Don't laugh at my 25MPG ('65 Mustang 6-cyl auto)

[Charlie Cheap]

Considering I am an OLD Hot Rodder and custom car builder, my friends were shocked when I sold a 1940 Ford Hot Rod coupe I drove for 12 years with a V8, and purchased a 1965 Mustang SIX CYLINDER AUTOMATIC. I bored it to the max, changed the cam, removed the 1-barrel and installed a 2-barrel, built a hotter ignition, opened up the exhaust, and installed taller tires. I totally rebuilt the car inside and out, and built it for highway driving on long trips. With Me driving and my wife riding shotgun (2 cornfed old folks), 15" radials, 2.83 rearend, using the air conditioning, running with the truckers in the NASCAR lane (70 to 75+MPH), hauling a weeks luggage, 2 lawn chairs, 2 umbrellas, tools, and my favorite vino, 25 MPG seemed okay. The car does NOT have overdrive but has undercoating, extra foam insulation, sound deadening material, a full size spare, and last year at 76 I weighed 216 and the wife didn't. After 54 years I am a lot smarter. Two months ago I sold the Mustang to build my 1967 Sunbeam Alpine with a Ford 1985 2.3 and A4LD overdrive. Using basic MPG tricks I expect mid to high 30's if I keep my foot under control. I will post my mods as I build.

[MetroMPG]

[Admin note for Charlie - FYI, it looks like some of your posts went into the "moderation" queue for some reason. Apologies for their delayed appearance.]


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Help out a young guy who's never had the chance to drive a first generation Mustang with some context: what MPG would an unmodified Mustang expect to see in that kind of driving?

[Charlie Cheap]

A first generation Mustang six with standard 3-speed got about 21 to 22 HWY...actual not hyped. The automatic C-4 running the air conditioner, hauling 2 adults with a weeks luggage got about 20 MPG. My 65 AS MODIFIED got 24 to 25 normal highway driving at normal speeds, using the AC, and sometimes doing 75+...just to stay with traffic. My 65 had much added undercoating, extra foam insulation, the AC compressor was switched from the old York (Hi drag) to a modern Sanden, with an aluminum radiator, fan shroud and flex-fan. Very seldom did I punch the gas because I got into a MPG habit, but it would do well over 100 MPH...DON'T ASK. The 6 was bored to the max at .060", with a new street cam, stock valve job, 2-barrel carb adapted, home built points ignition, 2.83 rear gears driving 15" radials (205x70-15). The C-4 did not have a lockup converter so it probably had between 3 and 5% slippage. My Sunbeam will have a lockup converter and Overdrive transmission with taller than stock tires in the rear. I was proud of my Mustang SIX and put it on the hood.

[MetroMPG]

Nice!

The cam: was that for added power, or to shift the torque curve down to make highway cruising more efficient?

Oldsmobile offered (or at least tested) such a cam in the 60's:

...the camshaft is the key. Intake duration is reduced from 286 to 250', and from 286 to 264' on exhaust. Overlap is reduced from 58 to 36', and lift is reduced from 0.472 in. on the 4-4-2 camshaft to 0.435 on the special ... camshaft.

The vital point of maximum torque is dropped from 3600 to 2600 rpm. - source

Unfortunately, the source web page is now offline. But it referenced a magazine article about the engine.


Lower lift & duration is the design of the special economy cam in the Geo Metro XFi as well.

[Stubby79]

Better MPG than I get...

