For simplicity sake and practicality, go with the monthly averages. After all, what we are looking for is a trend.


If any questions come up as to a particular period of time, I most likely can find the explanation in my notes.


Thanks again for all you are doing!

 

Actually, if I do the monthly average I can also do the all-in-one graph, although I may have to take two screenshots to get it all in. And with your notes, some of which I'm not sure I can read, we could annotate the chart.

 

A lot (heck most) of this was vastly more technical than my capabilities, but it was interesting.
However, I do have one idea/thought/question. Seems to me Alabama has places that provide non-blended fuels/no ethanol. I recall one Chevron having pure gasoline on our trip back from Florida.
Do you use ethanol-based fuels or pure gasoline (well as pure as they can provide)?

 

The fuel used is 10% ethanol enriched, 87 octane.

 

Hey, what's the best way to check timing on these old trucks? the little points are way down and unmarked, and the mark is damn near invisible on the balancer...

also could you go over your standard tuning procedure once you check your mileage every time?

 

Clean the balancer. Then highlight the marks with chalk, and then wipe the balancer down, which will leave the marks filled with chalk.

However, you are going to have to explain "standard tuning procedure once you check your mileage every time". I think you are referring to the increase in sensitivity that David is dialing into the vacuum advance, so will explain that. His vacuum advance is adjustable and he's turning it clockwise to decrease the spring pressure on the diaphragm, which allows the advance to come in with less vacuum. Each turn gets about 1 more degree of advance at the same vacuum, but total advance stays the same. For example, if he was getting 10 degrees of advance at 8" of vacuum, with one turn of the screw he'll get about 11 degrees at 8".

 

[QUOTE=1986F150six;14687183]It has been 9 days and 217.4 miles since the truck was filled up, at the completion of the trip to OK. This tank represents the normal driving done by me and can be compared to the previous data with the only difference being that the weather has turned considerably cooler at night. The onset of cool weather can be expected to decrease mileage according to the records.


9/23/14 217.4 miles 11.673 gal. 18.62 mpg town/mild


I had hoped to see an increase in mileage since the adjustments made at the OK GTG, but just like with the previously discussed highway mileage, it looks to be about the same as before, but the sometimes dragging while starting and the pinging while under load have been eliminated.


The next step is to adjust the vacuum canister two more turns [clockwise] which will cause the vacuum advance to come in sooner.[/QUOTE]


Following the additional adjustment of the vacuum canister mentioned above [this can be confusing, so to keep it straight, at the OK GTG the vacuum canister was adjusted by turning the Allen wrench two turns clockwise, which causes the advance to come in sooner while under a light load, so the canister has now been adjusted by a total of 4 turns clock wise], the next tank returned 19.55 mpg!!!

I was skeptical, even though I tried my best to repeat my normal driving pattern and the way I fill up the tank. I chose not to report until running another tank.


Upon filling up the tank which delivered 19.55 mpg, the vacuum canister was again adjusted by turning the Allen wrench two more complete revolutions [this makes for a total of 6 clockwise revolutions]. This morning, the tank was filled up and when the math was done, I was pleased to see 19.42 mpg. It looks like with the additional vacuum adjustment, there was essentially no change. However, one must take into account that we have experienced the first cold front of this year and the temperatures were quite cool [39 - ~72F] for a couple of days compared to what has been [~75 - 90F]. Records indicate that cooler weather adversely affects my mileage, so perhaps what was recorded is at least as good as the previous tank, when taking into account the cooler temperatures.


10/01/14 195.0 miles 9.974 gal. 19.55 mpg town/warm


10/08/14 191.0 miles 9.836 gal. 19.42 mpg town/mild


This morning after filling up, I decided to again make an adjustment. The vacuum canister bottomed out after 1/2 clockwise turn. The total adjustment is now @ +6 1/2 turns, which is the maximum. Even with all the adjusting, there is still no real pinging while under light load. Actually, at no point does pinging occur. So, technically, to quote Gary Lewis from a previous post, there is still gas mileage being "left on the table", but at this time, I will leave well enough alone.


Finally, let me mention something I have learned regarding optimally curving of a distributor. First of all, much can be gained!!! But, when I purchased a new "re-curved" distributor, I was asked questions such as: rear end ratio, transmission, cam specs, carburetion, weight of vehicle, operable EGR, etc. That made me feel like I was actually receiving one specially adjusted for my engine. The distributor was received with the maximum advancement engraved on the housing. Wow! But, after reading many posts in varying threads, a common theme is repeated by others who have purchased like distributors for many engine and truck combinations... they all are engraved to have a maximum of 24 degrees advance @ 3000 RPMs. Coincidence? I will not "bad mouth" the supplier since what they delivered has performed well for 4+ years, but was not optimally curved as has been determined by the recent testing and improvements. What I will say is that perhaps re-curving is best done by someone who takes the time and interest to individually tune the distributor to one specific engine.


