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Ford Crossflow 250 Performance Mods |
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The rules are exhast, carb, then maybe a cam. Any cam change on a Ford
requires a total engine rebuild becasue the stock components aren't
designed for a high lift cam. Low tension rings and the engine in
general isn't designed to go past 4500 rpm. Thats 300 rpm down on the
XE, and 800 rpm down on what the old XD iron head engines used to get
away with.
XF's are very prone to detonation with todays fuels, and you have to
check out the whole package very specifically to make it work well.
However, there are no major electronics to deal with if you change to
an XE ignition set up.
You can get to the 196 hp mark if you follow Dick Johnston SVO spec.
Use a good set of headers, thats a 18% power boost, 12% economy
improvement. Use the best exhast you can make. An XF is an absolute dog
to get a great exhast system on because the Watts linkage and spare
wheel well and plastic fuel tank prevent a preferable dual exhast
system being set up. And don't listen to any one else a dual system is
the the only option to make it sweet on the street.
Copy the EB XR6 exhast layout. It had a great extractor set, four
mufflers, twin exhasts to the diff, and then one pipe past the axle.
Becasue you don't run a catalyist exhast, then you should run a basic
dual outlet header (extractor). Then grab quite small pipes say from an
XA-XD Vee-Eight exhast system with two good big 2.125" glass pack
mufflers (resonators) at the front, and mount them backwards so the
serations are not facing into the air steam. You then mount two good
mufflers in the 2.5 inch range which flow at least 200 cfm each at 10"
flow pressure at the back. You then group both into one big single
63.5mm internal diameter pipe at the back. This is basically what the
XR6's first ran. The backpressure and sound is then times nicer than
the silly big singles everyone else runs. If you have money, you can
copy WasaIII
X pipe set-up. A balance pipe lowers the tone, and stopes it sounding
like a Cessna air plane at 1500 to 2500 rpm. Very important these days
with poloce getting edgy over noise.
Once the exhast is sorted, you can then go for broke on a good
intake. For my money, I'd get a Cain 4-bbl manifold and import a 4180
Holley carb off a 1984 to 1988 351 4-bbl Vee-Eight, or a 5.0 HO
Mustang. It's a brilliant carb, and is compatable with the stock Carter
fuel pump becasue it has a return line. Its rated at above 600 cfm, and
fits all the emissions bits.
Remove the stock XF EST computer, and run a reconditioned XD or XE Bosch duraspark with a the right module for the transmission
Then go buy a Kelford cam which has a single pattern, hydraulic 280 degree, 215 degrees lift at 50 thou duration figures.
Take the head off, and upgrade the valve springs, pushrods and
lifters and rockers, sled fulcrums, new collets, re cut valves.
Re-profile the combustion chambers to the XE set-up, which means
removing the high swirl ramp around the intake valve.
If the engine needs a rebore, then do the whole engine, with good rod bolts, good pistons and preped stock rods.
Don't go over 5000 rpm, and you'll have at least well over 200 ponies.
If you use the stock Borg Warner, have it rebuilt with EA clutch pack, and track down a looser coverter of about 2000 stall rpm.
If you have access to a 4 or 5-speed, amke sure you get all the
gear of the donar xe or XF 4.1 vehcile. 3.3 4 or 5-speeds will get
killed under the load. Toyota Hilux or Supra 5-speeds need the right
gear ratios and clutch to work on the aftermarket bellhousings.
Your ideal gear ratio is most likely a 3.45:1 limited slip EB to EL
XR6 diff, but the stock 2.77:1 open wheeler will be okay until you
source one.
Everyone says just wack an OHC in it, but unless you have a good
package from a wrecked vehcile, your better off doing the mods I've
suggested in little dribs and drabs.
Simple, Small mods = Sucessful.
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