Old Blue - 1984 XL Flareside

[ArdWrknTrk]

what you are describing is basically what i would suggest. my only caution would be to not turn them in beyond snug. wedging the screws in too hard can damage the seats. they snug up where they do. the slots for the screwdriver can land in any directional position. make a good reference for each individually and count the flats of the screwdriver as you go.

I have to agree with Mat.

Count the turns in and seat them lightly, 'fingertip tight' you shouldn't need to grip the screwdriver.

Maybe make some marks on your screwdriver handle (1,2,3,4 quadrants) that's what I did with with my flexy drive Lisle tool because it was so awkward getting at the rear corner screws of the 4180 on my old Mustang.

I'm mindful that you're in California and tuning for best driveability might not square with passing emissions.

So you might note how far you've backed them out and 'tune-down' before you go back for inspection.

[ckuske]

I have to agree with Mat.

Count the turns in and seat them lightly, 'fingertip tight' you shouldn't need to grip the screwdriver.

Maybe make some marks on your screwdriver handle (1,2,3,4 quadrants) that's what I did with with my flexy drive Lisle tool because it was so awkward getting at the rear corner screws of the 4180 on my old Mustang.

I'm mindful that you're in California and tuning for best driveability might not square with passing emissions.

So you might note how far you've backed them out and 'tune-down' before you go back for inspection.

Gotcha, thanks guys. I won't have much time to play with the truck tomorrow, but hopefully I can get to this sometime this week.

I'll make sure to note how much it takes to get from the current position of each screw to "barely snug", and then go from there. (For my own sanity to get back here if things go wonky, or as Jim said get the truck back to a known passing smog config)

Regarding vacuum - should I use the PCV port on the front? Or brake booster? Does it matter? (As long as it's not ported vacuum)

[mat in tn]

Gotcha, thanks guys. I won't have much time to play with the truck tomorrow, but hopefully I can get to this sometime this week.

I'll make sure to note how much it takes to get from the current position of each screw to "barely snug", and then go from there. (For my own sanity to get back here if things go wonky, or as Jim said get the truck back to a known passing smog config)

Regarding vacuum - should I use the PCV port on the front? Or brake booster? Does it matter? (As long as it's not ported vacuum)

vacuum for a vacuum gauge? they only need a 3/16" port so look for one of the smaller ports off a vacuum tree or even the cab/heater control.

[ckuske]

vacuum for a vacuum gauge? they only need a 3/16" port so look for one of the smaller ports off a vacuum tree or even the cab/heater control.

Thanks. I wasn’t sure if it was important to have one directly from the carb.

I know that sounds silly, but I prefer to confirm things instead of making faulty assumptions.

[ArdWrknTrk]

Thanks. I wasn’t sure if it was important to have one directly from the carb.

I know that sounds silly, but I prefer to confirm things instead of making faulty assumptions.

A vacuum gauge is dead headed so you're only measuring potential, not really using any vacuum.

A port in or closer to the plenum may have a more stable needle, but I always use one of the capped branches of my front vacuum tree (#1 intake runner)

[ckuske]

A vacuum gauge is dead headed so you're only measuring potential, not really using any vacuum.

A port in or closer to the plenum may have a more stable needle, but I always use one of the capped branches of my front vacuum tree (#1 intake runner)

Gotcha, thanks to both you and Mat.

I didn't get it on the road as life always interrupts me, but I did the procedure today. I started at 1.5 turns (I first bottomed the screws out, and counted 3.25 turns on that). The truck started fine, and ran fine at fast idle (I wasn't sure what circuit fast idle used).

I let it warm up, then kicked the throttle down. Engine died within a couple seconds.

I then started backing the screw off. It stayed running at 2 turns, but rough. I then went in .5 turn increments. These are the results in vacuum (hg):

2: 17

2.5: 20.5

3.0: 21

3.5: 21.5

4.0: 21.5+

4.5: 21.5+

After 4.x+ turns, I stopped seeing any vacuum difference and the exhaust was smelling pretty rich, so I turned the screws in to 4 turns total.

