Do no harm head work

[Jefferson71]

I am in the process of a clean-up on a replacement 2.8 w/ P79 for my 240. I haven't done any head work before, but would like to do a general clean-up that won't hurt anything. Not planning on un-shrouding the valves but would like to smooth out the areas I highlighted on the second picture. Seems like there is a bit of extra casting on the intake, and the lip on the exhaust looks like it could do with some smoothing out. I was interest in people's thoughts. I have read this site for years but not posted before. One last question, any harm in a final pass with 600 grit on the head surface to get what the scraper and scotchbrite missed?

 

Thanks for any input,

 

Jefferson

[BRAAP]

Good eye!

Remove that casting flash under the intake seat, and while are doing that, blend the radius of the intake port floor to the seat so it transitions smoothly, not a step.

 

For the exhaust, again, good eye. Radius that squared off edge so that you end up with smooth radius from the ID of the steel seat to the liner in the port. Pay particular attention to the short side radius, i.e. port floor. Blend and radius that squared off edge so that it transitions from the port floor to the seat with a smooth gentle arc, no steps or bumps, just a smooth flowing fluid transition from the seat to the liner. Helps in keeping the flow from separating and becoming turbulent in that region, i.e. more flow “out” of the chamber.

 

I would still recommend unshrouding the valves, even if you merely just lean the chamber wall back to the gasket edge, on either side of the chamber where the valve is closest to the chamber walls, this will pay off in gains in air flow at mid to full valve lift.

To protect your valve seats from the inevitable runaway cutter while carving in the chambers, find old scrap intake and exhaust valves and those will protect your seats while carving in the chambers.

 

 

This thread is good DIY L-6 porting primer;

http://forums.hybridz.org/showthread.php?t=110269

 

As for the deck surface, I do not advise spot buffing/sanding on the deck surface. The deck surface is far to sensitive for hand work and could easily result in a premature failed head gasket, seen it happen TOO many times to recall! Hit up your local auto machine shops and have it decked.

If the head is at all warped, even in the slightest, be sure to have the top surfaced as well, which means completely stripping the head down to its bare casting.

 

Hope that helps,

Paul

[WizardBlack]

I have a question to further the specific exhaust lip you referred to. As you follow into the port from the steel exhaust valve seat, you have a short ring of aluminum that is smaller in diameter (the area that should be opened up) and just after that, it opens up substantially in diameter for the start of the steel exhaust liner.

The steel liner is larger in diameter than the steel seat. The port floor can be worked to provide even laminar flow from the seat, past the ~3mm section of aluminum and onto the start of the liner. The walls and ceiling cannot. Should the aluminum section be opened up to the diameter of the inner diameter of the valve seat or should it actually be tapered open further (toward the starting diameter of the liner)? If you get past the very start of the liner (say, the first 8mm), it narrows in diameter somewhat (to maybe a bit larger than the seat diameter). I just figured on opening the aluminum section to a straight diameter and let it line up with the diameter of the liner further in. Am I explaining myself very well? LOL.