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Thread: Ready to start engine after carburetor rebuild...

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    Drag Racing Rookie HerboldRacing's Avatar
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    Default Ready to start engine after carburetor rebuild...

    I'm getting ready to start my engine for the first time since I've rebuilt my carburetor. I've got a couple of questions for you all...

    1) I got Autolite AR51 and AR52 spark plugs. I am going to try the AR51 (colder ones) first. What should I gap them to?

    2) I need to set the levels of several things... what's the best way to go about doing these...

    A) Fuel pressure level via regulator
    B) Float levels
    C) Four corner idle mixture screws / curb idle
    D) Accelerator pumps

    Now to set the fuel pressure the engine must be running, correct? That means I need to set B and C to good initial settings. I do have a vacuum gauge setup to set C but obviously need to do A and B first. What should the initial settings be? For idle mixture screws, all the way in? Or back it out some? Help.

    I'm going out to grab some lunch - hopefully when I return I'll have all the answers I need from you guys to do this engine restart successfully.


    Marvin Herbold

    1973 Plymouth Duster 340 Strip Car & 1965 Dodge Dart 270 w/ GT Interior Daily Driver
    Weblog - http://www.HerboldRacing.com
    Videos - http://www.YouTube.com/mherbold

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    2010 BAD POSTER OF THE YEAR Old_Demon's Avatar
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    I'd turn the mixture screws out about 1-1/2 turns, set fuel pressure at 5-7#. This is a Holley 4150, correct? Set the float levels at the bottom of the sight port / screw. Once it is started, set the mixture screws with the vacuum gauge connected to a full vacuum port for steadiest, deepest vacuum. That should get you started and ready to let the experts give you more / better advice.

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    Drag Racing Rookie HerboldRacing's Avatar
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    Quote Originally Posted by Old_Demon View Post
    set fuel pressure at 5-7#. This is a Holley 4150, correct?
    It is a 4150 HP yes - but how do you set the fuel pressure without starting the engine? If I just turn on the pump the gauge shoots past 12 and I panic and shut off the pump. I have the regulator screw almost all the way out. My buddy says its because the engine isn't running - right or wrong?

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    2010 BAD POSTER OF THE YEAR Old_Demon's Avatar
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    You should have a return line to the tank, and it should control the pressure without the engine running.

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    Director / Lifer speeddemon's Avatar
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    I agree. I had to plug one port, run one to the carb and one to the tank. One supply in.

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    Premium Member 73Duster500's Avatar
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    Looks like a Holley regulator. You need a wrench that fits the lock nut on the regulator. Use a allen wrench to unscrew the stud that screws into the regulator (you should have close to 0 fuel pressure when you turn the fuel pump on) screw the stud down until you get 7# of pressure. After you start getting pressure, look inside the venturi of the carb to make sure fuel is not coming out of the nozzles (boosters). If you have fuel bleeding out then tap on the needle and seat adjusters to see if it stops (they will stick sometimes on the initial filling) if they don't stop, then the floats are set too high, adjust them down and drain the fuel out of the bowls and start over. With a 10 AN line I would start with 7 or 8 #'s and you may go to 9#'s if the needle and seats will hold the pressure. You have to consider the weight of the fuel in the line and the acceleration of the car forward and the forces of that fuel weight moving back toward the pump. The pump had to overcome that weight.

    Looking Good.

    Last edited by 73Duster500; 11-09-2008 at 01:07 PM.
    One who snoozes looses!
    When the green light drops, the bull$hi!! stops! Or maybe the last yellow!

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    Premium Member 73Duster500's Avatar
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    On the enrichment screws, start with 1 1/4 to 1 1/2 turns out. Adjust to the highest vaccum or fastest idle.

    On plug gap, start with .035 and see if you can go to .040 and if that works, try .045. With your box and coil, I'd say that would be the limit. The closer the gap the easier it is to fire the plug under compression, but the wider the gap will start a bigger fire and quicker burn. It depends on the power the ignition has to jump the gap.
    Last edited by 73Duster500; 11-09-2008 at 01:14 PM.

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    Drag Racing Rookie HerboldRacing's Avatar
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    Quote Originally Posted by 73Duster500 View Post
    With a 10 AN line I would start with 7 or 8 #'s and you may go to 9#'s if the needle and seats will hold the pressure. You have to consider the weight of the fuel in the line and the acceleration of the car forward and the forces of that fuel weight back toward the pump. The pump had to overcome that weight.
    Thanks for the tips. We were able to get the issues resolved yesterday. We ran the motor and after figuring out why it wanted to run 2500 RPM (throttle cable needed adjustment) we checked the fuel pressure and it was holding steady at 8 pounds.

