Tuning a new Holley 2300 on a 304 - Nozzle size?

Discussion in 'General IH Tech' started by DouglasB, Jan 11, 2019.


  1. DouglasB

    DouglasB Farmall Cub

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    Trying to fine tune the Holley 2300 (7448) I recently installed on a 304 in my 76 Scout II. I am very green on carbs and how to get the most out of them, but I have looked at a dozen different How-To videos from Holley and various other websites and still can't find the sweet spot to make Godzilla really rumble and roll like the beast I know she can be. I originally plugged the carb in as a replacement for a 2210 that died on me, and with the new setup, she idles and runs like a champ until I stomp on the gas and then she bogs and grumbles pretty loudly and I lose power unless I ease off the gas and slowly get up to speed.

    So I'm assuming, based on what I have read so far, that I'm looking at a poorly adjusted accelerator pump. I'm the one adjusting it, so I know for fact that an inexperienced dolt is the one that adjusted it before and is also adjusting it now so that makes sense. I've started by buying a set of feeler gauges and think I am pretty close to having the gap down to the .015 at wide open throttle like Holley suggests but she still bogs under hard acceleration so I am trying to figure out if I have the right squirter on there or what else I need to do to get Godzilla up to speed. The nozzle that came with the carb is stamped 31.

    I haven't adjusted anything else outside of the accelerator pump and the idle mix screws, so the stock jets are still on there (61) and I haven't tinkered with the float level other than making sure it's right at the bottom of the sight hole (rocking the truck lightly causes it to spill out).

    If I could get a little info on what is working for people with my same setup, that may point me in the right direction. Thanks for the help.

    Edit: adding the info that this is a 7448
     
    Last edited: Jan 11, 2019
  2. Bussy

    Bussy High Wheeler

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    I'm by no means an expert and I'm sure others will chime in with better info but I was able to get my 2300 running great on my 304. If it was new out of the box, it should be tuned almost perfectly but since you didn't mention that I'm thinking it has been "tuned" a couple times. I had the same issues with bogging down on acceleration and was told it was the air/fuel mixture causing the problem. Ended up turning idle mixture screws all the way in and back out 1 1/4 turns, hooked up my vacuum gauge, and began turning each side out 1/8 turn at a time until I got the idle as high as it would go before going back down. That got my vacuum at 21 and it stayed. I then checked timing and ended up at 8* btdc and the Scout ran like a top. If you have the 7448 - manual choke, it has a high idle screw that I also tuned so that cold starts would idle at around 1800 rpm. Once my temp gauge started to move, I would push the choke back in and it idled at 725 and purred like a kitten. I didn't mess with anything else on the carb other than the idle mixture screws, the main idle screw and the high idle screw. Hope this helps.
     
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  3. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    The first thing you need to do it to post the List number of that unit so people here know what you're working with. There were many 2300's differing in lots of small and large details.
    Secondly, if it runs well at all speeds, once you get there, and under all conditions of load, it may just need a different (nylon) cam, or a different hole for the accelerator pump rod. I think that is described in the Service Manual, or possibly also online. I don't currently remember it well and don't have the time now to research it. Good luck
     
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  4. DouglasB

    DouglasB Farmall Cub

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    Good point. It’s a Holley 7448 with a manual choke. I bought it second hand, though the guy who sold it to me said he had planned to use it in a vehicle but decided to go a different way and never put it into use. That may be an exaggeration of the truth on his part, but the carb looked/smelled new when I opened the box (no gasoline smell or other obvious sign of use) so I took him at his word. Thanks for the help.
     
  5. DouglasB

    DouglasB Farmall Cub

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    Great info and a good list of things to try! It’s possible it’s been tinkered with before I got it, though the guy I bought it from claims he never used it. I’m not so sure about that statement now.
     
  6. MJlogan88

    MJlogan88 Farmall Cub

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    I would work with what you currently have to see which direction you need to go. If the accel pump cam is in the #1 position try switching it to the #2 position (or vice versa) and take it for a drive.

    If that helps the bog, then you know it wants a more aggressive and/or shorter duration pump shot. If it gets worse then it either wants a less aggressive and/or longer duration pump shot.

    Squirter size can play into this as well, smaller squirter will tame the shot and give it a longer duration. But if you don't have any parts on hand to swap just try and change the cam position and see how it reacts.

    On my Travelall just switching from the #1 to the #2 position made a world of difference on the light tip in stumble it had.
     
