EX-Turbo 250 
It's for sale. 
The guy blew it on the dyno just after topping 290 RWHP and some outrageous torque level. The bottom end is stock with a hone and new rings. It'd clean up fine for a daily. Seriously, it reflects the #6 leaning that can occur with large single carbs.
Cheers, Adam.
A
Anonymous
Guest
hence my constant push for all you carb fellas to getinto efi
EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI
SORRY HAD TO DO IT!!
CHEERS.JOE.
EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI EFI
SORRY HAD TO DO IT!!
CHEERS.JOE.
A
Anonymous
Guest
What about the carb question? Would the 600cfm with vaccum secondaries do without any modifications to it for a draw through application or would I overcarburate the engine? Or would i still need to rejet the secondaries to make them richer?
a non progressive tripower would solve that prob though.....
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Anonymous
Guest
Hmm. Someone mentioned VE under boost..
Cant help but think that ram tuning would help benefit peak VE at certain RPM conditions.. I recall someone already dispelled this idea with me, but then again, we are already under boost - 14.7lb/in, being atmospheric pressure. I reckon that ram tuning does have something to do with brake specific power production while under greater than atmospheric pressures. Current model XR6 Turbo has the dual runner inlet manifold, turbines begin to build boost at 1800rpm, the inlet runner vane switches from long to short at 3800rpm..
But then again, if the benefits are negligible, that will satisfy my interest in this topic..
Cant help but think that ram tuning would help benefit peak VE at certain RPM conditions.. I recall someone already dispelled this idea with me, but then again, we are already under boost - 14.7lb/in, being atmospheric pressure. I reckon that ram tuning does have something to do with brake specific power production while under greater than atmospheric pressures. Current model XR6 Turbo has the dual runner inlet manifold, turbines begin to build boost at 1800rpm, the inlet runner vane switches from long to short at 3800rpm..
But then again, if the benefits are negligible, that will satisfy my interest in this topic..
Slade - I'm not sure exactly about the mods. I only saw it after it was pulled down. Didn't note the fuel pump setup (was a little busy). I know it had serious heat issues. The whole bay was done in heatproof paint and there were cooling slots in the "lid", over the turbo dump pipe. There is some pretty hick engineering in it. It had a Toploader, and Granada diff. And a HUGE crossflow radiator secured with sash cord. 
I can try to find out more.
Adam.
I can try to find out more. Adam.
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Anonymous
Guest
Sorry about the delay, tatao, but I've been unavailable for a few days.
Okay, first a word about Ve. These log headed engines are lucky to see 75% Ve at peak torque. The design really is that bad... And the Ve doesn't change just because you add a turbo. What does change is that the mass of air entering the engine goes up.
The Buick 231 is a better design, but its Ve is probably no better than 85%. At the factory max boost setting of 9 psi, that implies a 0.85x(14.7/9)x231=321 CID engine. With an 850 CFM carb, that's 850/321=2.65 CFM per CID.
For a log-headed Ford 250 with a Ve of 75% and half a bar of boost, that works out to 0.75x1.5(250)= 282 CID. To calculate for a carb, use 2.65x282=747 CFM.
So no, a 600 CFM vacuum secondary carb would NOT be a good choice. Buy a Edelbrock 1407 or 1411, 750 CFM spread bore, vacuum secondary carb. They come pre-jetted 2% richer on the secondaries (for big-block engines). Slap it on a draw-through setup and never have to worry about it.
Okay, first a word about Ve. These log headed engines are lucky to see 75% Ve at peak torque. The design really is that bad...
And the Ve doesn't change just because you add a turbo. What does change is that the mass of air entering the engine goes up.The Buick 231 is a better design, but its Ve is probably no better than 85%. At the factory max boost setting of 9 psi, that implies a 0.85x(14.7/9)x231=321 CID engine. With an 850 CFM carb, that's 850/321=2.65 CFM per CID.
For a log-headed Ford 250 with a Ve of 75% and half a bar of boost, that works out to 0.75x1.5(250)= 282 CID. To calculate for a carb, use 2.65x282=747 CFM.
So no, a 600 CFM vacuum secondary carb would NOT be a good choice. Buy a Edelbrock 1407 or 1411, 750 CFM spread bore, vacuum secondary carb. They come pre-jetted 2% richer on the secondaries (for big-block engines). Slap it on a draw-through setup and never have to worry about it.
Stan,
Correct me if I'm wrong, but here is how I understand VE (albeit a simplified version):
VE is just the % of the CID that is actually drawn into the engine in a given revolution. I.E.: you said a 200 log head is lucky to see a VE of 75% (I would agree 100% with you on that). So that means for a 250 CI engine that gets 75% VE, that it would actually get 188CI per revolution. That's all under vacuum, engine having to draw air in.
