head porting
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Instructor
Joined: Jul 2007
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head porting
Need help as I began porting my 72 350 heads by grinding the ridge below the Intake valve seat to be smooth with the pocket walls. I was told this was the wrong thing to do. As these are number matching head what can I expect for performance . I was told putting 2.02 valves will correct this mitake to some degree.
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
You did OK, and didn't hurt anything to answer your question. If you don't want to pay to have your seats cut, keep them protected while you work. In a mild port job you clean up the port pocket, smooth out the walls as you say. You don't state your goal or what head casting # you are working with. I wouldn't think your effort will yield any significant performance gain. If performance is your goal, you might consider purchasing a proven head/cam combination. If you just want to experiment, invest in a book on head porting. Amazon.com has used and clearanced books on the cheap. David Vizard has a good book on head porting. Be careful, removing more material isn't always better.
Last edited by Red 69; Dec 7, 2007 at 08:47 PM.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Need help as I began porting my 72 350 heads by grinding the ridge below the Intake valve seat to be smooth with the pocket walls. I was told this was the wrong thing to do. As these are number matching head what can I expect for performance . I was told putting 2.02 valves will correct this mitake to some degree.
Next ... gain experience by working few junk heads.
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
I will shoot this to you straight. Do not even waste your time on the stock heads. Purchase a new set of performance heads and you will be happy.
I would not call it porting really as porting is the reshaping of the runners. What you can do is clean them up from the flashing match the intake side of the head to the gasket and to the intake and back cut the valves and have a good valve job done. This may give you another 20HP but think of all the work needed to gain that 20HP when for a few bucks more you can gain maybe 100HP with the right intake head and cam set up.
And I have been there before the good performance parts were around when you had to make due. That is no longer true. Thank Goodness lol.
I would not call it porting really as porting is the reshaping of the runners. What you can do is clean them up from the flashing match the intake side of the head to the gasket and to the intake and back cut the valves and have a good valve job done. This may give you another 20HP but think of all the work needed to gain that 20HP when for a few bucks more you can gain maybe 100HP with the right intake head and cam set up.
And I have been there before the good performance parts were around when you had to make due. That is no longer true. Thank Goodness lol.
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
The factory cutters left some abrupt changes where the cutter stopped and the as-cast areas meet. You will want to remove the "steps" where the cutter stopped and blend them into the port wall. If you have sucess there you might want to gently smooth the short side radius in the port right where it goes into the valve seat area. Smooth the radius and polish the surface there. The valve guide bosses can be thinned a bit as well. You might want to replace the guides before doing that. If you are not thouroughly wiped out by this time you could match the intake ports to a gasket but this is not going to add much HP so consider just cleaning up the casting flash at that point. Your call. Once all the grinding is done you can polish the grinding marks off. This process will take you probably a whole day or more so have plenty of cutters, sanding rolls and 
on hand.
This is just a "pocket port" job and might add 20-25 HP to the top end.
I would not bother with bigger valves personaly. The "993" head is a heavy big chamber head and will work pretty well "as is" because of the open chamber design. Not a fuelie head but better than the later smog heads that are thin and fragile.
-Mark.
on hand.This is just a "pocket port" job and might add 20-25 HP to the top end.
I would not bother with bigger valves personaly. The "993" head is a heavy big chamber head and will work pretty well "as is" because of the open chamber design. Not a fuelie head but better than the later smog heads that are thin and fragile.
-Mark.
