Building The Ultimate 250 Crossflow

A

Anonymous

Guest
I am just a week or so away from sending final payment to a friend in OZ who will locate and ship me a 250 Crossflow for my 68 Mustang.

The goal here is to have a real streetable car that runs on pump gas but is capable of smoking most V8s and ricers. Here is what I have so far..

Carby crossflow maybe set up for 4v carb
sprint manifold and headers
Port and polish
Bosch electric dizzy
I will be using a crossflow C4 bell and a us C4

Suggestions? Ideas?
 

SONNY

Well-known member
if you want to build a hot 250 get your mate to get a set of 200 rods and the acl piston kit to suit.the kit strokes it and because of the shorter rods the engines will buzz to 7,000rpm.this is a move in the right step to building a 250 thats got some coconut sized nuts.
 
A

Anonymous

Guest
Will US 200 rods and pistons do the trick? Azcoupe is selling custom pistons now...will they work?
 

aussie7mains

Well-known member
Some confusion here, the rods you need are the aussie 200ci six, 6.27 long. The pistons are ACL brand to suit this combination, it gives a long rod 250ci crossflow. Yanks 200 rods are no good.
As to the other objectives the Sprint manifold is only available as a teo barrel, so forget your four barrel.
The better way if you can afford it is triple Dellortos or similar.
Otherwise its all pretty conventional stuff. You best go with roller rockers , studs etc. Go to the Yella terra and crow cams website to see for your self.
A7M
 

SONNY

Well-known member
yes sorry i got it wrong the 200 rods are LONGER not shorter.but like i said it strokes the engine and they love to rev.acl has developed the pistons to suit aussie 200 rods to go in an aussie 250 engine.i don't know if your rods are the same as ours,but if you go this way get all the aussie stuff then its gonna work
 
A

Anonymous

Guest
I know some guys have modified a 2v head to mount a 4v carb. I was under the impression that the same thing can be done with a sprint.
 

xctasy

5K+
VIP
4-bbl conversions from stock 2-bbl manifolds.

Any thing can be if you alloy weld, but on the crossflow, your better buying the right kind, or adding a Barry Grant or similar 2-bbl to 4-bbl adaptor. Hacking up a good Ultraflow Sprint with a TIG welder isn't smart. The Aussie 250 2V non crossflow has the two inner tracts pitched appart 5.44", so Ford Oz had plenty of meat in the centre section for welding. Not so the crossflow.

See how close the inner runners are to the 2-bbl base?

1021DtO82DA9245intkaemanifold.jpg



There are Cain, Redline and Lynx 4-bbl intakes which suit, but are not as good as the stock, Sprint or triple Weber manifolds.

They do work and will be as got as Mustangaroos 4-bbl 2V conversion.


2-barrels:

The 2-bbl 500 Holley may yield 300 hp on a methonol burning oval track racer, but you'd be fortunate to get more than 215 hp with the Ultraflow Sprint because the 500 cfm 2-bbl is really only a 354 cfm carb.

Triple Webers:

The stock brake booster may hit a triple DCOE Weber instillation, may not. It depends on the car.

Just make sure you get the stuff for the alloyhead crossflows after mid 1980 until early 1993.

The top head is cast iron, from 1976 to 1980. The one below is 80 to 93 alloy Honda head

1004DtOXEFalconAlloyHeadIIHF5Hondacastcrossflowh.jpg



The 2-bbl manifold here isn't for the alloy head. It has a coolant path under number 2 intake. Don't get one of these.
Item4000NewImage4.jpg


This is not the Ultraflow Sprint, but its similar. If you want to hack one up like Mustangaroos, then it may be better to get a 4-bbl intake insted.

Item4000NewImage3.jpg
 
A

Anonymous

Guest
So if you use the 200 rods in the crossflow, what is the new overall capacity?

And how much higher will it rev? Will it really go as high as 7,000?

How much would these rods cost? How much would the forged pistons cost?

And would the 200 rods, and pistons be well suited to a to4 turbo on LPG crossflow?

