The typical A-series engine buildup threads always seem to be concerning producing more power. This thread is completely different.

I am interested in maximizing the fuel mileage capabilities of an A-series engine. Yes, even moreso than these cars could muster from the factory. I am competing in events called "Economy Runs" here in the US. My car is a '77 B210. It is the same car as seen in this thread: here. It's twin carbed 1608cc A-series will need to come out temporarily for these "Economy" events as it only gets 25 miles per gallon.

The B210 is a natural choice for these events because economy is exactly what the car was built for in the first place. But my 1608 has twin Dellorto 40mm carbs, small Crane cam, and has a fairly high compression ratio at 10.25 to 1. So now I'm thinking about going back to the stock fuel sipping configuration - or maybe even a bit further.

The plan was to remove the side drafts and reinstall the original intake and original Hitachi carburetor. Then a friend pointed out to me that the high compression I am currently running in the 1608 is a great for gas mileage. I had forgotten about that fact. That got me thinking and reading. I read an article all about compression ratios and how it effects power and economy. One quote says: "Increases in compression ratio do not only impact power generation; they also create gains in fuel efficiency. The higher the static compression ratio, the more fuel efficient it will be. This is the reason for diesel's superior economy over spark ignition engines."

It goes on to say that: "If an engine having an original static compression ratio of 8.0 to 1 was increased to 11.0 to 1, power would rise by only 5.2 percent, but fuel economy would improve nearly 20 percent!"

Now I'm thinking about building another A-series engine specifically for fuel mileage. Instead of detuning the 1608, it seems like a better idea to start from scratch with a low mile standard bore A14 block I've got here.

I read up about the different cylinder heads on this site in the Tech section. Unlike all of the "power" buildups for the A-series and the using better Oval port heads for maximum flow, it seems like the best bet for fuel efficiency will be the smaller round port heads. I checked my stock of heads and found a really nice condition "990" casting round port head. It is from a 1980 US spec A14. Here's what the cylinder heads article says about the 990 casting: These came on the "GFU" and "MPG" cars (USA-market B210 and B310 fuel economy champion models). Perfect!

So basically, I'd like to build a standard A14 engine but with high compression [10.5 or 11 to 1]. Yes, this will require expensive premium fuel [with some leaded racing gas mixed in as well to run, but I am trying to get 50 mpg with a B210. Has this ever been done?

Has anyone here ever experimented with trying to exceed the great fuel economy of the A-series engine?

Cheers,

Mike