How to get 40 mpg from a Ford 302 V8 | Video

Ever do something absurd just for the fun of it, but then accidentally make something that works a little too well?

That’s pretty much the story of how this person managed to get 40 mpg from a Ford 302 V8 by just replacing the carburetor with one from a lawnmower.

Driven5 UberDork
4/29/22 1:09 p.m.

Impressive results that would have been a lot more so had he actually driven a loop back to his starting point when measuring fuel economy, minimizing rather than maximizing the number of variables that could have affected his results. His electronically controlled valve metering air in after the carb is a bit of a 'cheat' too, but is also quite clever.

GRM did it first though:

fearlesfil New Reader
4/29/22 3:21 p.m.

Good for him. Some of the '60s V-8 tri-power carb setups were designed with a small center two barrel to operate alone up to half throttle to provide better economy, before the other two larger carbs would kick in. The popular spreadbore 4-barrel carbs used small primaries for similar reasons.

Some mid-late '80s carburetors were set up in a similar fashion to this guy's experiment, adding air after the carb to lean the mixture in a couple of stages based on local barometric pressure, to compensate for elevation changes (carbs get richer the higher in elevation you go).

A friend got his in-line six Gremlin up to 60 MPG at 55 MPH (the national speed limit in '78). Stock skinny highly-inflated tires, optimized ignition advance, Arco Graphite oil, 205˚ thermostat and the other usual tricks were tried first. What put it over the top was relocating the PCV valve to the breather hose, so the crankcase was referenced to near intake manifold vacuum. This reduced pumping losses and fuel consumption dramatically. We made a 200 mile trip Yuma to Phoenix and for fun took turns drafting each other the whole way, swapping the lead at the half way point. My '70 mustang 351 Cleveland (typically 18 MPG) made it with 3/8's of a tank where I usually took 3/4. He made it with only 1/4 of a tank (and the Gremlin had a smaller tank). Truly impressive experiment both for drag reduction and his modifications. After swapping a Chevy 350 and Ford 9" to the Gremlin, he tried the same PCV relocation trick, but that failed when one of the crankshaft seals was sucked inside out smiley

billstewartx Reader
4/29/22 4:43 p.m.

yea, but what kind of mileage did he get with the original 2 BBL carb on same setup? 

GameboyRMH GRM+ Memberand MegaDork
4/29/22 5:00 p.m.

Makes you wonder if a modern ICE vehicle could benefit from a tiny throttle body with a tiny injector and a mazelike intake tract that the car switches to in low-load use, could be done in software if both the tiny intake and the main intake have an e-throttle...

californiamilleghia UltraDork
4/30/22 6:06 p.m.

Arco graphite oil !

 I remember that , did it work any better than normal oil or modern synthetic.

te72 Reader
4/30/22 10:31 p.m.

I once followed a caravan of friends with their enclosed trailers, in my Miata, to an event out of state. I managed to drive about 200 miles, race for two days, and only used something like 7 gallons if I recall. Despite the autocross, I calculated the mpg to be somewhere in the 30's if memory serves me correctly.

californiamilleghia UltraDork
5/1/22 11:10 a.m.

Can we have 2 carbs , 

the "get up and go" carb and the "cruising" carb 

set the cruising one up for 70-75  mph

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