SO...if turbo forces more air into it, let's say at 14.7psi (1bar). ideal, under NA is 100% VE. meaning the engine would need 250CI of air per revolution. If you run boost of 14.7 psi, doesn't that mean you are cramming instead of 250 CI of air per revolution, now you have 500 CI per revolution. If you are running that boost, does it really matter what your original VE is? At that point, you engine (and the turbo) like a hydraulic system and the boost is equal at any two points in the intake area, so VE no longer matters. At 14.7 PSI, you are effectively running 200% VE since you are cramming 500 CI of air in a 250CI engine.
Maybe that is too simplified, but I don't understand how that doesn't work for easy math. Please let me know why you can't do this. I'm just trying to learn more.
Slade
Correct me if I'm wrong, but here is how I understand VE (albeit a simplified version):
VE is just the % of the CID that is actually drawn into the engine in a given revolution. I.E.: you said a 200 log head is lucky to see a VE of 75% (I would agree 100% with you on that). So that means for a 250 CI engine that gets 75% VE, that it would actually get 188CI per revolution. That's all under vacuum, engine having to draw air in.
SO...if turbo forces more air into it, let's say at 14.7psi (1bar). ideal, under NA is 100% VE. meaning the engine would need 250CI of air per revolution. If you run boost of 14.7 psi, doesn't that mean you are cramming instead of 250 CI of air per revolution, now you have 500 CI per revolution. If you are running that boost, does it really matter what your original VE is? At that point, you engine (and the turbo) like a hydraulic system and the boost is equal at any two points in the intake area, so VE no longer matters. At 14.7 PSI, you are effectively running 200% VE since you are cramming 500 CI of air in a 250CI engine.
Maybe that is too simplified, but I don't understand how that doesn't work for easy math. Please let me know why you can't do this. I'm just trying to learn more.
Slade
A
Anonymous
Guest
Good questions, Slade!
We've all read magazine articles that claimed something like, "with a turbo your engine can actually exceed 100% volumetric efficiency (Ve)..." What they really mean is that a turbo can force a greater mass of air into the cylinder than the cylinder will see under normally aspirated conditions. That's not the same thing as Ve, so those claims are a bit misleading. Ve is a product of the design of the intake system, including the manifolds, carb/FI bodies, ports, valves, etc., and refers to the volume of air that can be injested on each intake stroke. (So a 250 CID engine takes in just 125 cubic inches of air during each revolution at 100% Ve, not 250 cubic inches - these are 4-stroke engines, after all.)
The antiquated design of the Ford log head is highlighted in its lackluster power production. For instance, the true peak SAE net power of a 60's 200 CID I6 is only what, about 90 hp? That's only 0.45 hp per cubic inch displacement. Contrast that with the 170 hp produced by the 2003 Ford Focus SVT's 122 CID engine, which works out to 1.39 hp per cubic inch displacement - more than 3 times the power per cubic inch as an old Mustang engine! A cubic inch in the bore is a cubic inch, pretty much no matter the engine, but the design of the top end determines how efficiently the engine breaths, and hence how much power it can make.
When adding turbos to the mix, it helps to look at the weight of air forced into the engine, rather than the volume. That's because air has weight and can be compressed, which distorts the idea of a fixed volume. Of course, compressing any gas (such as air) adds heat to the gas, which complicates the equation, but we'll ignore that for now. As I said, air has weight, about 1 ounce per cubic foot (0.0755 lbs/ft^3) under standard conditions. If we boost an engine 1 bar, we are now cramming twice the weight of air (ignoring diabatic effects) into the cylinders as an unboosted engine, yet the volume hasn't changed. If the volume of air hasn't changed (although its weight has), then the Ve hasn't changed, right? That's why I wrote that adding a turbo doesn't change an engine's Ve.
So you are exactly right...Ve doesn't matter! At least not in the context we're discussing. I just used it as an "easy to use" yardstick to answer tatao's question about carb sizing for a draw-through setup. In a draw-thu setup, the carb doesn't see compressed air - it only senses the atmospheric air that flows through it, so CFM is a useful measure for sizing the carb. It still isn't exact, of course, but it's much better than simply guessing.
Hope this helps!