This sounds awesome to me. Are there any drawbacks?
 

SONNY

Well-known member
ok the 200 rods are cheap,just buy a burnt out 200 from the wreckers or private.they are good revers,because of the rod lenght and the angle of the pistons during running, a stock 250 doesn't rev that well,but thankfully acl has made a piston to suit the 200 rod in the 250,and thus sloving the resistance a stock 250 has.im not sure of the new capacity of this combo.the piston and ring kit,well i'm having a guess but round $700.this combo may suit a turbo lpg,its realy down to comp ratio i suppose,you would just have to ask them(ring acl brisbane)on what comp ratio it gives the engine,they will know.the only draw back i can think of is a sore neck from the tyre frying tourque.maybe someone else has more info on this
 
A

Anonymous

Guest
Sonny this is fantastic information. I am sitting here smiling my ass off reading what you have written about these 200 rods and acl pistons. I knew you could do it to the pre crossflow 250 but I had no idea you could do it to the crossflow as well!

Its like a double bonus, extra revs and extra capacity.

I would love to hear from anyone who has done it so I could get exact capacity and rev limits. Would anyone like to have a guess? (come on xtaxi you know you want to lol).

I really hope these 200 rods and acl pistons go well with boost.

thanks
 
A

Anonymous

Guest
theyll rev to 7,000?
im running lpg, using the conventional rockers/pushrods

i was aiming for 5,500 rpm
anyone got any info?
 
A

Anonymous

Guest
thek":2k9xh7lv said:
I really hope these 200 rods and acl pistons go well with boost.

i seriously doubt they would go well with boost, acl ranges give you the option between a 10:1 compression or a 11.8:1 compression ratio
 
A

Anonymous

Guest
OverDose":36a4fss6 said:
i seriously doubt they would go well with boost, acl ranges give you the option between a 10:1 compression or a 11.8:1 compression ratio

Damn I knew it was too good to be true. Thats way too high for boost.

Are there any good/easy ways around the high compression problem (for boost). Maybe taking metal out of the top of the combustion chamber? I forget what thats called.

Any other ways? This extra capacity and extra revs thing with the 200 rods seems too good to just give up on.

any help is great thanks
 

xctasy

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Yeah, I have done some calculations.


XR500 did some L/R calcs way back in 2002, and yielded some good figures on how the length to rod ratio affected intake pulses.

I made the statement that a wild 250 could get another 12 hp from running 6.27" rods rather than 5.88" rods.

Well, I won't go into the details, but I did a Mopar, Mini, and Falcon 200 250 graph, and ploted the results. I also used 54Fords 1600 cc Toyota details.

The result is that if you improve the stock 1.5:1 rod ratio (5.88" rod, 3.91" stroke) to 1.6:1 (6.27" rod, 3.91" stroke), the power per litre goes up half the increase. Each 0.1 increase yields a 5 to 7% imporovement in ratio, but only a 2.5 to 3.5% increase in power, if the cam stays the same. Optimised, the rev range and cam and power could possibly go up equal to the percentage improvement.


This 1.067 factor only gives a 1.034 power increase. Thats 4 hp on a stock 4.1 2-bbl, and about 7 hp on a 200 hp machine. I'm certain there is more to be had, but most cams are designed around the stock rod ratio, and the window area is changed by the rod ratio.

The power increase is linear from idle to full rpm, and the rev range can increase an small amount.

For you information, the use of 6.06" AU rods in a 250 on yields a 3% (1.03) rod ratio improvement, and only 1.5% power increase.

The second benefit is a huge reduction in side loadings, thrust loads, and wear. The thrust loads reduce vibration, and are likely to reduce the coupling load which creates harmonic vibration on the crankshaft. The torsional vibration period in the crank, rumoured to hit at 5300-5500 rpm on the Aussie 250, can be softened by a reduction in thrust loads. (The US 250 is going to be higher 'cause the crank and chain drive is much heavier, while the 200 Aussie engine could go over 6000 rpm or more without a harmonic, just like the XT5 Holden)

Summary is that the peak rev level is able to go upwards in addition to the power increase, so the rod ratio has two benefits.

