Q1. Intake - Will stock do? Will a Redline or Sprint make a big difference?
A1. Stock is Ok. I've got a Holley 2300 350/500 post in the making on how to fit one to a stock X-flow Weber intake. Its cheap and it works well, has EGR. Either Holley Weber, Holley, or stock Aussie ADM Weber, its very good at making power with excellent economy
The Ultraflow Sprint is simply the best performance 2-bbl manifold , but its not emissions legal. Stock ones have EGR. Redline, Lynx etc are non-emissions, and can be very good too. There is possibly a trade-off in economy with these intakes over the stock one. If you plan to see over 200 hp, get a Sprint manifold.
Q2. Port/Polish- Does a XF benefit from a mild port polish or is it best left alone?
A2. *On the exhast, polish away. No worries.
*Best fuel economy happens with stock head profiles.
*Polishing the intake conclusively looses mixture motion, causing early detonation and a loss of power at part throttle.
*De-dagging (mildly cleaning away roughness without polishing) is the best option.
*The chamber needs to be smooth, but not polished. Any obvious mix flows, or chuncks of alloy, need to be cleaned up.
*So long as long the quides are well supported, then it is okay to bullet nose them with a 30 degree chamfer, cut them away entirely if you have new phospher bronze ones fitted . The guides do cop a hammering on cross-flow because the valves are canted. Roller rockers help with longevity, and allow you to cut quides away without something nasty happening.
*The stock valve inserts can be re-profiled, using larger Cleveland stainless valves if you can get then machined to suit (DYNOED250 uses 1.96" intakes!), but you need to get some information on this. The inserts are very hard. Any increase in valve sizes on the x-flow help torque and power if the port profiles stay the same. Unless you have a post 85 HF6 head, there is no shrouding with this modification.
Don't do any alterations. Run it as it comes, but check its serviceablity.
Q3. Compression ratio- Remember this will be a driver
A3. The stock ignition is set up for best mean combustion pressure, with advance whic comes on quite strongly, then levels off after maximum torque (2500 to 2800 rpm). Some unleaded versions after 1986 have a MAP sensor which taylors advance to as high as possible. All this means the stock 9.35:1 or 8.8:1 compression ratio is quite okay. Never go above this unless you have some means of detonation control.
US gasoline is reported to suffer large variances in actual octane number because of transport issues, certainly more than in Australia. Don't go to high. Avoid the big bang. If you run a wilder cam, the stock ratio should be okay.
Q4. Cam -
A4. Use the standard line of Crow Cams as a template. Chevy OffRoad and Marine (COME) are also at the cutting edge. I'd certainly look at getting one of these. The engine needs to be built around the cam choice, but a cross-flow is never going to suffer if its cammed within the 256 to 280 degree total duration envelope. The stock cam retards things to a great degree, with not much lift or duration, and the head has small ports. Any cam will wake up the X-flow a great deal. Avoid cams over 280 degrees total duration if you are going auto. The 50 thou lift shouldn't go over 215 deg, or you will loose a good deal of low-end torque whic you will want for a daily driver. Economy suffers if the common rev range used (often 1000- 2500 rpm) is lower than the maximum torque area where the cam comes on song.
Q5. Pistons -
A4. Follow Jacks example. Low-tension rings and pistons used from 1985 on wards are not designed as performance items. These are very good items, but you need to figure if your doing to explore the 5000 rpm+ rev range much. If not, use them. The ring packs tend to flutter at high rpm due to the recommended ring gaps. ACL offer some awesome high performance pistons. Talk with alloydave, or check his posts.
The US 250 pistons, or espeically the HSC 2.3 items, are very good since they are designed for a high-rpm, more vibration ridden engine than any six. Using 2.3HSC pistons with 2.5HSC rods would be a very good combination, but the stock compression must come under 9.35:1, and the piston must not hit the head. Stock rods can expand or streach up to 30 thou at 5500 rpm.
Q6. Carb - 2v or 4v - will the stock 2v be ok?
