom, whereas the one I replaced did not. The old one would create more resistance to inflow would it not?

Now, the Haynes manual is saying 1/4" float level for 1970 Chevy truck, but the carb is an 1985 model which the book calls for 3/8" (for a Chevy 1/2 ton).

Which is the determining factor for setting the float level, the engine or the carb?

Thanks,
Rich

PS - anyone know of a chart that relates jets/rods to float level? I don't have a whole lot of time to try out all the combinations, I'd just like to get it close.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-26-2008, 09:49 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: texas
Posts: 119
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
the car that the carb is in, it also depends on what you are doing with the engine, drag racing you might want to raise float level to overcome the slosh effect of the fuel, but when you slam on the brakes the engine will try to starve and die, 1/4" is a good starting place for a daily driven vehicle, even 5/16th would be ok, but the 3/8" setting seems too low to me, set it around 1/4 and happy motoring, oh, the kit has a sheet of paper with a long list on the back with float settings for all kinds of cars and so on, most of them had slightly different bowls and filler blocks and on and on.... too many combos to list,
happy motoring
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-26-2008, 10:00 PM
Jmark's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,786
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
I have set almost all my qjets at 5/16" no matter what the book says. A tad lower if it's going to be bounced around alot in a truck.

An '85 carb will probably be a little on the lean side but should be ok on a fairly stock engine.

Mark
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-26-2008, 10:32 PM
kleen56's Avatar
Registered User
 
Last photo:
Join Date: Oct 2006
Location: Santa Clarita CA
Posts: 800
Wiki Edits: 0

Thanks: 4
Thanked 6 Times in 6 Posts
If I'm not mistaken, Edelbrocks are the same carbs as the Qjets. According to Edelbrock, the float should be 5/16". They recommend flipping the top upside down and using a 5/16" drill as a guide and measurement for float adjustment.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-26-2008, 10:55 PM
Registered User
 
Last wiki edit: Quadrajet
Join Date: Jul 2007
Location: Colorado
Posts: 107
Wiki Edits: 7

Thanks: 0
Thanked 0 Times in 0 Posts
On the fuel inlet with the windows. There isn't really a difference is performance according to all the testing that I have seen. The thought is that the windows would reduce resistance at the inlet and allow for more fuel flow at high RPMs. I have seen dyno tests where that was the only change made and it made no difference. So I don't think you need to worry about that.

I would agree with you that 9/16 is a little much. Although I don't know what you are wanting from the motor. i.e. off road or street performance, etc.. Basically though I would go with what the book says or what the previous float was set at. You can make very slight adjustments as necessary.

On the starting problems. If you think this is a fuel deliver issue. You might have a situation where the needle isn't seating properly, and allowing fuel to drain out of the bowl while sitting. While you have it apart. (Sounds like you will) You should take a check ball and place it in the fuel inlet where the needle will seat. Then take a puch and give it a few solid taps with a hammer. That should create a smooth surface for the needle to seat aginst.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 02-27-2008, 06:45 AM
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Maryland
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for all the tips.

Bull, I think your comment about the drainback is probably what my original problem was. When I disassembled, the needle clip was hooked through one of the holes over the pivot arm - something I've read about as a common mistake. I can see how that might prevent the needle from seating because it would be cockeyed in the cylinder. Once it started, it would run while I was fooling with the timing and such. The next day, it took forever to start. Probably because the bowl was empty.

Rich
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 02-27-2008, 08:15 AM
Registered User
 
Last wiki edit: Quadrajet
Join Date: Jul 2007
Location: Colorado
Posts: 107
Wiki Edits: 7

Thanks: 0
Thanked 0 Times in 0 Posts
You're absolutly right about that itstorque! The needle won't seat properly if it is through one of the holes! good find. If you can I would recommend using the check ball & punch while you have it appart, just for some insurance!
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 02-27-2008, 10:55 AM
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Maryland
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
What gasket sealer for carbs?

