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72 chevelle

Just got a 72 Chevelle. Want to make it more fuel efficient. Looking for the best way. Also, she appears to be running through a lot of water. This morning, radio leaked when I arrived at my destination. Thoughts?

72 Chevelle? Fuel efficient? That’s a good one–I needed a laugh this morning.

Obviously I meant the RADIATOR … not the RADIO … leaked this morning!!

Do a proper tuneup. Replace the plugs, points and condenser, distributor cap and rotor, spark plug wires, and fuel and air filters. OEM AC Delco parts should be fine, there are no magic solutions. Don’t expect much more than 10-11 mpg in city driving though. Summitt Racing or Jegs should be a good source for parts.

I did all this to a 69 Buick Skylark with a 350 2 Barrel Rochester and a Powerglide 2 speed transmission. City mileage increased from 8 mpg to 11 mpg. Adding a straight-thru muffler was good for ~1 mpg. Highway mpg was around 15 at 55-60 mph.

A leaking radio? Perhaps you meant the radiator. Where is it leaking, radiator cap, side tanks or fins? Check and replace the radiator and heating hoses if necessary.

Ed B.

I had a 1970 Chevelle, 307 with stock Rochester carb. Best mileage I saw was 15mpg, highway.

After you follow the advice about making sure it’s properly tuned, if you want optimal mpg, then you’ll need to drive like you have an egg between your foot and the gas pedal.

All you can do is to get a traditional “tune-up”, i.e.–replacing plugs, points, condensor, air filter, and fuel filter. And, you need to bear in mind that–unlike modern cars–this tune-up will need to be done around every 10k to 12k miles if you want to keep the car running at its optimum.

Keeping the tires properly inflated will help a bit. Replacing non-radial tires with radial tires will also help a bit.

The biggest problem that you are likely to run into is carburetor adjustment, if that becomes necessary. Any of the younger mechanics in the shop where you take the car are unlikely to have every worked on a carburetor. If it ever gets to the point where adjustment, or rebuilding, or replacement of the carburetor is needed, you will need to seek a mechanic who is over the age of 50.

As to the radiator, you just might have to replace it if simply doing things like soldering a top seam do not do the trick. Radiators have a finite life span, and this is shortened drastically if the previous owner(s) did not change the coolant frequently.

Don’t ignore the radiator leak as it can suddenly worsen, leading to overheating. If your engine overheats, it may sustain some serious damage.

I know it won;t be a Prius. But I wanted to get an extra 3-5 mpg.

Great advise guys thanks. Tune-up’s on the calendar this weekend. Thought I head of some new spark plugs that add a bit of efficiency. Also an air filter that allows more intake. And someone mentioned a Cherry Bomb exhaust system that …all taken together … would give it a little extra. As for the Radiator … just leaking from the top. Don;t see a leak anywhere else.

With your leaking radio, use a 1 meg pot for a drip pan to catch the grid leak. (Old tube radio freaks will know what I am joking about. I’m certain that even in 1972 the radios in CHevelles were transistorized).

Most of the good ways to get better fuel economy are going to be expensive. Putting a numerically lower gear set in the differential will help, but your acceleration will suffer. Transplanting a 700R4 into the car will help a lot, especially if you get one with a lockup torque converter. Reman units run around $1500, and you will likely have to make modifications to your tranny crossmember to make it work. If you have a long tailshaft TH350 in the car, your driveshaft will work, but it will have to be shortened if you have a short tailshaft. Electronic fuel injection will also help fuel economy, as well as improve driveability substantially. Out of these, the transmission swap will probably get you the best results, but changing your differential gearset will be the cheapest.

What engine and transmission do you have in this Chevelle? For the times, both the six and small block V-8 were efficient as compared with other engines. If you have the 2 speed PowerGlide, the gas mileage around town won’t be great.

I would tune up the engine with the parts specified by the factory–no fancy mufflers, air filters, etc. Non-factory specified parts probably won’t make that much difference in the gasoline mileage and you would be a very long time paying for these non-standard parts for any difference in gasoline mileage.

Get the car running the way the factory intended and enjoy the ride!

I used to own a '72 Chevelle Heavy Chevy big block. That was back when gas was cheap…and I used to complain about mileage then! It was a fun car, but I’m glad I don’t have to satisfy it’s appetite for gas nowdays!

Look at the radiator from the back side unless you see rotted out cross fins from the front. In that case, change the radiator without even checking from the back. If 5% tp 10% are missing from the back, you definitely need a new radiator.

For fuel economy, the vacuum advance has to work, not just hold vacuum. If the breaker plate does not move when vacuum is applied to the advance mechanism, replace it. Replace all rubber vacuum hoses that have hardened or cracked on the ends.

I almost forgot, make sure you have the hot air tube that goes from the exhaust manifold to the air cleaner. If it’s missing, you will use more fuel. The engine is always supposed to get some warm air. When warming up, it is supposed to get even more warm air. Check the heat riser operation too.

You use to be able to buy a fuel-injection conversion kit for GM small and large block V8’s. Sold by Holly. I did one on a 67 Chevelle with a 327. About a 2mpg increase.

Different rear-end and possibly a different tranny also…but the cost isn’t worth it.

Mike’s fuel injection idea is actually a good one. There are a number of these that are “plug & play” for stock commonly produced GM engines. Pick up any street rod magazine in the bookstore and they’ll have advertisements for these systems.

I’ve never put on ein, but a friend put one in an old 'Vette and was very pleased.

What engine and transmission?? Swap the points distributor for a factory HEI electronic unit used 1975-1981…

If it has a small block V8 and at least a 3-speed tranny, you will probably get about 15-17 MPG tops in mixed driving. If you’re doing that well, that’s as good as it gets.

It can be done…but it’s going to take a LOT of money to do it. I’ve put in an aftermarket fuel injection system on a small-block Chevy V-8 before…About 2mpg increase in gas mileage…from a pure money savings point of view…it wasn’t worth it.

That’s exactly the mileage I got (16mpg) with my 1970 Chevelle (307, 2 spd Powerglide, with 2bbl Rochester carb)