All Big Six 240 mods and tuning to increase economy (Open to all 240 owners & interested members)

[sixtseventwo4d]

Lets take a moment to all review the OP's post heading; it's for 240 tuning and getting better economy from it.
So, speaking directly about the 240, and nothing else; it's a happy and torquey little motor when operated within it's means. The optimum way to realize what a little gem it is; is by gearing it properly for the use you have for it. Adding an overdrive goes without saying and picking the right ring and pinion for how it will be used is going to be where diligence is rewarded.

 

[Jesse73]

Maybe this idea is ridiculous, but I think you may be limiting your potential efficiency by using the stock log manifolds. I thought about installing my Offenhauser intake and making an adapter plate for the stock 1 barrel just for grins and possibly as an example of “you don’t have to spent $1200 all at once” for a 4 barrel swap.
I wonder how a 1 barrel would do with a better intake?

Another idea regarding 1 barrels. My dad has a Stromberg 97 on his Willys jeep and it has tuneable jets. That goes a long way twords optimizing it for your needs

 

[bubba22349]

This topic has been discussed since ford made the first car.
A lot of time we get consumed with gas mileage and the cost to get it better. New cars get much better gas mileage than vintage or classic cars get, but what price do we pay? Try getting one fixed or making repairs yourself.

Just as a point of conversation:
Lets say we buy an old car or truck as we hot rodders do. Lets say for a truck it gets 12 mpg. Lets say we fix it to get it reliable total cost of truck, any repairs and upgrades, 10,000 dollars. Cost of a new truck 50,000 dollars, difference 40,000 dollars.
New truck gets 18 mpg (my son just bought a new F250 and got a little over 15 mpg on a trip), difference is 6 mpg. Is the additional cost for the fuel make up for the 40,000 dollars you did not spend on the new truck. 40,000 dollars in a money market account at 5% interest is 2,000 dollars. Will the 2,000 dollars cover the cost of the additional fuel required?
Let's say you drive 14,000 miles a year.
14,000 divided by 12 = 1167 gallons.
14,000 divided by 18 = 778 gallons
difference = 389 gallons, round up to 400 gallons.
cost of gas per gallon = 4.00 dollars.
cost for additional gas = 400 times 4 = 1,600 dollars, less than 2,000 dollars and you still have the 40,000 dollars in the bank.

Lets add to this the difference in insurance. If the truck is new you will want collision, old truck none. I have no idea what the cost would be so I am guessing say 1,000 dollars a year for the collision rider that you do not have to spend. The cost of the collision would pay for the insurance on the beater if you get one.

If you buy on credit and make a monthly payment for a new car take that amount and put it in a bank account every month for yourself.

If you want good gas mileage buy a cheap beater car for commuting. Honda civic, Hyundai accent, etc. I have a 2003 hyundai that I paid 3,000 dollars for maybe 7-8 years ago with 70,000 miles and it now has 182,000
miles. No problems, I get 32-35 mpg and it doesn't burn any oil. It has the original injectors and exhaust system

Getting back to the point on improving gas mileage, use the same logic for the cost. Now we are talking maybe 2-3 mpg for moderate changes or maybe 5 mpg depending on how much money you want to spend. Also we have to consider if it is an efi motor which makes improvements more complicated and costly. My point being, is the cost to make the improvements less that the money saved on gas. If this a daily driver it may be worth it. If we are just talking about basic maintenance items like, spark plugs, wires, cap and rotor, new injectors or carb rebuild, yes do it and start with cheapest first. The trap is replacing parts thinking they will improve mpg and find out when done there is no change. We should also not expect a large gain and be disappointed.

My advise is always have a second beater car. It is so stress relieving to know that if one breaks you have the other. Just keep the beater reliable and do the right maintenance on it.

BTW my wife has the new car (masda). I do not drive it or maintain it. She takes it to the dealer for all maintenance and so far no repairs but is out of warranty.
Enough rambling!

Wow alwill923, right on! This takes me way back to many decades ago with a conversation that I had with my dad in the early 1970's about this topic and about calculating the true cost of things and then how to determine if they would be a good investment or not. I was blessed with two great parents both of which grew up during the "Depression Years" they imparted as much of their Wisdom on me as I could handle over the years, like keeping your equipment you needed to depend on in good condition. So I have mostly always had older cars and trucks maintained them myself and when they were completely worn out either you rebuilt them or replaced them. Also any that were used for work or daily driving were maintained and also tuned and driven to get the best in MPG within reason, many of those would also get several budget Mods or later stock parts to improve both that power and economy too, while being otherwise basically stock.

