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Author Topic:   180 vs 200
rocco
Member
posted June 25, 2003 11:47 PM
Here in Ky and Tn we run lots of small bullring tracks. Gears from 6.20 to 6.50 or more are common. I've got a few cars with 180cc bowtie heads leaving all the 200-210cc Darts in the dust. And mud. Why is it that everyone wants these monster heads when the smaller runner heads give better acceleration? Sure the 200's will make more power(?) but the 180's seem to race better. Anyone else see this happening?


AIRFLOWDESIGN
Member
posted June 26, 2003 01:05 AM
I've seen this over the years and it's sad.
Ron


mod4
Member
posted June 26, 2003 10:17 AM
The relationship between velocity(180cc) vs total flow(210cc) is what you are seeing. Not only intake port size effects this, but also header diameter. Especially on lower HP applications.

We see the same thing here, but a 210cc head here is the "small" one.

dirtbuster
Member
posted June 26, 2003 11:08 AM
A lot of it is head design as well. Sure a 220cc head will make all kinds of power because of the volume but the 180cc will make good torque because of the velocity. With a good head design you could get the velocity of the smaller head but flow volume similar to the big head so you get the best of both worlds. You have to find that fine line between the two that you are comfortable with. Engine size, camshaft, carburetor even fuel type all play into this.


HRT187
Member
posted June 26, 2003 05:45 PM
The way I see it you want to be a little soft off the corners, I dunno maybe on the low line with good bite you'll be better off with the small runners.


rocco
Member
posted June 26, 2003 06:42 PM
the 180 heads give me more in the 'acceleration zone' or 3500 to 5500 rpm range. if i pull up beside you off the corner and carry it all the way down, i have you passed. same thing next corner, i pull you another car, then i'm gone. the inertia effect of the air-fuel because of higher speed should ram more mixture in the cylinder, net higher cylinder pressure, net more giddy up and go. we have no trouble turning these motors7800-8100 and still pulling. give me acceleration and i have you.


mod4
Member
posted June 27, 2003 01:15 PM
I just have to ask, what kind of car are you racing ?

On a super tight cornered 3/8's with a 6:90 something gear, we run 4400rpm minimum and 8000rpm max (limited late model).

I'm just wondering what car runs 3500rpm in the corner and pulls to 8100rpm with a 6:50 gear ?

rocco
Member
posted June 27, 2003 07:06 PM
imca cars. most times rpms are around 7300-7700. these cars are heavier than a limited car so you need more off the corners. the limiteds run a 7.05 to a 7.28 gears and turn 8500 plus, if you want to go fast.


rico 08
Member
posted June 27, 2003 09:48 PM
I know what you mean,I raced with dart sportsman's(200cc)in a factory stock class and i was always pulled off the corner by a friend of mine with double-hump heads,but 'bout the flagstand i would eat his lunch,this was with a 355 with cast iron exhaust tho,so maybe in this combo smaller runners we're the way to go,IF you can hook it up.


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