just what is the story on the 198. is this a desirable engine?i have been familiar with the 225 ans 170, but haven't really heard much about the 198.
i have 3 slants in my shop right now, 2-225, and 1-198. trying to figure which one would be best for my 40 plymee project.
thanks.
Chuck

The 198 replaced the 170 in 1970
The design made it possible to get a smaller displacement out of the tall (RG) 225 engine block. Doing that allowed Mopar to discontinue the seperate block casting (R) used for the 170 in order to save some $$

A 198 has the same 3.400 bore size as the 225 and 170.
The 198 has a 3.64 stroke and a 7 inch long connection rod.
The 198 engine was produced until 1974 so they are not real easy to find these days. Most people want them for the 7 inch con rod.
DD

Having owned and driven all three in stock form, put in a 225 with the 198 rods and 2.2 turbo pistons in it. You'll be glad you did.

_________________
Official Cookie and Mater Tormentor.

I guess I gave away my age without knowing it on this post. lol
that is why i didn't know about the 198. i was a 100% mopar guy in the sixties. all big block of course, and kind of did the kid thing through the seventies, then got into buildind streetrods, and of course chevy powered.

I really haven't wrenched on a mopar for 40 years. boy how time flew-by...
but now with this 40 plymouth project, and me not really caring about smoking the tires much anymore, i thought the slant six modified a little would be the way to go, so i guess i'm back on a new learning curve again.
i'm assuming the reason the 198 rods are preffered is because the 7" rods cut down on the rod angle, like the 6" rods do in the small chevys?
thanks for all your input it is always helpful.
Chuck

It's pretty easy to get 225 HP out of a 225 SL6. In a light car, that can get your blood pumping.

Yes on the long con rod SL6, the better rod ratio helps reduce mechanical losses but the real advantage are the light pistons, with thin rings that go with the 7 inch rods. A long rod 225 spins-up much faster then the stock 225 version of the SL6.
DD