how many RPM's a 225 Super six slant has going full?

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1972 Plymouth Duster 225 Super Six Slant

depends on the gearing, but I shift at 4500, or 4800 really getting on it, my cam wants to produce a lot more torque than ponies, also mine is a little more built than yours. The top gear guys shift at 6000 which is what I plan on for the next engine.
For daily driving I can shift at 2200 just fine and move with traffic.

well what i guess im trying to say its going down a track all way in whatever gear what the rpm would hit

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1972 Plymouth Duster 225 Super Six Slant

One limiter will be your stock cam, it runs out of steam at about 4000 rpm no matter what... on top of that your distributor will have stock springs so it'll be a slow goer ignition wise, then your 2.76 rear gear doesn't exactly make the car easy to throw down the 1/4 mile either (doesn't wind up fast enough between the shifts...)...

-D.Idiot

well thanks d

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1972 Plymouth Duster 225 Super Six Slant

Dont forget that your rotating a 4 1/8" stroke crankshaft. That's longer than most big block V8's.

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'63 Valiant V200 Convertible
225 Aluminum Block

that make alot of difference ?

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1972 Plymouth Duster 225 Super Six Slant

Big time yes.

The crankshaft stroke and the rpm determine piston speed. There are parameters in which a reciprocating IC engine can operate safely within.

Let's compare the 170 CI (2.8L) slant to the 225 CI (3.7L).

170 CI has a 3.125" stroke
225 CI has a 4.125" stroke

Some empirical data:

Stock engine max piston speed = 3500 fpm (feet per minute)
Heavy duty street/strip = 4000 fpm
All out race engine = 5000 fpm

To find max safe rpm:

Stock engine = 21000/stroke
Street/Strip engine = 24000/stroke
Race engine = 30000/stroke

Now, for our comparison:

21000/3.125 = 6720 rpm max. At 6800 rpm piston speed = 3541 fpm
21000/4.125 = 5091 rpm max. At 5200 rpm piston speed = 3575 fpm



So, one inch of extra stroke limits rpm by over 1600 rpm in otherwise similar engines. Huge effect.

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'63 Valiant V200 Convertible
225 Aluminum Block

I guess I'd better talk to the Hpak engine, your formula says max safe limit is 5800... my duster says 6200 is fine, but the clutch never likes it much...

-D.Idiot

kewl info

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1972 Plymouth Duster 225 Super Six Slant

It isn't how high you go (RPM) as much as how fast you get there (Torque). Lot's of big block cars that run the quarter mile under 10 seconds never rev over 4500 rpm a few lock out a little lower around 4200 or 4000 rpm. Watching a 440 stroker run is quite amazing......

There is no reason you can't make your slant make some big time torque and run well under 4000 rpm. The Chrysler engineers found that they never really tapped into the torque potential of this motor in a production automobile. Long (over 40 inches) 3 x 2 headers are a key as well as the long intake runners of the Hyper Pak. That combined with the long stroke of the motor will move a 3000 pound car or truck pretty quick.

Since these parts are hard to find, we end up using shorter length headers and shorter length intake manifolds which like to build power at a higher rpms.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ted, do you have an example of any headers like the ones you describe? Does anybody actually make anything like that? It'd be nice to have a direction to dream in.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

My last engine I built revolved around torque, horsepower is irrelavent in relation to moving a car down the road. In lamest terms I measure horses as a product of torque over time required to reach a given rpms.
I don't know about the big block going over 4500 rpms, but I do know that the original stroker small block going into the challenger was a 440 small block that produces a healthy amount of torque. The new engine will spin to 7500rpm but scarifices a substantial amount of torque to achieve that number. The engine has a given amount of power, which you can shift up or down the rpm scale to achieve your goal.
Simple terms: Last time I had my Duster in Corvallis I pulled up to a 4.6 stang. My motor shoves you into your seat from 700rpm to 3000rpm. Off the line the mustang had no idea what hit him, what let him catch me was he reved to 5800 rpm when I would shift at 4500rpm. Come the next red light I reved, he turned right.
By the way, don't street race.

There is actual data from the 60's when uncle 'Vic' Edelbrock used to do articles on 'bolt on power'... in one very documented article he used a 1967 383-2v Engine (oooohh a whole whopping 270 HP with the Stromberg WW 2 barrel...)... he proceeded to bolt on various intakes and exhaust changes and noted the stock cam and valve train achieved valve float at 6200 rpm....

Just gotta use your library card and do some diggin.. (or push your dad's stack of Cavalier magazines out of the way and dig into his old stack of Hot Rod and Performance magazines from 'them days'...)


-D.Idiot

think a 225 has a chance again a 4 cly acura manual?

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1972 Plymouth Duster 225 Super Six Slant