Hey all, I posted this over at Zcar a few days ago, and came here to get a second opinion as well as some numbers. It looks like I'd probably end up taking off the ridge below the valve seat, port-matching, and doing a mild polish. How dificult would this be for someonw w/ no prior porting experience, and about how much HP would this net me if I were to upgrade intake and exhaust in addition to the port?

It is difficult for an average guy to get really high quality results. It is important that all six combustion chambers have the same volume (within a very small tolerance) to get good results. Similarly, all the ports should be very uniform. This is exceedingly difficult to do with hand tools in the garage. I myself would leave it to the pros with the proper equipment.

It's not that difficult to cc chambers. I got good results using a graduated cylinder, but you can do better with a real burette. There was a BIG range in the chamber volumes in my head. I got mine within .5 cc. I checked the volume several times so that I could ensure that I got repeatable results.

People assume that the stock head has exactly the same size chambers and that every port flows the same from the factory. FAR FROM IT. If you do like you describe and don't go crazy making the ports huge I think you can make a very good improvement over stock.

A lot of the work on the L head is in the chamber unshrouding valves and taking out all of the sharp edges. A bunch more is in the bowls under the valve seats. The last part to worry about is the ports themselves. Common sense and some self control are all you need.

I tend to agree with both comments. I know how contradictory but it's more about common sense than anything else.

I think the best thing to do is read the "How to modify your nissan Datsun OHC" By Frank (Insert last name here don't have book with me at work). He describes things to be wary of like accidentally hitting a water jacket.

I think what you really need is patience. You could always pick up a junk yard head to practice on. I would get a pro to do the final touches and test it out on a flow bench. .

The primary area you will obtain a gain from is "pocket porting", ie: smoothing the "bowl" behind the valve seat. Care must be taken not to screw up the seat.

Removing casting flash and ridges in this area is a plus in all cases. If you have access to a burrette or graduated cylinder, matching your combustion chambers will also help, as Jon stated above.

The present position I've been reading on the various sites and in the magazine articles is that the port matching has much less impact on the normal street Z or other vehicle.

Port polishing on the intake side is also generally considered to be a bad thing, as you reduce turbulence, which allows separation of the fuel from the airstream in the port.

Other than the above, I've found it to be a personally rewarding therapy. starting with a 2.0 Ltr. Pinto in Law School. Definite therapy on breaks.

Good luck.

I think the book gav240z is talking about is how to hotrod & race your datsun by Bob waar. It has a section on head work. The book number is ISBN 0-936834-41-2

Woops sorry The book gav240z is talking about is written by Frank Honsowetz. book number ISBN 0-89586-353-7. Both books have alot of info.