Slight 'Surging' During Acceleration

hudsonguy
hudsonguy Senior Contributor
edited November -1 in HUDSON
My '49 newly rebuilt 262 is pretty well dialed in, except for one thing.



During normal acceleration, it's not really as smooth as I think it should be, and kind of surges (two forward/one back type of thing). I don't think it's too lean, by the looks of the spark plugs. I've got the richest combination of metering rods/jets in my WDO carburetor. I've got new, modern fuel delivery components all around. It's got a very strong spark from an electronic ignition. There are no vacuum or exhaust leaks as far as I can tell. I've presently got the timing set one mark advanced.



While chasing this issue this summer, I've slowly improved the running by basically enriching the air/fuel mixture by opening up the jets and/or decreasing the metering rod size. I guess the next thing to try is a slightly larger jet again. I've increased the stock .084 ID to about .086, which showed some improvement. I also raised the float level from 3/16" to 1/8" (1/16" change)



I'm in Wisconsin, and the fuel is 10% Ethanol.



Any ideas? As you can see, I'm kind of focused in on the fuel system, but don't want to overlook some other contributor.



Thanks for the help.

Doug

Comments

  • russmaas
    russmaas Senior Contributor
    Did you install a larger cam?
  • russmaas
    russmaas Senior Contributor
    Also I assume you rebuilt the carb. We soak carbs for 24 hours and glass blead clean through passages then flush with carb cleaner. Do you have WA1's or a a 2 barrel? Seems to me that the accelarator pump may not be totally open from debris. Bring the RPM's up and slam your hand over the top of the carb, this will draw the gas forward and may unplug it. You may need to adjust the accelarator pump also.
  • hudsonguy
    hudsonguy Senior Contributor
    russmaas wrote:
    Also I assume you rebuilt the carb. We soak carbs for 24 hours and glass blead clean through passages then flush with carb cleaner. Do you have WA1's or a a 2 barrel? Seems to me that the accelarator pump may not be totally open from debris. Bring the RPM's up and slam your hand over the top of the carb, this will draw the gas forward and may unplug it. You may need to adjust the accelarator pump also.



    I've got the original stock cam installed.



    I've got a carefully rebuilt 2 barrel WDO carb, that is absolutely clean inside and out, and the accelerator pump is adjusted to the book spec. of .281 (9/32").
  • junkcarfann
    junkcarfann Expert Adviser
    If all else fails, go to a shop that has an exhaust gas analyzer. That will tell you if you are lean or not. Modern gasoline does not provide an accurate spark plug reading as it somewhat did in the early days. I do not know how ethanol affects plug readings, but the exhaust gas analyzer will nail it.
  • [Deleted User]
    [Deleted User]
    hudsonguy wrote:
    I've got the original stock cam installed.



    I've got a carefully rebuilt 2 barrel WDO carb, that is absolutely clean inside and out, and the accelerator pump is adjusted to the book spec. of .281 (9/32").



    Your fuel pump may be suspect. Put guage on to check pressure.
  • hudsonguy
    hudsonguy Senior Contributor
    maasfh wrote:
    Your fuel pump may be suspect. Put guage on to check pressure.

    I've got a brand new Dave Kostansek rebuilt fuel pump on there. The previous pump was no different either.



    It shows about 3-4 psi at the carburetor while running.
  • SuperDave
    SuperDave Senior Contributor
    I would go back and look for vacuum leaks, perhaps the wiper motor circuit, vauum advance diaphram? gaskets? The fact that richening the mixture helps tells me there is excess air getting in someway. hang in there, it's gonna be something simple..

    Dave w
  • Uncle Josh
    Uncle Josh Senior Contributor
    Geoff Clark advocates LOWERING the float level 1/8 below spec. The specific gravity, is lower on the new gas. (Thinner, lighter) and won't lift the float as far, thus too high a level in the bowl, causing too rich a mixture and slopping over and stalling when you brake.



    I lowered mine on the 262 with WDO and it runs great.
  • hudsonguy
    hudsonguy Senior Contributor
    Uncle Josh wrote:
    Geoff Clark advocates LOWERING the float level 1/8 below spec. The specific gravity, is lower on the new gas. (Thinner, lighter) and won't lift the float as far, thus too high a level in the bowl, causing too rich a mixture and slopping over and stalling when you brake.



    I lowered mine on the 262 with WDO and it runs great.



    Geoff communicated to me since that post that he wasn't taking into account our 'corn gas' (10% Ethanol) that I'm using here in the Midwest. He can still get real gasoline in New Zealand.



    Jon from The Carburetor Shop advised raising the float 1/16" because of the Ethanol. He also advised either decreasing the metering rod diameter, or increasing the hole in the jets to make it richer, especially while I was breaking in a newly rebuilt engine.