Yes, the stock 2-bbl is Weber ADM is an unbeatable econo carb. But with 29 and 27 mm chokes, and only 34 mm throttles, its way to small for anything more than a stock engine tootling. There is nothing you can do to elevate its performance by changing the chokes. There are 31 and 30 mm chokes available, but that will only add a few hp, and then you must re-jet it as well. The 2.0 Pinto, 2.3 Mustang/Capri/Fairmont/Ranger carb is similar, and can be changed over as they are the same bolt pattern, but the auto choke housing hits the rocker cover. And it won't produce any extra power at all.
If you are planning any more than 130 hp, get a Holley 2-bbl 500 cfm carb. It's little brother, the 350, is too small to make a significant impact on a 250 cube engine. Dunno how the emmissions aspect is coped with unless you use a 2-bbl 5.0 GT carb from a 1982 Mustang, or the marine 2-bbls used on some 5.8/351's. I think they are Holley or Autolite, and they gave about 145 to 164 hp on those cars. These are emissions legal on the parent vehicle. The stock intake won't allow it to fit, as the electric choke collides with the rocker cover. You have to use a Racer Walsh-style HoleyWeber #5200 to Holley #2300 adaptor, and add another 0.8" (20 mm thick) phenolic or alloy adaptor plate to push the manifold out furher to gain some elbow room.
Any 4-bbl carb (465 and 600 cfm are popular) with Redline intake will probably hit the drivers side spring tower. I'd not use one myself.
Q7. Anything else major?
A7. Yes, bellmount holes are up the creek. No stock US trans will fit unless you have an adaptor, or got the engine with a stock Aussie gearbox.
Stock flywheels use 160 teeth, 13.3" diameter and Bosch starter motors. The stock crank will take flexplates from F150 300 or US 250, but its not certain if the stock Aussie C4 ran a 157 teeth flexplate or not. Stock Auto torque converters are 9.625", not 10.5, 11.4, or 9.25". So you need to get your transmission thoughts down on paper, as theres plenty to screw up a good scheme.
Auto BW's suck swamp gas.
Aussie C4's are quite adequate.
BW 4-speeds are different to you SR4, or SROD transmissions.
BW T5's are non-world class (nwc)
Toploaders are rare, but nigh on bullet proof.
BW 5-speeds found behind 3.3's are just trash.
All 1966 to 1993 OHV backing/sandwich/separtor plates are the same shape, but the thickness varies between some. Fords all over the world seem to have issues with run-out in ring gear and the accurate placing of the starter motor. If there is any miss-engaged starter problems, you should focus attention on run-out in the flywheel starter and ring gear.
Since your not fitting it to a Fox, FSP or Pacemaker headers will fit without modification. If you are keen on using a SBF V8 trans, either AOD or Top Loader, SR, or SROD, you need to make an adaptor which I've posted the dimensions of. These put the starter motor bellow the block, but that causes problems with the header tube, and you have to modify the down pipe.
The stock cast header is too restrictive, but its better than the US 250 by a huge margin. They do tend to rust out. OPen road cruising and light load fuel economy improves up to 12% with headers.
If all is stock, 131 hp net at the flywheel and 228 lb-ft will give you low 17 second quarters with a manual in a 3000 pound Mustang.
With headers estimated 155 hp and about 245 lb-ft, gives you about 16.3 second quarters.
With carb upgrade to 500 cfm, you loose some mpg and gain up to 175 hp net potential with a stock cam. 15.7 second quarters possible. Change the cam to 280 degree, about 195 hp, and 15 second quarters.
Don't run a big bore exhast as the car will get quite noisy. Smaller dual exhasts or well-muffled exhasts less than 2.25" diameter are better. Check with Jack on this.
You'll note that the x-flow isn't the smoothest engine in the world, but its always first out of the starter blocks in the traffic lights grand prix. It's more like a comparing a Cleveland V8 to a Windsor. The engine has a considerable amount of urge and character, whereas the stock log headed sixes fell quite tame and quiet.
Any of the above modifications will make a huge improvement to its on-road performance
