Holley off idle backfire problem - 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> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 05-18-2013, 07:57 AM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
Hello bogie I don't have a metering plate on the rear because I got the secondary metering block to replace it. The carb is brand new and the metering blocks are nice and good as I checked them with a straight edge. I am also using vacuum advance timing on full manifold ( about 30 at idle with vacuum advance). Holley said that was my problem and I tried it on ported and it did not make any difference. I like full manifold as it give better throttle response and nicer idle quality. I am running 16-18 initial and advancing it more makes no difference in how it runs. Cruising timing is around 50 degrees total and total timing is around 36 all in by 3000 rpm give or take a few. Using a lighter spring makes it come in too quick and one light and medium is still a little to quick and does not make much of a difference. I am using two medium springs and starts to advance at 1200 rpm. As of right now it has instant throttle response and just blipping the throttle will throw you back in the seat. If it was not for the backfire at times it's good to go.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 05-18-2013, 12:26 PM
T-bucket23's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Engine basic condition - how to check Last photo:
Join Date: Aug 2005
Location: Massachusetts
Age: 57
Posts: 5,149
Wiki Edits: 26

Thanks: 7
Thanked 109 Times in 94 Posts
Dont make the mistake of thinking you only have 1 issue. You could have a couple things hurting you. It seem you got the idle and cruise surge cleared up and these are both usually mixture related issues. The backfire on hard acceleration is almost always pump shot related and there is not 1 correct answer. I have fixed a lot of these type issues and it is usually a combination of the correct cam and shooter size.
When you changed the pump cam did you check the linkage to make sure there was no play in it. Most people miss this and it is important. Also when you go over a certain size shooter, the exact size escapes me at this time, you need to also change the shooter screw to the hollow one to allow more fuel.
The proper adjustment of the pump arm is critical. There should be no play between the arm and cam at idle and you need to be sure that at wot there is still some extra room for movement (.015)so you dont bend anything.

I have found the key to carb tuning is to change 1 thing at a time and on things like the pump arm adjustment. Mark it at base line and count turns when adjusting, this will allow you to go back to scratch if need be
__________________
Artificial Intelligence is no match for Natural Stupidity



Chet
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 05-18-2013, 04:26 PM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
Hello Tbucket I am only working on the accelerator pump circuit at this time as that's the last thing to get right. I have made notes of everything I have done with carb from stock setting. Trust me I know my way around a holley more then just a beginner. I have done hours and hours of research before I even do anything and one way is not always the right way as every engine is different. I have use the .035 shooter and it did not really help so I changed over the pump cam to a bigger shot with shorter duration and it still did not make a difference. I bought a holley shooter kit which has all the pump cams and shooter sizes so I have everything I need to tune.

Seems these holley's are known for having this issue on there vacuum secondary carbs mostly the 600 and street avenger series. And yes I always reset the pump arm when changing cams out. So far it seems to make no different if the orange cam is in the 1 or 2 position and the blue cam in the no 2 position. With the orange cam and the .035 shooter man it gets plenty of shot and its not a rich bog as it backfires.

I have had rich bogs before with other holley's and they never backfired just got a little sluggish and picked up. The backfire is not as bad as it once was and does not happen all the time just at certain times when you punch it quick.

From what I read when you go over the .040 size you have to use the hollow screw and the 50cc pump but man that is overkill and I should never have to use that.
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 05-18-2013, 04:51 PM
B.A.M.F
 
Last photo:
Join Date: Feb 2010
Location: New York
Age: 27
Posts: 252
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
just my 2 cents on this one, iv had this problem before. you will need a GOOD timing light, and a vacuum gauge. if its a holley double pumper put 72 primary jets in it and 73 in the rear for a higher rated cam. set your squirter cam back to the original position. the vacuum gauge needs to be hooked up to the intake manifold. fire up the engine let it idle till warm. start with your idle setting, typicall you want an idle of 500-800 rpms. than after you set the idle you want to set the idle fuel mixture. on either the left or right side of the metering blocks front and rear is a small recessed screw, start on the front metering block turn the screw in clockwise (right) until you hear the engine "stumble" then back out the screw until the idles smoothes out, repeat for the rear metering block. now your carb is set...for now.. with these setting you should be able to run the car and get rid of the popping and stalling if it persists you have to considerimproper valve adjustment, improper timing etc there are many many factors that will affect the way an engine runs
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 05-19-2013, 11:32 AM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
Hello this is not a double pumper but a vacuum secondary carb. I know its carb related cause everything else has been checked and set before any carb tuning was done.

