Carb question

[ammocj]

I did the duraspark some time ago and ran with the old feed back carb and a metering block I made. She ran good but fuel economey was horrible.
I finally got some time to rebuild an old motorcraft 2100 or 2150 (i don't remember, I bought it over a year ago) carb 1.08.
Anyway, there is a nipple on the power valve cover.
Is this a vent or does a hose off it need to run to something else?
I have all the extra nipples on the carb blocked for now and it seems to run ok.

Al

 

[kimcrwbr1]

I am pretty sure that nipple on the cover for the power valve goes to the nipple on the egr spacer right below it. It controls the power valve yes with no vacuum to it it keeps the power valve open all the time so you will allways be runnig rich at all speeds. when vacuum is applied it closes the valve when you dont need the fuel. To tell if you have a 2100 or 2150 the 2150 has the choke pull off pod on the firewall side of the choke the 2100 has the pull off incorparated into the carb body itself. You want the highest vacuum pressure possible at an idle so time it 10 degrees with the advance disconnected and plugged then hook it up to manifold vacuum (the tree) it should be around 20 degrees at an idle then adjust the idle air for the highest vacuum or rpm, 3 to 3 1/2 turns out from lightly seated and make sure they are within 1/2 a turn between them. Count the turns in then back out and make sure the engine is up to temp and the choke is all the way open before making any adjustments. Only after you time it and adjust the idle air can you adjust the choke. Comfirm the timing, hook the advance to manifold vacuum and plug any nipples on the carb off your not using, adjust the idle air and after it cools down adjust the choke in that order.

 

[kimcrwbr1]

Do you have the #50 jets in the carb you should get arount 17 mpg hwy once you get it dialed in maybe better depending on the health of the engine.

 

[ammocj]

AHH!
Thanks for the tips.
That partially explains my poor fuel economy.
I'll hook that hose today.
I'll drive it to work tonight and see how she runs.
I won't be able to tinker anymore until Wednesday.
I had the motor rebuilt a couple years ago so she is strong.
(if thats what ya call a 2.8)

Al

 

[kimcrwbr1]

Cool the best way I found was with the advance on manifold vacuum once you confirm the timing is at 20 degrees with the advance connected turn the idle air screws out three turns and set the idle speed get it up to temp then adjust the idle screws for the highest rpm or vacuum pressure adjust the idle speed do that a couple times until it dont rev any higher when you turn the idle air out. If you do it right your fast idle will be real high when the choke is closed you can preset that adjustment by putting it on the high idle cam V notch by manually closing the choke to around 1/4 inch give it gas and let up it should stay on the high idle cam then turn the high idle screw out to around 1100 rpm or whereever you want then the next day you can fine tune the high idle cold. The 2.8 aint no power house but mine hauls a load of gravel around pretty good on the rear axle.

 

[ammocj]

I've been pretty happy with mine.
I've hauled some firewood with it since retiring the 68 Power Wagon.
Once I find a 6' snowplow for it I'll probably sell the old Power Beast.

I forgot to check what size jets were in it when I rebuilt it, I just used the ones that came with the carb. I'll read the plugs eventually.

Any idea what the pump relief valve assembly nipple runs to?

Al

 

[kimcrwbr1]

Is that the nipple on the front of the carb pointing up. If so it is used to turn off the accelerator pump with vacuum pressure. I believe when you apply vacuum to it it keeps the accelerator pump from squirting fuel. I just leave mine disconnected do you have a pic of your carb.

 

[ammocj]

Yeah, it's the nipple poining up in front on that attachment that has 3 screws holding it on.
Seems that might save a bit of fuel too.
I do have a vacuum hose on the passenger side of the carb that isn't being used.
I may try hooking that up for my next tank of fuel.

This morning when I got back to town she started right up from cold (approx 38degrees) even though I had the choke missadjusted so it wouldn't choke or high idle.
A simple adjustment, but she just idled fine.
My slow idle now is steady, as it never seemed to slow idle at the same RPM with the feedback carb.
It's running so much better now.
I suspeect fuel economy has improved but we'll see once I run this tank out.

Thanks for the help. I'll try to get some pictures on my next day off.

Al

 

[dangerranger83]

I need to see if my power valve has a spot for a hose to connect to, if I havent alredy got it hooked up. Im getting 10mpg no matter how I drive her, in town or highway.

 

[kimcrwbr1]

I need to see if my power valve has a spot for a hose to connect to, if I havent alredy got it hooked up. Im getting 10mpg no matter how I drive her, in town or highway.

It depends on the carb there will either be a port internal with a cap with no nipple or if the power valve cover has a nipple you connect it to the EGR spacer just below the idle air screws. The carb I ended up using had the cover with no nipple but is was not ported internally. I had a extra cover with a nipple to make it work. Different power valves run on different pressures and if it has the deep cover it is a two stage power valve but in general high vacuum is closed and low vacuum is open the lower the number the leaner the mix will be.

 

[Twister]

I need to see if my power valve has a spot for a hose to connect to, if I havent alredy got it hooked up. Im getting 10mpg no matter how I drive her, in town or highway.

I get terrible gas mileage as well.

ammocj, do you mind posting a pic of the nipple you hooked a hose to?

 

[kimcrwbr1]

I get terrible gas mileage as well.

ammocj, do you mind posting a pic of the nipple you hooked a hose to?

On the bottom front the square cover for the power valve there should be a nipple center of the carb pointing toward the radiator. I took a pic but me and photobucket have to go to battle for me to get it here but i will try.

 

[kimcrwbr1]

http://www.autozone.com/autozone/pa...vd1l?counter=2&itemIdentifier=202756_0_0_1277 If you look at this carb it has the deep cover with the nipple for the power valve and probably has the two stage power valve. Photo bucket is doing maint but if you dont have a nipple on the cover you need to look at the bottom of the carb with the cover off the power valve there should be a port pulling the valve closed from the two venturies into the void there. if not you can drill a port or find a cover with a nipple. At the time I found mine was not working I had 4 carbs stripped and was inspecting them noting the difference in design and saw no way for the vacuum to get to the bottom of the power valve pulling it closed. 4 to 4.5 inches in Hg would be the stardard vacuum pressure that closes the power valve. I problems with fuel mileage until I put the vacuum advance on manifold vacuum giving it around 20 btdc at an idle and the idle air screws out 4 to 4 1/2 turns I think the idle air supplements the high speed jets so you dont have to push as hard on the skinny pedal and the vacuum pressure stays high enough to keep the power valve closed until you put your foot into it.

 

[Twister]

Ahh, don have it. I guess i should have read he was using the feedback carb

 

[kimcrwbr1]

Ahh, don have it. I guess i should have read he was using the feedback carb

I`m not sure if it is a feedback carb It just depends on the design if it dont have the nipple it is internal and you need to pull the power valve cover to see if it is ported or not it is a hole between the inside of the cover to that space between the butterfly ports.