 

[Blairsville Ed]

I added a few post on the big six portion under the Weber carb post but it may fit better in this section.
I had purchased a Holley 5200 from eBay for $10 with the intent of adapting it to my 1977 F150 , 300, c-4 trans truck, but after I started cleaning the carb I realized that I had purchased a smaller version of the Holley 5200 which came with a 23mm primary instead of the 26mm primary. After closer inspection it appears to be a 22mm primary and a 27mm secondary. On my 1968 F100, 240, 4 speed manual od truck, I’ve been using a Holley 5200 with both barrels at 27mm and an annular discharge booster on the primary side. It’s not as fast as the Weber 38/38 but on my test track which is pulling a fishing boat up a long grade, the Holley 5200 performed as well a the bigger 38/38. After watching the lawnmower carb on a 302 video, I’ll be trying the small Holley 5200 on the 240. I’m not sure how it will respond but I’ll give it a try.

 

[Soldmy66]

@63 Sprint - If you are looking for cost effective ways to increase gas mileage, you might find usable information on the ecomodder forum. They have a lot of information and people have done a lot of A-B-A testing.

 

[63 Sprint]

When this topic was started, I did not think about others that own a 240, or has an interest in how more efficiency and possibly a hp gain can be achieved in a 240. This topic is beneficial for others also. Ecomodder has good info, but it’s not specifically for a 240 engine. This is where this forum comes in. Members here can share their experiences, ideas and suggestions.

 

[alwill923]

WOW!! Did I open a can of worms. Just an old man rambling. Yes I did keep in topic to illustrate the cost vs actual gain in MPG.
For those who have not search my posts; I have have a 240 in a 65 F-100. I posted the conversion to the Mazda trans with pictures and my other mods. It is not a daily driver. I do not know the mpg. Probably 15-20 If I do not go over 60.
Lets talk about the Mazda trans and keep on the mpg topic. This is my experience with this trans.
My truck has 3.70 original gears (it came with a 3-speed). The first gear of the trans is 3.90 (3.9x3,7= 14.43), making first gear almost useless unless you are pulling a trailer and starting on a hill. With the overdrive I can go 70 all day long in OD and engine rpm is 2500 (70 is really to fast for the old truck even with slight suspension mods). my final ratio in OD is 3.70 x 0.80 = 2.96 good for mpg. (Tire size will change the numbers)
Getting to my point; Let say you have 3.08 rear gears. 3.08 x 3.90 = 12.01. This is better but then we need to look at the OD which will be 0.80 x 3.08 = 2.46 for a final drive. (Actually IMO the mazda trans gear ratios are too wide for normal driving)
Therefore, if the trans is installed with a 3.08 rear gears the final ratio in OD is becoming to small especially with a 240 engine. This is the problem! Your final rpm based upon the above would be 3.70 is to 2500 as 3.08 is to your rpm of 2081 at 70 mph. At less than 70 mph your rpm would drop into the teens. This will cause the engine vacuum to be low causing the carb to go into the power mode (rich air fuel ratio) thus using more gas. The truck will be sluggish to drive and with very slow acceleration causing you to step in the gas more, thus lower vacuum rich mixture and bad mpg. The truck will be miserable to drive making the OD useless and you may be driving in 4th gear most of time. With an efi it will be slightly different but to make the required horse power and the efficiency of the motor at low rpms an efi will still inject more fuel. You require a specific hp to move a truck at a specific speed.
Your mpg may actually decrease as you search for that 2-3 mpg more.

The whole idea is to run with the engine at the best efficiency point. This will be a combination of speed, engine rpm and gear selection. Is driving at very low rpms can be detrimental to gas mileage. My point is the transmission, and engine size must be coordinated with the rear end ratio. You may have to change the rear gear ratio to get the best use of the masda trans.

 

[Frank]

Therefore, if the trans is installed with a 3.08 rear gears the final ratio in OD is becoming to small especially with a 240 engine. This is the problem! Your final rpm based upon the above would be 3.70 is to 2500 as 3.08 is to your rpm of 2081 at 70 mph. At less than 70 mph your rpm would drop into the teens. This will cause the engine vacuum to be low causing the carb to go into the power mode (rich air fuel ratio) thus using more gas. The truck will be sluggish to drive and with very slow acceleration causing you to step in the gas more, thus lower vacuum rich mixture and bad mpg. The truck will be miserable to drive making the OD useless and you may be driving in 4th gear most of time. With an efi it will be slightly different but to make the required horse power and the efficiency of the motor at low rpms an efi will still inject more fuel. You require a specific hp to move a truck at a specific speed.
Your mpg may actually decrease as you search for that 2-3 mpg more.

