Carb bog vs timing issues? - 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 12-30-2012, 11:42 AM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Carb bog vs timing issues?

Ok. It's a performance built .040 350 SBC, custom built Pro Systems 4150, MSD Pro billet and 6AL, Blaster 2 coil. Timing started at 35 degrees total at 3000. Pro Systems carb has a slight bog spot right before transition to secondaries. I advanced the timing to 38 degrees and it helped, but there is still a very slight bog. Now, I have a 1406 Edelbrock that I had laying around. And the car runs very strong at 35 degrees timing, crisp throttle response, and zero bog. This makes no sense to me, having spent near $700 for the Pro Systems. I haven't had a chance to talk to Patrick yet. Any thoughts or ideas? Thanks

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 12-30-2012, 11:51 AM
OneMoreTime's Avatar
Hotrodders.com moderator
 
Last wiki edit: Health and safety in the shop or garage
Last journal entry: Yard Dog pic
Last photo:
Join Date: Jul 2004
Location: Washington State
Age: 70
Posts: 7,506
Wiki Edits: 3

Thanks: 77
Thanked 173 Times in 161 Posts
Are our secondaries coming in just a skosh too soon..a bog can be a sign of over carbed,,too much carb for the engine to absorb at a particular rpm..

Sam
__________________
I have tried most all of it and now do what is known to work..
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 12-30-2012, 11:59 AM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by OneMoreTime View Post
Are our secondaries coming in just a skosh too soon..a bog can be a sign of over carbed,,too much carb for the engine to absorb at a particular rpm..

Sam
That would sure suck. This engine is a Year One Power Crate 350 with the Edlebrock E-Tech heads and Performer RPM intake. 9.7:1 compression, hyd roller. 413 hp 444 tq is what is on the dyno sheet. I submitted the entire engine specs from the paperwork I got with the engine, vehicle info, with exception of the rear gear which changed after the carb was built. I believe this carb is a 780 cfm.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 12-30-2012, 12:28 PM
OneMoreTime's Avatar
Hotrodders.com moderator
 
Last wiki edit: Health and safety in the shop or garage
Last journal entry: Yard Dog pic
Last photo:
Join Date: Jul 2004
Location: Washington State
Age: 70
Posts: 7,506
Wiki Edits: 3

Thanks: 77
Thanked 173 Times in 161 Posts
All that is needed I think is an adjustment in the timing of the secondaries,,A tuning issue..

Sam
__________________
I have tried most all of it and now do what is known to work..
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 12-30-2012, 01:00 PM
lg1969's Avatar
Google "Tunnel Ram 406"
 
Last photo:
Join Date: Oct 2007
Location: Bohemia, L.I.N.Y.
Age: 64
Posts: 1,059
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 18 Posts
What is the gear ratio on the rear end?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 12-30-2012, 02:32 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 8,639
Wiki Edits: 0

Thanks: 364
Thanked 858 Times in 820 Posts
Patrick is the guy to talk to about "his" carb.When I bought a carb from him I made 1 jet change,nothing else
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 12-30-2012, 03:42 PM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by vinniekq2 View Post
Patrick is the guy to talk to about "his" carb.When I bought a carb from him I made 1 jet change,nothing else
Yes. I'm not making any changes without talking to Patrick. I've read too many things good about him!!! I'm just trying to make her I'm doing things right.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 12-30-2012, 03:45 PM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by lg1969 View Post
What is the gear ratio on the rear end?
The worst possible gear ratio GM ever used...2.56:1. Patrick said this would not affect The carb he built. I don't know?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 12-30-2012, 04:58 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 8,639
Wiki Edits: 0

Thanks: 364
Thanked 858 Times in 820 Posts
gears have no affect on the carb,or road racers would use different carbs.I had 2.73,now I have a decent 3.50
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 12-30-2012, 07:14 PM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
I put a couple more degrees in for a total of 40, which I think is too much, but it still starts and dies fine, has no ping, and carb smoothed out quite a bit. So, now I'm wondering how much is too much timing? Maybe a combo of ignition and carb timing?
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 12-30-2012, 07:48 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,285
Wiki Edits: 0

Thanks: 6
Thanked 400 Times in 394 Posts
The DP carb will want a lot lot lot more rear gear ratio.

