Date: Sat, 28 Dec 1996 23:23:52 -0800
From: Mike West <mwest@CDSNET.NET>
Subject: Re: Should I port & rebuild my own heads or buy?

>Just a wintertime thought. Having more time than money, I was wondering
>if I shouldn't just buy a set of used heads, and port and polish and add
>big valves myself. The price up here for 041 heads are 249 dollars each,
>which is 39mm and 32mm valves, and improved spark plug holes, and
>combustion chambers for 22% increase over stock flow. Can I port & polish
>to match these? Thanks,
>Courtney
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 Haven't seen any replies to this. The troops are all out playing with
the new toys or just fell asleep.  :-)

 Can you port, polish and add new big valves and get a 22% increase
in flow is what you want to know.

 I haven't looked at the various flow charts laying around here but
would suspect you could get a 10% increase in flow in a pair of dual
ports by p&p'ing them.

 Adding bigger valves: you got a mill? you'll need a mill to counter-
bore the heads for the new valve seats.

 Frankly I've never bought a valve seat but I imagine my flaps can
get them if I want them.

 So I suppose you could get the old seats out and get a machine shop
to c'bore the new seat holes for say $100 a pair.

 The reason for the price is set-up charges, not run time.

 Then you have to take them home and set up a sturdy work bench in
the kitchen.

 In the kitchen because you need access to the oven and the freezer.

 Sturdy because once you freeze the seat and heat the head, you have
to mate them and pound the seat in with great zeal.

 Now you can move back out to the shop and start working the new seats
down with whatever type stone till you get them close to where you
want them.

 You want them all the same height and within .005" using the face
of the oil cover seal as reference. The deal here is that all the
valve stems have to come out the same height on the other side when
you're done.

 The best seat for flow etc. they say is a 3 angle job.

 They use, say, a 30 degree stone inside, a 44-1/2 degree for the seat
and a 25 degree on the outer lip.

 Since we're doing this by hand, just go get a half dozen valves
ground to the 44-1/2 degree and lap them in by hand.

 When you get them all lapped and all the same height stem-wise on the
farside, you could say you have it whipped.

 Yes, they do have sets of stones to do this and tooling like guides
and stops etc., probably for a standard mill or maybe even for a hand
held air die grinder.

 I'm willing to bet it's cheaper to get Berg to sell you a set of heads
unless you want to build a hundred.

 I may even be exagerating the difficulty. They may come all at a nice
height for installing and have the 3 angle already cut.

I doubt it though since, the pounding in the seats is not exactly
piloted off the valve guide.

 Anyway, that's a rough idea of what it takes to get a set in there
and ground to the right dimensions.

 The improved spark plug holes is a case of welding the old hole closed and
boring a new one in a slightly different location.
  Mainly for better clearance from the new big valve seats.

 Hope I've not made it sound too negative.  :-)

 Bob Hoover would actually have a better idea of the possibilities  than I.

   west

Re: Should I port & rebuild my own heads or buy?