66 - 200 Mustang - Searching for a Direction - Pure Fun

Harlon

Well-known member
So if it hasn't become clear yet by my posts, I'm continually trying to find a suitable path to go with our 66 Mustang.

Right now it has an anemic 78 or 79 200 in it out of a Fairmont.
Per the door vin card it should have a 3 speed manual and 3.2 rear gear.
Whenever they swapped out the original 66 engine, they apparently swapped the manual tranny for a C4 auto.
The engine is tired and in need of Falcon 6 Performance treatment.

Where this is all leading is that, this car is a bit of a beater, and in large part not appropriate for any level of "numbers matching" back to original equipment resto. At least it doesn't feel like that would be a cost effective worthwhile venture. So in my mind that opens it up to building something that is pure fun.

Over the next few years we'll be refurbing rehabbing as we go. I think we've settled on starting with the drivetrain. Over the coming winters we'll move onto the suspension and braking systems.

We want to stay I6. This fall the plan is to pull the head on the 200 and have all the Falcon6 mods done by a local machine shop. Since it has become clear that our 66 is a Mutt, we're not as stuck on sticking with the 200. We have a 1970 250 available to us.

Here's where the questions start.

Real Question 1). 200 or 250 in a 66 Mustang. I've read it's not a bolt in swap. Is the added torque and horsepower from the 250 worth the extra hassle needed to install the 250 in a 66 mustang? Whether 200 or 250 is the choice, we'll be using the D8/9 head from the 200 with either shortblock. More torque equals more fun but is it enough more fun to compensate for the hassle?

Real Question 2). If you had your choice, what transmission yields the most fun hooked up to either a nicely rebuilt 200 or 250? We have a purely functional C4, but we're open to going back to a stick. Or upgrading to a T5 or AOD. I know this is a question of taste, but I'm looking for opinions. Is there a particular pairing that really shines above the rest?

Real Question 3). Is the 3.2 rear gear appropriate for our pure fun equation. If the 3.2 is a definitive weak link we'll look to change it out or upgrade to a stouter diff at this point.

Again I know this is subjective, but I'm looking for the experts advice. If you had your choice what engine(200 or 250), transmission and rear end combination would you put together for yourself in a 66 Mustang.

Thanks,
Harlon
 
Not sure of the actual total cost but if you are capable of some fabrication / mechanical work a turbo might be the lowest cost power increase that is doable somewhat quickly and low cost. Turn the boost up and just beat it till it flies apart. And keep an eye open for another used 200.
 
bmbm40":30h1m3sz said:
Not sure of the actual total cost but if you are capable of some fabrication / mechanical work a turbo might be the lowest cost power increase that is doable somewhat quickly and low cost. Turn the boost up and just beat it till it flies apart. And keep an eye open for another used 200.

Does sound fun, but not quite the direction I'm looking for. We want to build something we can enjoy for years to come, not weeks. Thanks for the interest all the same.
 
200 might B a "square(er)" motor - more race oriented, 250 might B a more tq oriented (Y its going in my Bronco).

For what U got now I'd put in the T5 (unless alota city or stop'n go, the C4 is 1 of the least parasitic of the autos & would B nice 2 keep), advance the timin 5*, frnt disc brakes, use the DSII ignition, & warm up that late model head. (just me, I don't know what 'fun' is 2 U, what you'll use it 4).

cam change? carb? valve train upgrade?…?

If U wanna cruse the twisties suspension/steer link mods, better tires, nice seat...

It's all in the subject line above

AND
don't forget any change to 1 part of the system effects the other parts of the system so *thorough research, *plan it out 1st (can't just slap on a part, coordinate them for safety, performance, durability, and lower end costs) & *stick w/that plan all the way thru to the final completion. The 'Handbook' has a nice 'staged' method of doin it so U can drive er while doin this. Get it from Matt at vintage inlines dot com. While waitin 4 delivery start the research by goin thru the whole Tech Archive (for free) by clickin on that name at the top of this page.

After that I was able to come here and ask the right questions to move forward.
Keep talkin, we're listenin!
 
The car will largely be driven in a small town. Mostly under 45 mph. Lot of stop and go. Only occasionally a run over 55. Virtually no highway driving.

Fun in this instance is really about getting to 35/45/55 in a hurry. Handling will be important but will be the next round.
 
Howdy All:

Q- "Does the 200 or the 250 make a better street engine?"
A- It depends. I', not trying to be funny. It really does depend. Yes, the obvious difference are accommodating a physically larger engine and less obvious is dealing with related issues of a longer stroke.

