But first, an old school technique for teaching economical driving was to place a cowbell upright on the floor. (Good luck finding one nowadays.) If the bell clanged (or fell over), it meant you'd accelerated, braked, or turned too fast. (Flying up off the floor meant a bumpy road, in case you hadn't noticed.)
Next up is replacing the air filter element. A dirty, clogged air filter means the engine has to work harder to draw air into the carburetor (or throttle body). This means the engine is expending power that could be sent to the rear wheels instead.
Do you have an open air cleaner (possibly from a previous owner), like the one in the following picture? If so, throw it away. (Or give or sell it to someone else.) Replace it with an OEM-style closed air cleaner with a snorkel tube.
![[image]](http://www.riffgan.com/misc/rv_net_stuff/1221.jpg)
These air cleaners are really only appropriate in large, relatively open engine compartments, preferably without a hood. The carburetor on your motorhome's engine is up in a hot, enclosed doghouse.
For efficiency (i.e., good fuel economy), your engine needs dense, cool air. The air inside your doghouse is hot and thin. The air cleaner snorkel allows the engine to draw in denser, cooler air. (That's why most newer vehicles have cold air intake systems.)
Aside from the engine intake needs, the hot environment inside your dog house is detrimental to engine performance. That's why I recommend one or two small marine bilge blowers, like the one below, and dryer vent hose to ventilate the doghouse. (Highway speeds and the engine fan don't really do much to displace the hot air in the doghouse.)
![[image]](http://www.riffgan.com/misc/rv_net_stuff/SFIB1130-01EN.jpg)
If you want to get fancy, you can use a bilge blower to (mildly) supercharge your engine, which will make it even more efficient. Just attach the blower output to the air cleaner.
Ideally, the air cleaner should be attached to the blower intake and the blower output attached to the carburetor neck. However, that's likely more involved than what most of you are willing to do. So the preceding is sufficient.
Next is to take a look at the inside of your tailpipe. It should have a white or light grey deposit inside it. Dark grey or black soot indicates a too-rich fuel mixture and wasted fuel. Black smoke coming out of the tailpipe is a sure indication of too much fuel being dumped into the engine. Likely causes are too large jets, bent or broke metering rods, or defective carburetor float.
(Blue smoke indicates oil consumption, usually due to defective valve stem seals, worn piston rings, or worn cylinder walls. Older Dodge OHV engines are notorious for disintegrated valve stem seals, which is the most likely cause of oil consumption. These can be replace without removing the heads -- google replacement procedures or ask me.)
If your engine has a four barrel carburetor, try to avoid using the secondary barrels. During normal operation, the secondaries are closed and the engine relies on the primary barrels for fuel-air mixture. Under brief heavy load, such as climbing a steep hill, the secondaries will open to supply extra fuel to the engine. This is normal and the intended, acceptable use of the secondaries.
Tromping on or flooring the accelerator and hard acceleration will also cause the secondaries to open. More often than not, this is simply a case of the loose nut behind the steering wheel wasting fuel. Steady, slow pressure on the accelerator will usually keep the secondaries from opening. (If they do open, it'll just be briefly before closing again.)
It should take 2-4 seconds to press the accelerator from idle to medium acceleration … continuing to wide-open acceleration will also cause the secondaries to open and waste fuel.
If the secondaries do open, they should close when you reach cruising speed and back off the accelerator. If they don't , it means your carburetor linkage is gummed up and you're wasting a lot of fuel. Cleaning the linkage with spray carburetor cleaner and re-lubing with graphite should solve the problem. If not, you probably have bent linkage or a seized butterfly valve shaft.
Hard braking for stoplights and stop signs also wastes fuel, although that might seem counter-intuitive. Anticipating stoplights and stop signs, and letting up on the throttle, saves fuel. Otherwise, you expending fuel maintaining speed before braking hard to lose momentum. (Easy on and off the brakes when approaching stops decreases momentum while preventing brake overheating and excess brake shoe/pad wear … and saves fuel because your foot is on the brake pedal rather than the accelerator.)
(On manual transmission vehicles, I often get stopped by cops for a brake-light check. This is because I use anticipation and downshifting to slow the vehicle, rather than the brakes. Quite often, I don't even have to use the brakes to come to a complete stop.)
People who keep one foot on the accelerator and the other on the brake pedal obviously have money to burn. It wastes fuel by making the engine work harder to overcome the (slight) brake friction. It also causes brake overheating and premature wear on the brake shoes/pads. (I watched one lady I was following do this for over ten miles -- her brake lights were even on while she was accelerating up a steep hill. She very well could have found she had no brakes, due to overheating, if she actually had to stop.)
Next up is more expensive modifications to improve fuel economy.
* This post was last edited 09/18/17 09:24pm by Griff in Fairbanks *
1970 Explorer Class A on a 1969 Dodge M300 chassis with 318 cu. in. (split year)
1972 Executive Class A on a Dodge M375 chassis with 413 cu. in.
1973 Explorer Class A on a Dodge RM350 (R4) chassis with 318 engine & tranny from 1970 Explorer Class A
eyeteeth wrote:
A little good news / bad news game. The Tomco-Inc link I provided earlier, they don't carry/stock/produce the Float bowls any longer (They do have some NOS for the 1 3/8 bore). Bad news... However, I am still able to use the linked PDF to scour the inter webs to find someone selling a carb with the proper float bowl for parts. Cheap... Good News.
