Throttle pedal travel and vehicle performance

Discussion in 'General IH Tech' started by Rollercam, Oct 25, 2019.


  1. Rollercam

    Rollercam Farmall Cub

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    First off, I am still very much in the learning process as it comes to scouts and really as it comes to classic vehicles in general. I have never had to do much diagnostics and tinkering on an older vehicle and much of it is foreign to me. However, I would really like to learn how to do much of this stuff myself over the next few years.

    Anyway, on to my questions. My scout is the first scout I have ever ridden in. So, I have nothing to compare the performance to.

    I have a 1978 scout II with a 345, 4 inch skyjacker lift, 3.73 Dana 44s front and rear, a prestolite distributor with pertronix electronic ignition, Holley 7448 2300 carb. I have owned the scout since March of 2016, but I bet it hasn’t had 30 miles put on it until about late August 2019 when it was finally back together. Since September, I have put around 200 miles on it as I tackle little gremlins here and there.

    It starts fine, appears to idle well, stumbles a bit off-idle until it is warm, but then runs fairly smooth. However, when leaving a stoplight or starting from a standstill, I can put the pedal to the floor and the scout moves like a snail (i.e. a guy on bicycle could probably beat me to 25 miles an hour). I am not expecting a race car by any means, but I am just wondering if this is normal or not. Top end speed seems to be there. I can hit 65-70 (that is about as fast as I want to go right now on this suspension) and the engine feels smooth and steady.

    I guess I just feel like the engine is down on power. Maybe it is not, but I honestly just don’t know. I have had one guy listen to it and tell me it was missing badly and was way out of tune and yet I have had another guy (who I do trust) tell me it is idling well, but likely needs some tweaking. (I watched/listened to video on here of a scout running and it sounded decent to me, but you experts immediately said it was running on 7 cylinders).

    Where do I start? What do I assess first? I think it is running rich and has even “desieled” a few times when I turn it off. It has stalled on me twice at idle and I can smell raw fuel strongly under the hood and it acts flooded, yet, I am not sure if it died from not enough fuel or too much fuel because the under hood fuel filter seems nearly empty when this happens. I am not an experienced or skilled diagnostician when it comes to cars. I am sure all of this related to the sluggish performance, but again, I am not sure of where to start.

    I have read all about tuning carbs and I get lost quickly. It is overwhelming.

    Any advice and help would be appreciated. Just remember, talk to me like newbie in simple terms.



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    Last edited: Oct 25, 2019
  2. fredsterra

    fredsterra Y-Block King

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    One thing I have noticed on mine. 345 (392 sq bore intake) and 1406 Edelbrock carb with LoCar accelerator cable kit. I used a piece of thin wall 1x1 square tubing and drilled to match my
    accelerator pedal mount..
    Much improved overall performance and doesn't feel like i am always pushing the pedal to the floor.

    Quick tip to do this. Tack weld the bolts at the inside of the tube. and drill the floor out from 5/16" to 3/8'. Makes it much easier to mount and you and tighten the nuts from the outside without having someone hold the bolts!

    And this will push the pedal out almost equal to the brake pedal. But after you get used to the new location is no problem.
     
  3. RDC279

    RDC279 Farmall Cub

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    Pull the Spark plugs and see what they look like. If you find a wet one that cylinder is missing. If they are all black it is to rich. That is what I would start with.
     
  4. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    You did a thorough job of explaining your short comings in terms of vintage vehicle understanding and diagnosis. We've all had to start somewhere. The difficulty on our end is the ability to accurately assess and diagnose a vehicle condition through the ether of cybernets without benefit of being able to see, hear, touch, taste, feel and smell the way you can. The devil is always in the details. These vehicles aren't top fuel dragsters with the ability to stick you so firmly into the seat from the G-forces of a full throttle launch that you couldn't reach forward and grasp a $20 bill taped to the dashpad in front of you. But, a 345 engine in proper state of tune should absolutely be able to accelerate a Scout sized vehicle well enough to merge with traffic, up to and including the ability to chirp oversize rear tires on dry pavement. So, something is clearly not ok with your situation. The issue could be just one simple thing, or it could be a host of things conspiring to give you the launch force of grandpa's Rascal Mobility scooter on a weak battery charge.
    Very first thing to check is, can the throttle linkage be manipulated by hand at the carb to achieve wide open throttle? If not, why? Then, can the same state of manipulation be achieved via the foot pedal? This takes two people, one to watch the linkage and one to stomp pedal.
    Now, in all your verbose explanation of your own limitations, you omitted an obvious and critical piece of vehicle data...What friggin transmission is behind the engine? Remember when I said the devil was the in the details? He just shoved is pitch fork in your hind end right there.
     
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  5. Dana Strong

    Dana Strong Lives in an IH Dealership

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    Very good point. I'm guessing you have an auto transmission since you didn't mention a clutch or the gearbox, right? Here's another consideration if the vehicle isn't accelerating reasonably:
    If the engine is working properly and accelerating linearly wrt the throttle, then the power is being lost somewhere else beyond it.
    If the engine doesn't speed up when the throttle is depressed under load, the problem is likely (at least mostly) there.
     
  6. Rollercam

    Rollercam Farmall Cub

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    It is a 727 auto. I do not think it is shifting correctly to begin with and is essentially getting to third gear too soon. Of course, this puts the drivetrain at a mechanical disadvantage going into third gear so quickly at a low rate of speed and low rpm.

    However, even when I put it in first and shift it “manually”, I still have little get up and go. Even in first gear from a dead stop, I couldn’t get the tires to chirp unless I was running over bird. I bet I couldn’t even get the tires to spin on wet, oily pavement.



