200 vs 250

[MeanGreen&Fireball]

I have searched thread after thread hoping to find something comparing the 200 to the 250 in a turbo application, but came up empty handed. Which engine is best to turbo in a mild to wild street setting? The 250 holds the records as far as max power but I’m guessing that was in quarter mile application. The 200 revs easier but which one is more reliable to turbo? I’m sure the stroke and rod angle play a big part as well. I have both the 200 and 250 just wonder which one is best to throw money into?

 

[aussie7mains]

I have searched thread after thread hoping to find something comparing the 200 to the 250 in a turbo application, but came up empty handed. Which engine is best to turbo in a mild to wild street setting? The 250 holds the records as far as max power but I’m guessing that was in quarter mile application. The 200 revs easier but which one is more reliable to turbo? I’m sure the stroke and rod angle play a big part as well. I have both the 200 and 250 just wonder which one is best to throw money into?

Ok, here is my two pennys worth. It hardly matter what the displacement once your boosted, the blower/turbo will dictate the torque output. The engine displacement just has a bearing on where the peaks occur. Your US 200s have very short rods, which IMO is something of a laibilty. Our Aussie ones have long rods. The other problem might be getting the best transmission, from my look it seems your 200s have a different bellhousing pattern to the US 250 which has the SBF pattern which gives you a wide selection of trans. Getting a decnt clutch might be an issue. I run a blown 200ci (long rod crossflow six) this works very well, after having a twin screw blown engine I would not look at a turbo. Another consideration might be getting the compression ratio low enough in the 250, you will need pistons with a big dish to get down to 8.5:1 or so for petrol, LPG can tolerate 9:1 with a 1 bar boost. For a street car torque at lower RPMs is what you need. Check my posts on the blown 200s. As to absolute maximum power, the guys down here that race the turbo sixes nearly all have destroked cranks and rev the absolute TITS off them, 9000rpm! But this is RACE, nothing happens till 5k, then all the power arrives by the truckload. Most of our racers are BArra DOHC now, people will tell you 500kw is achievable of stock bits!

 

[powerband]

the 200 vs 250 debate is very alive with small block ford six enthusiasts for good reason. Both engines offer their advantages. Basic SBF-Six is a robust platform and forced induction addition is not too complicated.

the modest OEM compression ratios of the 200/250 are adaptable easily to low to mid boost applications. U.S. heads are mostly same and plenty of forum - data on mods.

not having any engineering degree or personal machine shop, I study the data, do the math, and build with my resources and budget.

my favorite machinist always tells me: "... your choice, it's just horsepower per your cubic dollar... "

Although the 200 uses same integral intake cylinder head, the 250 basically is the stroked version of the 200 and the added rod length adds to the piston speed and reciprocating forces as well as increasing usable torque/powerband. The 'under-box' bore/stroke of the 7 mains contribute to a anvil strong bottom end. 250 stroke is .784 " longer than 200.

Current SC'd 250 runs up to 5-8 lbs easily with occasional enthusiasm well over 10 so far... I had machinist check but not mill head to retain OEM D3xx large compression chambers (@ 60cc's). With 'modern' @.045 composite gskt, SCR is @ 8.7:1.
.
@ 3 yrs - 5K miles with available boost.

Ford Small Block Six 250 CID inline . Stock block and cam with blueprinted matched 60 cc chamber head, HD V8 valve springs, ARP head bolts. Holley 2300 - 7448 2Bbl heavily modified for blow-through/ boost, Aeromotive 1:1 boost referenced regulator and FI electric pump and return at tank. Flame Thrower rev-limited HEI ignition - DS II distributor modified for vac and centrifugal boost advance limiting. Vortech V-2 centrifugal supercharger with pulley ratio spec’d for inline six 250' powerband. Centerforce weighted clutch, T5-Z 'Cobra' 5 Speed, 3.80 rear. AM radio and bench seat.



earlier turbo 250 had Buick derived Draw-Thru setup on OEM block and worked head.
. . .

Started with getting engine running well NA, next added turbo and significant ignition timing mods. slowly increased boost and carb tuning for safer AFR's until boosting too optomistic at over 1 bar.. ... .

.


have fun

 

[pmuller9]

The previous two post tells you what you need to know.
The 250 will have a much wider power band than the 200 especially with a turbocharger.
The 250 can use the Molar "Power Adder" "H" beam rod made for the 300 six which will increase the rod length and decrease the piston weight as well.
You originally were looking at a 52 mm turbo and wanting a power band from 2500 to 5500 rpm.
Has that changed?

