250ci turbo questions

blackbird64

Active member
Hi i am brand new to this forum Im 17 i got a 1964 ford falcon 2 door i6 model with a 250 i6 lined up for it im trying to get as much info on the 250 as possbile i want to build it to a performance engine out of the 250 with hei ignition, large valves, 278/272 cam, forged internals, vvc carbs, from the math i did in a perfect system it has about 155 hp at 0lbs boost but at 30lbs of boost it should make 465hp but i want to know if i should have one huge turbo at 30lbs going to one of my vvc carbs or if i should have two turbos at 15lbs each going to two vvc carbs and if two ill probably have to custom build an intake manifold please let me know what your thoughts are thanks- blackbird64 8)
 
I hope you are joking... You will never get a 250 to take 30PSI for more then seconds... nor would a cam with so much overlap work well with a turbo.
 
Your calculations are not complete. You forgot to factor in the increased air temp which lowers the air density

At 30 lbs of boost the turbo outlet air temp is over 300 degrees F.
Math wise the power only doubles.
You would need an intercooler with 100% efficiency to get 3x power level at 30 lbs of boost.

Fuel wise you would not be able to control detonation with pump gas at those air temps and the engine would be damaged in seconds.

At high boost levels it is best to use an EFI system where both timing and air fuel ratio can be controlled based on load.

The power level you want is more easily obtained with much lower boost using the CI aluminum head.
Getting good flow with the stock 250 head is best done by cutting off the intake log and building your own manifold.
Here is a good example: /viewtopic.php?f=22&t=74307

The 278/272 turbo cam is not a bad choice but you really need to know the finished port flow of the head before you can figure the cam profile.

When you use two turbos instead of one, the boost level remains the same for each. It is the air volume that is split, not the boost.

Additional info:
30lbs of boost is a gauge pressure not absolute.
Absolute is 30 + 14.7 = 44.7 at sea level.
1/2 of 44.7 = 22.35 absolute or 22.35 - 14.7 = 7.65 psi gauge.
If you split 30 lbs of boost it is 7.65 psi instead of 15 psi

Is this for street use or strictly track?
 
I ran 20psi no problem on a stock bottom end 200 but even I would be iffy about tossing 30psi even on a built bottom end. That said, Ide definitely love to see it and would encourage you without feeling bad to do it and see what happens...for science sake :LOL: Never know actually, might hold up. There was a time when 10-15 was thought to be the ragged edge around these parts!

Matt
 
I forgot to say that i have a classic inlines cast iron head its not a crossflow though, and the cam was one that classic inlines said would be good for turbo applications also i wasn't planning to use pump gas i wanted to run racing gas or maybe alcohol i want about 450-500hp is that possbile with a turbo 250ci i6
 
pmuller9":2g9dhi3g said:
Your calculations are not complete. You forgot to factor in the increased air temp which lowers the air density

At 30 lbs of boost the turbo outlet air temp is over 300 degrees F.
Math wise the power only doubles.
You would need an intercooler with 100% efficiency to get 3x power level at 30 lbs of boost.

Fuel wise you would not be able to control detonation with pump gas at those air temps and the engine would be damaged in seconds.

At high boost levels it is best to use an EFI system where both timing and air fuel ratio can be controlled based on load.

The power level you want is more easily obtained with much lower boost using the CI aluminum head.
Getting good flow with the stock 250 head is best done by cutting off the intake log and building your own manifold.
Here is a good example: /viewtopic.php?f=22&t=74307

The 278/272 turbo cam is not a bad choice but you really need to know the finished port flow of the head before you can figure the cam profile.

When you use two turbos instead of one, the boost level remains the same for each. It is the air volume that is split, not the boost.

Additional info:
30lbs of boost is a gauge pressure not absolute.
Absolute is 30 + 14.7 = 44.7 at sea level.
1/2 of 44.7 = 22.35 absolute or 22.35 - 14.7 = 7.65 psi gauge.
If you split 30 lbs of boost it is 7.65 psi instead of 15 psi

Is this for street use or strictly track?
 
a reply to pmueller i want it for racing im not sure about strictly track/strip but i plan to race it my end goal is to run at most 10 sec quarter mile.
 
If it were strictly track you could run on Methanol.
The block could be completely filled with HardBlok and coolant would only run through the head with a small radiator and electric pump.
You wouldn't need an intercooler which means you don't have to store bags of ice.
The static compression ratio would be 10:1

If you are strictly track on gas then the static compression ratio can be as high as 9:1.
Recommended racing fuel is VP C16 or if you want to run an oxygenated fuel for a more complete burn and extra power, VP Q16
An ice water intercooler will get you maximum power with the least amount of boost. It also makes the car run more consistent since the incoming air temp is better controlled.

If there is a chance you may want to run it on the street using 91 octane pump gas at low boost then it is best to have an 8:1 static compression ratio.

As always the amount of power available is determined by the cylinder head and needs to be the first item you focus on.
The finished head's combustion chamber size is needed to figure the piston dish volume.
The port flow will determine cam, turbocharger size and the rest of the induction system.

The better the head flows, the less boost is needed to make the target power and it also makes it possible to run the engine on the street with 91 octane pump gas and still have a lot of power.

