Harry's 345 Rebuild

[harrywt]

So I finally got to some porting. My exhaust manifolds do not have openings for air injection. Did I goof when I removed the whole hump? All indications were that it was solid metal and it turned out to be true. Doesn't mean that I didn't do something stupid on purpose...
@Robert Kenney
@ihpartsjeff

 

[harrywt]

Adding to Jeff's porting recommendations, the valve bowls are very important both intake and exhaust.
1) Looking into the port from the valve head direction, any overhang or machining termination below the seat must be removed and blended into the main port before it turns the corner. Use care not to undercut the seat area, only remove material perpendicular to the valve head.
2) The guide boss's needs to be profiled to minimize/reduce it's projected area. Thin at the opening not to cut into the guide press fit OD.
3) The short side radius (port floor) needs to be blended into the valve bowl.

These take many hours to accomplish and can't be rushed, but the reward is significant. If you are not experienced in port flow dynamics, I recommend taking them to a reputable performance shop.
I'll look through my head pictures and see if I can find some before and after port photos that will be relevant to the IH port style.

so I should go ahead and remove the valves? Is there any reason so label parts with cylinder #? I think no since the valves and seats will be reground.
@Robert Kenney

 

[Zaedster]

Keep removing metal; the more you remove in the correct spots, the better. Obviously, be careful not to go too far. You don't need to touch the intake. Last time I did this, it took me most of the day.

Yes, remove all your valves and clean them thoroughly. They probably need a valve job anyway, especially the exhaust valve. Make sure that everything you remove and reuse goes back to its original place if you aren't sending them to a machine shop, or things may not work as well (or at all). They are likely worn out. I would have had them check the head for cracks before even starting.