I want to thank each of you who have contributed to this thread and helped my truck operate much more efficiently!

 

Let me guess...
They are a sponsor here on this site?

BTDT.

I get my DSII distributors from Reincarnation now.
Scott knows his stuff and actually puts them on a distributor machine to check them.

 

Excellent! I'll hazard a guess that next summer, when the temp warms back up, you'll see right at 20 MPG on your normal weekly runs. That's really good MPG. And, you still don't have pinging at any point? If that is the case then you may still have MPG being "left on the table". But, it is probably minimal.

As for how to get that MPG, here are couple of the things that would have to be considered:

• Shift mechanical advance curve: You don't have any pinging now at full throttle so may not have all the timing the engine can stand from the centrifugal advance. Changing the spring(s) to lighter one(s) would bring the advance in earlier, similar to what we've done on the vacuum advance. In other words, the overall timing would be the same but you'd get it earlier in the RPM range. (I don't think adding more total mechanical advance would help as that only occurs at 3000 RPM and you never get there.) In my experience this can add significantly to the low-RPM power. And, it is something that can be put back - albeit not in a couple of minutes as it can be on a Chevy dizzy.
• Total vacuum advance: Many vacuum advance cannisters have a shoulder which hits a stop to limit the max advance it'll give at full vacuum. This shoulder can be cut down a bit to get more than the total vacuum you are currently getting - 18 degrees if I remember correctly. But, this isn't always easy to put back since material has been taken off. Sometimes you can solder something on. Or install a screw to make it adjustable.

But, I'm not sure the view is worth the climb. If you are happy with what you have then the plan to "leave well enough alone" is probably a good one.

 

Okay, here is something I have been working on. It is definitely "old school" and not nearly as graphic as a spread sheet, but the following information compares the mileage in yearly increments beginning with when the truck was purchased. By using yearly increments, all variants based on seasonal changes are averaged out.


Looking at the information in a "snapshot" reveals that improvements and mistakes were made in the quest for better gas mileage. Thank goodness, with the assistance of members of this forum, significant improvements have been made during this last year!


The last increment is not complete, but shows what the truck is now returning up to this date.


3/12/08 - 3/09/09 7774 mi. 489.53 gal. @ $2.899 avg. 15.88 mpg avg.


3/17/09 - 3/16/10 9094 mi. 561.12 gal. @ $2.329 avg. 16.21 mpg avg.


3/18/10 - 3/12/11 8410 mi. 528.44 gal. @ $2.639 avg. 15.91 mpg avg.


3/22/11 - 3/10/12 8043 mi. 510.88 gal. @ $3.409 avg. 15.74 mpg avg.


3/18/12 - 3/06/13 9981 mi. 604.81 gal. @ $3.329 avg. 16.50 mpg avg.


3/14/13 - 3/11/14 8161 mi. 538.32 gal. @ $3.169 avg. 15.16 mpg avg.


3/18/14 - 10/20/14* 6848 mi. 366.79 gal. @ $3.239 avg. 18.67 mpg avg.


* = real time data, but not yet a full year interval.

 

First, I want to once again, thank Gary and Jason for their efforts in fine tuning the engine in my truck while at this year's OK GTK.


It seems that most gains were made with advancing the timing to 14 degrees BTDC and bringing in the vacuum advance at an earlier point [previously detailed]. This final change was accomplished over several tanks after I returned from the OK GTK.


The gas receipts have once again accumulated in my billfold, so I will report the latest before recording in my log.


10/20/14 196.7 miles 10.349 gal. 19.01 mpg town mild-warm temp.


11/05/14 204.0 miles 10.956 gal. 18.62 mpg town cool-mild temp.


11/18/14 185.7 miles 10.076 gal. 18.43 mpg town cool-cold temp.


11/26/14 221.0 miles 11.425 gal. 19.34 mpg town cool temp.


12/09/14 217.0 miles 12.197 gal. 17.79 mpg town cool; extra short trips


12/17/14 188.6 miles 10.134 gal. 18.61 mpg town mild-cool


Thanks, again, everyone who has provided input!

 

I was happy to help, and one reason was due to my curiosity about what could be done. Your engine and tranny is a good combo to tune since you have a manual tranny and can tip-in the throttle and instantly hear if it pings. It was fun.

 

Now, what would it do with bed cover, fender skirts, free flow exhaust, low rolling resistance tires, full wheel covers, smaller mirrors, cladding on the front of the grill and head lights/ turn signals and something under the bed to smooth out the area just in front of the rear bumper???

 

Sounds, ugly. Like the 87+ trucks. (Sorry to those that have them, but…) Much of what you described is what they started into with the next generation. But your truck would respond well and quickly to those things, as it doesn't have one of the biggest losers - a C6. Rusty probably wouldn't show enough increase to register with some of those changes, but yours would. However, if you are wanting to get Prius MPG then why start with an 80's pickup?

 

Because, an 80's pickup is what I have!