Carbide bits work best to start, if you want it to be smoother then finish with a sanding flap wheel.

porting a 12v
 

I have a 96 cummins with 300,000 miles on it. Is it worth having head work dun if it all check's out good. I want to get it deck, o ring and maybe a port job. Any advice?


Brandon

a four stroke engine is all about the cylinderhead,charging in with a rotary grinding tool and no port pattern to work to will most likely cause increased turbulence in the port,properly ported heads really make the difference,and this difference is achieved by using a flow bench to determine the best flow. a certain degree of lift at the inlet valve is set with the camshaft,it,s almost universally done at .50 thou lift.flow needs to be precisely equal accross all cylinders in a multi.hence if you see a tuner who works heads and he has no flow bench-avoid.
it would be a better bet to use a flap wheel to merely remove any imperfections from the ports,think clean rather than alter.
if you are determined to do it yourself,i would start hanging round a head building shop-see how much work goes into a properly modified cylinderhead.
clessie cummins was damn clever,and a good engineer to boot,his products can take serious power hops due a sound initial design.

and wheres a good place to find carbide bits?

hardware store.

Most "pro" autoparts stores like NAPA and Carquest have em. Any autoparts store that carries ATD tools will be able to at least get em. I like the ones that are somewhat cone shaped as you can get into tight spots with the tip, but can really hog out the metal with the larger diameter base. And they last a LONG time. What really eats them carbide cutters up is weld slag... Does em in quick.

dont agree with anythng in this post. I have ported heads for a long time (a few records have fallen). Summit racing has a porting kit that has most of the things needed. there is no such thing as an air dremel it called an air grinder. Sanding rolls are your freind. On a 12v cummins you are not going to get numbers, just go in there and clean ( smooth) it all out.

numbers as far as wat?

numbers meaning CFM on a flow bench. No matter what you do you are not going to get a high number for example a small block chevy stock is around 230 on intake port,a real good aftermarket alum ported is 325.

your right, but anything is better than the stock 12v head. with a good port job 200+ cfm can be done which is way better than stock. There are some new alum heads for the 12v's that will flow 300+ cfm .... but they cost more than the whole truck lol