Just curious about the opinions of various board members on the qualities of the various slants. Just so we are all on the same page lets list the specs on these engines... (HP and torque in gross scale, as in grossly exaggerated).

170
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Bore: 3.40" (86.4 mm)
Stroke: 3.125" (79.4 mm)
Con. rod: 5.669" (144.0 mm)
Rod ratio: 1.814
Displacement: 170.2 cu in (2.8 L)
Peak HP: 115@4400
Peak Torque: 155@2400


198
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Bore: 3.40" (86.4 mm)
Stroke: 3.64" (92.5 mm)
Con. rod: 7.006" (178.0 mm)
Rod ratio: 1.924
Displacement: 198.3 cu in (3.2 L)
Peak HP: 125@4400
Peak Torque: 180@2000


225
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Bore: 3.40" (86.4 mm)
Stroke: 4.125" (104.8 mm)
Con. rod: 6.699" (170.2 mm)
Rod ratio: 1.624
Displacement: 224.7 cu in (3.7 L)
Peak HP: 145@4000
Peak Torque: 215@2800


Now that, that is squared away... here are my observations.

170
-The only engine that is oversquare
-Rod ratio is better than the 225 but not as good as the 198
-Lowest peak HP and torque but known for being able to rev much higher than a 225, which changes up the low peak HP numbers. But still not tons of torque
-Tied for highest RPM at peak HP (a slant at 4400RPM probably sounds awesome!)
-Though it is smallest it is still quite sizable by todays standards

198
-Only engine that is "square"-ish
-Best rod ratio
-Widest RPM gap between peak torque and peak HP
-Lowest peak torque (possibly best highway economy?)

225
-Undersquare
-Worst rod ratio
-Tons of low-end torque but doesn't like to turn nearly as high as the 170
-With all that stroke and less-than-great rod ratio the rings get a good work out.
-Seems to be most popular and readily available engine.
-Also seems to be most sought after for performance.


Can anybody give any advice on what might cause one to select one displacement over another for performance/economy/boosting/etc.

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'66 Dodge Dart

The horsepower and torque numbers are meaningless; see here and here.

170: easiest to make rev highest
225: easiest to make into torque monster
198: best for robbing connecting rods from.

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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 rod ratio isn't bad at all for the 225, there are many other OEM engines with even lesser that are still capable of 7000 RPM and good HP and torque. Look at the 454 Chevy(6.135" rod and 4.000" stroke)I built many for my personal hot rods in the past, and had several that were over 600 HP N/A and were great street/strip engines, also look at the 347 Stroker SBF with a (5.315" rod and a 3.400"stroke), I built many of these for customers in the 5.0 Mustang heyday that made 430 HP and 440 ft. lbs of Torque and more and were an awesome street/strip engine combo. The 455 Pontiac is a 4.125" Bore and a 4.210" stroke with a 6.625" rod, its undersquare and a bad L/R in theory, but many have proven to be awesome race engine combos and real performers. And my personal favorite, an NMCA 455 SBF with a 4.130" bore with a 4.250" stroke and a 6.100" rod length, another undersquare and poor L/R on paper. it was a nitrous engine, but made 768 HP N/A @ 7000 RPM, and was sprayed with 400 horses of nitrous and dynoed at 1168 HP @ 7000 RPM. Never let a formula dictate how or what to build, there are many engines that contradict them. The only formula you should use to build an engine is for compression ratio.

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There's no such thing as too much cam....only not enough engine!

Unless you have a specific application in mind (such as setting a land speed record requiring high revs or building an ultra efficient hyper-milage engine), at this late date I would pick a 225 just for ease of finding parts and for the fact that the 225 was produced the longest (pun intended!).

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Casually looking for a Clifford hyperpak intake for cheap.

Good stuff as usual Dan. I only included the HP and torque numbers for rough comparison between the various engine, however I ought to have added that disclaimer for any new comers that don't realize the huge variance in the various engines.

