Deburring the burrs off quadrajet? - 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 05-26-2012, 06:24 AM
Registered User
 
Join Date: Aug 2006
Location: Alexandria, VA
Posts: 1,747
Wiki Edits: 0

Thanks: 4
Thanked 64 Times in 62 Posts
I read through one recent article where the guy adjusted the secondary air valve delay on the Quadrajet because he was running a 4 speed. I will try to sum up his explanation.

High vacuum on the choke pull-off keeps the secondaries locked out until you accelerate, and then the low vacuum lets the pull-off extend, and the secondary flaps open based on air flow. The delay on the pull-off can be reduced by opening up the small hole in vacuum fitting. The spring tension that holds the secondary flaps closed is also adjustable (allen wrench and set screw), so you have a combination of spring tension and the pull-off delay working on the secondary air flaps.

If you are running an automatic trans the secondary air valve delay only happens as you first hit full throttle, and it gives the carburetor time to make the transition without suddenly dumping the secondary flaps open. However, if you have a 4 speed you will have the throttle quickly opening and closing 4 times. The first time off the line it might be okay to have a normal secondary delay, but as you hit gears 2-4 you want a much shorter delay because you are already at a high rpm.

Some folks take all the tension off the secondary spring and remove the connection to the pull-off. The carburetor may work this way, but now your secondaries are just mechanical, and you have lost most of the ability to "tune" the transition.

Bruce

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 05-26-2012, 07:16 AM
Registered User
 
Last wiki edit: General Motors transmissions Last photo:
Join Date: Mar 2006
Location: near Yellowstone park
Posts: 4,211
Wiki Edits: 27

Thanks: 11
Thanked 233 Times in 219 Posts
sounds good.

Years ago I reworked my old ford 4 barrel, the long carb. It had lots of casting die mis- match, I removed the mis-match flash and used fine sand paper on dowels, I reworked the secondary kick in linkage, accelerator pump. I had cleaned up the ports, matched to the gaskets, some grinding in the combustion chamber. When it was done , you put your foot down It would drone , sounded like 3 2's .
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 05-26-2012, 08:59 AM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,678
Wiki Edits: 0

Thanks: 17
Thanked 281 Times in 261 Posts
Quote:
Originally Posted by sc2dave
Don't you mean richen, since more airflow would need more gas?
no, the stronger signal will cause it to run rich
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 05-26-2012, 12:07 PM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 75gmck25
I read through one recent article where the guy adjusted the secondary air valve delay on the Quadrajet because he was running a 4 speed. I will try to sum up his explanation.

High vacuum on the choke pull-off keeps the secondaries locked out until you accelerate, and then the low vacuum lets the pull-off extend, and the secondary flaps open based on air flow. The delay on the pull-off can be reduced by opening up the small hole in vacuum fitting. The spring tension that holds the secondary flaps closed is also adjustable (allen wrench and set screw), so you have a combination of spring tension and the pull-off delay working on the secondary air flaps.

If you are running an automatic trans the secondary air valve delay only happens as you first hit full throttle, and it gives the carburetor time to make the transition without suddenly dumping the secondary flaps open. However, if you have a 4 speed you will have the throttle quickly opening and closing 4 times. The first time off the line it might be okay to have a normal secondary delay, but as you hit gears 2-4 you want a much shorter delay because you are already at a high rpm.

Some folks take all the tension off the secondary spring and remove the connection to the pull-off. The carburetor may work this way, but now your secondaries are just mechanical, and you have lost most of the ability to "tune" the transition.

Bruce

Thanks!
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 05-26-2012, 12:09 PM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by timothale
Years ago I reworked my old ford 4 barrel, the long carb. It had lots of casting die mis- match, I removed the mis-match flash and used fine sand paper on dowels, I reworked the secondary kick in linkage, accelerator pump. I had cleaned up the ports, matched to the gaskets, some grinding in the combustion chamber. When it was done , you put your foot down It would drone , sounded like 3 2's .

Sweet, that I was thinking about do same.
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 05-26-2012, 01:14 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
There's no point in doing anything (other than for personal satisfaction) to the secondary side casting unless there's some huge gaping mismatch, etc.

On the primary side, the booster rings and the venturi can be carefully smoothed where there may be a casting mismatch or casting flash or et cetera. If there's a mismatch between the baseplate and main body, that can be taken care of- but in the carbs I've seen, this has not been a problem, nor has there been any significant amount of casting irregularities. I'm wondering if the carb you're practicing on is abnormal in that regard... and I would want to see the actual carb that's going on the engine to see what it looked like before drawing any conclusions from the carb you're working on now.

The fit of the base plate gasket can be more of a flow problem than any casting irregularity; if the gasket intrudes into the throttle bore, removing THAT will help more than anything.