 

[MeanGreen&Fireball]

Ok, here is my two pennys worth. It hardly matter what the displacement once your boosted, the blower/turbo will dictate the torque output. The engine displacement just has a bearing on where the peaks occur. Your US 200s have very short rods, which IMO is something of a laibilty. Our Aussie ones have long rods. The other problem might be getting the best transmission, from my look it seems your 200s have a different bellhousing pattern to the US 250 which has the SBF pattern which gives you a wide selection of trans. Getting a decnt clutch might be an issue. I run a blown 200ci (long rod crossflow six) this works very well, after having a twin screw blown engine I would not look at a turbo. Another consideration might be getting the compression ratio low enough in the 250, you will need pistons with a big dish to get down to 8.5:1 or so for petrol, LPG can tolerate 9:1 with a 1 bar boost. For a street car torque at lower RPMs is what you need. Check my posts on the blown 200s. As to absolute maximum power, the guys down here that race the turbo sixes nearly all have destroked cranks and rev the absolute TITS off them, 9000rpm! But this is RACE, nothing happens till 5k, then all the power arrives by the truckload. Most of our racers are BArra DOHC now, people will tell you 500kw is achievable of stock bits!

Thank you for sharing your knowledge on the subject. My early 200 has the smallest of the transmission bolt patterns and wouldn’t stand up to much more power, I was looking at a 1980 200 zephyr that shares more similarities of the sbf bell. I also have a 1970 250 that has a large log head with the larger combustion chamber. I should be able to get a lower ratio for turbo applications. Sounds like the longer rods of the 250 are preferred. The Aussie ford parts are far superior in every way. I’ll be sure to check out your post. Thanks

 

[MeanGreen&Fireball]

The previous two post tells you what you need to know.
The 250 will have a much wider power band than the 200 especially with a turbocharger.
The 250 can use the Molar "Power Adder" "H" beam rod made for the 300 six which will increase the rod length and decrease the piston weight as well.
You originally were looking at a 52 mm turbo and wanting a power band from 2500 to 5500 rpm.
Has that changed?

Pmuller9,
I purchased that turbo a few months ago and all the goodies to go along with it, except for the cam. I’m ready to start the project, but started wondering which engine would be best…. Sounds like the 250 is preferred. I held off on the cam until I was completely settled on which engine to run. Man, you have an excellent memory, yes …I’m still wanting a power range of 2500 to 5500.
I’m discovering that the 250 doesn’t have near the aftermarket options that the 200 has. I’m guessing everyone just runs a stock timing chain and stock harmonic on the 250s? Thanks for all your help.

 

[MeanGreen&Fireball]

the 200 vs 250 debate is very alive with small block ford six enthusiasts for good reason. Both engines offer their advantages. Basic SBF-Six is a robust platform and forced induction addition is not too complicated.

the modest OEM compression ratios of the 200/250 are adaptable easily to low to mid boost applications. U.S. heads are mostly same and plenty of forum - data on mods.

not having any engineering degree or personal machine shop, I study the data, do the math, and build with my resources and budget.

my favorite machinist always tells me: "... your choice, it's just horsepower per your cubic dollar... "

Although the 200 uses same integral intake cylinder head, the 250 basically is the stroked version of the 200 and the added rod length adds to the piston speed and reciprocating forces as well as increasing usable torque/powerband. The 'under-box' bore/stroke of the 7 mains contribute to a anvil strong bottom end. 250 stroke is .784 " longer than 200.

Current SC'd 250 runs up to 5-8 lbs easily with occasional enthusiasm well over 10 so far... I had machinist check but not mill head to retain OEM D3xx large compression chambers (@ 60cc's). With 'modern' @.045 composite gskt, SCR is @ 8.7:1.
.
@ 3 yrs - 5K miles with available boost.

Ford Small Block Six 250 CID inline . Stock block and cam with blueprinted matched 60 cc chamber head, HD V8 valve springs, ARP head bolts. Holley 2300 - 7448 2Bbl heavily modified for blow-through/ boost, Aeromotive 1:1 boost referenced regulator and FI electric pump and return at tank. Flame Thrower rev-limited HEI ignition - DS II distributor modified for vac and centrifugal boost advance limiting. Vortech V-2 centrifugal supercharger with pulley ratio spec’d for inline six 250' powerband. Centerforce weighted clutch, T5-Z 'Cobra' 5 Speed, 3.80 rear. AM radio and bench seat.



earlier turbo 250 had Buick derived Draw-Thru setup on OEM block and worked head.
. . .