[Charlie Cheap]

MetroMPG, the cam specs are more important than most realize. Lift and duration seems to be the BIG info most understand, but OVERLAP and when the Intake Closes make a big difference. Think of it this way; if the intake is still open as the piston moves UP the cylinder, pressure drops lowering compression. The valve needs to be open long enough to fill the cylinder with fuel/air before it closes. Also, with a lot of overlap vacuum suffers, which is used to advance the timing on my points dizzy. I used a TRUCK cam used for pulling in pickups and Vans, putting the maximum torque in the 2000 to 3500 RPM range. I don't remember the duration, lift, overlap, etc. but it worked. The cool-air intake I made pulled air from in front of the radiator, which is about 50 degrees cooler. Say 90 outside, 140 under the hood over the exhaust. Notice I cut an eyebrow-opening on that side of the hood to vent heat also. This is TEXAS so "cold-air intakes do not exist...just cool-air. A denser air charge burns better and Hot Rod magazine proved it even on a stock motor. I make mine out of PVC because metal holds heat. Why pull in cooler air then heat it on the way to the carb? I am an ASE certified mechanic who retired from a city shop as superintendent and was charter president of the Dallas Area Street Rods. Much of my engine knowledge came from being a motorcycle nut for 2 decades as I studied the internal combustion engine.

[cRiPpLe_rOoStEr]

Last year while walking the dog in a street where I usually see some interesting rides, I had a chat with the owner of a 6-cyl early Mustang about how they are quite underrated, as most folks seem to be more overwhelmed about the V8.

Originally Posted by Charlie Cheap

Much of my engine knowledge came from being a motorcycle nut for 2 decades as I studied the internal combustion engine.

My first opportunity to study internal-combustion engines involved motorcycles too.

[Charlie Cheap]

I got serious about engine study as a young teen, and worked on my own motors from age 18. I built V8's for decades then bought a 6-cylinder for a daily driver. That motor was not a power house but was economical and moved the little Mustang well. It was a 67 with auto but no air. After selling my V8 powered 1940 Ford coupe I bought a 65 Mustang 6-cylinder with automatic and air to begin my study of smaller automotive engines in MY cars. The Ford 200" motor has the intake manifold cast into the head, making any intake mods a problem. My understanding of horsepower and torque gave me the knowledge to modify the little 6 for better economy AND HORSEPOWER. Matching parts is the trick, after deciding what one wants to do with the motor. Basically, building for torque in the rpm range expected. If a car turns 3000 rpm at 75 mph, then the cam needs to make it's torque in that range. Making a good hot-long spark in that range is also important. Allowing the engine to breathe better helps both HP and TQ. Matching transmission gearing, rear axle, and tire size makes a major difference in overall performance. Tuning also helps.

[cRiPpLe_rOoStEr]

Originally Posted by Charlie Cheap

Matching parts is the trick

Sometimes there are interesting setups matching parts from engines of different automakers. I remember some folks using Volkswagen conrods on modded Renault engines for example.

[Charlie Cheap]

Rooster, I mix-matched parts to save money but also to get more MPG.
1. Reduce Drag...Lower the car and remove any "hang-on items." Narrow front wheels reduce friction/drag. The radiator fan causes engine drag, so use an electric fan, fan clutch, or flex-fan. The AC compressor hurts, so upgrade to a more modern Sanden if your car has an old Ford York. If using AC, once car is cool, cut the AC a little...higher temp. Actually open car windows cause a lot of drag, so using AC on a mild setting can be helpful...really. DO NOT hang mufflers or any under car parts lower than the body line. Bonneville cars often use a full belly-pan, and modern factory cars have partial pans up front under the engine. Air Dams help do the same thing...there is a lot of turbulence under there. 2. Weight...is a big MPG killer. DO NOT haul a lot of tools around in the trunk, or lawn chairs, ice chest, laundry, Beer, laptop, clothes, the kids toys, etc. and MPG will go up. If you never use the back seat (not talking Love Life)...remove it. Replace the spare tire and jack with tire sealer/foot pump/tire plugs. I used plugs in 120 MPH cop cars for over 10 years. Install as recommended. If you do 90% in town driving with gas easy to get...fill the tank half full. Half a tank of gas is heavy. If you want engine building tips...ask. I have done this for decades with cars that were 1948 or older (Street Rods) and later cars are much easier.