What's "better"...200 or 250?

[blueroo]

I want to keep a six in my car but I'd eventually like to step up from the 170 to either a 200 or 250.

Originally I was thinking 250 with the whole larger displacement thing. But now I'm not so sure.

On one hand, there's the 250 with the obviously larger displacement in its favor. The other hand there's the 200 with what appears to be more performance parts.

Any suggestions on which route to go?

 

[CZLN6]

Howdy Blueroo:

All else equal, displacement will win out. Your question was, "What's best?" Which begs the question, "For what?"

The problem is in getting each engine to an equal place. While both engines have the same bore the almost 4" stroke of the 250 lends itself to be more torque. Consequently, the 200 will rev faster, the 250 will generate more torque for a given rpm.

Another factor is that the valve size will remain very close to the same, due to a limited bore, so intake and exhaust flow efficiency will be limited. Larger displacement appreciates greater flow. Trying to increase valve size past the 1.75" Int, 1.5" exh, has limited returns due to valve shrouding from proximity to the cylinder wall. Both have the same stroke to rod length ratio, so that's not a factor.

Finally, for optimum performance quench height should be in the .035" - .040" range. Quench height, aka deck clearance or compression height, is the combined height of the thickness of the compressed head gasket and deck height, the distance from the top of the piston to the top of the block.

On a stock 200 the compressed head gasket measures .025" and has a deck height of about .025". Not ideal, but not too bad and fairly easy to remedy with block decking and assembly with one of Mike's new .035" thick head gaskets or a NOS piece.

On a stock 250, the head gasket is the same .025", but the deck height is anywhere from .100" to .150"!!!! Too much to remedy easily or cheaply.

As far as performance parts availability, that's about a push. What's available for a 200 can also be used on a 250

The problems with oil pan shape and front pulleys from early engines to late are the same for later 200s and 250s so that's a push too.

Trans options is a big plus for the 250 as they have a V8 type bell.

What's best? You decide.

That's my two cents, for what it's worth. Hope it helps.

Adios, David

 

[blueroo]

Ah I forgot about the whole intended use part. While I'd love to build a twin turbo, multiport efi, dry sump, etc etc 250 coupled to a T56 with a 9" IRS, that probably won't happen unless I win the lottery.

So I'm not looking for an absolute "holy crap I'm suddenly in the trunk" kind of build. Instead what I want is nice 200 or 250 that's fuel injected (think Tempo/Taurus efi), uses 87 octane without a problem, averages around 25-26mpg and maybe 140hp/170ft lbs to the rear wheels.

Just an average get the job done efficiently yet still have some fun kind of engine.

 

[rbohm]

8) for your fairlane i recommend using the 250 for a decent street engine. since the fairlane is a bit heavier than the falcon, it can use the greater torque at the lower rpms. i am going to put a 250 in my 64 falcon id that helps you make up your mind.

 

[falcon fanatic]

I'd have to say 250. While there may be more parts available for a 200, the ones that really matter are also available for a 250: cams, rocker assemblies, headers, ignition, head (!!!). About the only thing you'd really be missing is the adjustable timing gear, and that's presumably on the way. For exactly the same $$ as a 200 build, you could have an engine with 25% more displacement and everything that implies...[/i]

 

[sp_alloy_head]

I vote the 200. The 200 is much easier to get into the engine, no deck height issues(my 250's pistons are .120 below the deck), no need to mess with the centerlink, no need to modify the radiator support, you can keep your mechanical fan if you choose to use it and you can use almost any carb/aircleaner combo without having to worry about hood clearance. I understand that there are remedies for each of these problems but why would you want to deal with it for a mere 50 cubic inches and marginal performance boost?

By the way if you still decide build a 250 I have 300 rods and pistons you may want

 

[350kmileford]

I know the majority of 200's had 7 main caps, definitely a plus. Did the 250's?

 

[in2hotrods]

By the way if you still decide build a 250 I have 300 rods and pistons you may want

What's this about the 300 rods for a 250? Never heard anything about that, some kind of stroker on the cheap perhaps?

 

[in2hotrods]

I'm getting ready to put a 250 into my 63 Fairlane. I haven't started just yet but I do have most of the parts in waiting. As long as you're not in a hurry then I will let you know how it goes.

Also, any progress on those seatbelts? Pics?

 

[Rustang Racer]

I've had both in the same car. I would go with a 250. A lot more torque, which is what is fun for a street car. Its a little harder to cram the 250 in the engine bay but I think its worth it.

 

[sp_alloy_head]

in2hotrods here is the 300 rods information

Howdy back Ken and All:

There are two other options to consider to solve the huge 250 deck height problem. they are;
1. Use a longer 300 Ford six rod with the Keith Black 305 pistons with a 1.26" deck height. This combo has the advantage of reducing the deck height .090" and giving a slightly better rod/stroke ratio.
Rod Length & weight;
250 =5.88" 592 grams
300 =6.21" ??? grams
Difference = .330" longer

Rod Length to Stroke ratio;
250 = 5.88" : 3.91"= 1.5:1
300 = 6.21" : 3.91"= 1.58:1

Deck the top of the block to achieve zero deck height. Use a FoMoCo composite head gasket (NOS if you can find one) with a compressed thickness of .037". I'm hoping Mike will announce the Cortico .038" gaskets for 200/250 soon.

