What cam for super heavy/sumo?

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KartRacer89

Member
Quick question, what’s a good cam for a 400+ total weight? Right now I have an 043-073 installed, but I’ve got a 7x and a 98-3 to drop in as well. A friend told me that his choice would be the 96-3 Old Master.
 
I would personally go with the 96-3 but I have wondered how well the 7x worked with a heavier driver. I would get ahold of Brian Carlson on here as he quite knowledgeable with the good old flattys.
 
04-03 is not a bad cam .
7x I believe is kinda a top end cam .
96-3 or old master pull good .
Is it not keeping up currently?
 
flattop1 said:
04-03 is not a bad cam .
7x I believe is kinda a top end cam .
96-3 or old master pull good .
Is it not keeping up currently?
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No I’m not able to keep pace with the other karts, I’m at least 0.5-1 second off the leaders pace every time and get lapped. I’m making sure tires are prepped/staggered through the night, as well as making chassis adjustments and gear changes. In years past, I was a top 5 kart on a different chassis with a different motor and different set of tires, that was before I turned into a fat body. It’s a Burris only track, and most likely the main culprit is probably the tires, setup and clutch. I know the best thing I can do is lose the weight and make the total package lighter. But until I achieve that goal, I would at least like to try and get the motor more dialed in for my size, then I can worry about the other things.
 
flattop1 said:
Current max rpm's ?
Spring pressure is right .
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Max RPM depends on gear but in 6600-7000 range usually.

I didn’t check the spring pressure when I installed the current cam, I just installed the springs it called for and sent it like the amateur I am. That’s something I’ll need to pay more attention to in the future.
 
KartRacer89 said:
Quick question, what’s a good cam for a 400+ total weight? Right now I have an 043-073 installed, but I’ve got a 7x and a 98-3 to drop in as well. A friend told me that his choice would be the 96-3 Old Master.
Click to expand...
07-3 would be my choice -- or 96-3 and open the lash up a bit. 7X & 04-3 work better for lighter classes and high rev (only if) you have a really good flowing carb. 04-3 is more sensitive to ignition timing than other cams as well. Get the timing, the right muffled pipe, and the springs right and that 04-3 will turn some revs. (72-7300 and still make good power up there.)


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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
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37 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Valve spring set-up is extremely important on flattys. Getting around corners fast is the most important factor in kart racing.
 
Weight is more a function of the gear you need to run. Cam is more about the rpm range which is dictated by the track configuration. Is it a paper clip or a circle?
 
.5-1 second is quite a bit. How old are the rear bearings? If you are running the same gear as the leader try going up 3 teeth on the rear or up 1 on the driver, your choice. Also check your brakes and make sure they are not rubbing. Move axle left to right and make sure when chassis shifts the brakes are not rubbing. Scratched my head a half a season one year to find out my problem was the pads were rubbing.
 
I used to do a lot of Champ kart engines and have tried all you listed but my favorite was also the 07-3 cam especially on tight turn tracks. On more open tracks customers liked the 04-3 but personally my own engines had the 07-3. Just make sure the springs are right use a good lifter and have the lifter bores welded up because all of those cams are hard on the blocks.
 
sundog said:
Weight is more a function of the gear you need to run. Cam is more about the rpm range which is dictated by the track configuration. Is it a paper clip or a circle?
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The track is sort of egg shaped. 8th mile. As far as gearing goes, I’m usually on a 13 driver (get out of the corner faster) and adjust the bottom gear according to RPM; I try and keep RPM around 66-6900 at the end of the straight.
But maybe I need to try a 14 driver more.
 

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What's your rpm off the corner?
I had/have what I thought were pretty good engines . A uncle franks , a dover , one I built. .
Until I got this last one from Waller , its hands down better then any other I have had..
If you have the cam I would try it .
 
flattop1 said:
What's your rpm off the corner?
I had/have what I thought were pretty good engines . A uncle franks , a dover , one I built. .
Until I got this last one from Waller , its hands down better then any other I have had..
If you have the cam I would try it .
Click to expand...
Off the corner, around 5000. My drops are usually 1000ish, but not higher than 1500.

So from reading the old thread, I understand that maybe I should take some timing out, is that right?
 
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