I'm not really thinking about builds too much, just curious in the characteristics of each of the engines. The basics are well known (170 revs high, 225 isn't going to enjoy the revs but will produce tons of torque), but what about the 198? Will it rev up like a 170 or do the heavy rods slow it down? Or is the 198, as Dan said, only good for swiping rods from?

Just trying to think outside the norm of a 225 bottom end.

_________________
'66 Dodge Dart

My 198 dynoed at the wheels running pig rich at 98hp. (black smoke blowing!) Stock cam, air cleaner, over jetted 318 BBD, .090 off the head and heavily ported with stock valves. Hooker headers.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

250 HP from a 170 means creating 1.5 HP per cubic inch.

250 HP from a 225 means creating 1.1 HP per cubic inch.

All other things aside, there's no replacement for displacement.
(At least with the "primitive" engines we have chosen as our favorite hobby)

- Mac

I know that this is just a modded 225 but anyone know what, and at what rpm, the peak HP and Torque is for the 260 slant in the stroker article? With all that low end torque, sounds like the best build for a daily driver.

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76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

Only Doc could tell you about the 260 from the stroker article.

I know displacement is a huge deal for torque, but HP is just as dependent on RPM. Just seems like a turbo 170 would rev well and achieve similar displacement to a 225, not to mention a nicer power:weight ratio. But I'm not engine guru or turbo guru either.

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'66 Dodge Dart

Displacement is not contingent on engine rotative speed, induction configuration, or anything else besides bore, stroke, and number of cylinders.

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

Sorry for the ambiguity of the word displacement there. I simply meant that a boosted 170 that displaced (read: moved) near as much fuel-air as a 225 and could rev higher would probably produce better HP.[/i]

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'66 Dodge Dart

Dan:
Displacement in normally aspirated engine is dependent on stroke, bore and number of cylinders yes, but forced induction changes the equation when more air/fuel is stuff into those bores, and the resulting power output is as if those dimensions or number of cylinders were substantially increased.

In other words if you double the charge over what a normally aspirated engine would see, the engine’s ability to do work increases as if the engine size has been almost doubled… That doubling was just a SWAG’ed number pulled out of my hat as I don’t have the formula’s at hand to explain this relationship.

So if one would want to add a left leaning bank of six to his existing slant, making a V12, a cool idea but rather a tough nut to crack technologically with all that metal work, all one has to do is rig up a compressor of sorts say, a super charger, or turbo charger, and stuff a lot more air & fuel in to that factory six displacement to cause the engine to perform as if it were doubled in size.



Horse power is a rate dependent on rpm that predicts the ability of an engine to deliver its torque over time. In other words the higher the horse power rating the faster the engine can deliver torque, torque is the number that dose the work; foot pounds on these shores. Another way to look at it is work = force x distance, and horse power explaines how fast that pound gets moved over said distance.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Yes wjajr, horsepower being a measurement of power is calculated work/time (horsepower is actually calculated as (RPM*torque)/5252, 5252 is some crazy constant that I don't really understand). And I think most of use want our slants to do work as fast as possible

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'66 Dodge Dart

…but does not change the displacement, which is short for "piston displacement" and is dependent only on bore, stroke, and number of cylinders.

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

Funny you should ask...

That 260 engine currently "lives" in our 66 Dart wagon (the "tow car") that my son Allen also drives daily. The main "performance limitation"... still has a 1 bbl carb on it.

We just got back from the Redding SL6 race and there was one of those portable "chassis dynos" there on Sunday, with a "racer special" price of $19.95 for a test.
Allen put the wagon on the dyno and it made just over 100 HP at the rear tires. Torque number were high but I do not remember the actual amount.
The dyno operator said that he should have started his test measurements, for this vehicle, at a lower RPM, they started recording numbers at 2500 RPM and the engine was already at a high torque value.
They also started looking for "a problem" when they saw the HP numbers flatten-out at around 3500 RPMs... then they saw the 1 bbl carb. and said: "there's your problem".

I will see if Allen can "jump-in" with more details...
A few different SL6 cars went onto that chassis dyno and many put-out some pretty good numbers.
DD