So, after everything I'm 3/4 turn richer than before at the moment, we will see how that goes. I was going to crank the idle RPM down but didn't want to introduce another variable, so we will test as-is first to see if the tip-in is better.

[mat in tn]

Gotcha, thanks to both you and Mat.

I didn't get it on the road as life always interrupts me, but I did the procedure today. I started at 1.5 turns (I first bottomed the screws out, and counted 3.25 turns on that). The truck started fine, and ran fine at fast idle (I wasn't sure what circuit fast idle used).

I let it warm up, then kicked the throttle down. Engine died within a couple seconds.

I then started backing the screw off. It stayed running at 2 turns, but rough. I then went in .5 turn increments. These are the results in vacuum (hg):

2: 17

2.5: 20.5

3.0: 21

3.5: 21.5

4.0: 21.5+

4.5: 21.5+

After 4.x+ turns, I stopped seeing any vacuum difference and the exhaust was smelling pretty rich, so I turned the screws in to 4 turns total.

So, after everything I'm 3/4 turn richer than before at the moment, we will see how that goes. I was going to crank the idle RPM down but didn't want to introduce another variable, so we will test as-is first to see if the tip-in is better.

i just did the exact same thing to my 2150 today on my v6 model. it worked out to where the idle screws are backed out further than on a holley for sure. sitill waiting on parts before a test drive can be done.

[ckuske]

i just did the exact same thing to my 2150 today on my v6 model. it worked out to where the idle screws are backed out further than on a holley for sure. sitill waiting on parts before a test drive can be done.

I warmed it up and drove it around at 4 turns. Not really any different.

I opened it up to a total 4.75 turns, maybe a *little* improvement, but not much. How much more should I try to back them out?

Maybe I have a vacuum leak somewhere still (manifold, carb, etc?). If it wasn't in the normal boots/fittings etc, would it only manifest at idle like it does? I have ran a couple smoke tests and can't find anything.

Normal acceleration/driving is just fine. It's just the transition from idle to the main carb circuit.

[ArdWrknTrk]

I warmed it up and drove it around at 4 turns. Not really any different.

I opened it up to a total 4.75 turns, maybe a *little* improvement, but not much. How much more should I try to back them out?

Maybe I have a vacuum leak somewhere still (manifold, carb, etc?). If it wasn't in the normal boots/fittings etc, would it only manifest at idle like it does? I have ran a couple smoke tests and can't find anything.

Normal acceleration/driving is just fine. It's just the transition from idle to the main carb circuit.

Transfer slots clogged???

I might go back to 3.75 turns. 21" hg seems 'good enough' but ultimately you want to tune for highest idle and a good transition.

I wonder if the timing is advancing properly (smoothly)

I know EEC-IV is dependent on the ECU but the symptoms kinda mirror a sticky advance.

[ckuske]

Transfer slots clogged???

I might go back to 3.75 turns. 21" hg seems 'good enough' but ultimately you want to tune for highest idle and a good transition.

I wonder if the timing is advancing properly (smoothly)

I know EEC-IV is dependent on the ECU but the symptoms kinda mirror a sticky advance.

So, I will be the first to admit that I am still learning regarding the intricacies of carburetion.

When the idle is set a bit higher than it should be, the hesitation is minimal or even gone. I don't like having the truck idle at 1200 RPM in drive though. That being said, it seems that functionally the higher idle causes higher vacuum, or perhaps maybe even takes the idle circuit out of the equation. If there's no transition from the idle circuit to the main circuit, there's no hesitation.

I'm reasonably confident the carb is clean and overall functioning properly. But, I think the high idle "good behavior" is a good hint. What else besides the transfer slots may be involved. Does the level of vacuum control the power valve? Maybe I have a power valve or something else that is "too firm". What can get take out of the equation with a higher (too high) idle?

If I am making someone chuckle with this train of though or using the wrong nomenclature when thinking through this, I apologize.

I leave this alone for a week or two then it starts bugging me again...