Well, for comparison sake....I had about 30-hours into porting my PI castings and most of it was dedicated to finishing.you think theres still more to be taken out? because i wouldnt mind taking the valve train back out to do some more work and smooth them out some more, towards the end of them i did a little rushing , and yes i have atleat 10+ hours of work in them...
Dang.... now i want to port them more
I'm sure that's the plan....which can be done.....but it takes a lot of work and patience to accomplish. Most are better off just saving themselves the hassel and springing for the PI castings and calling it a day.He ported and polished his npi so they are better than just stock pi heads.
Well, for comparison sake....I had about 30-hours into porting my PI castings and most of it was dedicated to finishing.
If you really feel as thought you want to go at them again, try to take pictures of each port individually from the same angle and compare them to one and other. Then take the port that seems furthest along and go from there. The intake side can afford to have a little more volume taken out of them, but again....there's no need to go hog wild. Concentrate mainly on shaping the port as you enlarge it. Once you've got it out to where you want it, perform the same work to each of the other 7-ports one at a time until you're satisfied that they're near identical. A good hand port job should end with the ports being at least within 5% of one and other. Getting yourself a vernier caliper to gauge your progress along the way will certainly make things easier. Stare at them long enough with just the naked eye will probably drive you nuts.
Once you've got all the ports identical, it's time to break out the sanding rolls and get to work. Sand all of the little nicks and scrapes left by the carbide cutter out of the wall surface. Each little crevasse, bump and abrasion acts as an obstruction for incoming air. The smother and more fluid you can make the pathway into the combustion chamber, the better it will flow. Remember....velocity is key here.....not just volume! There’s no need to go with a polished finish on the intake side, but at the same time don't leave an abnormally rough texture to the port walls either. You should be able to finish them off with something around 60-80 grit that will leave a nice visual cross hatched pattern on them and walk away happy.
Perform the same steps to the exhaust side, but go one step further and polish them to a mirror finish…the shinier the better. Doing this will reduce the chance of carbon deposits sticking to the walls and allow flow levels to remain constant while reducing the chances of hot spots on the areas where high build up might normally be a problem.
Again....don't go overboard on the volume. Try to visualize the airflow as it enters the intake and flows into the heads. The outside turns are where the airflow is going to lay up running through the head, so this is where the majority of your porting and reshaping should take place. Inside turns aren't going to see near as much air, so a slight contouring and resurfacing should be all they really need.
Good luck...and again, be patient. Porting a set of heads although less expensive, will take you a LONG TIME to do correctly, so don't get discouraged. Take a break if necessary....walk away from them for a few days if you have to. It will all be worth it in the end.
No sweat...and whatever you do, stay away from the valve seats. One deep nick in them and it's pretty much game over.
They look good. Thats what my cobra pistons looked like, check to make sure you have enough PTV clearence, because I did'nt. Hope it works for you.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?