  9. #9
    Premium Member 73Duster500's Avatar
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    From the other site.

    Looking good.



    Originally Posted by 73Duster340
    Wow - thanks for mentioning that. Seems kind of obvious, but I would probably not have thought of making sure the battery voltage is the same across all the tests.



    If you go to this page on my web site you'll see all the details that I've been able to figure out about my car so far.

    http://www.herboldracing.com/the-duster

    The carb is a Holley 4150, model 8804 which is 830 CFM according to their web site. It has been modified for racing by Max Flow Racing. Here is a pix:



    You can view most of the pics I have taken of the car here:

    http://gallery.herbold-family.com/ma...2_itemId=10331

    The albums are sorted in chronological order so the last pages have the most recent pictures. You can see most of the work being done on the car in the "Day 1", "Day 2", and "Day 3" albums. They are the same pictures as on my blog, just without the commentary.

    Ok Thanks,

    On the fuel level adjustment:

    Make sure you have no open fires or sparks around when doing this!

    Do one bowl at a time.

    There are two brass plugs with a screwdriver slot on the slide of the bowls, take them out and fuel may run out. If alot of fuel runs out the float levels are too high, if fuel doesn't run out then you need to adjust them.

    The nettle and seat adjustment is under the two, looks like plastic negative terminal battery covers or rubber caps, I don't know what they are, Ha! Pull them off and there will be a flat locking screw and a hex nut together on the top of each bowl front and rear. You need a 5/8" boxed end wrench (well an open end will work also) and a pretty good size straight slot screwdriver. Hold the hex nut and use the screwdriver to loosen the hold down screw on top. Don't have the fuel pump running, fuel will leak out (spray) between the lock screw and the nettle and seat adjuster nut. You turn the hex adjuster clockwise to lower the level in the bowl and counterclockwise will bring the level higher in the bowl.

    Also, you could take the nettle and seats out and make sure there isn't any trash in them it doesn't take much to hang one open or stop one up. You can get the gaskets at O'reillys or Auto Zone or other auto parts.

    Tighten the lock screw down for the next step.

    Turn the fuel pump on and see how much fuel runs out of both holes in the side of the bowls. If alot of fuel runs out, then turn the pump off and pull the lower bowl screw on each bowl (right or left doesn't matter just the easiest to get to) and drain the fuel out of the bowls (I use a cut off coke can or beer can to catch the fuel) to get it lower than the sight holes in the bowls. Screw the hex nut down (clockwise) two turns (or untill the fuel is lower than the sight hole) and turn the pump on, turn the hex adjuster counterclockwise until you have fuel just weeping out of the sight hole (front, on the back bowl I usually run the level higher since the fuel runs to the back of the bowl on acceleration). Hold the hex nut and tighten the lock nut.

    Let the pump run and if the levels stay the same put the brass plugs back in and go race!

    If fuel fills the bowls up then you have something (trash) or the nettle is sticking (tap lightly on the lock screw, that usually works to free it up) in the nettle and seat.

    Now that I've got you confused, Ha! After you start and see what going on it pretty straight forward.

    Good luck!

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    Drag Racing Rookie HerboldRacing's Avatar
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    Quote Originally Posted by 73Duster500 View Post
    On the enrichment screws, start with 1 1/4 to 1 1/2 turns out. Adjust to the highest vaccum or fastest idle.

    On plug gap, start with 35 and see if you can go to .40 and if that works, try .45. With your box and coil, I'd say that would be the limit. The closer the gap the easier it is to fire the plug under compression, but the wider the gap will start a bigger fire and quicker burn. It depends on the power the ignition has to jump the gap.
    If it helps, I figured out that my old plugs (NGK GR4's) were gapped at .040. You probably meant to try going to 0.040 - 0.40 is nearly half an inch of gap! That's some spark!

    Since the plugs I have now are side gapped I think 0.035 makes sense.

    A couple of questions... I'm running the AR51's now. How do I know if it's right to change out to a hotter plug (I also have AR52's on hand)?

    Also - how do I tell if I can gap the plugs some more... does the car start backfiring at speed if the gap is too big?