Even the 300 is lugging and weak turning that slow. 3.08 rear and E4OD= final drive ratio of 2.19:1. 1900 rpm@70. It will not pull a bridge overpass in OD, and never has more than 10" intake vacuum, if it's perfectly flat. . Don't know what the engineers of that era were thinking, but that's as tall gearing/ road speed as some semi diesel trucks. Absolutely awful, OD is useless, haven't engaged it in years.
Maximum economy is not found with the engine in a bind. Thy need to be allowed to rev into the meat of the torque band at high road speeds for max economy, the shorter the stroke, the higher that ideal rpm.

 

[pmuller9]

Even the 300 is lugging and weak turning that slow. 3.08 rear and E4OD= final drive ratio of 2.19:1. 1900 rpm@70. It will not pull a bridge overpass in OD, and never has more than 10" intake vacuum, if it's perfectly flat. . Don't know what the engineers of that era were thinking, but that's as tall gearing/ road speed as some semi diesel trucks. Absolutely awful, OD is useless, haven't engaged it in years.
Maximum economy is not found with the engine in a bind. Thy need to be allowed to rev into the meat of the torque band at high road speeds for max economy, the shorter the stroke, the higher that ideal rpm.

My 4500 lb van has a 3.6L V6 that makes peak torque at 4400 rpm and peak power at 6400 rpm.
It is at 1750 rpm at 70 mph and gets 25 mpg at that highway speed.
Maximum economy is NOT found with the engine cruising in the middle of the torque band.
I wrote about this previously in the MPG thread.

 

[Frank]

My 4500 lb van has a 3.6L V6 that makes peak torque at 4400 rpm and peak power at 6400 rpm.
It is at 1750 rpm at 70 mph and gets 25 mpg at that highway speed.
Maximum economy is NOT found with the engine cruising in the middle of the torque band.
I wrote about this previously in the MPG thread.

Yes sir, you did, and I learned something from it as to why the same 300 mentioned above got 25-26 mpg @ 1600 rpm/60 mph, 8-10" vacuum repeated regularly on a monthly trip, the piston ring friction and RPM. It got this mileage as an efi engine. As a carb engine it can not duplicate that- it requires more rpm and vacuum to attain max economy, which is still less than it's former EFI numbers. The pumping friction, as you explained.
My most economical vehicles were pre-OD era, some with relatively low gearing. Unless it's EFI, everything I've run gets better mileage with more RPM and less bind.

 

[pmuller9]

It got this mileage as an efi engine. As a carb engine it can not duplicate that- it requires more rpm and vacuum to attain max economy, which is still less than it's former EFI numbers. The pumping friction, as you explained.

Thanks for the reply.
If I’m reading this correctly, Please remind me.
What intake and carburetor did you use to replace the EFI system?
Did you keep the stock cam?

 

[Frank]

Thanks for the reply.
If I’m reading this correctly, Please remind me.
What intake and carburetor did you use to replace the EFI system?
Did you keep the stock cam?

This is the '90 f150. Crower 192/252 cam, premium gas. Ran it a few years with the factory ECM, all emissions removed except PCV. No Cat. Ran exceptional, and I am not exaggerating the economy. Flat region, at sea level.
Last 8 or so years, Offy DP intake, Ambler-curved DS2 and Holley 390 4V. 17-18 mpg on the same road that used to be 24 with EFI. This is a 60 mph cruise. Economy is slightly better in direct drive (2300 rpm), 15-16" vacuum vs OD (1600 rpm) 8-10" vacuum.
Based on your data on pumping loss, especially rings, I'll presume the benefit to the wet induction system at higher engine speed is being countered by the increased pumping friction.
The port injection/ computer control is superior at low rpm/ low vacuum/ highway loads over a wet intake/ mechanical carb in the same conditions.

 

[pmuller9]

Where you monitoring the air/fuel ratio between overdrive at 8-10” and direct drive at 15-16”?

 

[InlineDave87]

My 4500 lb van has a 3.6L V6 that makes peak torque at 4400 rpm and peak power at 6400 rpm.
It is at 1750 rpm at 70 mph and gets 25 mpg at that highway speed.
Maximum economy is NOT found with the engine cruising in the middle of the torque band.
I wrote about this previously in the MPG thread.

To piggy back on that, my ecoboost at 75 mph will spin about 1900 rpm and get me roughly 18-20 mpg. At 65 mph will spin at 1500ish rpm and get me 23-25 mpg. Additionally if i were to go up to 80mph you can here the boost kick in and mpg would drop down to like 13-14 mpg. And it was roughly the same when i had my 2008 f150 4.2 auto minus boost.

 

[Frank]

Where you monitoring the air/fuel ratio between overdrive at 8-10” and direct drive at 15-16”?

No sir.

 

[alwill923]

Ponce De Leon was looking for the fountain of youth, same thing here. Take what you have and do the best you can with it, save your money and live with the results. Its a truck!