Im going to be tackling a head porting job soon on my 400 iron heads. I have done some cleaning up of heads in the past. Mostly gasket matching and removing casting lines. However a full "polished" job i have never done. Im not building a tricked out engine, but the head work would give some much needed improvement.

So im looking for some pointers on how to do the full polish.

 

Don't worry about getting a shiny polish on the intake side, it won't put up any power 80 cart roll is all the would be needed. Make sure you do your cart rolling side to side so the incoming charge has something to "grab" to. It help with the fuel atomization. Don't focus much on the opening and the actual runner it's self it's already got enough flow going on. Your bowl is going to be important here.


Get your valve job "roughed in" basically it's just a throat cut. When blending the throat take it to 90 percent. Which by that I mean 90 percent of what the valve size. Don't go bigger the 90 percent you'll blow the throat out killing flow. You want to widen the bowl and make every a smooth radius no bumps or steps. Short side turn is the biggest problems on those heads. Once you get them disassembled you'll see what I mean. It goes up, then down to the runner. You want to take it and make a nice smooth radius turn into the bowl. This is also where you need to be the most careful because it can destroy the flow if done wrong. Other then the short turn don't touch the floor.

Narrow the guide down and if possible make a tear drop shape. You've gasket matched already so that's good. If you get it on the flow bench and the air speed is a fast you can slow it down by taking a little out at the pushrod pinch.

Now on the exhaust side I try to get it smooth as possible not for flow but so the carbon and unburnt fuel has nothing to grab on to, it keeps it from building up on it and if you ever have to clean it in the future you'll be glad you did it.

A good valve job can pick up a lot on flow. Get new valves and have them back cut. Your looking at about 30 bucks for backing the valves. It'll pick up about 10 to 15 cfm on your low lift number

 

Blending the seats in will net you a big improvment. Like said get the valve seats roughed in and remove the edge of the 60* cut and blend it in good.

 

Thanks for some pointers guys.

I already had figured i wasnt going to be doing much to the intake side. Its a stock C rotating assembly with kb 177's. the big improvements over stock specs will be the cam and head work. For a street truck, head work beyond gasket matching and smoothing the exhaust port is most likely over kill. But i never know, this thing may get stroked many moons down the road

Since these heads are 2V (open chamber), I would think cleaning up the combustion chamber would do some good. Eliminating high spots would eliminate hot spots, and help control detonation.

 

If you want look into chamber shaping too, don't just look at the convergent side (bowl area) but look at the divergent side (chamber side) of the valve job too.

 

exhaust port work sides and top mainly. port match int/exh. like said earlier work bowl area and turndown to valve.

 

Check "My 400 Build" in the 335 engine series area. I just put a cutaway of what you should be able to do on the exhaust side. I'll post pictures there when I'm finished.

 

Just remember that on the other side of that iron is water. So don`t go too far. What worked for me was to ink the ports w/magic marker and then lay the gasket over and put a couple of bolts to line it up, then scribe around with a pick. Take the gasket off and shine a light through the port so you can see what your doing. Use a grinding bit that is of good quality w/ rounded tip and rough it out. then use the sanding rolls to clean it up. I prop the head up on a 2x4 to get a good angle to see into the ports and use wd40 on aluminum heads to keep the bit from clogging.

 

when you get a chance if possible. If your block is bare set heads on it with head gskt and a couple bolts to hole on block. now flip over engine a scribe bore to cyl head. pull head off and look at your combustion chamber and see if centered or something you can improve on. valve shrouding upgrades are possible around intake, smoothing potential. it all matters! engine is a airpump!

 

Hi. I am new to this board, and just saw your post. Have you done any work to your heads yet??? Pics? My first question would be what tools do you currently have to work with??? air or electric die grinder??? Carbides??? shape/size??? sand rolls??? In my opinion, having the right tools can be the most important thing. If you have the wrong tools, you will learn to HATE porting heads very quickly. Let me know.
Dave