Low RPM miss.

[OUTFXD]

Jacquiline has started something new,  When she heats up,  she starts missing at idle.  I have to feather the gas petal to get the RPMs up to start moving,  Then she continues to miss upto about 1400 RPM.  The longer I drive,  the more RPMs she will miss at.

 

I;m about 80% sure this is a carb problem.   but, I mean,  its a carter B&B1.  there is only so much that can go wrong! 

 

this may accelerate the "replace the carb" project.

 

p.s.  the accelerator pump drip is back. 

[vintage6t]

Might be running lean. Have you noticed higher operating temps as well? If so, connect a vacuum gauge to the intake manifold then slowly adjust the mixture screw for max vacuum.

[Sniper]

He's got carb issues, fix that first then see where you are.

[OUTFXD]

1 hour ago, vintage6t said:

Might be running lean. Have you noticed higher operating temps as well? If so, connect a vacuum gauge to the intake manifold then slowly adjust the mixture screw for max vacuum.

Running temp is a dead solid 160.  a little higher on 90+ degree days.   Just trying to patch her together enough till I can afford a different carb.

[DJK]

Found this side note in my repair manual: too little dwell = hi speed miss, too much dwell = low speed miss.

[Ivan_B]

16 hours ago, OUTFXD said:

p.s.  the accelerator pump drip is back. 

Are you overflowing? Check the float, level, seat and needle. I've just had these issues, turned out my seat was full of debris.

13 hours ago, OUTFXD said:

Running temp is a dead solid 160.

Are you using a 160 thermostat? I am on the stock 180, and it runs about 190-200 on hot days, while the manual says that "overheating" is specifically 212 and above ?

[Sniper]

1 hour ago, Ivan_B said:

while the manual says that "overheating" is specifically 212 and above ?

 

That would be because they used water and a no pressure cooling system, be like boiling a pot of water on the stove, at 212 (altitude depending) it starts to turn to steam.

 

More modern engines, with a pressure cap, raise that temperature.

[OUTFXD]

3 hours ago, Ivan_B said:

Are you overflowing? Check the float, level, seat and needle. I've just had these issues, turned out my seat was full of debris.

Just replaced the needle and seat "just in case".. The seal is amazing,  Pressurizes the heck out of the fuel line. Float was about 1/4 inch below carb deck,  I changes it to the specified 1/32.   No change,  Put it back to 1/4.  no change. Fuel only reahes about 1/2 way up  the float bowl.

 

3 hours ago, Ivan_B said:

Are you using a 160 thermostat?

That I am.  I had enough issue getting a thermostat that actually fit the car from the local parts haus,  I decided not to push the matter.

[OUTFXD]

7 hours ago, DJK said:

Found this side note in my repair manual: too little dwell = hi speed miss, too much dwell = low speed miss.

Hadnt considered this,.  I will have to look into it and get back to you.

[Sam Buchanan]

5 minutes ago, OUTFXD said:

Just replaced the needle and seat "just in case".. The seal is amazing,  Pressurizes the heck out of the fuel line. Float was about 1/4 inch below carb deck,  I changes it to the specified 1/32.   No change,  Put it back to 1/4.  no change. Fuel only reahes about 1/2 way up  the float bowl.

 

That I am.  I had enough issue getting a thermostat that actually fit the car from the local parts haus,  I decided not to push the matter.

 

Do you have the correct float?

[OUTFXD]

1 minute ago, Sam Buchanan said:

Do you have the correct float?

Its the float that was in the carb when I got her,  looks the same as the floats in the documents I have seen.

[Ivan_B]

Where is it dripping from, again? If the fuel is coming out of where it is not supposed to - something isn't right. Is it dripping down the manifold after a drive? With the fuel at 1/2 of the bowl capacity, it should not be leaking from anywhere.

Edited August 21, 2023 by Ivan_B

[OUTFXD]

2 hours ago, Ivan_B said:

Where is it dripping from, again?

On the bottom of the float bowl there is a little opening for the arm that actuates the accelerator pump. this is where it is dripping from.

 

[OUTFXD]

has anyone tried putting longer studs  from manifold to carb  and putting a rubber isolator pad  between the carb and manifold to help isolate the carb from engine heat?  

