View Full Version : Low fuel consumption indicates HP problem

Marc R
05-02-2002, 12:14 AM
" I have a '63 v-8 formerly rated at 195 hp (with a 2 barrel carb). Recently upgraded to a 4 barrel carb - estimated 250-hp.

Now for the question - I just installed a floscan fuel monitor. Wide open the engine only reads 15 gal per hour - at 10% of Hp for fuel I believe the reading should be closer to either 19.5 or even the 25 (for 250 hp).

Perhaps the full 4 barrels are not active so it is only reading the full 2?

Or is something going on and the engine is not providing the power it should???


Marc "

05-02-2002, 07:32 PM
"Since when is low fuel consumption a problem? ;^) (just kidding!) While the 4 barrel carb and intake will add some power, I don't think you're going to get 55 more HP out of it. Also, more info would be helpful. What engine is it? What RPM do you reach at WOT? Did you re-prop? Are all the butterflies fully open at WOT? Is the engine running properly (no bogging, missing, backfiring, etc.?) Is the fuel pressure correct? Are all fuel filters clean?

It's a common misconception that a bigger carb alone will give big increases in power. Usually not true unless the original carb was way too small. On a '63 vintage engine this is a possibility, however, since many manufacturers made an economy 2-barrel and a performance 4-barrel version of the same engine. But even then, the difference was around 10% if no other mods were made.

On a modern inboard or I/O, slapping on a bigger carb almost never adds much power, and can cause fuel usage and throttle response problems. The reason being that today's engineers closely match the flow rate of the carb to the designed power output of the engine.


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