Generally speaking, reworking the castings of a carb w/o any empirical way of measuring changes is like porting a cylinder head w/o a flow bench. What looks good may in fact be the exact opposite of what the carb needs, and w/o knowing what is happening as you make changes, the results can be worse than if you had done nothing at all, so if you decide to do anything, do not change the shapes, angles of attack, or any other parameter that was a designed-in feature of the carb. Keep things to a minimum- smoothing obvious flaws and mismatches, and leave the rest alone.

Also, everywhere the casting is ground on or polished removes the protective finish from the zinc of the carb body, and that can lead to the dreaded attack of the "white stuff" that's mentioned anytime old carbs are talked about.

As far as jetting and calibrations, they have to be optimized for the engine anyway- and w/o knowing whether the carb was spot-on, lean or rich to begin with, there's no way anyone can say you need to add or remove fuel, nor what circuits may be affected, or even if one circuit may want more fuel while another circuit wants less. So instead of worrying about any changes caused by the work you're contemplating doing, plan on taking care of all of it when the carb is set up for the engine and vehicle.

Lastly, I can tell you this: There's a lot more to be had in setting up the APT, idle/transition and main circuits, and the secondary tip-in than there is in dickering w/the castings.

Last edited by cobalt327; 05-26-2012 at 01:19 PM.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 05-26-2012, 01:27 PM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by cobalt327
There's no point in doing anything (other than for personal satisfaction) to the secondary side casting unless there's some huge gaping mismatch, etc.

On the primary side, the booster rings and the venturi can be carefully smoothed where there may be a casting mismatch or casting flash or et cetera. If there's a mismatch between the baseplate and main body, that can be taken care of- but in the carbs I've seen, this has not been a problem, nor has there been any significant amount of casting irregularities. I'm wondering if the carb you're practicing on is abnormal in that regard... and I would want to see the actual carb that's going on the engine to see what it looked like before drawing any conclusions from the carb you're working on now.

The fit of the base plate gasket can be more of a flow problem than any casting irregularity; if the gasket intrudes into the throttle bore, removing THAT will help more than anything.

Generally speaking, reworking the castings of a carb w/o any empirical way of measuring changes is like porting a cylinder head w/o a flow bench. What looks good may in fact be the exact opposite of what the carb needs, and w/o knowing what is happening as you make changes, the results can be worse than if you had done nothing at all, so if you decide to do anything, do not change the shapes, angles of attack, or any other parameter that was a designed-in feature of the carb. Keep things to a minimum- smoothing obvious flaws and mismatches, and leave the rest alone.

Also, everywhere the casting is ground on or polished removes the protective finish from the zinc of the carb body, and that can lead to the dreaded attack of the "white stuff" that's mentioned anytime old carbs are talked about.

As far as jetting and calibrations, they have to be optimized for the engine anyway- and w/o knowing whether the carb was spot-on, lean or rich to begin with, there's no way anyone can say you need to add or remove fuel, nor what circuits may be affected, or even if one circuit may want more fuel while another circuit wants less. So instead of worrying about any changes caused by the work you're contemplating doing, plan on taking care of all of it when the carb is set up for the engine and vehicle.

Lastly, I can tell you this: There's a lot more to be had in setting up the APT, idle/transition and main circuits, and the secondary tip-in than there is in dickering w/the castings.

Thank you for this. This Carb I'm practicing with to get comfortable with to learn it. It was actually one of your advice to me about a year ago. I'm just wondering if it's safe to deburr. I'm Burr freak. Lol
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 05-26-2012, 02:14 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by Freddyfingaz83
Thank you for this. This Carb I'm practicing with to get comfortable with to learn it. It was actually one of your advice to me about a year ago. I'm just wondering if it's safe to deburr. I'm Burr freak. Lol
I don't recall telling anyone to do any grinding on the castings- unless it was a special case of some sort. Or maybe you mean working on the Q-jet in general (like rebuilding it)... but anyway, as has been said:

Don't change the shapes of anything- just remove irregularities and nothing more.
Pay attention to how the base gasket fits
Secondary side is a waste of time unless there's huge problems
There are probably better ways to spend your time- but as long as the shapes are left intact, other than the loss of the protective finish, no harm/no foul.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 05-26-2012, 11:33 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
If you are a "burr freak", I bet you're familiar w/Cratex points. Using them will provide the very highest finish of any "Dremel-type" points, especially on curved and/or intricate castings. Some come mounted, others can be mounted on a small arbor w/screw (you know the arbors- like used for the small cutting discs).

I would avoid using stones altogether- they will leave a rougher than stock finish, and generally are not as precise as I believe is needed for that type of work.

There are paper sanding discs (400-600 grit and finer) that are fine enough; backing them w/a round piece of plastic cut from a coffee can lid can give enough backing to allow smoothing and polishing, when mounted on a small arbor.