Started with getting engine running well NA, next added turbo and significant ignition timing mods. slowly increased boost and carb tuning for safer AFR's until boosting too optomistic at over 1 bar.. ... .

.


have fun

I need to go through and read more about your build. Thank you for the information and tips. I probably need to look into custom pistons as well. I wasn’t looking to run more than 8 pounds of boost but it sounds like the cast pistons are pretty weak. Thanks again

 

[aussie7mains]

Thank you for sharing your knowledge on the subject. My early 200 has the smallest of the transmission bolt patterns and wouldn’t stand up to much more power, I was looking at a 1980 200 zephyr that shares more similarities of the sbf bell. I also have a 1970 250 that has a large log head with the larger combustion chamber. I should be able to get a lower ratio for turbo applications. Sounds like the longer rods of the 250 are preferred. The Aussie ford parts are far superior in every way. I’ll be sure to check out your post. Thanks

I would not go worrying about rod length, use what they come with, as to pistons I run stock Ford flat top cast pistons in mine, they are used but in OK shape, I put new rings on them and used a standard bore block, honed to give some new crosshatch to bed in the rings, the engine is stock except for a small (215 @ 0.05) hydraulic cam and all new valve train parts, it idles nicely and quietly. I have seen 18psi on my manifold pressure gauge and have driven 5000km so far without problems. IMO I would try the stock stuff and see how far you can get, custom pistons are $$$$. Our crossflow heads are vastly better than your log heads, they have much better porting and bigger valves, aluminium gives better thermal properties and save a tonne of weight, but difficult for you guys.

 

[powerband]

... try the stock stuff and see how far you can get, custom pistons are $$$$.

occasionally 200/250 TRW - original forged pistons show up cheap on E-Bay. 'Have a set haven't used yet but had my machinist confirmed they use standard rings. He said OEM design limits boost use since has same rings and - wide oil slots - as OEM. The OEM pistons held up until over @ 15 lbs boost and meager Fuel/Ign. controls.

. . .

do the data, the math and build what you can afford...

 

[pmuller9]

I wasn’t looking to run more than 8 pounds of boost but it sounds like the cast pistons are pretty weak. Thanks again

If you decide to get custom pistons, Autotec/Racetec pistons are the least expensive.
The price for a set of six dish pistons will be around $600 come the new year.
That is for the Autotec 4032 alloy forged pistons.

A custom piston for forced induction will have a wider upper ring land that will decrease the chance of breakage.
It will also allow you to turn up the boost later without fear of damage.
There have been more than one piston and rod failures due to accidental boost runaway.

The custom piston will allow a CH for zero deck while providing enough piston dish volume for the correct low compression for turbocharging.
The 250 cast pistons sit way too low in the cylinder at TDC for quench.
You also get the option for a 1/16" ring pack.

Below is a 300 six Autotec piston for turbocharging on an aftermarket connecting rod

https://fordsix.com/attachments/20210823_184000-jpg.8110/

 

[fast64ranchero]

I built a "rather exotic" stroked 250 4.125 stroke the main problem I had was piston side load wear and timing chain issues. unless you can find a good aftermarket timing chain I would steer clear of the 250 for a "wild" build. I haven't looked lately but at the time I build my 250 the only timing chain available was stock replacement and every brand was built by one Chinese manufacturer. The crank gear broke 3 times at idle (I assume from the lopey cam) the combo wore out the pistons/cylinder walls in 3k miles but it did make good power (444whp and 501 ft lbs) at 18 lbs boost. in the end I wouldn't do it again. my build is on this site and on the Classis inlines site in the dyno room.

 

[Jmustang_65]

I built a "rather exotic" stroked 250 4.125 stroke the main problem I had was piston side load wear and timing chain issues. unless you can find a good aftermarket timing chain I would steer clear of the 250 for a "wild" build. I haven't looked lately but at the time I build my 250 the only timing chain available was stock replacement and every brand was built by one Chinese manufacturer. The crank gear broke 3 times at idle (I assume from the lopey cam) the combo wore out the pistons/cylinder walls in 3k miles but it did make good power (444whp and 501 ft lbs) at 18 lbs boost. in the end I wouldn't do it again. my build is on this site and on the Classis inlines site in the dyno room.

