At 01:43 PM 11/10/98 -0900, Baker, G. wrote:
> There's got to be a "head" historian out there somewhere that can
bolster my confidence in whether or not to enlarge these valve seats.
I've had a couple of heads done up with valve seat insrets. Actually they
were both early MGB 18 heads with valve sizes similar to the MGA 16 head
from the MGA 1622 engine. I've also seen MGA 15 heads (MGA 1500 & 1600)
with the valves increased to MGB valve sizes. The water jacket is not
along side of the valve seats, but is under the seats, and is deep enough
so that installing valve seat inserts is not a problem. If you're going
with larger valves and seat inserts, just be sure the inserts are not so
large as to run into each other.
After the new seats are installed it is necessary to clean up the
transition within the ID of the seat between the seat and the casting. If
the new seat protrudes into the port area, it needs to be cut back to match
the wall of the port. If the ID of the new seat is larger than the port in
the head, the port should be enlarged a bit to match the ID of the insert.
If you're thinking about valves more than one size larger than stock, I'm
in the gray zone, couldn't say for sure. I have heard that there is quite
a lot of material available for cleaning up and enlarging the ports without
running into the water jacket, but if your doing big time porting you
should ask someone with more experience.
Barney Gaylord
1958 MGA with an attitude
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