Motorcraft 2150 too lean?

[grnmtn]

I installed a new 2150 with #47 jets and electric choke. It was already nuttered and Team Rush. Timing is 8 tdc The Good: It cranks right up, choke pulls off, idles great, no hesitation when accelerating, no rich exhaust odors at idle. However when driving at highway speeds of 50mph+ and you slightly let off the gas, the valves ping and then it goes away if you accelerate again. The plugs are all white which is an indication of too lean to me. Would changing to a #49 jet correct this or could it be another issue. I can find no vacuum leaks with starter fluid.

 

[Lumpy Grits]

When you set the timing-Did you disconnect the vac line from the dizzy and plug it?
Have you ck'd for vacuum leaks??
What plugs are you use'n???
Fill the tank with premium gas--
LG

 

[grnmtn]

Timing was set correctly, I'm using stock Champion plugs gapped to .045 per TeamRush. Premium gas. I even backed the timing down to 5 deg and it still does it. I'll go over the vacuum lines and carb gasket again.

 

[CJ]

I would definitely try a slight jet up - especially if the plugs show lean.

 

[Lumpy Grits]

I would definitely try a slight jet up - especially if the plugs show lean.

Agree---
IF-you find no vacuum leak(they have a known history of base leaking).
Go up one jet size at a time.
My bet-Vacuum leak at the base plate-
LG

 

[CJ]

~~~ I can find no vacuum leaks with starter fluid.

Agree---
IF-you find no vacuum leak(they have a known history of base leaking).
Go up one jet size at a time.
My bet-Vacuum leak at the base plate-
LG

Yep, many times the base plate gasket leaks due to the countersunk holes leaking by. A very easy fix.

Since we were told that starting fluid tests were done I hope we check both base plate gasket leaks and jet sizes.

 

[johnnyreb]

and ditch the champion plugs. Get some autolites

 

[Lumpy Grits]

and ditch the champion plugs. Get some autolites

Nut'n wrong with Champs-They were OEM

Try this for hunt'n that leak at the carb's base.
Make up a spray bottle of VERY soapy water.
Bring engine up to temp and spray the carb's base area.
IF you see the bubbles pulled inside the carb-There's the leak. Engine 'tone' will change also.
Do the same around the intake manifold.
This works better than the carb cleaner routine.
LG

 

[Fastatv]

Lots of opinions here with several ideas. In regards to the jetting, I would not think that would cause a pinging issue, tho some may disagree. Pinging is usually caused by advancing the timing to far, sometimes quality of fuel, and I have seen this caused by excessive engine heat. If the carb was excessively lean, while cruising at 50 mph, you would experience a surging of the engine....which indicates a lean carb condition ( or a bad vacuum leak ). Do you experience that?

 

[Bent]

Is your EGR system functioning? If it has been disconnected, you need to replace the vacuum advance for one with about 12 degrees of advance. A distributor on a EGR motor will have about 16 degrees vacuum advance. When you let off the throttle you get a vacuum spike that will advance the timing too much if the EGR system isn't working. I recently went back to the EGR set up on my AMC 258 i6 / 4.2l just so I could run a lot more advance on my HEI. I'm using the adjustable vacuum advance and the mechanical advance kit.

 

[grnmtn]

Update, I found a small vacuum link with the soapy water at the carb base. I replaced the gaskets and that leak is fixed. I still get a slight ping now when letting off the gas but it is 80% better than it was. The EGR has been removed and I plan on trying to tune the distributor. I am currently running ported vacuum to the distributor from the carb. Will switching to manifold vacuum help with the timing advance?

 

[Torxhead]

The later CJ 258s are set up for a manifold vacuum, check with a vacuum schematic for it. Running with the egr will make your combustion chamber temp cooler.

 

[Lumpy Grits]

The later CJ 258s are set up for a manifold vacuum, check with a vacuum schematic for it. Running with the egr will make your combustion chamber temp cooler.

Run the EGR.
LG

 

[Bent]

Update, I found a small vacuum link with the soapy water at the carb base. I replaced the gaskets and that leak is fixed. I still get a slight ping now when letting off the gas but it is 80% better than it was. The EGR has been removed and I plan on trying to tune the distributor. I am currently running ported vacuum to the distributor from the carb. Will switching to manifold vacuum help with the timing advance?

Manifold vacuum gives you more control at high RPM. In a Jeep you want ported vacuum so you have no vacuum at idle and vacuum increase as you open the throttle. This increases off idle advance (and torque).
Larger jets will help a little. EGR has a richening affect because it displaces oxygen. I'm running #46 in my MC2100 with functioning EGR.

 

[Torxhead]

Yup, Bent is right, the AMC 258 i6 / 4.2l uses ported vacumn for the Motorcraft distributor.

 

[grnmtn]

I figured out the problem this weekend! The carburetor had a power valve rated at 3 instead of 7.5. I swapped it out with one from Holley and the problem has gone away.