Use with a Chevy 305 Keith Black (KB 153) piston in a standard bore of 3.736" with a 1.26" pin height. These pistons would require an overbore of .056". Plans would include milling a recess into the piston top which mirrors the combustion chambers. The goals will be to create a higher quench-to-bore ratio, lower CR, lighten the piston, reduce knock tendency, and maximize combustion efficiency.

The advantages of using the 300 rods are- longer, for a slightly improved rod-to-stroke ratio, likely tougher than 250 rods. The 300 are designed for higher load truck application and have the same rod and main journal dimensions as a 250 I think.

The only extra machining would be to rebush the small ends to accommodate the larger Chevy .9273" wrist pin. The 300 rods small end measures .9122".

2. Use longer 1986-’90 Taurus & 1986 Sable 2.5 HSC rods with the flattop HSC or OEM dished replacement pistons. This has the advantage of reducing the deck height .110" and giving a slightly better rod/stroke ratio.
Rod Length & weight;
250 =5.88" 592 grams
2.5 HSC =5.99" ??? grams
Difference = .110" taller

Rod Length to Stroke ratio;
250 = 5.88" : 3.91"= 1.5:1
2.5 HSC = 5.99" : 3.91"= 1.5319:1

Deck the top of the block to achieve zero deck height. Use the thinnest composite head gasket available to optimize the quench effect.

Use with an HSC flattop piston, with plans to mill a "D" shaped dish into the top. The goals will be to create a higher quench-to-bore ratio, lower CR, lighten the piston, reduce knock tendency, and maximize combustion efficiency. The stock replacement large dish Calif Emmissions pistons would work too. Standard overbore sizes would apply to both of these pistons.

The advantages of using the 4-cyl rods are- longer, for a slightly improved rod-to-stroke ratio, tougher than I6 gear. The four cylinders vibrate much more, rev to a much higher RPM, produce more power per cylinder, carry more load per cylinder than a six, and suffer more detonation than a I6 was ever designed for.

These combinations will have a more ideal deck clearance, likely have a lighter reciprocating weight, and be able to tolerate CR in the 9.5:1 range, at sea level, with 91 octane gas.

Plans are to use ARP rod bolts, polish the rod beams, balance the whole rotating assembly, and polish the piston tops and the chambers.

In any case, mill the head only enough to ensure it's flat. It is critical to measure all volumes to verify CR. Reshaping the combustion chambers to reduce CR, unshroud the intake valves and match chamber volumes may be necessary.

A couple more options to consider.

Adios, David

 

[blueroo]

Ok, two more questions...

1) Can the big bell 200 and/or 250 be adapted for use with a small block V8 flywheel, pressure plate, clutch, bellhousing, etc?

2) Would there be any real performance gain by using a 200's crank in the 250? (if I'm thinking right the shorter stroke when compared to a normal 250 would result in less torque but still have more torque than the normal 200 would and a shorter stroke would result in better breathing {I've heard longer stroke motors tend to run out of air at higher RPMs})

 

[in2hotrods]

The 250 shares the same bellhousing pattern and flywheel bolt circle as a 302. However, the Flywheel or Flexplate must be neutral balanced.

 

[rbohm]

1) Can the big bell 200 and/or 250 be adapted for use with a small block V8 flywheel, pressure plate, clutch, bellhousing, etc?

yes both can, but the 200 flywheel bolt pattern is smaller, and the 250/302/300 flexplate/flywheel will have to be redrilled to fit the smaller pattern. with the 250 you only have to rebalance the flexplate/flywheel to a "0" balance, or use a 300 wheel.

2) Would there be any real performance gain by using a 200's crank in the 250? (if I'm thinking right the shorter stroke when compared to a normal 250 would result in less torque but still have more torque than the normal 200 would and a shorter stroke would result in better breathing {I've heard longer stroke motors tend to run out of air at higher RPMs})

you would be going backwards. use the longer rods indicated and higher rpm breathing becomes less of a factor. unless you are going to race this car in anything more than a street modified class, you are not going to turn above 6000 rpm. if you are going to race in the higher classes, classicinlines has an excellent head that will cure any breathing problems you might encounter, and those that you cant cure with the new head, you can cure with either some port work, or a forced induction system.

 

[xctasy]

Due to the weight increase of the 250, its 25% increase in capacity doesn't give a 25% increase in power or performance. Especially since the biggest glitch, that nasty block deck matter, results in little extra power over a 200, and the problem is not fixable without a full rebuild. Dollar for dollar, the 250 is a very expensive option.

Its big V8 bellhousing has to use a 157, 160, or 164 tooth flywheel or flex plate, meaning the early pre 63 Fords need hammer work around the firewall to fit. The early 200's only need a little 132, 138 or 148 tooth item, heaps of space, and you can find a better range of bellhousings and transmissions if you are smart enough to read the articles.

The engine mounts need to be regigged to suit, and engine height forces the carburettor into the bonnet, so you have to look at a trim air cleaner or a pod style K&N item.

Fuel consumptionof a 250 increases generally 5 to 6 miles to the gallon over the 200, due primarily to the camshaft and breathing requirements becoming progressivley worse as capacity goes up.

The braking and steering and diff strength needs with a 460 pound 250 engine will be more than a 365 pound 200 cube engine. A stock Falcon has a 20:1 steering box needing 5.5 turns lock to lock. Adding a 250 increases the steering loads up to the equivalent of a 16:1 steering gear with 4 turns lock to lock. Unless you have a pre 63 Ford or power steering at the moment, the 250 will make a post 1964 Falcon, Fairlane or Mustang very heavy to steer.

Having said all that, the 250 is still a lot of fun to spend time behind.