250 swap

[pcoup41]

right now I have a 66 mustang with a 200 and t5 conversion. I just got a 70's 250 that I would like to put in. what is all involved in the swap? I believe I have read somewhere on here that it will fit. will that oil pan work? and will my t5 bolt up to that block or will I still be using the adapter? thanks

 

[Invectivus]

I'm planning on doing the swap as well, you should buy the falcon performance handbook, it goes into the swap on falcons and i think the 64/65 square bodied falcon would be similar to a 65/66 mustang. There might be some steering linkage modification, you'll need new motor mounts, and the 250 shared the bolt pattern with the 5.0, so you can get a late model cable bell and upgrade to a better pedal feel and lose the adapter plate.

 

[FalconSedanDelivery]

I bolted the 250 into my 65 using factory 6cyl mounts , there is no steering linkage problem using those mounts , as for the T-5 adapter you will need a different one , or use a 5.0 bell from 87-93

 

[MustangSix]

I did this years ago and it will fit, but it's more work than you might think. The engines are different enough to make it challenging. Most of the details are at http://www.fordsix.com/250swap.php.

The 250 is bigger in all directions by an inch or so and that's just enough to create clearance issues with the fan, hood, radiator, and sometimes steering linkage. Your current flywheel and bellhousing will need to be replaced along with the starter. The clutch linkage on a 250 is like a V8 so if you have a Z-bar pushing the linkage, that will need to be changed out.

It can be done, but the performance difference between the two engines is mostly in torque output. Unless you step up to a 2v or aluminum head, there isn't much HP to be gained from the extra 50 cubes.

 

[FalconSedanDelivery]

I did this years ago and it will fit, but it's more work than you might think. The engines are different enough to make it challenging. Most of the details are at http://www.fordsix.com/250swap.php.

The 250 is bigger in all directions by an inch or so and that's just enough to create clearance issues with the fan, hood, radiator, and sometimes steering linkage. Your current flywheel and bellhousing will need to be replaced along with the starter. The clutch linkage on a 250 is like a V8 so if you have a Z-bar pushing the linkage, that will need to be changed out.

It can be done, but the performance difference between the two engines is mostly in torque output. Unless you step up to a 2v or aluminum head, there isn't much HP to be gained from the extra 50 cubes.[/quote]
I disagree and I just did the swap , Its a bit taller but no biggie , like I said I used the mounts from a 65-66 mustang , bolted it right up , I even had the bigger bell 164, and not much difference , yeah right , my log head has run within a tenth of the fastest Aluminum headed 200 on this forum ( normally aspirated ) and that was in 90 degree temps with 85% humidity and on a track that goes up hill 13 ft from start to finish , AND if I have enough time after the bracket finals ( which I qualified for ) I am swapping the six back in and It Will go 13's without spending 2000 dollars on just a head , THERE is no replacement for Displacement , nuff said

 

[MustangSix]

FSD, it's definitely doable. Been done many times and the extra cubes are nice to have, but I still say, this isn't a one-day bolt in swap for a 200. Not that hard, but lots of details to contend with. On a scale of 1 to 10 I give it a 3.5 just for all the little stuff you have to contend with.

I don't think you give yourself enough credit for all the work that you did on those things. You put a ton of effort into making the combo perform really well and if anyone told me that they could duplicate what you've done without a lot of work, I'd be very skeptical.

 

[FalconSedanDelivery]

Point Taken , Well Put .

 

[dayman]

I just completed a 250 swap into my 66 Mustang. It really is not hard, but it did take more time than I thought.

I already had a T5 in the car with headers an dual exhaust. I used a 5.0 bellhousing, zero balance flywheel, and a hydraulic clutch setup.

I also used an OZ 250 head and intake with a Holley 350. Lokar pedal and cable to connect the throttle.

Motors mounts were easy with the Maverick frame mounts. I relocated the mounting holes to lower the engine for more hood clearance. I am still working on the breather. I am using a low profile top hat I bought from CI and remotely located filter.

Exhaust - I took it to the muffler shop and had pipes bent and welded. $60.00 total.
Radiator worked, hosed worked, but I did install electric fan. It is tight for a mechanical fan, but it could be made to work.

Good luck if you decide to do the swap.

I like the extra torque and I get a better clutch setup than was available for the 200 engine.

 

[xctasy]

A 250 1-bbl is sort of like a 318 or 360 2-bbl Mopar LA. Stock, its nothing at all, but it is the most responsive engine to the right modifications around

As a stock swap, the extra 50 cubes is expensive, any non power steered steering loads up a lot more due to the engine being 460 pounds rather than 365, and there is not a 25% improvement in top end power. The stock 250 makes 155 hp gross, or 93- 100 hp net, while the stock 200 makes 115/120/125 hp gross or 87 to 95 hp net. Rwhp is usually 67 for a 200, but only 6% greater for the stock 250. 71 hp would be all you'd see from any 250 1-bbl combo from any year, 1969 to 1980, no difference.

Reason for the non proportional power growth is the stock 250 has a major 103 thou block deck height to piston miss match via wrong sized con rods, and a long stroke, and still the same poor 1.5:1 rod ratio as the 200. As the engine grows in cubic inches, the breathing becomes more critical to good power, and the stock 250 just doesn't even come close to a 25% power increase unless the deck height, intake restrictions and carburation are delt with.

When the mods are made, the 250 is a standout engine. Stock, only the 1971-1976 Aussie 250 1-bbls ever even came close to 155 hp gross. The Aussie engine came out with a 9.2:1 compression ratio designed for 97 octance leaded gas, had a 256 degree cam.

The US 250 was most likely purposely a hobbled horse which just with a con rod change, could have eclisped a 164 hp gross 2-bbl 260 or 190/ 200 hp gross 289 or any 240 or 300. Over in Australasia, a log headed 200/3.3 six makes 9 to 11% less power than an Aussie 250/4.1, despite the gross ratings being 25 hp different. That becasue the base 200/3.3 over here was a long rod tall deck block with 6.27" rods and 9.38" tall block. Even so, the 250 was a bit of an Xmas pudding...fat, heavy, and nothing to inspire the consumer to get up and jive. Of course, after a nice fat cam, a turbo, or a 2V head, different story.

 

[MustangSix]

I guess my point is that if you want to do the swap you need to follow thru on a couple of things to make it worth the effort. A bone-stock 250 is not that much more powerful than a lightly breathed on 200.

On a 250 the compression height and the cylinder head are the keys.

 

[bmbm40]

Fascinating conversation on 200 and 250 pros/cons. That is why I visit here everyday. I know this thread concerns use in a Muatang.
My 3800 pound Bronco had a 1980 200/points ignition and 29" approximately tires and would not pull the grade from Carson City to Lake Tahoe in 3rd 1:1 to the top. About halfway up shift to second and crawl along about 30 mph. Now with a 1970 250/DSII and taller 30" tires approximately with a five speed, power steering and no mechanical fan. It pulls 4th 1:1 all the way very easily at 55 and accelerates anytime you want to close to 70 where it makes more noise than I want to hear so I back off. No floor mats or carpet anywhere. The 200 I bought used at the wrecking yard so know little about it other than it started right up and sounded good no smoke. The 250 had about 80,000 miles and according to the previous owner just had a valve job, runs good no smoke all stock.
For my use that increased low to mid range torque was an easy bolt in performance increase. The five speed enhances the overall performance/driveability but the direct comparison of the same two gears, both 1:1 on the same road show what the 250 provides. The od fifth is great, the old 200 would have struggled but the 250 just cruises along no strain.