Carb vacuum diagram - 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 04-03-2007, 01:11 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,284
Wiki Edits: 0

Thanks: 5
Thanked 399 Times in 393 Posts
Check the little cork donut shaped gasket that goes between the carb body and sec vac diaphram. If it is missing or leaks
between the vacuum housing and carb body, the vaccum signal that opens the secs at WOT, will be too late.
It will not build fast enough.
Usually when things are working right, No vac leaks, the lightest white spring is way way too light causing the secs to open too fast.
Generally a medium silver ( plain), yellow or purple spring is best for performance use.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 04-03-2007, 01:18 PM
Registered User
 
Last photo:
Join Date: Mar 2007
Location: MOORE OK.
Posts: 25
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by MIKE FROM SM
What makes you think the secondaries are opening late?


Well it's a 2 speed powerglide and I'm already in the upper rpm's when it starts to open. I would say around 4,000-5,000 rpm. Around 4-5K rpm I'm already doing close to 50 in first gear. ( I know I have really tall gears) But I was hoping with the other two barrels opening earlier. That that would help me off the line more. With a white spring ( the lightest) I would expect them to start to come on around say 2,500 rpm or so. I don't know maybe this is right where they are supposed to come on at.

Last edited by 2_Late_I_Won; 04-03-2007 at 01:29 PM.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 04-03-2007, 01:29 PM
Registered User
 
Last photo:
Join Date: Mar 2007
Location: MOORE OK.
Posts: 25
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by F-BIRD'88
Check the little cork donut shaped gasket that goes between the carb body and sec vac diaphram. If it is missing or leaks
between the vacuum housing and carb body, the vaccum signal that opens the secs at WOT, will be too late.
It will not build fast enough.
Usually when things are working right, No vac leaks, the lightest white spring is way way too light causing the secs to open too fast.
Generally a medium silver ( plain), yellow or purple spring is best for performance use.
That's what I thought. I thought the White one was way to light to be functional for most situation and car set up's

I checked cork gasket it's there and intact but I'm not saying it isn't leaking from there. I'll probably will replace it just because if it's not a problem now it soon will be. Thanks
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 04-03-2007, 01:41 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,284
Wiki Edits: 0

Thanks: 5
Thanked 399 Times in 393 Posts
Quote:
Originally Posted by 2_Late_I_Won
Well it's a 2 speed powerglide and I'm already in the upper rpm's when it starts to open. I would say around 4,000-5,000 rpm. Around 4-5K rpm I'm already doing close to 50 in first gear. ( I know I have really tall gears) But I was hoping with the other two barrels opening earlier. That that would help me off the line more. With a white spring ( the lightest) I would expect them to start to come on around say 2,500 rpm or so. I don't know maybe this is right where they are supposed to come on at.
What you are feeling in the seat of your pants while driving is not the secondaries starting to open.
They are actually opening right off idle (with the white spring) and opening too, too fast.
When they open too fast the engine airflow thru the carb is not fast enough. The carb cannot meter the fuel. (lean bog,soft acceleration). Then once the engine airflow ( speed) thru the carb catches up, the fuel flows properly and makes power. You feel that as a power surge.
Remove and reinspect the diapharm and diaphram housing seal for a leak. Use the thumb over the holes method.
make sure the little check ball is in the housing vac passage. Try a stiffer med tension spring. Try raising the float level a little on the sec side. (faster fuel metering reaction)
You really need to switch to a secondary metering block with jets and rear sec jet extensions. The fuel in the sec bowl gets pulled away from the sec jets on acceleration.
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 04-03-2007, 02:50 PM
Registered User
 

Last journal entry: car is painted
Last photo:
Join Date: Feb 2007
Location: Santa Maria, CA
Age: 38
Posts: 158
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
With high gears and pg the secondaries should open very late. The engine should rev up smoothly. If it doesn't, the secondaries are opening too soon. Keep putting in a stiffer spring until it does rev up smooth. Or put some low gears in that thing.
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 04-03-2007, 02:58 PM
NXS's Avatar
NXS NXS is offline
wind & fire = guides to power
 
Last photo:
Join Date: Nov 2004
Location: Oklahoma
Posts: 1,534
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
jet extensions with high gears and PG...on a carb that will barely open the secondaries, LOL! don't make him spend any more than he has to, k??

2-late, can you get me a good pic of the primary/secondary linkage off the driver side of the carb?
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 04-03-2007, 04:26 PM
Registered User
 
Last photo:
Join Date: Mar 2007
Location: MOORE OK.
Posts: 25
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by NXS
jet extensions with high gears and PG...on a carb that will barely open the secondaries, LOL! don't make him spend any more than he has to, k??

2-late, can you get me a good pic of the primary/secondary linkage off the driver side of the carb?

Yeah I'll do my best may take a day or two but I will try to take lots of pictures all the way around so everyone can see what I'm talking about.

It feels smooth the whole time I can just hear and feel the extra "boost" when the secondaries open up.

Thanks Guys talk to ya tomorrow Brian
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 07-28-2013, 08:38 PM
Registered User
 
Join Date: Jul 2013
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 2_Late_I_Won View Post
My secondary isn't opening on my old school Holley 625-600 cfm carb. I don't know jack about carbs. but I know the diaphragm is good. I took it off and put a vacuum test to it and it stayed down. So I know that is good. I started it up and didn't feel any vacuum where the diaphragm goes and didn't feel any vacuum. I put the air hose to it to blow out any thing that might be blocking it but nothing came out and it blew freely. Like I said I don't know that much about Carbs so any help would be greatly appreciated.
I'm having the same problem on my 600 cfm holley 4175. I'd like some ideas too.

Robin
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 07-28-2013, 11:55 PM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls/Suncrest, WA
Posts: 5,284
Wiki Edits: 9

Thanks: 113
Thanked 139 Times in 130 Posts
Just take the information in this thread and run with it...
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
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:
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
Vacuum advance hooked up directly to manifold....is this bad????? Steve-0321 Engine 69 03-10-2014 06:10 PM
vacuum advance help batman09 Engine 14 09-09-2004 10:42 PM
Vacuum advance from my carb to Dist.Do I need it? batman09 Engine 9 09-07-2004 10:22 PM
Vacuum hose routing diagram? 87442lover Engine 2 01-24-2004 09:08 AM
Mustang V-6 motorcraft 2150 carb. vacuum routing? 87442lover Engine 1 04-24-2003 11:51 AM


All times are GMT -6. The time now is 06:44 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.