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1985 2.8 Carb Adjustments


Get a dial back timing light before you try to recurve the centrifugal advance, you'll be glad you did.
 
Get a dial back timing light before you try to recurve the centrifugal advance, you'll be glad you did.

My current timing light has a dial bolt into for advance. How exactly do you use that function when setting up your timing??
 
Set the base timing, then increase the rpms while watching the timing mark move. Once it stops advancing, turn the knob until the mark is back where you set it. The number on the dial is how much advance you have. Once you know how far it advances you can better decide where your base timing should be set to arrive at the total you want. If you're willing to tear the distributor apart you can change the amount of centrifugal advance. Pull the reluctor off the shaft- keep track of the roll pin that keeps it from spinning- unscrew the stator and lift it out, remove the vacuum advance unit and the 2 screws retaining the base plate and lift it out. You'll see the weights and the arms on both the upper and lower distributor shafts, notice the 2 different openings in the arms, the longer opening will give you more centrifugal advance if you need it. To realign it you'll need to remove the inner snap ring so you can slide the upper shaft up enough to rotate it about 1/2 turn, drop it back down aligned with the longer slot, and reassemble the whole thing. Recheck the advance as before. You'll want to note the rpm where the advance is all in, I like to see 2800-3000 as a ballpark.
 
Set the base timing, then increase the rpms while watching the timing mark move. Once it stops advancing, turn the knob until the mark is back where you set it. The number on the dial is how much advance you have. Once you know how far it advances you can better decide where your base timing should be set to arrive at the total you want. If you're willing to tear the distributor apart you can change the amount of centrifugal advance. Pull the reluctor off the shaft- keep track of the roll pin that keeps it from spinning- unscrew the stator and lift it out, remove the vacuum advance unit and the 2 screws retaining the base plate and lift it out. You'll see the weights and the arms on both the upper and lower distributor shafts, notice the 2 different openings in the arms, the longer opening will give you more centrifugal advance if you need it. To realign it you'll need to remove the inner snap ring so you can slide the upper shaft up enough to rotate it about 1/2 turn, drop it back down aligned with the longer slot, and reassemble the whole thing. Recheck the advance as before. You'll want to note the rpm where the advance is all in, I like to see 2800-3000 as a ballpark.

Thanks for this info.

I found this after I asked you:


I don't know if I'm ready to dive that deep into the distributor yet, but I will try the tab bending you mentioned before. Hopefully that will get me close!
 
There are 2 springs under there, a light one that is always under tension and 1/2 turn away a stiffer one that's usually loose when not spinning. The weak one affects the rpm that the advance begins and the stiffer one will affect the upper rpm. If you're getting any advance below about 1000, the weak one is probably OK and you should try tweaking the stiffer spring. Go in small increments and keep rechecking. If the total advance isn't enough and you want to send me the distributor I'll rotate the upper shaft for you.
 
There are 2 springs under there, a light one that is always under tension and 1/2 turn away a stiffer one that's usually loose when not spinning. The weak one affects the rpm that the advance begins and the stiffer one will affect the upper rpm. If you're getting any advance below about 1000, the weak one is probably OK and you should try tweaking the stiffer spring. Go in small increments and keep rechecking. If the total advance isn't enough and you want to send me the distributor I'll rotate the upper shaft for you.

I'll play with it, and update this thread with my results. If I hit some snags I might tag you in lol. Just keep an eye on this thread. I'm out of town this weekend, but next week I hope to get some time to work on it.

On another note, I went and pulled the jets out of my 2150A carb that was on it. Looks like they were #49. I need to pull the top off my other carb and see what the 70's offered up in comparison. I'm at around 800' above sea level. If the ones in there now are smaller, I'll swap in my 49's and experiment. I might order some other sizes later and see what gives me the best results.
 

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Change one thing at a time so you know what worked and what didn't. I would address the centrifugal advance first and swap jets later. I have a bunch of 2150 jets, too.
 
Change one thing at a time so you know what worked and what didn't. I would address the centrifugal advance first and swap jets later. I have a bunch of 2150 jets, too.

Good advice. I'll start with the timing. Time to get a good timing light on order.
 
@19Walt93

I played with my dial back timing light with the RPM gage. What a handy tool!

My RPM's were about 1,000 out of gear, so I backed or down to 850 out of gear.

So my initial timing is set at 12 BTDC. I checked it on warm engine, vacuum advance unhooked. My total timing looked to be 40 degrees, and it was at 2750 rpm (with vacuum advance hooked back up). I don't think there is much more to be done with that?

I think biggest gains (if any) will be to adjust the lash on the valves. After that I'll look into rejetting the carb or trying a couple of different jets.

I made a quick video of it running. Don't know if this is noisy for a 2.8? This is a warm engine.


Also, I think I solved my hesitation issue on a cold start. I just happened to notice tonight that my fuel filter that screws into the carb was dripping while it was running. A very small slow drip. I'll bet money my carb bowl leaks down after I shut it off for a few hours and it is not filled back up when I go to punch it to pull out in traffic etc. I went and bought a new filter tonight and installed it. No more leaks. I think that will cure a lot of the issues and it will probably start even easier now.
 
Carb engines start much easier when the carb bowl is full of fuel.... Just saying. I suspected something along those lines for a while, but I didn't have a chance to confirm it.
 
I'm not saying you aren't right in your theory... but I suspect it's pretty unlikely.

That fuel pump will deliver enough fuel to fill that float bowl in a matter of seconds. Not being full pulling into traffic... I just can't see it.

Did you smell fuel every time you walked up to the vehicle?
 
I'm not saying you aren't right in your theory... but I suspect it's pretty unlikely.

That fuel pump will deliver enough fuel to fill that float bowl in a matter of seconds. Not being full pulling into traffic... I just can't see it.

Did you smell fuel every time you walked up to the vehicle?

I didn't notice any fuel smells, but I don't have an EVAP canister or anything hooked up on this at the moment either, so I could be ignoring it.

It could be a combination of leaking fuel inlet and maybe the float isn't set exactly right.... Not sure.

I will say that I had to pump the accelerator about 5 times to get it to start cold before. Any before I could ever take off after it ran for a couple of minutes I would have to pump the accelerator hard twice to get that stumble out of the way (basically acted like it had no fuel).

This morning, two pumps started right up with less cranking and never had a cold stumble. (Bowl was full of fuel I'm sure) I know before when I had to restart it in the morning was because the bowl was empty now.

I'll keep an eye on it as I'm back to driving it everyday after my trip.

Maybe it would leak more severely than I saw?

Not saying you're wrong, things just weren't lining up for me on the cold stumble....
 
Well the proof is always in the results...

Still having trouble getting my head around it.
 
A few pumps when cold is normal... or necessary to reset the choke. Kinda sounds more like an issue with the accelerator pump or something to me? Seem to remember that there were multiple holes you could put the pump rod on, and different lengths of pump push rods? Maybe it's stumbling because the pump isn't delivering fuel to the squirters exactly when it's supposed to?

I don't think I've ever owned a carbureted vehicle that worked perfectly. My old F250 ran so good when it warmed up... but it was a cold blooded bastard if you messed with the gas pedal before it ran for a minute or two. I remember waiting in several cold, dark parking lots because I flooded the stupid thing after being impatient. Your posts are always so nostalgic for me. 😂
 

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