The distributor mechanical advance curve needs a lot of work.

Not enough inital at idle. You want 24-26deg at idle 34-36deg at max advance
a 10deg advance curve.

Your MSD distributor requires a sepecial $33 distributor advance stop bushing to achieve the required timing curve.

If you must use a 2.56 gear ratio get a vac sec carb. 600 to 750cfm vac sec holley or 600-750 edelbrock.

The double pumper will work if you get a agreessive rear gear and a high stall converter.

4.10's and a 10" 3500 stall if you want to go fast.

The bushing to set up the distributor timing curve is found here
http://www.4secondsflat.com/MSD%20Di...r%20Tuning.htm

Last edited by F-BIRD'88; 12-30-2012 at 08:01 PM.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 12-30-2012, 10:43 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: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by Hacksaw View Post
I put a couple more degrees in for a total of 40, which I think is too much, but it still starts and dies fine, has no ping, and carb smoothed out quite a bit. So, now I'm wondering how much is too much timing? Maybe a combo of ignition and carb timing?
When adding total timing helps, this is really telling you that you really need to be adding initial timing. Then limit the mechanical advance to keep the total timing from being too high.

The info here was originally on the GM HEI but the timing info applies universally.

Get the timing sorted out first then concentrate on the carb tuning. Readjust the idle mixture screws for highest vacuum/fastest idle rpm as you work on the timing but leave the other carb circuits alone until the timing is done.

You might need to add duration to the accelerator pump(s). This is done with either a pump cam change, or to a smaller shooter. More on tuning the Holley accelerator pump here.

Good luck.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 12-30-2012, 10:46 PM
Hacksaw's Avatar
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 40
Posts: 249
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by F-BIRD'88 View Post
The DP carb will want a lot lot lot more rear gear ratio.

The distributor mechanical advance curve needs a lot of work.

Not enough inital at idle. You want 24-26deg at idle 34-36deg at max advance
a 10deg advance curve.

Your MSD distributor requires a sepecial $33 distributor advance stop bushing to achieve the required timing curve.

If you must use a 2.56 gear ratio get a vac sec carb. 600 to 750cfm vac sec holley or 600-750 edelbrock.

The double pumper will work if you get a agreessive rear gear and a high stall converter.

4.10's and a 10" 3500 stall if you want to go fast.

The bushing to set up the distributor timing curve is found here
Tuning MSD Distributors
Thanks for the info. I do have a 600 elect choke Eddy sitting on the shelf as a back up carb. As for the gears, my car that burned up had 4.10 rear and I was hoping to use it. However, the fire burned the car and the rear axle didn't make it like I hoped. The gear in my 70 Chevelle that I bought is a 2.56:1 and I don't want to run this. It's just temporary until I can pick up another 12 bolt with around a 3.55:1-3.73:1 rear gear and Posi or Powertrax locker. My converter is a rebuilt glide converter and it's 2500 stall in a turbo 350. Should I run the Edelbrock 600 with some jetting and metering rods and tune the MSD until I get the proper rear gear? Sounds like I need to do that... Thanks again
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 12-31-2012, 01:24 AM
lg1969's Avatar
Google "Tunnel Ram 406"
 
Last photo:
Join Date: Oct 2007
Location: Bohemia, L.I.N.Y.
Age: 64
Posts: 1,059
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 18 Posts
Like F-bird 88 wrote, You need gears of you want to run a DP type carb. The 3:55- 373 gears will work. For now with the 2.56 gears use the eddy 600.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 12-31-2012, 05:17 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: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
If you just mat the gas from a stand still or at lower rpm, it may bog because of the gears.

But if the bog is there when the carb transitions into the secondaries- even w/the engine up into the powerband- then there's a problem or problems that need to be addressed.

The carb size needs to be verified, too.
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
Carb/timing issues Pops59 Engine 3 04-25-2011 09:34 PM
timing issues...please help theV8man Engine 15 06-15-2010 11:39 AM
HELP!!! Bad bog and 50 degrees total timing? Eagle1 Engine 38 06-29-2008 05:00 PM
Timing issues i think Wmurp4 Engine 4 08-13-2006 04:27 PM
timing issues Ferox Introduce Yourself 1 10-07-2004 08:04 PM


All times are GMT -6. The time now is 08:26 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.