Turbo-Blow Thru 200 vs 250
- Thread starter powerband
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The addition of a turbo to a tri-power 3 x 1 bbl carbed traditional log head 200 or 250 changes the strength needs of the ancillaries. The gearbox, the axle, the drive shaft, the clutch, the sizing of the gearbox and clutch and axle to get a good factor of safety means the 250 will require more truck/F150-style componentry. Thinks like con rods, pistons and engine breathing you'll have a handle on already. After turbo charging, how much power will a 200 and 250 likely have, and what drive train artilllery will match those power and torque levels?
A turbo 200 can use normal lighter duty small I6 X-shell or Fox body bits or Ranger parts ( You'll get away with 8" locker or LSD from a Maverick, Pinto or Mustang II or Granada, or even de-armed four link 7.5 or 8.8", and there drive train parts, the SR, SROD, T5 or Granada RUC Toploader is easy to find and replace ).Turbo it with a mild 9 psi boost ratio, and already those parts now need to be able to hack 200 times 1.6, or a 320 cubic inch strength drive train. (Std boost ratio calc, not including heat soak, is [[9+14.7]/14.7], or 1.6 or so).
The extra 25% torque a stock normally aspriated 250 has over a 200 requires heavy duty parts, 240/250/300 I6 parts, or 221/255/260/289/302 level parts. Turbo it with a mild 9 psi boost ratio, and already those parts now need to be able to hack 250 times 1.6, or a 400 Big block strength drive train.
Examplars of turboing have said turbo charging is a reaplacment for displacment. You need to look at your projected power levels, and baseline that against a similar benchmark Ford V8 engine. Then you'll probably find a 200 is the cheaper option, or that you might want to go for a super mild 250 and come back on the boost levels, to look after components.
A turbo 200 can use normal lighter duty small I6 X-shell or Fox body bits or Ranger parts ( You'll get away with 8" locker or LSD from a Maverick, Pinto or Mustang II or Granada, or even de-armed four link 7.5 or 8.8", and there drive train parts, the SR, SROD, T5 or Granada RUC Toploader is easy to find and replace ).Turbo it with a mild 9 psi boost ratio, and already those parts now need to be able to hack 200 times 1.6, or a 320 cubic inch strength drive train. (Std boost ratio calc, not including heat soak, is [[9+14.7]/14.7], or 1.6 or so).
The extra 25% torque a stock normally aspriated 250 has over a 200 requires heavy duty parts, 240/250/300 I6 parts, or 221/255/260/289/302 level parts. Turbo it with a mild 9 psi boost ratio, and already those parts now need to be able to hack 250 times 1.6, or a 400 Big block strength drive train.
Examplars of turboing have said turbo charging is a reaplacment for displacment. You need to look at your projected power levels, and baseline that against a similar benchmark Ford V8 engine. Then you'll probably find a 200 is the cheaper option, or that you might want to go for a super mild 250 and come back on the boost levels, to look after components.
xctasy
.. thanks for the detailed response - 8) : I'm working up pros/cons' of a bottom-up' built 200 or 250 for TC/SC . The car/drivetrain choice has complementary parameters as you well detailed.
It's simply economic considerations: the somewhat rev-limited/induction starved but strong 200 OR the much longer stroked (somewhat more rev-limited) 250 version for a somewhat-cruisable/weekend dragstrip capable engine that somewhat confidently keeps-the pin-in-the-grenade...
Not planning on using tri-power porting, likely modify late head intake for 2/4Bbl blow-thru after boost/ intcool' and fabricate a short flange to blower next to starter ...
thanks xctasy , et al...
my friendly machinist said he's ready to help, he likes the phrase:
"It's just horsepower per cubic dollar..."
have fum
.. thanks for the detailed response - 8) : I'm working up pros/cons' of a bottom-up' built 200 or 250 for TC/SC . The car/drivetrain choice has complementary parameters as you well detailed.
It's simply economic considerations: the somewhat rev-limited/induction starved but strong 200 OR the much longer stroked (somewhat more rev-limited) 250 version for a somewhat-cruisable/weekend dragstrip capable engine that somewhat confidently keeps-the pin-in-the-grenade...
Not planning on using tri-power porting, likely modify late head intake for 2/4Bbl blow-thru after boost/ intcool' and fabricate a short flange to blower next to starter ...
thanks xctasy , et al...
my friendly machinist said he's ready to help, he likes the phrase:
"It's just horsepower per cubic dollar..."
have fum
Okay, the best bet for performance is the 200 in that case. The difference in power between a stock configuration single 1, 2 or 4bbl carb 200 and a 250 is 9% when referenced against periferal weight gains with the 250. The axle, trans and gearing sweeps away some of the power increases unless you get into the engine. There should be a 25% power gain with a 250, but there isn't unless you use some American talent.
When you step into a more port on port kind of triple carb engine, you can easily overcome the 250 biggest negatives to power,
1,its disproportional all up weight gain,
2.its no better Length of Rod to stroke, and
3. its worse oversquare long stroke design.
