You are more likely to have a shop sell you something you don't need rather
than not sell you something you do. I have not personally seen a brass seat
that has had a problem from unleaded gas. On a race engine you might but I
don't think it is a big problem on a street car. Here is where you might have
a
problem. Most of the heat is shed from a valve through the valve seat. If your
clearances are tight the valve can overheat. This could cause seat damage.
If you check your valve clearances every once and a while and notice that one
always seem to be tight then you could have a problem. If someone has a head
with a receded valve seat please post a picture. If the brass seats need
replaced go with the hard seats. Otherwise I would leave them alone.
keith williams
In a message dated 9/14/2008 10:30:19 P.M. Pacific Daylight Time,
drlsmith@dccnet.com writes:
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
**************Psssst...Have you heard the news? There's a new fashion blog,
plus the latest fall trends and hair styles at StyleList.com.
(http://www.stylelist.com/trends?ncid=aolsty00050000000014)
________________________________________
Support Team.Net http://www.team.net/donate.html
Datsun-roadsters mailing list
http://www.team.net/archive
http://autox.team.net/mailman/listinfo/datsun-roadsters
|