Has anyone tried to STROKE a 200 inline 6?

[JMB]

Has anyone tried to STROKE a 200 inline 6?

Can it be done?

Is this a good modification to do? Thanks in advance.

 

[rocklord]

Ford did it. It's a 250. In Argentina, it's a 221. Both increased the deck height to increase the stroke.

You're about at the limit on the 200. Any cost associated with increasing the stroke on a 200 isn't worth the incremental amount you would gain.

 

[fastfalcon_19]

isnt a 200 a stroked 170?

 

[fphillips]

The 170 has a 3.5 bore to the 200 3.68.

http://classicinlines.com/SmallSixSpecs.asp

 

[rbohm]

The 170 has a 3.5 bore to the 200 3.68.

http://classicinlines.com/SmallSixSpecs.asp

8) note also that the stroke was upped from 2.94 to 3.126 in the 200 also.

as for stroking the 200, there is not enough room to stroke that engine enough to make a difference.

 

[CZLN6]

Howdy All:

Good question JMB- The answers already given are good. There is another reasonable option. That is off-set grinding the rod journals when turning the crank. Most machine shops can do this. An offset of .020" increases the stroke by .040"- .020" on each end of the stroke. It also reduces the deck height from a typical .025" to .005", which is good. And, theoritically, smaller diameter rod bearings have less drag. IF you have to have your crank turned down anyway, offset grinding is a good option. Increasing the stroke from 3.126" to 3.166". I don't know, right off, how much displacement that would gain, but if you believe that every little bit helps, there's a little bit. I'll run some numbers on the calculator and get back to you.

Adios, David

 

[rocklord]

You would only gain 2 cubic inches on a 0.020 offset grind.
Of course, if you then overbored 0.060 the displacement would jump to 209.

With the cost of acquiring rods with smaller crank bearings, I don't think it would be worth it.

 

[rbohm]

You would only gain 2 cubic inches on a 0.020 offset grind.
Of course, if you then overbored 0.060 the displacement would jump to 209.

With the cost of acquiring rods with smaller crank bearings, I don't think it would be worth it.

8) actually .020"us bearings are a standard undersize and widely available.

 

[Thad]

There is an engineering limit to stroking an engine. Increase stroke means shorter rods or less compression height piston. Due to piston to cylinder side load the rod can't be shortened past a certain ratio, and/ or physical restriction; piston height, there is only so much room between the pin and piston top for the ring stack. Then there is cam position. All limits.
When the factory reaches these point they would go to a taller block, 200 to the 250 / 302 to the 351 and so on. Economics says they would have gotten the most cubes from a block before going to a redesigned block and new casting.
What small amount you could stroke the 200 is not worth the cost or effort when there is the readily available factory stroker version, the 250.

 

[JMB]

Thanks guys for the replys.

CZLN6,

Thanks for the info.
As you mentioned - by off-set grinding the rod journals , I would have to get smaller diameter rods & bearings.

(For every action there is a re-action) Will the smaller diameter rod bearings cause the life span of the bearings to not last as long as the stock size?

Also, can we still buy a NEW Crankshaft for the 200 6? Thanks.

 

[CZLN6]

Howdy Back:

JMB- standard 200 specs come out to 199 ci. By offset grinding the crank journals by .020" and an overbore of .030" the ci jumps to 204, and the CR goes from OEM of 9:1 to 9.2:1. HP jumps from 120 to 125 @ 4,500. My guess is that most of the HP increase comes from the increase in CR.

I am not aware of any decrease in engine life due to undersized bearings. I do not know if a new 200 crankshaft can be purchased. There may be one out there in the New Old Stock (NOS) market somewhere.

Adios, David

 

[rbohm]

8) actually smaller bearing journals will mean longer bearing life as bearing speed is reduced. the difference is small in this case though.