The best head is the CI aluminum.
http://classicinlines.com/alumoverview.asp
You can no longer order directly from Classic Inlines.
Check with "does10s" who is a member on this forum

Second choice is the OZ 250 2V head.
http://classicinlines.com/OZ250-2v.asp
They are really getting hard to find and if you have to ship one from "Down Under" plus pay a premium price, it is a lot of money.
It is one of those items you keep a Look Out for in case one turns up that is close and reasonable.

Third is to modify the stock log head by machining off the intake log leaving the individual intake ports open and adapt or make an intake manifold to fit.
Here is a very good example of DIY ingenuity: /viewtopic.php?f=22&t=74307

What year is your 250?
 
Ok so with stock head 30psi will not work i understand that, now i have a cast iron head from Australia my dad bought years ago it has a 2 barrel intake with it i believe it to be the OZ250-2V but my dad bought a cast iron one because it was cheaper and he likes the heat tolerance cast iron has he didnt want the aluminum to warp whether or not that could happen idk and dont know the exact year of my 250ci i beleive it to be the earlier year with 155hp,
 
blackbird64":ga9otk8k said:
Ok so with stock head 30psi will not work i understand that, now i have a cast iron head from Australia my dad bought years ago it has a 2 barrel intake with it i believe it to be the OZ250-2V but my dad bought a cast iron one because it was cheaper and he likes the heat tolerance cast iron has he didnt want the aluminum to warp whether or not that could happen idk and dont know the exact year of my 250ci i beleive it to be the earlier year with 155hp,

There is NO head that will let you put 30PSI on that engine, the bottom end just won't take it without things like custom billet crank/rods/custom forged pistons, etc...
 
RichCreations":cnbr4hbe said:
blackbird64":cnbr4hbe said:
Ok so with stock head 30psi will not work i understand that, now i have a cast iron head from Australia my dad bought years ago it has a 2 barrel intake with it i believe it to be the OZ250-2V but my dad bought a cast iron one because it was cheaper and he likes the heat tolerance cast iron has he didnt want the aluminum to warp whether or not that could happen idk and dont know the exact year of my 250ci i beleive it to be the earlier year with 155hp,

There is NO head that will let you put 30PSI on that engine, the bottom end just won't take it without things like custom billet crank/rods/custom forged pistons, etc...

well some years of 250ci had forged cranks and rod id just have to get forged pistons from inline classics but if there is no way of 30 psi what is max power with boost
 
Here is an intake that will fit the 2V head.
http://classicinlines.com/proddetail.as ... IMC&cat=31
You will have to check with Does10s to see if they have one.

We haven't talked about rods and pistons yet but there is no problem.
The one Falcon that went 10.90s with a turbo 250 did so with 17 lbs of boost using the CI aluminum head, 274 cam.
It recorded 423 hp at the rear wheels.

You should be able to duplicate that performance with the 2v head with a little more boost and larger cam.

Look through this thread for an example of a home made intake.
/viewtopic.php?f=22&t=74307
 
i would really like to be about there power wise i just would like to not have to buy an aluminum head, but for cam would you guys go with classic inline turbo cam 278/272 or something more radical
 
blackbird64":3hcavm88 said:
i would really like to be about there power wise i just would like to not have to buy an aluminum head, but for cam would you guys go with classic inline turbo cam 278/272 or something more radical
You can get the job done with the OZ250 2V head that you have.

With a good primary tube exhaust manifold (not a stock log type) the exhaust duration can be the same as the intake.
The duration will be more than the 278/272 cam.
The .050" duration will be around 230 degrees.

I should have noted that the FSP-250-IMC intake manifold that fits your OZ250 2V head has the bosses so you can install injectors for use with EFI
http://classicinlines.com/proddetail.as ... IMC&cat=31
 
my head isnt aluminum though mine is Australian just not aluminum it looks like this [ima<img src="http://fordsixperformance.com.au/wp-content/uploads/2013/07/250-2v-ford-cylinder-head-300x198.jpg" alt="ford-250-2v-head"/>ge][/image]
 
It doesn't have to be aluminum to work well. It is more about the design than the material.
The important part is that it doesn't have a log intake manifold.
 
right now like you were saying the cam intake and exhaust can be the same what is a good cam for max of 20lbs boost oh and im guessing other things take into play such as valve size ,springs, rockers, ignition etc
 
blackbird64":2aifwcch said:
right now like you were saying the cam intake and exhaust can be the same what is a good cam for max of 20lbs boost oh and im guessing other things take into play such as valve size ,springs, rockers, ignition etc
The engine needs to produce just over 200 hp without boost to get 500 hp with 20 lbs of boost.
The OZ250-2v head should be able to make the power between 5000 and 5500 rpm using a cam with around a 232/232 .050" duration .500" lift on a 112* LSA.
I would go with Schneider cams.
For race application I would use a solid lifter cam with EDM oiling hole lifters.

blackbird64":2aifwcch said:
and for fuel i have two vvc carbs about 1250cfm each

If we go optimistic and look at the 250 six at 6000 rpm and don't adjust for VE and carburetor pressure drop, we get 434 cfm.
A 500 cfm carb will easily supply the air needed in a blow through set-up
1250 cfm is way too big for this application
 
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