The longer stroke of the 250 was dealt with by Ford engineers by building a taller block. Taller to the point of leaving a .150" deck height to get a corporate compression ration of 8:1. The poor mans solution for dealing with this problem is to deck the block .025" or so, taller 255 V8 engine pistons for another .085". All of which leaves a deck height of .040". Not good for an efficient quench effect. And a huge compression ratio problem.

The compression ratio problem can be partially dealt with by dishing the top of the pistons- Machining $$

The point and bottom line is you can accomplish more with a 200 with less cash due to machining and exotic parts.

In your case, given your end goal, building a 250 with stock parts may give you what you want. In the end, there is no substitute for cubic inches- unless it is cubic dollars. The problems of the tall deck height are not deal killers. You can live with it- I did.

I've been thinking about your other question too. I'll get to that later.

Adios, David
 
CZLN6":2mmaky3x said:
The point and bottom line is you can accomplish more with a 200 with less cash due to machining and exotic parts.

Adios, David

That might be the answer right there.

I read the tech article on swapping a 250 into a first gen Mustang "again" last night. The "hassle" of install doesn't seem too bad.

Seems that it really becomes more about is it financially worth it.

Depending on how I dealt with the deck height vs hood clearance I'm looking at dropping the engine, modifying/replacing the hood. I think I saw that Clifford has a header specifically for the 250. I think they're basically a wash with the 200 header $$$ wise. The 250 comes with a C4 bell housing so I'm good there. I plan on going electric fan either way so no additional cost there.

Hassle - not so much
$$$ - could be significant between additional short block matching and if I go the expensive route and replace the hood.

I need to dig into the actual costs to rebuild the 250 short block. Need to go back to the tech articles and see what it will take to get the CR into the low 9s and put $$$ to it.
 
Howdy Back:

Your 200 C4 tranny will not fit the 250 bell housing without modification. Sorry.

I used Clifford header too. No Classic Inline or Vintage Inline at that time.

Keep it coming and keep reading.

Adios, David
 
CZLN6":11vj2znf said:
Howdy Back:

Your 200 C4 tranny will not fit the 250 bell housing without modification.

Sorry,..., and keep reading.

Adios, David

Thanks for the info. I've been working my way through your book this morning working on putting together a table of differences between building the 200 and 250. Parts wise I should be able to get close to a cost differential between the two builds. Good exercise either way, so we can see if we can afford what we want to do on our budget.

Is the problem with the C4 itself or the bell housing. With the 250 I can get a C4 w/bell housing. The bell housing is a V8 housing. The C4/ housing came out of a 70 302 Mustang. I was going to just buy the housing.
 
I would go with the 200. Use your late model head & get a machine shop do a direct mount for a 2bbl carb, be it a Holley or an Autolite.
Mill the late model head .070" & use a Victor head gasket to get your compression ratio up over 9-1. Zero deck the block would be a plus. Bore the block .030" using dished seal power pistons.
You already have a DS11 distributor that will need to be recurved for your combination. PM me if you need that done.
Get a set of headers & go with a crossover or X pipe to a full dual exhaust system.
The 250 will give you hood clearance problems & is not worth the hassel for what you want out of your 66.
 
As mentioned above, I'd stay with the 200 but add a cam, mill the head, etc. there's a selection when it comes to carburation. 2Bbl Holley, Weber, etc. Three singles (I'm running that), even fuel injected. If you want to go with a manual transmission, a T5 is, in my opinion, the only choice for a fun driver. Combine that with an 8" rear with 3:55 or even 3:73 gears and it'll put a smile on your face each time you drive it.
 
The longer stroke of the 250 was dealt with by Ford engineers by building a taller block. Taller to the point of leaving a .150" deck height to get a corporate compression ration of 8:1. The poor mans solution for dealing with this problem is to deck the block .025" or so, taller 255 V8 engine pistons for another .085". All of which leaves a deck height of .040". Not good for an efficient quench effect. And a huge compression ratio problem

Dave, and Forum,

The 250 short block for this build is a 70. I'm plannng on utilizing the 78/9 (read can't remember which it is. 78 or 79).

Per the Ford6Performance website and handbook:

70 - 250 - 9:1 compression
70 - 250 - 62 CC chamber head

79 - 200 - 62 CC chamber head

If I want to keep the engine in the low 9s compressionwise, shouldn't I just go with minimal honing and decking to true the surfaces and compensate for the modern head gasket. Otherwise I'll quickly push the engine into detonation on premium gas?

If the 250 short block was a later engine with the 8:1 compression I'd need to get more aggressive with reducing deck height and chamber size to bring the CR up, correct? But because this is an earlier 9:1 block it should be a more straightforward operation?

Am I on the right track at least in regards to the right formula for this 250 configuration?

