Cam choice

B

Bodydropped

Member
I have a .30 over animal that I built as a Sbo with a ppm head, I have a .308 cam in it atm and ultra light flywheel. I have a new .356 cam for it but was we run alot of bull rings and wondering leave the .308 in it or go to the .356
 
Need more info before you decide on a cam.
What size carb are you using?
Which PPM head? What size valves? Port volume, flow?
Are you using ratio rockers?
I assume stock stroke.

Assuming you're using a 28mm carb with the PPM billet head, it'll carry a whole lot more than a 308 (or even 356) lift cam.
Personally, I have my own preference of a .310 lift cam that Randy @ Dyno grinds for us. Couple that with 1.25 or 1.3 ratio rockers and it provides good power and reliability. I've used this combination for years and use it in other builds as well.

One thing that most amateur builders do not understand is that good, consistent, reliable power is not made by simply bolting "hop-up" parts on. It's more than an accumulation of parts. All these parts need to work in harmony with one another like a symphony orchestra. From carb and intake flow to ignition timing and exhaust pipe, all parts working together to make beautiful music on the dyno and on the track.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
37 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
CarlsonMotorsports said:
Need more info before you decide on a cam.
What size carb are you using?
Which PPM head? What size valves? Port volume, flow?
Are you using ratio rockers?
I assume stock stroke.

Assuming you're using a 28mm carb with the PPM billet head, it'll carry a whole lot more than a 308 (or even 356) lift cam.
Personally, I have my own preference of a .310 lift cam that Randy @ Dyno grinds for us. Couple that with 1.25 or 1.3 ratio rockers and it provides good power and reliability. I've used this combination for years and use it in other builds as well.

One thing that most amateur builders do not understand is that good, consistent, reliable power is not made by simply bolting "hop-up" parts on. It's more than an accumulation of parts. All these parts need to work in harmony with one another like a symphony orchestra. From carb and intake flow to ignition timing and exhaust pipe, all parts working together to make beautiful music on the dyno and on the track.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
37 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
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Not sure the valve size but I got a complete motor less crank from a guy who ran drag bikes, I kept the head setup and put it on a stock bottom end. It’s a 33mm carb not sure the ratio on the rockers but he had this on a stroker bottom end. I understand the harmony of everything, was my first build and it’s done good till it broke the crank on the clutch side. I was impressed how good it ran but our engine builder even dynoed it and said it was good power for what it was.
 
Bodydropped said:
Not sure the valve size but I got a complete motor less crank from a guy who ran drag bikes, I kept the head setup and put it on a stock bottom end. It’s a 33mm carb not sure the ratio on the rockers but he had this on a stroker bottom end. I understand the harmony of everything, was my first build and it’s done good till it broke the crank on the clutch side. I was impressed how good it ran but our engine builder even dynoed it and said it was good power for what it was.
Click to expand...
That's a big carb for that displacement. I'm not saying that is what cause the crank to break, but the amount of fuel filling the cylinder made it hard to digest no doubt.
No replacement for displacement. That larger volume "might" be able to take the 33 carb, but still that's a big carb for your engine. I see a lot more 28s being used on SBO engines. The 33 is what we start our big blocks (390s etc) out with.
 
CarlsonMotorsports said:
That's a big carb for that displacement. I'm not saying that is what cause the crank to break, but the amount of fuel filling the cylinder made it hard to digest no doubt.
No replacement for displacement. That larger volume "might" be able to take the 33 carb, but still that's a big carb for your engine. I see a lot more 28s being used on SBO engines. The 33 is what we start our big blocks (390s etc) out with.
Click to expand...
My other Sbo with stock style head has a 28 on it, I just ran this one as it just how I got it, the bottom end I don’t know how many races was on it when I built it other than the rod and piston looked new. I rejetted the carb and got it to stop milking the oil and the plug would read good. Motor was built for 2 years and had maybe 5-6 races on it when it broke, my plan was already new rod for that winter and I got a different cam at the same time.
 
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