Third benefit is that effective compression is lowered by half a percent, and this allows a higher compression without detonation. The increased residence time (the time at which the piston is near the very top of the movement, subject to heating) increses detonation, but unless there is problem with the closeness of the piston to the flame front, then it won't hurt the compression ratio you can carry.


As I've said, I want to do a full-up run on a 200 cube Aussie long block.

One with a custom 144 crank, ( 6.27" rods, +80 thou 186 pistons)

then a 170/188 crank , ( 6.27" rods, 2.13:1 L/R, adjustable decompression plate)
then a 200 crank, (6.27" 200 rods, stock pistons, 2.0:1 L/R)
then a 221 crank , ( 6.27" 300 I6 rods, 1.8:1 L/R)
and then a 250 crank. (5.88" rods, 1.5:1 L/R)

I'll be money the test results yield the same data.

I'll leave you with one thought. Why does a 16% bigger 351C 4-bbl only have a 6.5% power increase on a 302C 4-bbl (149 kW verses 140 kW), or a 25% bigger 250 only have an 8.9% power increase (98 kW verses 90 kW? Answer. Rod ratio and bore to stroke ratio!

Back to my traditional head up a$$ pose.
 
A

Anonymous

Guest
so ideally if you were to get a xf motor, 250crank, 200rods, acl pistons, which apparently would be good for 7000rpm, and use a decompression plate to bump the compression down to 8:1 would it still be good for 7000rpm? or does the compression ratio controll revs?

and what top end could handle those revs? rollers be good for 7000rpm?

apparently 9000rpm is possible, but soon after the piston/conrod came flying out the block
 

xctasy

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OverDose":2o7jn0ui said:
so ideally if you were to get a xf motor, 250crank, 200rods, acl pistons, which apparently would be good for 7000rpm, and use a decompression plate to bump the compression down to 8:1 would it still be good for 7000rpm? or does the compression ratio controll revs?

and what top end could handle those revs? rollers be good for 7000rpm?

apparently 9000rpm is possible, but soon after the piston/conrod came flying out the block


I have heard from the ex Repco engineer who did dyno runs on the 250, that early 250's were able to take 7500 rpm without granading.

As for the alloy head, you have to posilock and fit 7/16 studs, and I doubt the fatigue resistance of the cast crank at 7000 rpm would be very good.

The stock Honda alloy casting has really small intake ports, and I can't see it liking the rev range. 2V's and early iron x-flows have much bigger ports.

The 200 rods are nothing special either, and rod bolts need to be stronger V8 Windosr spec to clamp things down. I'm certain 300 I6 6.21" rods would be heaps stronger. The integrity of the main seal for early XF's is an issue even on a street engine. I can't imagine a seal taking the revs without springing a leak unless its been converted to the 302 neoprene seal. There is still a harmonic period where a 250 crank shakes hard somewhere in the 5 to 6 grand level.

Out of my depth here. Talk to the oval track guys, A7M, Dynoed250, yadda yadda. They should know.
 

aussie7mains

Well-known member
Must correct a few missconceptions here.
The 200 rods will NOT increase capacity of the 250, its still a 250 and given the size of the block I wouldnt be bothering to make it any bigger, stick with the long rod 250.
The valve train on the crossflow will limit rpm to around 7000, and it will need lotsa work to be stable at that. 6000 is much easier, but even then costly.
Why not go straight to the later AU OHC engine, its already got longer and better rods, a better bottom end and its got a stable reliable OHC system with a head that flows better than the crossflow.
Theres cams around from Crow now and even a variable cam drive if you really want one. The intake is very good, twin tuned tracts.
this is all in and engine thats still relaitely cheap and physicaly the same size as the crossflow. just much more modern.
If your really serious and inline ford six power look into that?
A7m
 
A

Anonymous

Guest
I assume those OHC motors are fuel injected? I want a real simple setup ( ie. carby ). But if they are better then the xflow and the ignition and fuel injection is not too complex may be worth looking at.

