Thread: Rebuilding a 292 for mpg

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I'm in the process of gathering parts to rebuild my Ford 292. Engine is like new but has really low compression because of 312 rods which were installed by the machine shop (long story there).
With gas prices now and in the future, I think some increase in economy is required, and would like your input. Here is the motor's current stats, and my thoughts on some new one's:
Currently-
Bored .080 to 305 inches
Cam 270 duration, .420 lift (relatively low lift due to rocker ratio of 1.43
:1, with 1.54 rockers it would be .460),
Intake valves 1.92 and exhaust 1.51,
Dual exhaust with 1.75 inch pipes to 2 inch in/out mufflers, then to short
2 inch side turnouts with exit just behind cab,
aluminum 4V intake, dual plane, with 2V adaptor and 2V autolite,
compression now approx. 7.5:1,
rearend 3.00,
mpg approx 10,
Pertronix Ignition,
Idle vacuum 11.5,

Planned-
Cam 260 duration, lift .420
Increase exhaust valve size to 1.6, if it will fit
Increase compression to 9.5:1 with rods, .041 quench, and surfaced
heads.,
keep a 2V carb, but increase venturi size from 1.02 to 1.14,
rebalance motor,
replace flywheel with aluminum unit,
reuse pistons with new rings (pistons now have 500 miles on them)
Total vehicle weight is 2750 lbs wet, and its a 46 1/2 ton Ford truck.

Thoughts or suggestions?

go to a small 4v carb, you'll actually get better gas mileage as long as you keep off the secondaries...... i've seen guys completely block off the secondaries for economy, but the 4v has smaller primaries..... but you still have those secondaries when you wanna open it up a little bit....other than that i dont know too much about Y blocks

Good point. Something like a 390 Holley. What about increasing the size of the exhaust valves? My thinking was that it would increase the volumetric effieciency which would help with mpg. I'm just taking a guess on the cam.

valve size increases dont always help... you might be able to get away with going a little bigger, but truly bigger valves wont help much.... going lighter will get you more improvement on the engine..... lighter valves are more expensive... but they help..... they get pricey though.... i spent $400 just on valves when i did my heads because i wanted to get them as light as possible

I think you are on the right track with the quench and bumping the compression up. Is that .041 quench with zero deck pistons? The 390 carb should work too. Is the intake a long and narrow runner type? That would optimise lower rpm torque and increase mpg too. Those small valves will be dandy for higher port velocity too as long as they aren't the choke point. Polish the combustion chamber and maybe coat the piston tops too. I think Speedway has some ceramic spooge for that. You can look into some of the tricks that the emissions cars have been using for economy like electric fans and running a tad hot plus the cam grinds too.

Originally Posted by w2zero

I think you are on the right track with the quench and bumping the compression up. Is that .041 quench with zero deck pistons? The 390 carb should work too. Is the intake a long and narrow runner type? That would optimise lower rpm torque and increase mpg too. Those small valves will be dandy for higher port velocity too as long as they aren't the choke point. Polish the combustion chamber and maybe coat the piston tops too. I think Speedway has some ceramic spooge for that. You can look into some of the tricks that the emissions cars have been using for economy like electric fans and running a tad hot plus the cam grinds too.

The .041 I'm figuring is with a .025 steel gasket and pistons .016 down. In the Y-block world the 1.92 intakes are large, as are the intake ports on the heads and intake runners on the manifold. Actually I think poor port velocity is a main problem now, caused by the mismatch between cam and compression, which in turn pushed me to a small 2V carb after trying a 600 4V. But hopefully that would improve a bunch with increasing comp.
The combustion chamber polish and piston top coating: is your thought there to deter detonation at 9.5:1?
There is an electric fan and fuel pump on now.
I really dont know what an appropriate cam would be. The 260 duration and .420 lift is just something that is less horsepower oriented than mine, but more so than stock. I figured (right or wrong), that decreasing the duration would increase port velocity.

Yep, 260 is the mildest cam Isky grinds for that motor. Should work great with the 9.5 max c.r.

http://www.iskycams.com/onlinecatalog.html