Alright....some case porting info.
Please note that I have [limited] experience with 62T cases only. In fact, I am not sure how you would go about porting 61X cases - though I think Keith Head does it. I believe Slymo ran one of his 61X ported cases.
Tools and materials:
- Rough grit sandpaper
- Metal epoxy (Devcon, and the like)
- Grinder, slim profile (Dremel for me)
The important thing first: You'll be porting only the top case half - the 62T part . The bottom part is the 6M6 case half, the same on all 650s, 701s, 760s.
First, you need to clean out all the voids on visible from the top. Clean them with paint thinner, or something - you want the gunk, grease, and chunks out.
Take sandpaper to the inside of the voids where you can, to rough it up.
Once those voids are clean and dry, you need to fill them up with metal epoxy. I used the two parts stuff that comes in sticks from Randy @ Watcon. Great guy, full of information, too.
Stuff it in there good, fill up those voids. Your goal is to fill them up to the top.
The case porting will grind right through some of the case walls. The epoxy keeps everything together - essentially, you're making everything much beefier, so that you can take material away during porting.
Look at the flywheel area - there are a few deep spots in there that need epoxy. Make sure the area is clean, grease-free and dry, then put epoxy on.
Let everything cure, and make sure the top of the case (base gasket mating surface) is smooth and even. Take some sandpaper to it to straighten it out if needed.
Now on to the porting: Basically, you need to grind channels into each top corner of each intake port, for a total of four tunnels. This channels fuel/air mixture right into the transfer ports. So, grind a tunnel from the intake to the transfers - it's not that hard, just look at the pictures for guidance.
Make sure the tunnels are evenly sized.
Next, take some sandpaper and rough up every surface inside the top case that will have fuel/air mix going through it. All of the intake port, the bottom bowls of the transfer ports, etc...(it's a good idea to do this to the transfer tunnels on the cylinder as well)
The rough surface will promote better flow characteristics than the stock smooth surface.
Last thing: Finger filling. Looking at the intake ports of the 62T case, you'll see the infamous fingers. You have two options: Leave them alone, or fill them with epoxy.
If you fill with epoxy, do it like before - sand, clean, degrease, dry, then put epoxy on. The goal is to make the divets in the fingers disappear and to create a smooth top surface at finger top height.
Essentially, this reduces the volume available to air in the intake tract. This leads to higher air velocities through the intake tract. The advantage is better throttle response, as any change in throttle will get to the engine quicker (through higher air speed).
This comes at a significant trade-off. Less volume for intake air/fuel leads to weaker bottom end power. Freestyle case porting often leaves the fingers unported, for this very reason.
That's all I've got.
The first two pics are my cases, the third is Mile's Able stroker from last year, and the last shows what epoxied fingers should look like.
