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monster head

Guest Anonymous

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Guest Anonymous

Since I know nothing about doing heads... I will quote someone else so I won't be the one who points out taking a freshly cut valve and using it to mash sand into a freshly cut and machined seat is the dumbest way to get a valve to seal..

"Lapping valves is as old as the internal combustion engine. I've been told the owner's manual of the Model-T recommended lapping on a regular schedule, maybe once a year. A valve job at a machine shop puts a precise bevel on the valve and seat surfaces which is superior to what you can do with lapping. After you lap the valves a few times, you will have a groove in the seat which is not desirable, so you'll have to have them ground and or replaced. If a valve is seriously burnt, it must be replaced. Lapping is the least costly, least effective and easiest repair to burnt valves. "

"Monty uses Serdi equipment *wow same shit I use* to cut a 3 angle seat in the new cylinders. The seats are cut with such precision that Monty does not find it necessary to lap the valves. Monty’s shop is one of the few to have such a piece of equipment. The Valves are ground to perfection as well. The valve guides are honed as instead of being reamed. This insures a precise fit.

Barrett’s outfit engages in a lot of more or less standard hotrodding and blueprinting techniques (including cylinder porting and flowing, for example, and super-finicky mass balancing of rotating parts), but one thing you'll never catch Barrett doing is lapping valves to seats. "I don't believe in it," Barrett barks. "You can never completely get all the lapping abrasive out of the seat, no matter how you clean it. Those lapping crystals are extremely hard. The seat, by comparison, is somewhat soft. When you lap the valve, a certain amount of abrasive gets embedded permanently in the seat, and you've just created a lapping arbor. You should see what a valve looks like after it's gone up and down on that seat a few million times. It gets like this . . ." Barrett, short of cocktail napkins, fumbles for a yellow pad. Taking a pen out of his pocket, he draws a valve in cross-section. The face is guttered and grooved. "This is what you get from lapping. I see them like that all the time."

Barrett explains (quite correctly) that if the geometry of the valve face and seat are correct to begin with, there is no need for lapping whatsoever. Achieving that kind of close fit with hand-held seat grinders is impossible, so I asked what Barrett uses to achieve high accuracy face and seat angles. He smiled from sideburn to ear lobe. "Come over here," he beckoned.

Barrett brought me over to an area dominated by a pair of large red machines with the name "Serdi" emblazoned across them. I knew immediately what he was going to show me. (Serdi owners are like kids at Christmas, they just have to show off their favorite toys.) Barrett showed me the patented Serdi floating-on-air head design of the Serdi 60, which he uses to cut valve seats at exactly the desired angle (plus-or-minus I don't know haw many seconds of arc). Then he turned on the Serdi 4000 valve machine, chucked up a valve (I say "chucked," but the valve was actually held in V-block-type stem holders), and gave me a quick demonstration of how to grind a valve face correctly, to high accuracy. Barrett turned the machine off and handed me the valve. It had a perfect looking grind, the face actually looked polished (to an RA of about 10 micro-inches). "With these two machines, our valves never need lapping,""

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