Ever build a 200 /250 stroker?

[64 inboard]

Hi all,
Its been a while since my last post. A little over a year ago,I bought a 1964 "Correct Craft " inboard boat with what we believe to be a 170 il. six, . This is my first 6 beater ride and really have grown to love it...
( great sound + low fuel consumption= happy wallet )....but , Ive been contemplating anything I can do to get a few more horses out of the ol girl.

I bought a 200 for 20 bucks that needs a rebuild, and I also know of a 250 in a barn ,that the guy wants a hundred for. . I understand the 250 bellhousing wont bolt to the boats mounting plates, so that engine trans-plant is out of the question. Ive been told a 200 bellhousing is the same as a 170s,
sooo...
My question is, can a guy take the crank out of a 250 and put it in a 200? It looks like they both have 7 main bearings and the sizes are the same?

Is this do-able, if so, what head would be best? Any other quircks? Anyone done this?
Thanks for your input!

 

[XFlow_Fairlane]

crank won't swap over. too much stroke for the 200 block.

the 200 will bolt inplace of the 170 though. best bet is to rebuild the 200 with the 250 head on it and raised compression.

 

[64 inboard]

Im assuming the block height is too short on the 200?
Are there different combustion chamber sizes between the 200 and 250s?
what type of comp. ratio do you end up with?

 

[addo]

The 250 crank has some larger sizes on the balancer snout and (I think) rear main seal running surface.

Strokers are generally impossible because rod throw strikes the camshaft. I reckon you could get an Aussie or Argentine 221 crank into a 200 but that's probably the realistic limit - and even then you would need to doublecheck all working clearances after grinding!

200 crank in a 170 gives 188 - not sure on the rods to choose.

Cheers, Adam.

 

[Rustang Racer]

Yeah, the block height is too short. The 250 engine overall is something like 1.6 inches taller than the 200. I think the combustion chamber size depends more on the year of the head than engine type. In 1965 I think the 200 had a 52cc head and about 9.2:1 compression. Later in the 60s and in the 70s I think it was more like 62cc with compression in the low 8.x:1 for emissions reasons.

 

[64 inboard]

Thanks for the info ... sounds like the 200 transplant is going to be the best/ most cost affective way to go..

 

[xctasy]

Becasue I am a New Zelander, I'm supposed to argue withg addo. In this case, I won't. The 200 is thw best swap.


If you've got a spare 2 US grand you have another option which will yield over 223 cubic inches.

1) Use the Aussie or Argentine 221 crank. This has a 3.46" stroke,

2) cut the crankpins down to 1.931".

3) Then fit six Datsun 280 ZX rods

4) Use US Zolliner 3.70" pistons, as used in Fords latests 5 liter Quad Cam V8.

5) After that, the pistons come up about 200 thou above the block, so just fit a huge copper gasket there. The rings fall about 25 to 40 thou short of the top of the block.

6) You'll have to use some aftermarket 2.3 HSC puishrods,

7) and the 14 Aussie X-flow 3.3 or 4.1 studs to allow the head to be bolted down without hassels, but its pretty easy.

Piece of cake.

The conrod to to cam clearance was improved on later cams after the 250 came out in 1969, so as long as you use the aftermarket camshafts or a post 1969 cam, you have 53 more cubes.

Remember, the 200 is the smallest and lightest all iron I6 in the world for its capacity, and its pretty easy to get another 23 to 28 cubes using available parts if you are prepared to rebuild an engine.

The Ford I6 is narrower, shorter and shallower and tougher than any other I6 engine its size. As a pleasure boat engine, its hard to beat!