  7. MJlogan88

    MJlogan88 Farmall Cub

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    Also, since you have a manual choke, try choking it off just a little when you drive it. If that helps or cures the stumble then you know you are too lean
     
  8. Bill Bennett

    Bill Bennett High Wheeler

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    Chandler, AZ. The elevation looks to be just over 1000 ft. Can't do much 'down' driving from that location. Would be considered close enough to 'sea level' operation. The #61 main jets would be the usual size main jets for that carb for 'sea level' to 2000 ft elevation. If your choice for fuel has the 10% Ethanol added, you could try going to the #62 main jets. As has been mentioned, the white accelerator cam with the accelerator pump linkage in the #2 hole seems to work best for my location at +80 ft above sea level in Los Angeles. The #31 accelerator pump squirter jet seems to work well here. Do you get a strong fuel shot through the #31 accelerator pump jets when the throttle is opened quickly? Are you measuring the accelerator clearance where the accelerator pump lever activates the pump or where the white accelerator pump 'cam' slides under the accelerator pump linkage? It should be measured at the pump lever. Is it possible the 'return spring' inside the accelerator pump is missing?
     
  9. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    Check to make sure that your throttle pedal is able to fully open the throttle linkage when fully depressed. This will take a helper. You be the watcher of the throttle linkage at the carb while a helper stomps the throttle to the floor. Then, while held in that position, you grab the linkage at the carb by hand to see if you can open it beyond what the foot application could do. Get a vacuum gauge connected to intake manifold vacuum while the engine is at hot curb idle to give us a number we can sink our teeth into.
     
  10. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    I forget the jet size but I remember cam selection was important and then before I was done I had changed the squirters, too.

    But the point about the throttle is a good one.

    I used to set my linkage at idle for just a touch of play/slop.

    Now I put the throttle at Wide Open Throttle and put the pedal to the floor and set the linkage.

    If it doesn't come back to idle your pedal needs replaced.

    It should have enough slop that on a manual the clutch relay rod won't cause the idle to shift when it rubs the accelerator pedal.

    It also means no more broken accelerator cables when you smash the gas to WOT.

    (Ok, so maybe I have had more trouble with that than most people. :). )

    Sent from my Moto Z (2) using Tapatalk
     
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  11. Rjones

    Rjones Farmall Cub

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    I'm going through the same thing now with a 4412 on a 345. I've gotten it pretty close. I bought an accelerator pump cam kit and just went through them one at a time, trying all the holes, until I found the best one. I initially put in a smaller squirter, thinking it made sense to have a little smaller shot of fuel off idle. That was wrong in my case, I put the stock one back in, and may go up one from there. Also power valve comes into play off idle too. Sounds like you're on the right track. Drive it some and check the plugs for jet size.
     
  12. DouglasB

    DouglasB Farmall Cub

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    I didn't even think about the throttle pedal not pulling open the throttle all the way when fully depressed and so it was the first thing I checked when I got home from work and fortunately/unfortunately it does pull open the throttle fully when it's all the way down. A vacuum gauge is one more thing I've already added to my list, because I don't own one yet. I did swap out the cam (It had a red one in there. I installed the white one.) and fired her up last night to head to the store and test it out when I caught the eye of my wife... so I powered it back down. She didn't say a thing, just gave me that look. The one that says I'd be much better off going back inside than to the parts store so I can't give you a reading yet. When I do I'll report back.
     
  13. DouglasB

    DouglasB Farmall Cub

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    Sounds like, ideally, our settings shouldn't be much different. I'll likely stick with the 61 jets and the 31 squirter for now based on your experience, but I did remove the existing red cam and plugged in the white, though I haven't had a chance to test it yet (for the sake of wifely harmony) but will and report back. The measurement for the clearance is at the pump lever, but I'll double check my measurement and see if it can be tweaked a bit. I suppose it's possible the "return spring" is missing, but I haven't checked that specifically.
     
  14. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    With the engine off and looking down the throat, do you see a constant jet of fuel lasting a few seconds or more when you open the accelerator linkage and if you quickly release and reapply it, do you get the same effect? If so, the accelerator pump is probably fine.
     
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  15. Erik VanRenselaar

    Erik VanRenselaar Y-Block King

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    The Holley spec for the wide-open throttle accel pump lever gap is to ensure the pump diaphragm doesn't bottom out at WOT. At normal idle throttle position, the end of the spring-loaded adjustment bolt should just barely touch then end of the pump level. That is important for instant accel pump response and a proper pump stroke. The Holley accel pump cam kit (#20-12), which consists of eight color-coded pump cams, is usually needed to adjust the pump shot for the proper fuel shot volume and duration. For info, the #7448 on my Scout II's 304 works best with a blue pump cam in the #2 screw position.
     
  16. Bill Bennett

    Bill Bennett High Wheeler

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    How much larger 'shot' does the Blue cam provide over the stock White cam with both cams in the #2 position?
     
  17. DouglasB

    DouglasB Farmall Cub

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    Had a chance to try doing this today and can say it's a solid shot of fuel both on the initial and the quick subsequent application of the throttle so by that metric, the accelerator pump seems to be in working order.
     
    Last edited: Jan 13, 2019 at 6:28 PM
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  18. DouglasB

    DouglasB Farmall Cub

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    Nice! I will make a note to myself to try the blue cam if the white one I just switched to doesn't seem to do it. I got the 8 cam kit and so swapping them out will be pretty simple.
     

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