What cam should I use....?

[zack_novak]

Im stripping down one of my motors to rebuild, and I thought about putting a racing cam in it. I have a stock bottom end but the top end was rebuilt with an 88cc big bore kit. Which cam should I use? Im looking for a little more power/speed. Links and input are helpful.


Thanks

 

[b52bombardier1]

I have the Dr ATV cam in one of my ST90 engines - do not expect miracles. It is louder at the exhaust and I had to bump up the main jet from a 68 to a 73 (maybe a 75, can't remember) to keep from overheating my engine by being too lean. All for maybe a 2-3 MPH increase in speed. Hardly worth it and I would not do it again. The only reason it got done on this engine is that I won the cam and the heavy duty valve springs in the 2011 So Cal CT90 Tech Weekend in Moreno Valley.

Rick

 

[69ST]

If you're talking about the "fast road" cam, it's worthwhile but, like Rick said, don't expect miracles. I've not tried tuning an ST90 motor, as far as I am aware it was the weakest tune of its engine series...which is different than the Z50-based family, including the CT70.

You're adding 22% to engine displacement, gaining some static CR in the process, so the cam will compliment the setup nicely. Stepping-up to an 18mm carb would likely give you a little more, still. I'd estimate about 25 - 30% power increase, which translates into roughly a 10% speed increase. With carb jetting, gearing and point gap optimized, I'd expect a top end in the high 40s from this setup.

 

[theraymondguy]

Swapping in the '88 Kit' race head looks worthwhile:

Race Head for 88cc Bore Kit - All Models

Includes top end gasket kit, a new piston kit to go with the larger valves, race cam etc. No carb but it's a bit cheaper setup than the full kit:

Race Head 88cc Bore - 20mm Carb Kit - All Models

 

[ctynot]

put a stroker crank.will do more than head

 

[drb930]

I have a Crower Cam 4-sale for the E-22 head, should fit...

 

[Merz]

I have the "mini monster" cam from dratv. It made a pretty noticeable gain at higher rpms. Low rpm feels the same. I got valve float after I installed it, so i got the hd valve springs and now it runs great. I tried the dratv race cam also, but couldnt get it to run right. I have the 88cc kit, stock head, 20mm carb.