 

Thought just popped into my head while I was considering  a heat shield for the carb.

[Sniper]

Rubber is too flexible, it'll warp.

 

 

[Sam Buchanan]

Here is the shield I use, it is isolated from the carb. I don't know how effective it is but I've never had vapor lock problems. But that may also be due to running a full-time pusher electric fuel pump.

 

Spacers are usually a phenolic material, but most of these cars probably never had a spacer.

 

 

Edited August 21, 2023 by Sam Buchanan

[wallytoo]

many of the bigger trucks got a "spacer" for the carb - a governor...i pulled the guts from it, so it now in fact IS a spacer.

 

[OUTFXD]

1 hour ago, Sam Buchanan said:

pacers are usually a phenolic material, but most of these cars probably never had a spacer.

 

1 hour ago, Sniper said:

Rubber is too flexible, it'll warp

 

I meant Rubber as a General Idea,  I actually have no idea what spacers are made from,

[Hickory]

Float bowl being half full isn't real relevant, floats float so the fuel should never reach the top. I would empty the bowl and blow compressed air through all of the passages, check out the accelerator leak. Test drive and then adjust the points and retest. I hate doing multiple adjustments and then find out it's fixed but don't know what fixed it.

Edited August 22, 2023 by Hickory

[Ivan_B]

4 hours ago, OUTFXD said:

On the bottom of the float bowl there is a little opening for the arm that actuates the accelerator pump. this is where it is dripping from.

 

Okay, since you have the same Carter I do, you either still have the fuel level way to high, so that it is getting into the accelerator lever opening, or you have a crack in the lever channel or the bowl, somewhere. Check both carefully. I am not seeing any other way for the fuel to get up there.

 

For the carb heat insulating spacers - yes, these are available, but mostly for newer cars. I think Sniper found this one: https://scoutparts.com/1BBL_Carburetor_Base_Gasket_with_Heat_Shield_Isolator_860449R1_Scout_80_Scout_800/p13375

Supposedly, it will insulate both the carb base itself and the bowl. I have seen thick plastic insulators for just the carb base, too. You might just get some generic carb insulating material and cut your own. Just make sure that the main channel is exactly inline with the carb and the manifold.

[Sniper]

10 hours ago, Ivan_B said:

I think Sniper found this one: https://scoutparts.com/1BBL_Carburetor_Base_Gasket_with_Heat_Shield_Isolator_860449R1_Scout_80_Scout_800/p13375

 

That damn Sniper, he's like Savoir Faire, he's every where.  lol, I do not remember that part.

[kencombs]

So many things can cause a low speed miss.   Low compression due to a valve leakage is one, either a sticky valve, leaky valve or not enough clearance.  Slight leak will cause too much loss past the leak to avoid a miss at low speed, but faster piston upstroke will retain enough mixture to make power.
 

 

Since yours misses only when warm, I think I'd recheck valve clearance and maybe use some magic in the gas to lube the stems.  Can't hurt.

 

edit:   And a compression check of course.   I don't think I've ever encountered a carb issue that caused cylinder to misfire at low speed only.  Unless my understanding of a 'miss' is different than most.   A miss in my vocabulary is one cylinder that fails to produce power.  Carbs have never done that IME.

Maybe a condenser?   Random miss on all rather than one specific?

Edited August 22, 2023 by kencombs

[Ivan_B]

1 hour ago, Sniper said:

lol, I do not remember that part.

You sure did, and not so long ago, too:

 

[Hickory]

One of the most basic checks is check the plugs right after a miss has developed. Are they wet, are they crusty and oil/carboned, or are they a nice coco. Mark how they look and position then switch them around and recheck.

[OUTFXD]

Plugs are black and glossy, I believe that means rich fuel mixture.

 

I found a "Factory Rebuild"  Carter B&B E6TI for a 41 dodge flathead. w/Manual Trans  What are the chances of that fitting?

 

<edit> Correction for the above,   I went out and pulled the plugs and they are a weird dog ******* brown and ashy. Not a healthy beige.

Edited August 22, 2023 by OUTFXD