Hi,
If you have Brass intake seats ,which are sock , They MUST be
replaced .They will be pounded-out and a stock valve will be "sunk" in
the head and will fall out of the head eventually .
If you have steel ,or a derivative ,you may be ok . That said ,
Nissan does not publish actual valve heights/ Stem lengths ,so they
could not duplicate the dimension . They may have had spring heights
dimension ,that is controlled by this number ,however their method
would have involved using valve shims under the valve springs .This
doesn't change the relationship with the actual stem length ,or valve
position relative to the seat . Since you had them install bigger
valves ?? , that would have raised the valve and made stem lengths
shorter
than spec ,possibly . Anyways , Seat material used in the 1960's was
designed for Leaded Gas ,how would they know ,unless the seats
had bean changed ?
Steve Ehlers
www.risingsunperformance.com
Daryl Smith wrote:
Thanks for the note Steve, and others as well.
I provided the machine shop with the list of spring specs/heights
and stock valve dimensions with the work order.
Seats? This is the SECOND shop that has told me that the stock
seats in the aluminum head were in good shape, would be fine with
the unleaded fuel, and there was enough material there to modify
for my oversize 1.70" intake valves, and 1.35" exhaust valves.....
I had suggested that they should change the exhaust seat since the
new valve was almost 2.3mm larger, but they were adamant that it
was fine and they didn't need to be changed.????
Is this a case of "we just don't want the work"???
Here's hoping this discussion saves someone else some
time/money.......
Daryl
----- Original Message ----- From: "Steve Ehlers"
<stevenehlers@charter.net>
Hi,
This is typical of poor quality machine work .Even with a slight
interference angle made on seats and valves ,there should be NO
leakage . If the head wasn't assembled you can seal the valves with
a thin grease coating ,as we do when building a combustion chamber
matched high Performance head set up .If the valves had been lapped
in during the valve work a problem would have been seen in contact
or possible run out on the seat .Quality machine work can't be
assumed by the end user if you don't know the details of a quality
job .
For example , did you have new steel intake seats installed ,and at
the right valve height ? Can the Machine shop even provide you with
the correct stem height dimension . I doubt it !
Good Luck ,
Steve Ehlers
www.risingsunperformance.com
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