A little good news / bad news game. The Tomco-Inc link I provided earlier, they don't carry/stock/produce the Float bowls any longer (They do have some NOS for the 1 3/8 bore). Bad news... However, I am still able to use the linked PDF to scour the inter webs to find someone selling a carb with the proper float bowl for parts. Cheap... Good News.
Yeah, I found a much better used 6518s on eBay several years back and had my BIL run it through his hot tank. Cleaned it up really nicely...now I have to get another rebuild kit so we can put that one on the beast. And keep the old one as spare parts - it has seized adjustment screws and the replacement one has working screws.
'73 Concord 20' Class A w/Dodge 440 - see profile for photo
Contrary to reputation, four barrel carburetors have the potential for better fuel economy than two barrel carburetors. This is because the venturis in two barrel carburetors have to be large enough for the highest anticipated engine load. The primary venturis on four barrel carburetors can be relatively smaller because the secondaries can take up the 'slack' in response the occasional heavy engine load. (i.e., acceleration or climbing hills.)
The four barrel carburetors have a reputation for greater fuel consumption because many owners make excessive use of the secondaries.
Both my 318 engines had two barrel Carter BBDs. I anticipate a 2-4 MPG increase when I switch the '69/70 318 to a four barrel Carter AFB. (Switching also requires a different intake manifold ... a four-to-two barrel adapter is a less effective -- and unacceptable -- alternative.)
People sometime change carburetor jets in a usually misguided attempt to increase engine power. Unless you have lots of knowledge and experience, doing so very rarely succeeds. Usually, they just cross the too-large line and 'fall off the cliff'. (Larger jets usually just cause excess fuel being dumped into the engine without significantly affecting engine power.)
I discovered an ignorant previous owner had drilled out the jets when I rebuilt my '80 Bronco. (Drilled out because the jets were larger than any standard jets for that carburetor.) I couldn't find the right size jets. So, I had to get the next smaller size and carefully drill them out a 64th at a time. (I had to make a special drill-press jig just for that task.)
People rarely go to smaller jets because it reduces engine performance. (In this case, falling off the cliff means the engine stalls under load.) However, small jets are appropriate if you're sure the carburetor is dumping excessive fuel into the engine ... but only if you're sure.
Zert to zert is 28.25"
DS930 is the right drag link for you.
Thinking I might have to try and cancel first thing in the morning...
eyeteeth wrote:
Griff... are you SURE its the DS930? My friend said it was 28.25 between the zerts... didn't you say the DS930 was only 24"?
Thinking I might have to try and cancel first thing in the morning...
Griff... are you SURE its the DS930? My friend said it was 28.25 between the zerts... didn't you say the DS930 was only 24"?
Thinking I might have to try and cancel first thing in the morning...
Oops, you're right ... I got the two lengths confused. DS1000 is correct, with listed length of 29.1 inches.
This means you have the lighter duty front axle option, which is identical to the B100/200/300 vans. So, you can get front end parts from regular parts stores, rather than places specializing in medium duty parts.
However, always have the parts counter person crosscheck against B100/200/300 parts ... someone could have listed incorrect 4000/4500# parts due to lack of knowledge, misunderstanding differences in axles, or making assumptions.
Difference between measured 28.25 and published 29.1 length could be due your friend having difficulty measuring what you have now ... it could also be due to what points they were using for the published length.
I would assume zerk-to-zerk is best but the engineers might have thought otherwise. Likewise, someone might have measured or WAG'ed it, when putting together publication. (The 32" length you mentioned was likely from someone actually measuring one ... and incorrectly using LOA length.)
Again, I apologize for the confusion ... I should have looked back at the previous posts, which I was careful to ensure I listed correct published lengths.
Depending on who you ordered it from, they should have a no problem cancelling it, or allowing you to return it. (This is one of the reasons I prefer buying locally ... plus most Alaska businesses have economical shipping channels, which online vendors can't match or even come close to.)
* This post was edited 09/07/17 07:34pm by Griff in Fairbanks *
You have to be very careful with eBay offers ... they're often mislabeled or misidentified. (Been there, done that ... and have roughly $100 worth of parts that aren't what they claimed.)
While searching eBay years ago, looking for Dodge automatic transmission parts, I ran across a listing for "Chrome Dodge automatic transmission pan." The description was for a "chrome Dodge THM350 automatic transmission pan."
For those who don't know, the THM350 is a Chevy/Buick transmission ... to the best of my knowledge never used in a Mopar vehicle.
I was curious, so I dug out my transmission pan gasket chart. The pan in the listing's pictures was for a C6 transmission ... which is a Ford transmission. (Needless to say, I made note to never buy from that seller.)
In another case, a listing was selling "354 hemi valve covers." Problem was the pictures didn't show the holes in the valve covers for early Hemi spark plugs. (The spark plugs go through the valve covers into the tops of the cylinder heads on early Hemis ... not through the sides of the heads like most other Mopar engines.)
Other listings have offered used parts for two to three times what it would have cost to buy a new or reman part from the local parts store. One listing offered a used upper radiator support for a 1990 Ford E150 van ... for $150. I bought a new one from the local Ford dealer for $50. (I needed one to fix the van after my wife hit a moose ... bent everything above and in front of the water pump.)
This isn't to say I haven't found good deals on hard to find parts on eBay. Instead, it means you have to be knowledgeable and careful buying off eBay.