Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
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> holley carb backfires threw carb
User Name
Password
lost password?   |   register now

Thread: holley carb backfires threw carb Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

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.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
05-25-2011 10:03 AM
T-bucket23
Quote:
Originally Posted by 222222
hi, it backfires a idle when you check for throttle response ,which is the ****s. as for ignition i put a hevy duty petronicks coil in , im thicking of removing the points , and putting level 2 petronics in and i know the dis not 180 all though it would still run as long as you put number1 on the back side have done that before .
Ok lets get to basics, since you are running points, how did you set them. I would check them with a dwell meter to be sure they are in 28-32 * range to start with. Point when setup will work fine, they are not as trouble free as electronics but they were use for many years.
My gut feeling is your accelerator pump arm is possibly not adjusted correctly or the squirter is to small. There are several articles on this adjustment. If it is adjusted too loose it could cause the lean pop and can potentially take out the power valve. There should be no play at idle and at WOT you should be able to move it about .015 more, this will avoid bending parts. A blown PV can cause sooty plugs.
Also have you checked the Pertronix instructions to see if it will run on the resistor wire of if it requires full battery voltage. If it requires full voltage and you are running it through the old resistor wire this will cause all sorts of issues.
05-24-2011 08:47 PM
222222
dis

lg i do have ahi ill try thatand get back to you on howit work ,just getting ready togo to a swap meet in langly bc ihave alot of stuff trying to get rid of. by the way anybody interesed i setw camelback w r gm replacement intake for lt 1 or 302, trypower complete w nyear to match carbs redone ready to go, 2 sets of aluminum heads 851 (corvette 435hp) set cast iron heads hp every aluminum intake for big block single double open plume ZL1 heads intake valve covers 3247 carb , have 4 3247 carbs 67 66 1 still has factory stamson bowls, dz 780 carb , also complete cross ram ready to bolt and go ,nos bumberretts for 69 z 1 ZL1 motor for sale number 306 of 427 made . 55 chevy pick up in stages to finish w boxed frame c 4 corvette suspension no, no ,rust garented. lots more but i dont want to bore you cars for sale 1 z28,1 70 chevelle ss ,1 65 corvette , 166, corvette bought house in scottsdale
05-24-2011 09:32 AM
lg1969 You are still running points? Get rid of it. The bearing in the distributor may be worn. To have sooty plugs and backfire I think you may have a very weak ignition system.
05-24-2011 07:53 AM
222222
back fire

hi, it backfires a idle when you check for throttle response ,which is the ****s. as for ignition i put a hevy duty petronicks coil in , im thicking of removing the points , and putting level 2 petronics in and i know the dis not 180 all though it would still run as long as you put number1 on the back side have done that before .
05-24-2011 06:25 AM
T-bucket23
Quote:
Originally Posted by 222222
hi ,yea ithought of that so changed itto 6.5 ,how many times can you back fire a valve before you have to change it .Ichecked the valve i guess suck on the valveony and lisen for air to pass is this right
When exactly does it backfire, when accelerating, at idle at cruise.
A blown power valve will not make it backfire, it can however be damaged by a backfire. Usually backfire through the carburetor is caused by a lean condition, firing order or timing issue. There are other potential causes like a sticky valves or electronic ignition issues but they are not as common.
05-23-2011 04:36 PM
222222
Quote:
Originally Posted by 67-4-fun
also look for a blowed out power valve
hi ,yea ithought of that so changed itto 6.5 ,how many times can you back fire a valve before you have to change it .Ichecked the valve i guess suck on the valveony and lisen for air to pass is this right
05-23-2011 04:35 PM
454C10 put the light on 20 then set the timing marks at 0.
05-23-2011 04:25 PM
222222
z28

so on my balancer that would be 14d my timing light is just a light with the degrees on it and i just put it on o and look @ my balancer and put it to my marks
05-23-2011 04:14 PM
454C10 run more timing. try 20 initial.
05-23-2011 02:56 PM
67-4-fun also look for a blowed out power valve
05-23-2011 02:17 PM
222222
back fireing through the carb

hi, been reading comments about backfireing through carb, i still have the trouble, checked the plugs ,wires, vac, valves, distributor,timming when i put timming a 12d it worked better, but still back fired . the carb was a 780 went to a 750 worked better but still.the dis is good got to be some body who has a solution to the problem, 69 302 z28, oh no vac leeks checked intake also
02-13-2008 03:38 PM
talleyho set it at 20 btdc an a little twirp in the tire.power braked it and SCRRRRRRR.smoke everywhere and bits of tire flyin!maybe my gearing is just real high.anyways thank YOU ALL BIG KISSES MUAHH!
02-08-2008 09:20 PM
T-bucket23
Quote:
Originally Posted by duntovman
oooh yes i did when and engine is 180 only means that number one and number 6 are crosswired by the dist. or mabye your not wise enough to know that .they will still fire and run if the timing is advanced far enough .
Oh I get it, so you fire the plug while the exhaust valve is open. How exactly does the uncompressed charge burn and force the piston down.
As I said before it is impossible.
Please dont give out bad information as many people rely on this to get there vehicles fixed.
Thanks
Chet
02-08-2008 03:29 PM
454C10 check out this ignition timing write up.

http://www.vetteclub.org/technicalti...101Article.pdf

he is saying 10 initial, 30-35 with mechanical added in, and 45-50 total with the vacuum advance. Of course this is most likely with a stock cam. I had better mpg with a little over 50 degrees and have read a few other timing papers stating the same thing. A bigger cam than stock, needs more timing to run right so that may be the reason why I found the need for a little more timing.
02-08-2008 03:02 PM
454C10 no, with vacuum advance connected it should be over 50 degrees when revving the engine in park at 3000 rpm.

yes, 38 degrees total of just mechanical advance (not including vacuum advance)

Best mpg for an old school sbc is 50 to 53 degrees while driving down the highway with no load (high vacuum). The extra timing from the vacuum advance drops out quickly when the throttle is opened for passing activities.
This thread has more than 15 replies. Click here to review the whole thread.

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


All times are GMT -6. The time now is 08:18 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.