I had a 600 quick fuel street slayer carb on this last year and it ran fine out of the box but the idle fuel curve was to rich and could only go 1/2 a turn on the idle mixture screws or it would be pig rich but unfortunately I had an accident with the primary metering block but quick fuel does not sell separate cast metering blocks so its on the side for now but you could smash the throttle or do what ever you wanted to and it ran fine with no backfire off idle just with this holley.

The quick fuel carb had also smaller air bleeds so it had a richer fuel curve and the idle feed restrictions were a massive .035 front and .040 in rear as to where my holley setup was .027 front and .031 rear and that makes a big difference on idle transition af ratio. I opened the holley ifr's on the front to .030 and left the rear block alone and it now has a way better idle and no more surging during low rpm driving but I don't want to go any bigger and mess up my block.

I have done hours and hours on the holley 600 vacuum secondary carb which shares the same metering blocks as the holley 670 street avenger and do a google search and you will see how many people have this problem with all sorts of engine combos and cam sizes. This is what I am stuck with so need to make it work.
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 05-19-2013, 07:32 PM
B.A.M.F
 
Last photo:
Join Date: Feb 2010
Location: New York
Age: 27
Posts: 252
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
gotcha , so ll that being said wouldnt it be worth it to sell the carbs you have and spend the money one time on a GOOD carb instead of wasting tons of man hours trying to fix the one you have, as they say you can polish a turd but its still a turd.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 05-20-2013, 08:57 AM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
I got a new set of metering blocks coming in the mail for my quick fuel carb. Its not the original blocks as they are not for sale by quick fuel but they are for vacuum secondary carbs 600-750 so I am going to try a few more things and if it does not work then I am putting it on and see how it goes. I have compared both carbs and the quick fuel carb tower has smaller air bleeds by a small number so it had not only a richer fuel curve but richer air bleed size as well. The idle was way richer then my holley but I never had any backfire problems or stumbles as it ran like a charm. Metering block got stuck and no matter how much I tapped it with a rubber mallet I could not get it off. So from user error I tried a small screwdriver to pry it off and well I ended up breaking the timed port tube off and gouged the block across the sealing line I learned that's not a good way to do this. Lesson learned. I can't make my holley air bleeds any difference as they are not screw in type but the quick fuel carb has all that stuff.
Eric
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 05-20-2013, 09:07 AM
lg1969's Avatar
Google "Tunnel Ram 406"
 
Last photo:
Join Date: Oct 2007
Location: Bohemia, L.I.N.Y.
Age: 64
Posts: 1,054
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 18 Posts
Replace the primary metering block with a known one that works. 90% of the problem is the idle circuit is calibrated for emission at a cost of having off idle stumble and surge and sometime backfire.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 05-20-2013, 09:15 AM
gearheadslife's Avatar
MentalMuffinMan
 
Last photo:
Join Date: Nov 2012
Posts: 2,157
Wiki Edits: 0

Thanks: 94
Thanked 268 Times in 250 Posts
Quote:
Originally Posted by toddalin View Post
I run a 600 dp so it is not exactly the same. The carb's PO could not get it to work right. It had a stumble and would backfire, much like you allude to.

The PO had changed the stock shooter (which is a 25) to a 31 chasing the problem thinking, as most people do, that it was a "lean bog."

Dyno testing showed the opposite and it was a rich bog cause by too large of a pump shot. I believe this lets fuel puddle in the manifold that eventually backfires. I changed the squirters to 21 and that cured most of the problem. I then moved the pink cam from position 1 to 2 on the secondaries to get a smaller pump shot and that seems to have done the trick.

BTW CarCraft had a similar problem with their 600 dps and filled the 25s with epoxy and drilled them out to 22s before realizing that Holley sold 21s. It fixed their bog too.

not a holley guru, but didn't holley tech line basicly say the same thing?
and you brushed it off..
have you even tried a smaller shooter than the first one??
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 05-20-2013, 10:57 AM
Registered User
 
Last photo:
Join Date: Apr 2012
Posts: 132
Wiki Edits: 0

Thanks: 1
Thanked 9 Times in 9 Posts
Quote:
Originally Posted by gearheadslife View Post
not a holley guru, but didn't holley tech line basicly say the same thing?
and you brushed it off..
have you even tried a smaller shooter than the first one??
I've never discussed this with Holley Tech line or even saw their tech line. In fact most everything I see on the Holleys, from Holley and others, says to use a larger squirter in the event of a bog because they figure it is typically a lean bog.

It is when I saw the article in CarCraft that I considered the smaller shooters for a rich bog and the dyno pulls confirmed this.

You must have me confused with someone else.