4.Its cubic inch to port area and carb area equation
Those negatives can be amortized as gains if you can change and optimize the cam, the carb port area and rod ratio, the 250 can then show the algebraic 25% power boost. But without those negatives becoming pluses for the 250, a turbo 200 shows a good power gain as a turbo engine. If you look at FordSedanDeliveries inconsistant but great 220 hp power level over a 180 odd hp rating typical of the 200 tripower, you see a porportional gain. But when we see others with 205 hp with just a worked 200/500 cfm 2-bbl, the 250 triple carb doesn't cut a 256hp like it should to be proportional. Yet a full house alloy headed 4-bbl 200 can make 266 flywheel hp. Unless those four 250 negatives above into postives by very specific attention, every air flow limited 250 will remain a torquey engine down on specific power compared to the 200. And that makes the 250 take on more of a sidevalve/flat head V8/347 SBF type character, with great dollops of torque, but a lack of sweet gains past maximum torque.
My recomendation for a turbo or supercharged six when those four negatives aren't mitigated is the 200 six. To qualify, the boost ratio increase is linear with the 200, but the 250, its not a cube for cube 25% deal.
My FAZER engines are all 250 sixes, because I work on the unpopular, and miss-understood aspects of L/R, B:S (
) and AI (aspirational index). The 4-bbl and 2-bbl air flow limited NASCAR and oval track engines show how cam timing should be done, the US Chevy 454, Oldsmobie 455, the Pontiac 455 show how to over come L/R ratio handicaps, the Super Cobra Jet Ford 351/428/429 engines show how to get power without detonation, and the 225 Mopar slant how to make a long stroker deliver torque. American cam designers pave the way to sucess, and the Europeans (Raymond Mays and Rudds AC Ace RS 2600 Stage 5), and Australians (Bill Santuccione, Harry Firth, Dave Bennett, Phil Irving, Frank Duggan, Larry Perkins and Dick Johnston) just crossed the tees.
The 200 is perfect as it is, but with the 250, Ford stuffed up because the L/R ratio is still woefully bad, and the other three facets, bore to stroke, and the three indicies of aspitations index (port area and carburation area and geometrics) are plain lousey. These factors were identified in a swot analysis by Bill Santuccione in a 1990 Australian StreetMachine article, and if the 250 was a V8, any American would have fixed the stuff ups with camshaft and intake design. The US has fixed it now...its the Classic Inlines head!
When you step into a more port on port kind of triple carb engine, you can easily overcome the 250 biggest negatives to power,
1,its disproportional all up weight gain,
2.its no better Length of Rod to stroke, and
3. its worse oversquare long stroke design.
4.Its cubic inch to port area and carb area equation
Those negatives can be amortized as gains if you can change and optimize the cam, the carb port area and rod ratio, the 250 can then show the algebraic 25% power boost. But without those negatives becoming pluses for the 250, a turbo 200 shows a good power gain as a turbo engine. If you look at FordSedanDeliveries inconsistant but great 220 hp power level over a 180 odd hp rating typical of the 200 tripower, you see a porportional gain. But when we see others with 205 hp with just a worked 200/500 cfm 2-bbl, the 250 triple carb doesn't cut a 256hp like it should to be proportional. Yet a full house alloy headed 4-bbl 200 can make 266 flywheel hp. Unless those four 250 negatives above into postives by very specific attention, every air flow limited 250 will remain a torquey engine down on specific power compared to the 200. And that makes the 250 take on more of a sidevalve/flat head V8/347 SBF type character, with great dollops of torque, but a lack of sweet gains past maximum torque.
My recomendation for a turbo or supercharged six when those four negatives aren't mitigated is the 200 six. To qualify, the boost ratio increase is linear with the 200, but the 250, its not a cube for cube 25% deal.
My FAZER engines are all 250 sixes, because I work on the unpopular, and miss-understood aspects of L/R, B:S (
) and AI (aspirational index). The 4-bbl and 2-bbl air flow limited NASCAR and oval track engines show how cam timing should be done, the US Chevy 454, Oldsmobie 455, the Pontiac 455 show how to over come L/R ratio handicaps, the Super Cobra Jet Ford 351/428/429 engines show how to get power without detonation, and the 225 Mopar slant how to make a long stroker deliver torque. American cam designers pave the way to sucess, and the Europeans (Raymond Mays and Rudds AC Ace RS 2600 Stage 5), and Australians (Bill Santuccione, Harry Firth, Dave Bennett, Phil Irving, Frank Duggan, Larry Perkins and Dick Johnston) just crossed the tees. The 200 is perfect as it is, but with the 250, Ford stuffed up because the L/R ratio is still woefully bad, and the other three facets, bore to stroke, and the three indicies of aspitations index (port area and carburation area and geometrics) are plain lousey. These factors were identified in a swot analysis by Bill Santuccione in a 1990 Australian StreetMachine article, and if the 250 was a V8, any American would have fixed the stuff ups with camshaft and intake design. The US has fixed it now...its the Classic Inlines head!
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