The Quadrajet air horn gasket is quite intricate and I was wondering what you guys use for gasket sealing material.
All the stuff I use is to sloppy or goopy not to clog one of the little holes.

Rich
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 02-27-2008, 12:04 PM
Jmark's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,786
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
EVERY carb gasket goes on dry. Never use any sealant on any of the carb parts/gaskets.

Mark
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 02-27-2008, 12:47 PM
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Maryland
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
That's what I was hoping to hear.
Thanks for all the tips everyone, I'll post back after I get it back on the engine.

Rich
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 02-27-2008, 03:57 PM
Member
 
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 50
Posts: 4,021
Wiki Edits: 0

Thanks: 0
Thanked 23 Times in 23 Posts
float setting depends on the fuel pressure.

Older q-jets (pre 74) have a 1/4 to 5/16 inch setting and new carbs used 3/8 to 1/2 inch. This is because newer model fuel systems use a few more psi of fuel pressure. I got this information from Cliff himself, the guy who wrote the book on Q-jets.

I recently switch to a Q-jet and found the 3/8 inch float setting works for my engine. A 1/4 inch setting cause it to blow black smoke on a warm startup.

76 jets, 54M rods, short accel pump, J-hanger, and a CE secondary rods works good on my engine with 17 inhg vacuum at 800 rpm. Idle air bleed are about 0.054" ( i think). Use new jets and rods (summit racing).

I had bad results trying to re-use the top gasket. So, between tunes, now I always change it. You can get them for a few dollars each (summit racing).

my BBC (413cid, 9:1 cr) truck (4300 pounds empty) gets 10 city and 15 mpg highway with the q-jet. th400, 3.08 gear, duals, stock manifolds, 206/212 at 0.050 cam. The holley did 8/12 mpg.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 11-02-2010, 07:53 PM
Registered User
 
Join Date: Sep 2010
Location: North Carolina
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Float settings for a quadrajet on a 350 SBC

mine is cutting out coming out of the turns on my street stock racecar. What settings should I use? Gas is also over flowing into the back barrels when it is floored.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 11-02-2010, 08:17 PM
Registered User
 
Last wiki edit: Quadrajet
Join Date: Jul 2007
Location: Colorado
Posts: 107
Wiki Edits: 7

Thanks: 0
Thanked 0 Times in 0 Posts
The flooding is the first issue that you need to address. Are you using a high pressure/high flow fuel pump? If so you will probably need to get a fuel pressure regulator. The flooding into the rear barrels indicates that the fuel pressure is overcoming the pressure that the float is placing on the needle valve. If you aren't using a high pressure pump and you don't think the pressure is too much, then you could have a couple of other issues inside the carb. In most q-jets, the float is made of a foam and can become fuel logged causing it to sink and not place the correct pressure on the needle valve. Another issue could be the needle valve & seat itself. I have had issues where the needle seat loosens and then fuel comes up through it's threads. Also you could have a damaged needle seat & valve that isn't sealing properly.

One test that I have preformed in the past, is to remove the carb top (air horn) and then disconnect the hot wire from the distributor. While I hold the fulcrum of the float/needle valve I have someone turn over the ignition so that the fuel pump runs. This will allow you to see if fuel is flowing when it shouldn't be or if the level is too high.

A WORD OF CAUTION!!!!!! ---
Make sure you wear eye protection. After your friend turns the motor over, there will be pressure under the needle seat. If you release the float fulcrum you can be in for a face full of fuel. I know for experience that it will ruin contact lenses
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: 2 (0 members and 2 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
I'm going to make a bonfire out of my car blown69stang Engine 36 08-22-2005 03:36 PM
Quadrajet carb riesman20 Engine 8 04-25-2004 03:08 PM
how would you make it legal?? spooki General Rodding Tech 8 08-31-2003 09:16 AM
Story time. Halloweenking Hotrodders' Lounge 17 05-19-2003 10:16 PM


All times are GMT -6. The time now is 09:04 PM.


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.