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  7. 1975IH200

    1975IH200 Y-Block King

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    Your TV linkage is mis-adjusted.
    Do you have a Service Manual ?
    Can you post photos of your carb and throttle / TV linkage ?
    Please.
     
    Last edited: Oct 26, 2019
  8. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    That's if it's even installed. Throttle Valve rod by the way. All too often they get omitted all together. Bad idea with the TF727 auto trans. So Mr. Rollercam, could you please provide us with some underhood pictures from several different angles?
     
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  9. INT77345

    INT77345 Farmall Cub

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    could it be the transmission is not getting 1st gear. as in its starting off in second or third ?
     
  10. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    Sure could if the shifter linkage cable is out of adjustment enough to physically prevent the linkage from moving far enough forward to engage breakaway 1st.
     
  11. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Yeah this is very important. There are a lot of variables. Where on the throttle arm the pivot ball is mounted (most critically, its "radius") and the throttle cable adjustment. With the pedal mashed to the floor the throttle should rotate nearly 90 degrees. If it's only opening "half way", say a 45-degree range of motion, the engine will feel pretty gutless no matter what other hot-roddy things have been done to improve performance.

    Best played with when there's no fuel in the float bowl though.
     
  12. Rollercam

    Rollercam Farmall Cub

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    Thanks for all of the thoughts and suggestions. I will do my best to get some good quality pictures up tomorrow. I have been doing fall festivals with the kids for most of the day today.

    I know this kind of stuff is difficult to diagnose from a distance, but having a starting point is nice.


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  13. RinTX

    RinTX High Wheeler

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    I was thinking the same possibility
     
  14. Rollercam

    Rollercam Farmall Cub

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    It goes through all of the gears, but I believe it does so too quickly. It shifts from 1st to 2nd around 10 miles an hour or less. It then almost immediately shifts from 2nd to 3rd. So, I am in 3rd around 15 or less miles an hour. Again, I know that this is potentially a big part of the issue, but correct me if I am wrong, but would the gear selection and shifting problem be removed from the equation if I put the transmission in first gear manually, take off in first, and then shift manually through 2nd and then into 3rd? Even when doing that, the scout still feels sluggish off the line. Again, no way I could even remotely chirp or spin the tires from a dead stop in first gear.




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  15. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Just read your first post. Not saying it's part of the main problem, I'm sure it's not, but is the choke engaged when you you're experiencing this stumbling? Just curious. The 7448's manual choke doesn't open with the throttle like the electric/automatic choke does. So if you try to drive it with the manual choke engaged all the way, or even half way, it'll run like dog poop.

    Also, did you check the other non-transmission performance related things?

    Hopefully the auto trans guys will have a good answer for you. I've never owned a vehicle with an auto, so I'm no help with that.
     
  16. Rollercam

    Rollercam Farmall Cub

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    Yes, I have checked the choke to make sure it was wide open. You are correct that if the choke closes even a bit after the truck is warmed up it will stall out. I will double check everything, but I don’t think that is the issue at this point.


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  17. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    The suspected throttle valve rod either being adjusted too short or missing altogether (actual status unknown there) is certainly AN issue, but not THEE subject issue, since you are still experiencing sluggish performance even in manual mode. So we need to scratch deeper, while still not forgetting to properly address the TV rod thingy too. It is vitally important for the performance and longevity of the trans.
    So what about my throttle linkage questions? You got full travel there or don't ya? Does the engine rap out to full throttle quickly and consistently when you work the throttle in Park? Have you checked your brakes? Is it possible that you have one or more dragging, placing and undue burden on the engine? Will the truck roll freely when out of gear?
     
  18. Rollercam

    Rollercam Farmall Cub

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    Here are some pictures. I hope these are pictures of what you guys were wanting to see regarding the linkage. The top picture is at WOT.

    [​IMG][​IMG][​IMG][​IMG][​IMG]


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  19. Rollercam

    Rollercam Farmall Cub

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    On a different note, is the PCV vacuum drawn from the manifold on this engine? Is the EGR drawn from the base of the carb? Can I block off the EGR port on the “UFO” looking piece? Can I then block off the vacuum port on the base of the carb?

    Also, what is this threaded port on the top of my valve cover? I thought it was part of the PCV system, but I am not sure

    [​IMG]

    It had a piece screwed into it with a hose running to the underside of my open filament air cleaner. Does this need to remain. I was wanting to just use a breather, but this may not be possible with that threaded piece on the valve cover. Most breathers I can find are push in.

    I was just trying to clean things up a bit and get rid of another under hood hose if it was not necessary.


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  20. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    The TV rod is there, so that's good. That part of the linkage looks ok. Based on your complaints of the trans upshifting too fast, the length of the rod may need to be adjusted longer by removing a circlip so that the clevis can be slipped off the pivot and turned counter-clockwise. That can wait though, until you've gotten this more pressing issue sorted out. The PCV vacuum can be sourced as it is or from the fitting at the rear of the carb. Either works the same. You can leave the EGR plugged. The item you removed from the Valve cover is a flame arrestor. It is filled with steel wool that can be cleaned with solvent and blown out with comp air. You need to have some way of drawing filtered air in. Either go back to how it was or install a motorcycle air breather that looks like a mini air filter. You can thread a short piece of brass or copper pipe into that hole and then hose clamp the MC style breather to that. But right now, unfiltered air and any crud that wants to fall down in the hole is being drawn in. Not good.
    So do the wheels roll when you take it out of gear on a slight slope and no brakes applied? What does the engine do when you pin the throttle while in Park? I'm just trying to rule simple shit out, but I need simple answers to simple questions. Feels like I've asked these questions more than once. That tends to upset me a little. Trying to remain patient. Please help me help you.
     

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