Doing more work, cam change advise?

[stargazer7467]

im starting my little string of winter modification and was curious on my current cam selection. Heres what i have.

Hemi Predator-
billet flywheel
billet rod
Robertson loop header, and straight under seat header
arc .625 carb and intake
4* advance key
26lb valve springs

Im about to get a new head thats milled .065 and full port and polish job with 25mm and 28mm valves.

Im currently running a Mamba Jr. cam, would i be a better route to use the regular Mamba, or any other cam for that matter?

Thanks!

 

[OND]

We run a NR Racing 274 lift short track cam in our open karts with the same head you are talking about with great results, I don't know how It compares to Tim's Mamba cam tho. Good Luck .
Oh over 8000 rpm's is easy !

 

[stargazer7467]

i can squeeze 7400rpm out of my mamba jr i have now. The question i guess is , am i short changing myself with the mamba jr's, shorter duration with all the port work?

 

[ole4]

what rocker arm ratio? The hemi uses a arc kohler flywheel that already has 32 degrees timing why are you wanting to add 4 more degrees? What are you using it on? Cam selection has a lot to do with your application, gear ratio, clutch or TC. Not sure what a full port is can you tell us more details? If the intake runner CSA is stock and just bowl work done then it will work well with the JR. The lift on both cams are the same. You will get more benefit with the mamba SR but then you will lose some low end. If the intake runner was enlarged (Which I have found to be unnecessary unless you are building a drag race 10,000rpm engine) Then that will already kill the low end and you might as well go with a hotter cam. Can you get some pics of the head with the valves removed

 

[stargazer7467]

i havent purchased the head as of yet, and the advance key was installed befor ei had the flywheel, is the flywheel's 32* optimal? It is hard to start at times. my gear ration is 12/60. Its on a minibike.

 

[ole4]

They work well and I pull start them. If you get the head take some pics and post them. You can just install flywheel with a standard key to start with. The older FW had 28 degrees of timing (If i remember correctly)