Long rod + longer dwell time makes it harder for the crank to push the piston back up.

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Official Cookie and Mater Tormentor.

The best substitute for cubic inches, is cubic money.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Yes it does, up to a point. Sometimes boost is just not practical or allowed by class rules though.

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Official Cookie and Mater Tormentor.

H'mmmm. I donno. That may be so, but it also makes it easier for the piston to push the crank down, so at worst I think you're looking at a wash.

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

See? I said earlier it is all speculation with no solid proof of anything.

All I know is that my long rod motor won't 60' for shyt until you hit it with the hose.

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Official Cookie and Mater Tormentor.

Thats exactly right Slantzilla, they will be low on coming up to the torque curve.


But it has been proven what goes on between short & long rod engines and one thing right off is the short rod engine will make a few more HP, but it will come into its power band quicker also, but then it want pull past peak HP very far ( short shifting needed).


The long rod engine will be very soft until it gets spinning but then it will spin a lot farther , and make power past the peak HP. The best way to make use of a long rod setup is with a 4 speed leaving the line at about 5500 rpm and shifting at about 7200 RPM, ofcourse it needs the right cam to do this.


In the circle track game they use the short rod engines for when they need to come off the corner hard and use the long rod engines when they need to turn crazy RPM.

Overall power is effected very little, but how the power comes on and the range it works in will be effected quite a bit.



Jess

we have one thing they dont torque with our 4.125 inch stroke we can scare the crap out of them then if we build our engine and produce even more torque and horsepower they will go home and give his grandma back her civic.

you see they dont concentrate on as much power as we do they think "building there engine" is cold air intake and a bean can muffler you wont find much more then that under there hood

LONG LIVE THE SLANT SIX

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1973 plymouth duster 225 slant six .30 over, erson 270 cam, 9.5 to 1 compression, big valves, headers, and a holley 4 bbl
http://cardomain.com/ride/3135091

hey that thing got a hemi? naw its just a slant six

Don't put any money on that. The "stuff" that is readily available for the ricer crowd is nothing short of amazing, and they are starting with 40 year newer technology.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

but do you think half of the guys driving tuners just want them for the looks

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1973 plymouth duster 225 slant six .30 over, erson 270 cam, 9.5 to 1 compression, big valves, headers, and a holley 4 bbl
http://cardomain.com/ride/3135091

hey that thing got a hemi? naw its just a slant six

I am not going to say they are all only for looks.... yes there are ALOT of them that look, and sound ridiculous, but there are true "tuners" out there.

I think that is the main difference,

Ricer vs. Tuner

Ricer = Wannabe's driving around with coffee can exhaust, a ridiculous sound system, and only sound like they are going fast, while not having any more performance than stock.

Tuner = A purpose built import machine, not specifically targeted at cruising around with loud music, but able to hold its own @ races.

I have alot of respect for those guys (and gals) out there who have put down a few hundred + HP with their little cars. They do not make really any torque at all, but for their building purpose, they really dont need it. They can easily use the RPM.

I drive my bone stock SL6, and I can get them off the line, but once they wind up, I better be gone, or its game over.
~THOR~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Ok I regret saying that it was from a tuner magazine cause I think people imediatley lost sight of what information was given. Besides the tuner world while something different is an adversary when built right, just like the slant six is to the big block.
I always told people that the every engine is different due to the engine's "character". I believe this article more scientifically explains what I was talking about. Which was this, the 198 seems to be the better prepped engine for racing due to stroke vs bore and rod length. Both ideas covered in the article originally written. However, like the big blocks or 350 the 225 are great motors for the torque they produce which seems to be rather larger than what they should be giving on paper. Cool, that is what can drive a car for us. But for the guys who want to really push a slant six I was thinking it would take information given above would show tricks and ideas that really make up that last little bit. Perhaps reinforcing why the 170 really doesn't seem to hold up NA vs the 225. Also, why Slantzilla's 198 was such a beast.

Agreed.


~THOR~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Well, at least that guy wrote it as if it was all new information :-p

Trust me, V8 and I6 guys have known this information (and much more than presented there) for the past 60 years. If you read write-ups on the very earliest American OHV v8s like the Olds Rocket, Cad 331, and Chrysler 331, specific reference is made to the fact that they tended to be far more oversquare than the flathead inline engines that they replaced. If you read the history of the slant-6 itself, the under-square 225 variant only came about because of the need for more displacement to fill the gap between the 170 and the smallest v8 at the time. Going undersquare wasn't their first choice, it came about because they weren't allowed to lengthen the slant-six block (not even by 0.25"!) or widen the bore spacing to allow the same displacement with a bigger bore.

The modern-day tendency back toward square or undersquare (compare the Ford 5.4 to the 351, the Chrysler 5.7 Hemi to the 318 or 360, etc.) designs has been driven almost entirely by emissions. Smaller diameter bores have less quenched volume between the top ring and the piston crown where hydrocarbons can hang out unburned and be exhausted.

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But the ones that say "short rod" don't have the laws of physics on their side
I don't think I agree on either point. For one thing, "overleveraging" , even if real, is just for a tiny portion of the stroke. Change other parameters so that cylinder pressure peaks at the right time, and its not an issue. And short rod increases cylinder filling? I don't see how. Short rods move the piston down REALLY fast, which means that the peak instantaneous port/valve flow has to be higher. Seems to me like a smoother/slower intake event puts less demand on the port and results in overall better VE.

But those are debatable points.

I think the REAL take-away that is NOT debatable is this: If you change nothing but the rod length, then one engine or the other was not optimized and its not a fair comparison. A long rod engine of the same displacement will need very slightly different timing events (both valve and ignition) than a short-rod engine of the same displacement. But if you do optimize EVERYTHING, then the long-rod engine will always win by at least a small margin. The myth that a short rod engine has more low-RPM torque is just that- a myth based on the fact that at a short instant in the cycle, the short-rod engine will have a higher mechanical advantage than the long rod engine. However the long rod engine has the advantage across a LONGER portion of the crank cycle, and you just have to twiddle the timing events to keep the cylinder pressure high during the advantaged part of the stroke. That's why a built 340 will easily run neck-and-neck with a built 360. It gives up 20 cubic inches, but the big-bore/short-stroke/long-rod architecture buys it all back, and is more reliable overall because the mechanical stresses and peak piston speeds are lower.

True words!

But even THAT is a bigger problem with a short-rod engine, because the peak stress on the rod bolts goes up REALLY fast as you decrease the rod ratio.

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