BIg torque good mileage

[Anonymous]

I am thinking of using a 250.
Isky cam 1000-3800 rpm
1/6 rocker ratio
10.5:1 compression ratio
webber 38 carb with open hood scoop
clifferds headers single outlet
dura spark ignition
performance muffler

This is an idea, any remarks or suggestions?

I want 14+ mpg around town and 18+ highway cruising


Early Bronco

ford bellhousing
performance clutch
nv4500
limited slip rear 4.09:1
33" bfgs

 

[Anonymous]

if you had yer regular sized tires then it'd be easy you might even get over 20=0 depending on how you drive but with those 33's maybe:|

 

[Anonymous]

In this setup I would probably shift up at 3000 rpm.

If i could find a shorter duteration cam I would probably use it.
I wanted to find a cam 1000-3000.

What is the highest compression that has been achieved on premium pump gas?

 

[MustangSix]

On 92 octane you can probably go as high as 9.5-9.6:1 without detonation. The 250 doesn't tolerate high compression because of the significant deck height which leads to lack of quench.

 

[Anonymous]

what will longer rods do for a 250?

I hear that it will riase the compression, add torque, keep the revs down, and they do not break as easily.

 

[Anonymous]

any body ever modify the head to use glow plugs?

 

[xctasy]

Six HSC 2.5 rods from base modle Taurus/Tempo/Topaz I4 machines are the idea!

They are 6" long, should fit the 250 six.

This should give just enough room for the right compression height 255 V8 or 250 V8 piston.

A deap dish of about 12cc in the piston, is needed to give a low enough CR.

http://falconperformance.sundog.net/compcalculator.asp

Input Values: with 12 cc piston chamber.
Number Of Cylinders 6
Bore Diameter [inches] 3.700 (20 over with new pistons)
Stroke Length [inches] 3.910
Combustion Chamber Volume [cubic centimeters] 62
Head Gasket Compressed Thickness [inches] 0.025
Head Gasket Bore Diameter [inches] 3.81
Piston To Deck Clearance [inches] 0.00
Select Piston Type
Dish [positive cubic centimeters] 12cc
Volumetric Efficiency: 80%
RPM: 4500


Results:
Displacement, [cubic inches] 252
Displacement, [liters] 4.1
Static compression ratio 9.8:1
Cubic Feet per Minute required @ 4500 rpm, [cfm] 263
Estimated Horsepower @ 4500 rpm
(Assumes altitude of sealevel, barometric pressure of 14.696 and 60° air supply to carburator) 164 hp net

With 7 cc piston dish,

Results:
Displacement, [cubic inches] 252
Displacement, [liters] 4.1
Static compression ratio 10.4:1
Cubic Feet per Minute required @ 4500 rpm, [cfm] 263
Estimated Horsepower @ 4500 rpm
174 hp net

As per Jacks advise, I'd say 14 cc would be needed in the piston dish to get a 9.5:1 compression.

Hot tip is to use HSC 2.3 flat-tops (0 cc) with a special thick 79 thou gasket. I think Mark P noted one? You may get 10:1 with that.

As Jack says, the piston is parked about 104 thou below the top of the block. On all small or big Ford sixes, decking the block is the single best thing you can do. Just adding long rods on the 250 will increase compression and reduce detonating from the hard, hot edge of the lip of the bore. I'm not certain how it works exactly, but when the piston comes up to the top of the block, it shrouds and quenches the flame front. All engines produce more power this way, even if the compression ratio is similar.

In all race engines, pistons that park at the top of the bore are preferable. There are some other issues to deal with, but basically the idea you have is very sound.

 

[Anonymous]

what about using a 144 head on the 250 with the longer rods?

will I need a bigger intake?