I read that the standard motor for the 72 Darts was the 198 cu.in. but I've only seen 225s.

From: Valiant.org: (for 1972) The 198 cid slant six was standard on all models; a stroked version, the 225, was optional.

I guess what I'm asking is: what displacement s6s were offered in what years?

198 base
225 option

most cars were optioned up to the 225

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Slant Cecil

For North American-market A-bodies, engine availability was:

170: base engine 1960-1969
198: base engine 1970-1974
225: Optional engine 1961-1974, base engine 1975-'76.

The 225 was the only slant-6 offered (any model, any market) after 1974.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I know that if the bypass hose is ~ 1.5", its a 170. The 225 has a longer (~ 2.5") bypass hose. How can I visually identify a 198?? thanks

You can't, easily, without looking at the block's stamped ID numbers. The 198 and 225 used the same RG (tall) block; the displacement difference was created by a different crankshaft and connecting rods.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I just checked on the VIN decoder: LL23B2R "B" is the 198. C would be a 225. any advantage, one vs. the other? or is the 198 only good as a conrod donor for the 225?

Well, sure, a B rather than a C will tell you what engine any given car started out with, but it's been 33 years since the last 198-equipped car left the factory...!

The 198 takes less fuel and puts out less power and might have a little more RPM capacity than the 225. I don't know if anyone's tried a full-boogy hot buildup of a 198. Doc...?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The gentleman I bought it from was the 2nd owner, and indicated its just as he bought it. I think he bought it 20+ yrs. ago, at that time it had ~40K miles. So I'm assuming its the original motor. I'll go looking for the vin on the block. If someone could tell me where to look for it?? lol

A low-miles unit would probably have its original engine or an identical warranty replacement item. Just check the engine ID number stamped at the top of the block under the frontmost spark plug, behind the alternator/coil bracket. A 1972 198 would be stamped H 198, while a 1972 225 would be stamped H 225.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Don't have the page doc posted, but someone did a hyperpak buildup on a 198 with one of the MM mopar only lobe profiles from comp cam... It had a nice high VE in the mid to upper rpm range...

-D.Idiot