  11. #11
    Premium Member 73Duster500's Avatar
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    Quote Originally Posted by HerboldRacing View Post
    Thanks for the tips. We were able to get the issues resolved yesterday. We ran the motor and after figuring out why it wanted to run 2500 RPM (throttle cable needed adjustment) we checked the fuel pressure and it was holding steady at 8 pounds.
    Well, glade to see you got it running well. Hope everything works good at the strip the next time out.

  12. #12
    Premium Member 73Duster500's Avatar
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    Quote Originally Posted by HerboldRacing View Post
    If it helps, I figured out that my old plugs (NGK GR4's) were gapped at .040. You probably meant to try going to 0.040 - 0.40 is nearly half an inch of gap! That's some spark!

    Since the plugs I have now are side gapped I think 0.035 makes sense.

    A couple of questions... I'm running the AR51's now. How do I know if it's right to change out to a hotter plug (I also have AR52's on hand)?

    Also - how do I tell if I can gap the plugs some more... does the car start backfiring at speed if the gap is too big?
    Yelp, that's what I meant. I was typing as fast as I could and wasn't looking at what I typed yet. I'm correcting now, Thanks for the correction.

    Us old guys usually talk like someone else knows what we're talking about, Ha! Ha! I was typing as fast as I could and wasn't watching what I was typing. I was saying 35, 40, 45, but I put the . in there also, it's a easier and a quicker way to say .035, .040 (thirty five thousandths). Also, on power valves I use 35, 45, 65, which is 3.5, 4.5, 5.5, ins. of vaccum, so sorry about that and thanks for the correction.

    On the plug gap, if the ignition doesn't have the power to jump the gap (if it's too wide), then there is not a spark, then no fire, then no burn in that cylinder, so it will flutter, backfire through the carb, pop, or miss.

    On the heat range, if it is too cool it'll usually load up and will pop under load. It's hard to explain that to you. It's experience and reading the heat pattern inside the plug, on the ground strap, porcelain, and electrode: Here's some links for you to study, if your going to stay in racing, then it's best to learn how to read the plugs.

    http://cochise.uia.net/pkelley2/sparkplugreading.html

    http://www.autolite.com/carcare/techSpecs.php

    http://www.dragstuff.com/techarticle...ead-plugs.html

    http://www.glowplugs.com/

    http://performanceunlimited.com/docu...degapping.html

    http://www.dragstuff.com/techarticle...ark-plugs.html

    http://www.sparkplugs.com/sparkplug4...g+Chart&mfid=0

    And yeah, I never been accused of being an English teacher, Ha! Ha!

    Hope this helps.
    Last edited by 73Duster500; 11-09-2008 at 01:57 PM.

  13. #13
    Premium Member 73Duster500's Avatar
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    Quote Originally Posted by 73Duster500 View Post
    Yelp, that's what I meant. I was typing as fast as I could and wasn't looking at what I typed yet. I'm correcting now, Thanks for the correction.

    Us old guys usually talk like someone else knows what we're talking about, Ha! Ha! I was typing as fast as I could and wasn't watching what I was typing. I was saying 35, 40, 45, but I put the . in there also, it's a easier and a quicker way to say .035, .040 (thirty five thousandths). Also, on power valves I use 35, 45, 65, which is 3.5, 4.5, 5.5, ins. of vaccum, so sorry about that and thanks for the correction.

    On the plug gap, if the ignition doesn't have the power to jump the gap (if it's too wide), then there is not a spark, then no fire, then no burn in that cylinder, so it will flutter, backfire through the carb, pop, or miss.

    On the heat range, if it is too cool it'll usually load up and will pop under load. It's hard to explain that to you. It's experience and reading the heat pattern inside the plug, on the ground strap, porcelain, and electrode: Here's some links for you to study, if your going to stay in racing, then it's best to learn how to read the plugs.

    http://cochise.uia.net/pkelley2/sparkplugreading.html

    http://www.autolite.com/carcare/techSpecs.php

    http://www.dragstuff.com/techarticle...ead-plugs.html

    http://www.glowplugs.com/

    http://performanceunlimited.com/docu...degapping.html

    http://www.dragstuff.com/techarticle...ark-plugs.html

    http://www.sparkplugs.com/sparkplug4...g+Chart&mfid=0

    And yeah, I never been accused of being an English teacher, Ha! Ha!

    Hope this helps.
    bttt

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