The 21 is the smallest made by Holley.
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 05-21-2013, 08:48 AM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
I am going to try a smaller shooter but I have not had a chance yet to do so. The metering block is fine as it was from my old carb and it did not have all these problems like I am having now. All I did was swap out the towers and they were both holley 600 vacuum secondary's I just kept the 80457 tower cause it has the electric choke and a new base plate. I sold my old one on ebay but for some reason it did not have all these problems like this one is. I will post back what I find out by going to a smaller shooter.
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 05-21-2013, 08:56 AM
lg1969's Avatar
Google "Tunnel Ram 406"
 
Last photo:
Join Date: Oct 2007
Location: Bohemia, L.I.N.Y.
Age: 64
Posts: 1,054
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 18 Posts
Did you make sure you install the right gasket on the throttle plate and one between metering block and carb body? You may have a blocked passage.
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 05-21-2013, 01:43 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: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by eric32 View Post
I am going to try a smaller shooter but I have not had a chance yet to do so.
Are you now thinking the hesitation is a too-rich condition? I think you know a smaller shooter will extend the shot duration, but won't help a too-lean at the hit of the throttle accelerator pump condition.

Too rich of an accelerator pump shot can sometimes be confirmed by having someone follow your vehicle to watch the exhaust at the hit of the throttle. Black smoke = too rich.
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 05-21-2013, 05:13 PM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
gearsheadlife said he had something like this before and to try a smaller shooter. It won't hurt anything as I can always go back to where I was. I am going to test it tomorrow when I have some time as I had stuff to do today. I went cruising up a small hill and the funniest thing happened I gave it a small easy shot of gas to go up the hill from a stand still and it backfired twice really fast and not the normal once like it usually does. Yes the gaskets are the correct ones as the only thing I changed out on the carb was the front and rear metering blocks and they have the correct gaskets. Base plates is whatever holley has on it and I have not had the bottom apart as it was all new. I have no vacuum leaks as the idle is nice and steady on the vacuum gauge and goes back and forth between 15-16 inches. I am about ready to take this thing and throw it over a fence. The previous carb was the exact same thing and it did not do this at all and I took the metering block from it and put it on this holley which is the same thing except it came with electric choke. This is driving me nuts as it seems its getting plenty of a pump shot and changing things really does not make any difference. Something is going on with the carb as previous one it did not do this backfire at all just when I put this one on I will post tomorrow of what it does changing the shooter does.
Reply With Quote Quick reply to this message
  #30 (permalink)  
Old 05-22-2013, 01:19 PM
Registered User
 
Last photo:
Join Date: May 2008
Location: ohio
Posts: 1,406
Wiki Edits: 0

Thanks: 27
Thanked 41 Times in 38 Posts
All right guys here is the final results. I went down to a .028 shooter and the backfire still happened so in order to rule things out as it no being enough I put a .037 shooter on and that still did not get rid of the backfire and it hurt throttle response as at that point it was getting too much shot.

Best results for throttle response is with the stock .031 shooter so that is what I put back on and it give a nice clean crisp throttle response. Now the backfire problem does not happen all the time just at certain times. I reved the throttle once and just barely touching the throttle it backfired in park so I don't know what else to check on this damn thing.

Shooter size is not the issue as nothing gets rid of it and I opened up my idle feed restriction on the primary block to .033 from .031. This is a older block and checking the new one I just got its .031 already so I did not make too much of a change to it and now hooking up my vacuum gauge my idle is a lot more stable since its not so lean and the idle mixture screws are at 1 1/8 turn out and I also checked my float level and they are at the half way point on the glass window so they are good.

Everything had checked out ok and I don't know what else to do with the dang thing. It runs very strong on 2000 and up and also cruises very good and idles good just the occasional backfire if you hit it really fast and hard. Even unhooked the pcv valve to hook up my vacuum gauge and did not make any difference so I know it is not an issue.

One interesting thing I tried is I put a towel over top the primary and the engine died so could that mean anything? Doing it by hand does not do anything.

Its had so many backfires it looks like a cannon that was shot. I checked the power valve and its still good.

Holley was no help and looking through all my books I did all the checking and tricks and don't know what else to do. Might take it totally apart and pull the base plate off and check for any casting flaws as I read someone had a off idle stumble but no backfire problem and he finally took his carb apart and he had casting flash in the throttle plate keeping the mixture almost blocked off but still run. O well back to the drawing board. Thanks folks for input.
Eric
Reply With Quote Quick reply to this message

Recent Hotrodding Basics 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 Idle adjustment problem/question pszikszai Engine 3 07-13-2010 06:56 AM
backfire while idle hoggvillemechanx Engine 1 11-09-2009 05:45 AM
Erratic Idle and Backfire Will H Engine 5 02-12-2009 05:08 AM
Backfire from only one side at idle jspencer916 Engine 8 02-14-2005 08:10 PM
Backfire at idle NOlowrider Engine 8 12-18-2004 07:44 AM


All times are GMT -6. The time now is 01:57 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.