We've all read magazine articles that claimed something like, "with a turbo your engine can actually exceed 100% volumetric efficiency (Ve)..." What they really mean is that a turbo can force a greater mass of air into the cylinder than the cylinder will see under normally aspirated conditions. That's not the same thing as Ve, so those claims are a bit misleading. Ve is a product of the design of the intake system, including the manifolds, carb/FI bodies, ports, valves, etc., and refers to the volume of air that can be injested on each intake stroke. (So a 250 CID engine takes in just 125 cubic inches of air during each revolution at 100% Ve, not 250 cubic inches - these are 4-stroke engines, after all.
)The antiquated design of the Ford log head is highlighted in its lackluster power production. For instance, the true peak SAE net power of a 60's 200 CID I6 is only what, about 90 hp? That's only 0.45 hp per cubic inch displacement. Contrast that with the 170 hp produced by the 2003 Ford Focus SVT's 122 CID engine, which works out to 1.39 hp per cubic inch displacement - more than 3 times the power per cubic inch as an old Mustang engine! A cubic inch in the bore is a cubic inch, pretty much no matter the engine, but the design of the top end determines how efficiently the engine breaths, and hence how much power it can make.
When adding turbos to the mix, it helps to look at the weight of air forced into the engine, rather than the volume. That's because air has weight and can be compressed, which distorts the idea of a fixed volume. Of course, compressing any gas (such as air) adds heat to the gas, which complicates the equation, but we'll ignore that for now. As I said, air has weight, about 1 ounce per cubic foot (0.0755 lbs/ft^3) under standard conditions. If we boost an engine 1 bar, we are now cramming twice the weight of air (ignoring diabatic effects) into the cylinders as an unboosted engine, yet the volume hasn't changed. If the volume of air hasn't changed (although its weight has), then the Ve hasn't changed, right? That's why I wrote that adding a turbo doesn't change an engine's Ve.
So you are exactly right...Ve doesn't matter! At least not in the context we're discussing. I just used it as an "easy to use" yardstick to answer tatao's question about carb sizing for a draw-through setup. In a draw-thu setup, the carb doesn't see compressed air - it only senses the atmospheric air that flows through it, so CFM is a useful measure for sizing the carb. It still isn't exact, of course, but it's much better than simply guessing.
Hope this helps!
Stan,
Clear as mud...
Forgot the whole 4 stroke thing. but the 3rd paragraph cleared it up on me. I forgot, you can only put in so much volume into the cylinder and that isn't changing with the turbo, it's the weight (hence amount) of air that changes. I completely forgot about that. Now I understand that VE doesn't change.
Slade
Clear as mud...
Forgot the whole 4 stroke thing. but the 3rd paragraph cleared it up on me. I forgot, you can only put in so much volume into the cylinder and that isn't changing with the turbo, it's the weight (hence amount) of air that changes. I completely forgot about that. Now I understand that VE doesn't change.
Slade
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Anonymous
Guest
Does the Edelbrock Performer Series 750 cfm carburetor have mechanical or vaccum secondaries?
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Anonymous
Guest
Well, I'm chugging down the draw-thru track. Picked up a '79 Buick setup. Turbo Technology in Tacoma, WA looked at the cartridge and said it had recently been rebuilt and looked good. Got a rebuilt Buick turbo Q-jet on the way. Planning to build an all mechanical system, with one exception. An MSD 6-BTM to retard advance under boost. Old school. Sort of Ak Miller--"J" pipe and all. Been reading up on water/alcohol injection.
OZ head has new seats and guides and Gary's half done with the porting. Short block is about ready to assemble.
Looking forward to getting it on an engine stand so I can start mocking up the turbo setup.
OZ head has new seats and guides and Gary's half done with the porting. Short block is about ready to assemble.
Looking forward to getting it on an engine stand so I can start mocking up the turbo setup.
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Anonymous
Guest
Hey guys, sorry I took so long to answer, but I've been out collecting that 'hostile fire pay'...
Anyway, the Edlebrock 1407 (manual choke) and 1411 (electric) both have vacuum secondaries. They are really license-built Carter AFB carbs, if you remember those from back in the day. An excellent carb and good value for the money, they are ideal for draw-thru turbocharging mid-sized engines like our log-head Fords.
Congrats Graeme! It is good to see someone getting close...
I will be playing in the sandbox for another couple of months, but am looking forward to getting back to my project when I return home.
Anyway, the Edlebrock 1407 (manual choke) and 1411 (electric) both have vacuum secondaries. They are really license-built Carter AFB carbs, if you remember those from back in the day. An excellent carb and good value for the money, they are ideal for draw-thru turbocharging mid-sized engines like our log-head Fords.
Congrats Graeme! It is good to see someone getting close...
I will be playing in the sandbox for another couple of months, but am looking forward to getting back to my project when I return home.
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