If you want to take a few photos or do a write up on your progress (or both), they can be added to the Crankshaft Coalition wiki; another member (LT1Silverhawk) started a page on Q-jet carbs that the info might work well in.

Good luck.
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 05-27-2012, 12:48 AM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by cobalt327
If you are a "burr freak", I bet you're familiar w/Cratex points. Using them will provide the very highest finish of any "Dremel-type" points, especially on curved and/or intricate castings. Some come mounted, others can be mounted on a small arbor w/screw (you know the arbors- like used for the small cutting discs).

I would avoid using stones altogether- they will leave a rougher than stock finish, and generally are not as precise as I believe is needed for that type of work.

There are paper sanding discs (400-600 grit and finer) that are fine enough; backing them w/a round piece of plastic cut from a coffee can lid can give enough backing to allow smoothing and polishing, when mounted on a small arbor.

If you want to take a few photos or do a write up on your progress (or both), they can be added to the Crankshaft Coalition wiki; another member (LT1Silverhawk) started a page on Q-jet carbs that the info might work well in.

Good luck.

Beautiful advices! Many thanks!
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 05-28-2012, 01:11 AM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by cobalt327
I don't recall telling anyone to do any grinding on the castings- unless it was a special case of some sort. Or maybe you mean working on the Q-jet in general (like rebuilding it)... but anyway, as has been said:

Don't change the shapes of anything- just remove irregularities and nothing more.
Pay attention to how the base gasket fits
Secondary side is a waste of time unless there's huge problems
There are probably better ways to spend your time- but as long as the shapes are left intact, other than the loss of the protective finish, no harm/no foul.



Sorry for the confuse, What I mean is I never rebuilt quadrajet no before and I am not Comfortable with it. Like you said get quadrajet from junkyard to take apart and put it together until I have better understanding and more comfortable with it then go ahead rebuild real one. So I call it dummy quadrajet.

I do not wish change shapes.

Do you mean installing bronze bushing on secondary throttle is waste time?
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 05-28-2012, 03:11 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by Freddyfingaz83
Sorry for the confuse, What I mean is I never rebuilt quadrajet no before and I am not Comfortable with it. Like you said get quadrajet from junkyard to take apart and put it together until I have better understanding and more comfortable with it then go ahead rebuild real one. So I call it dummy quadrajet.

I do not wish change shapes.

Do you mean installing bronze bushing on secondary throttle is waste time?
OK, I understand you. Good to use a "dummy" Q-jet to practice on, I agree!

Bronze bushings are only needed on the primary side.

Good luck and keep us posted.
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 05-28-2012, 07:47 AM
Registered User
 
Join Date: Dec 2010
Location: wisconsin
Posts: 77
Wiki Edits: 0

Thanks: 0
Thanked 5 Times in 5 Posts
Several years ago I built some Q-jets for a circle track car that a buddy of mine was racing. The first one was a 1973 chevy truck 454 core and worked pretty good. I was bound and determined to build a better one and stumbled across the same number carb. I did like you are thinking and deburred and polished the main body and carb top. After all that work it didn't seem to make a difference. The biggest thing is to make sure everything seals up good. Make sure the throttle shafts are rebushed, the main body,carb top, and base plate are flat. Any litltle vacuum leak will throw your calibrations off. This is the number one problem with these carbs.
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 05-28-2012, 12:57 PM
Skylark
 

Last journal entry: 70 SF 455 project
Join Date: Jun 2011
Location: Fallon, Nevada
Age: 31
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by vpd66
Several years ago I built some Q-jets for a circle track car that a buddy of mine was racing. The first one was a 1973 chevy truck 454 core and worked pretty good. I was bound and determined to build a better one and stumbled across the same number carb. I did like you are thinking and deburred and polished the main body and carb top. After all that work it didn't seem to make a difference. The biggest thing is to make sure everything seals up good. Make sure the throttle shafts are rebushed, the main body,carb top, and base plate are flat. Any litltle vacuum leak will throw your calibrations off. This is the number one problem with these carbs.

Yes, I have repeating listening from everyone who work with quadrajet said biggest plm is seal failure that cause leaking. Best way to plug bottom end tubes and top is tapering and put screw with wrapped with expoy sealer? I was told the common issues with older quadrajet like mine is leaky bottom tubes that kept empty bowl.
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
Converting from external choke quadrajet to electrical choke quadrajet silentpoet Hotrodding Basics 4 10-03-2011 01:38 PM
Anti-Sieze on cutting burrs oldschool hero Garage - Tools 2 08-31-2011 09:52 AM
Deburring pistons barnym17 Engine 2 11-29-2007 07:39 AM
carbide burrs volkswagentuned Garage - Tools 12 10-14-2005 02:11 PM
Quadrajet novatech Engine 16 04-24-2003 11:44 AM


All times are GMT -6. The time now is 06:26 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.