What about my C4? One advantage of the xflow was that I can get a C4 bell.

What about cost?

Any links or info on the OHC I6?
 

xctasy

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A7M, you are so right. The OHC is the only game in town if you want revs galore, but I'll put my spin on things.

For what I'm about to say, I hope its not too negative, because the OHC stands head and shoulders over the x-flow.

Firstly, this is complicated because untill you've been left high and dry with a foreign EFI engine with no parts back-up, you can't begin to realise the hassle and stress involved. Over here, they are easy to get from wreckers or aftermarket supplies or Ford, and they are so tough! Like, 221 hp and 270 lb-ft tough on the 4.0 XR-6 versions. Some stock early 3.9 TBI's were less than 170 hp, and only 228 lb-ft.

The x-flow OHV swap Jack did into his 66 Stang was a fairly cheap pick-up as foreign engine swaps go, but he spent lots getting everything sorted, and had JD and help from all the way (and possibly you A7M).

It's not fair to for any of us lucky Aussies or Kiwis to say that an OHC engine is an easy swap into an American Ford. I've been intimately involved with electronics since 2000, and all I can say is they are a crock of endless stress unless you know the ins and outs. If you follow the factory systems from a late model Falcon and put it in a Mustang, bank on a total need of about 5 US grand (assuming 1500 delievered, service assistance and wiring help to run the stock EEC Falcon wiring loom, or buying an aftermarket ECM) and three months from the time its landed. I'M NOT KIDDING!!!!. The OHC is also longer than a US 250, so you have to look at getting the right serpentine drive and radiator parts sorted.

My friend Richard got his EFI X-flow and wacked it into his Cortina for a fraction of the cost.

Everything new has no parts support from Ford US. The stock gearbox, fuel lines, ECM, belts, and all the ignition bits are foreign.

Since the customer calls the shots on what he wants, the person providing the components must ensure that the customer ends up with the best compromise between performance and service.

Spyke said:-
I assume those OHC motors are fuel injected? I want a real simple setup ( ie. carby ). But if they are better then the xflow and the ignition and fuel injection is not too complex may be worth looking at.

The OHC is a great, strong engine if you have the later 4.0 liter engine. The earlier 3.9 OHC wasn't that flash. All OHC engines are injected.

Engine mounts...just use 200 US three bolt mounts. Most ohc's have the same block pattern, but after 1998, they got a huge alloy sump and other mods which make fitting them tricky. Ones after 1995 had no distributor, but it returned in 1996-1997.

The OHC wont take a C4 unless you convert to the SBF adaptor I use. The six has the starter nesting where the cam was in the old ohv I6's, and needs the US SBF starter fit a V8 C4 behind it.

The stock SBF C4 will then fit. A stock American 200 C4 wont fit without a lot of work, and the V8 C4/C5's are more common anyway.

Stock OHC T5's are avaliable with the OHC, but they have a different clutch and flywheel to the US stuff. Jack uses the stock Aussie bellhousing, and then a standard T5.

Most OHC's have BTR LE 65 fully electronic 4-stage autos, or early ones have the Borg Warner 55 3-stage. The BTR interfaces with the TPS and igniton, so its not easy to fit a C4 unless you use the T5 manual electronic EFI, and fit a vehicle speed sensor.


Most people look at Supra 5-speed manual gear boxes and the Castelmane Rod Shop adaptor from CRS.

Lastly, if you want no electronics, the best option is to take a later 1992-1994 4.0, adorn it with the 1988-1991 OHC 3.9 TBI intake, and bolt on an 1987-1993 x-FLOW 250 Weber ADM 34 carb. You use the Aussie XE distrubutor, and may have to devise an electric fuel pump. There is the option.

Basically, you take all the later electronic gear, and throw it in the trash, and use this intake manifold. It runs fairly close to the shock tower, but should be okay.

ohc.jpg


As for websites, there are many. Please go through George's posts on his X-flow Cortina in the Aussie Forum, and look at the links he had.
 
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