How's your new 200 going?

 

[aussie7mains]

I built a "rather exotic" stroked 250 4.125 stroke the main problem I had was piston side load wear and timing chain issues. unless you can find a good aftermarket timing chain I would steer clear of the 250 for a "wild" build. I haven't looked lately but at the time I build my 250 the only timing chain available was stock replacement and every brand was built by one Chinese manufacturer. The crank gear broke 3 times at idle (I assume from the lopey cam) the combo wore out the pistons/cylinder walls in 3k miles but it did make good power (444whp and 501 ft lbs) at 18 lbs boost. in the end I wouldn't do it again. my build is on this site and on the Classis inlines site in the dyno room.

We have one made in Australia, they are good, not sure of fit for your 250s:-https://www.ebay.com.au/itm/362096092147?epid=2234151423&hash=item544e9be3f3:g:114AAOSwD0deGIrt

 

[fast64ranchero]

We have one made in Australia, they are good, not sure of fit for your 250s:-https://www.ebay.com.au/itm/362096092147?epid=2234151423&hash=item544e9be3f3:g:114AAOSwD0deGIrt

on our side of the pond the 200 and the 250 timing chains are different due to deck height and cam location. your link states that chain fits both. would be great if it fit a US250

 

[rocklord]

We have one made in Australia, they are good, not sure of fit for your 250s:-https://www.ebay.com.au/itm/362096092147?epid=2234151423&hash=item544e9be3f3:g:114AAOSwD0deGIrt

Unfortunately, the timing chain for the OZ 250 will not fit the US 250.

Someone on the forum modified gears from a SBF 302 along with a chain from a Toyota 4cyl to work on the US 250.
If found, I'll post a link to the thread.

 

[rocklord]

Here's the thread for the double roller timing chain for the US 250.

Roller timing chain for 250

Well. I can't say that this has been an easy path to travel,...and I'm still not there yet, but there is a light at the end of the tunnel. I decided to copy Does10's method of making a roller chain for a SBF work on a 250. So I went out and bought a true roller set from Summit under their brand...

fordsix.com

Most of the links in the thread are dead.

 

[rocklord]

Here's the original post by Does10s.

SBF timing set installed on Kelly's 250!

Well it looks like this is going to work! Kelly's shortblock is reassembled! It's not running yet, but will be in a few weeks. She races again Labor Day Weekend. I've been at this for awhile waiting patiently for my machine shop to finish up the required machine work. Anyway here's what I did...

fordsix.com

 

[xctasy]

In 2012, Both Mike1157 and Does10s used one specific kind of dual 302 SBF timing sprocket sets, which use the common with the 1275 GT and Cooper S BMC based Toyota and Holden 308 double roller timing chain pitch.

See

TIMING CHAIN for TOYOTA 6R 7R 8R CELICA RA23 RA28 HIACE HILUX CORONA 18R/18RC 2.0L, GMH Holden 308.

It is a 62 link chain with provision for link removal. The chain was devised in 1968 for common BMC, Toyota and Holden usage, and is made via a common white box good supplier.

The crank snout will have to be trimmed down 50 thou, or the crank and cam sprocket trimmed down to suit. There are a few different ways to do it.

Then the crank damper , you can use the removable neutral balance aftermarket pulley.

 

[drag-200stang]

Each engine has its pluses and minuses, I choose to run the 200 mainly because it sounds smaller, and it was the one that was available in a 66 Mustang.
When a faster 2JZ-2 competitor says to me why a am not as fast as them, I can say, look dude this engine was designed before the engineer that designed yours was born and just look at that Integral intake manifold. That is another reason that I will not remove the log even though I have the equipment and skill to do so and choose to work around it.

 

[gus91326]

Each engine has its pluses and minuses, I choose to run the 200 mainly because it sounds smaller, and it was the one that was available in a 66 Mustang.
When a faster 2JZ-2 competitor says to me why a am not as fast as them, I can say, look dude this engine was designed before the engineer that designed yours was born and just look at that Integral intake manifold. That is another reason that I will not remove the log even though I have the equipment and skill to do so and choose to work around it.

I'd also argue that a lot of the work on the 200/250 is people trying things since there isn't a lot of support. Like an LS, there is no guesswork with the JZ family of engines. Just buy the part and drive it.