    I'm going to check my vacuum system with a fine tooth comb, although it's fairly simply, since I've got electric wipers. I've got a Chrysler slant six distributor that I modified and put in there a couple years and 14,000 miles ago. I'm beginning to think that maybe the vacuum advance is either leaking or just not working correctly. It still looks new, but stranger things have happened. I drove the car again yesterday, and it just doesn't have the power it should during acceleration. There is a definite stumble there. I didn't really accelerate very hard until after my engine was broken in, but now that I've got a couple thousand miles on it, I can drive it a little harder, so this problem is just now showing itself.



    Well, I've got about a month to figure it out, with a west coast trip looming in August. I definitely need every ounce of power I can get for the mountains. I wouldn't want to be leaving today.



    Thanks for all the (hopefully ongoing) help and advice!



    Hudsonly,

    Doug
  • russmaas
    russmaas Senior Contributor
    Pop a timing light on there see if it is advancing. Also what kit did you put in the carb? (Daytona)There is a spring on the accelarator pump that has to be put on the pump itself and a spring thats sits inside the bore of the accelarator pump.
  • nick s
    nick s Senior Contributor
    perhaps it is not fuel or vacuum, but electrical.

    are you possibly shorting out inside the distributor under full advance? the short, killing the ignition would drop the vacuum momentarily removing the short and allow ignition until the advance is achieved again. could this not allow the engine to run fine at idle and cruising thorottle while surging under load.
  • hudsonguy
    hudsonguy Senior Contributor
    russmaas wrote:
    Pop a timing light on there see if it is advancing. Also what kit did you put in the carb? (Daytona)There is a spring on the accelarator pump that has to be put on the pump itself and a spring thats sits inside the bore of the accelarator pump.

    I'll definitely check the timing advance using the light first.



    I bought a carb kit from The Carburetor Shop, because it's the only one I could find that not only came with new gaskets, idle jets, accelerator pump, etc., but also had new main jets and return springs for both the metering rods and the accelerator pump.



    Randy, do you mean the short extension spring that acts on the horizontal pivot shaft, along with the compression spring under the pump itself? If so, they're all there. I will double check everything, however.



    Nick, I'm going to check that electrical possiblity out too.



    Thanks to all,

    Doug
  • russmaas
    russmaas Senior Contributor
    hudsonguy wrote:







    Randy, do you mean the short extension spring that acts on the horizontal pivot shaft, along with the compression spring under the pump itself? If so, they're all there. I will double check everything, however.

    Yes the accelerator pump itself is a shaft and has a leather round bottom. It has a spring that sits above the leather round bottom and goes up the shaft. The Daytona kit does not give you that spring so must reuse the original. Then another spring sits inside the bore which Daytona supplies.
  • hudsonguy
    hudsonguy Senior Contributor
    russmaas wrote:
    Yes the accelerator pump itself is a shaft and has a leather round bottom. It has a spring that sits above the leather round bottom and goes up the shaft. The Daytona kit does not give you that spring so must reuse the original. Then another spring sits inside the bore which Daytona supplies.

    I guess I haven't seen a spring like you describe that sits above the leather. I've got several WDO's, and they only have a spring below the leather, in the bore that pushes the pump up. Wouldn't a vertical spring on top be working against this spring?
  • hudsonguy
    hudsonguy Senior Contributor
    hudsonguy wrote:
    I guess I haven't seen a spring like you describe that sits above the leather. I've got several WDO's, and they only have a spring below the leather, in the bore that pushes the pump up. Wouldn't a vertical spring on top be working against this spring?



    Well, I finally found the problem. It did turn out to be somewhat simple. Two years ago, I converted a Mopar slant six distributor to give me electronic ignition. That 'rebuilt' unit had only about 12,000 miles on it, and the bushing that guides the shaft had worn out. Since the air gap is so small (.006-.008") it didn't take much slop in that shaft to throw things way out of whack. That explains why I had such a random pattern of 'slight misfires', and a general lack of power.



    Put together a new unit, put it in the car, and Holy Moly!! It cruises now! Smooth as silk, plenty of power...what a difference!



    Word of caution; just because it's been 'modernized' and uses readily available replacement parts, doesn't mean you might not end up with junk 'rebuilt' parts from your local Napa (or whomever) parts store.



    Thanks for all the help and ideas here. If Nick S. hadn't mentioned the distributor, I'd probably still be trying to root out the problem from my poor carburetor. I'd would've eventually gotten there, but it no doubt saved me some time.



    Nebraska, here we come!



    Hudsonly,

    Doug
This discussion has been closed.

Categories

In this Discussion