Thanks,
Harlon
 
It seems like you really don't know where you are with a 250 until you pull the head and actually measure. They seem to vary drastically. Mine was @ .108" iirc stock never cut and they are all over the place with others. I think if you're going straight stock, except maybe a slight cam upgrade, I'd deck to get the engine to 9:1 @ 60cc chambers w/ a .045" gasket to give yourself some wiggle room.

If you want to really build the engine look at what Lavron is doing on his 250 build. He's doing a great job managing the issues so far:

https://fordsix.com/viewtopic.php?f=1&t=77057
 
1st - CC that head 2 C where ur at. Never deck a block as 1st recourse. The system works together, can't put surfaces back (like carpenters do).

"...I used Clifford header too. No Classic Inline or Vintage Inline at that time…."
VI and 'Speed Daddy' low, low price ToDay need 2 B in ur cost accounting if ur going w/headers.

"...The 250 will give you hood clearance problems & is not worth the hassel for what you want out of your 66…"
I have 8 ways to 'raise ur hood' & have provided these pointers 4 eight yrs here. PM for info.

Keep talkin
 
'puter problems
 
Okay, I did some more reading.

Quench - is the issue with the 250 and the .150 deck height a problem because of quench? If optimal quench is .040, reducing the piston face to cylinder head surface to accomplish this (or at least get close) reduces the combustion chamber volume to a point that pushes CR beyond reasonable levels.

Sorry, thinking out loud. Trying to wrap my head around the principles.

Econoline - thanks for the link
 
Howdy Back Harlon and All:

FYI- FoMoCo started the process of moving away from a head casting with a 52 cc combustion chamber with the advent of the '69 250 "M" head casting. By about '75 all head castings had moved to 62 cc combustion chambers. All 200s and 250s used the same dished piston. While this was going on FoMoCo advertising ranged from 9:1 down to 8:1 with no other physical changes other than the combustion chamber size.

The Federally mandated change in advertised horsepower rating of 1972 effected advertising data as well, again, with no physical, internal change. The bottom line here is- use great caution when using advertised FoMoCo data.

On your three questions, I'm still struggling but here are our choices. I choose a 250 for my '65 Ranchero. My brother choose a 200 for his '60 Ranchero. Both manual trans- mine an SROD 4speed, his a T-5. With similar engine builds Dennis' 200 revved faster. My 250 had more torque. Granted, Dennis' '60 was lighter than my '65. In the end, not a huge difference in performance.

So, my opinion, as of today, given your parameters, I' suggest a 200 build. (That's the engine I will do next) And IIWIYS I'd go with an auto trans. Yes, a T5 manual is great fun for those rare occasions when you can get-it-on and stir the shifter. But 99% of the time you'll be cruising. The C4 with a 3.2:1 rear gear ratio is just about right for mostly city driving.

Select a cam and compression ratio that compliments the package and enjoy. Hooking the new 2V carb to the down shift linkage on the C4 will be interesting. That's an adaptation I will need some day.

On the rest of the vehicle, build with light weight in mind. Both of our cars stayed with 4 lug wheels and drum brakes, but upgrade to dual bowl master cylinders and new flex hoses. Never a problem. We both changed the steering Shaft to later 2 piece designs with deep dish steering wheels for safety.

On suspension and handling choose your tires and wheels first and compliment from there. The biggest single factor in ride, handling and safety are the tires.

This may sound simplistic but many hours of brain gymnastics, back-and-forth, and rethinks have gone into this response for you. Now I can't wait to hear what you decide. So keep us posted.

Adios, David
 
Thank you for your time and commitment.

I greatly appreciate everyone's input. It always amazes me how much you can learn in a forum like this.

TMI - I'm a stay at home Dad(sigh) recovering from lower back surgery to repair a herniated disc(sigh) so I have way too much time to read/think. I've spent hours reading through several 250 builds here on ford6. Like anything, right is a matter of opinion. About 4 am this morning I think I came to the conclusion that for the $$$ to do the 250 rightish I could do a really nice 200.

It's that damn practicality though, when I start thinking that way it's too easy to slip from rightish 250, to really nice 200 to ,..., oh never mind I won't go there.

As a 17 year old I dreamt of nothing but swapping a 351 Cleveland into my 62 Falcon Coupe. I looked at a 55(I think it was) Desoto with a Firedome hemi in it. Rareish, undesirableish early Hemi. Looked into what building the engine would cost. 8-10 grand. One of the builds I read last night said they had a little over 5 grand in their 250 with the aluminum head. Somewhere in the 1500-3000 range for a nice 200. If you want something unique done well it's going to cost $$$. I just try not to look at the math for how much horsepower and torque you can get out of a sbf for the price of the raw aluminum head.

Bad thoughts!
 
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