From: darling@simlab.arc.nasa.gov on behalf of Dave Darling [darling@simlab.arc.nasa.gov] Sent: Thursday, April 29, 1999 9:13 AM To: pelicanparts@csi.com Subject: Re: Dropped valve seats (Was: Re: bad valve adjustment screw) >Date: Thu, 29 Apr 1999 09:12:24 -0700 >To: Peter Bridge >From: Dave Darling >Subject: Re: Dropped valve seats (Was: Re: bad valve adjustment screw) >Cc: "914" <914@rennlist.org> >Bcc: >X-Attachments: > >At 8:19 AM -0700 4/29/99, PBridge130@aol.com wrote: >>It's virtually always the exhaust seats which are problematic, because >>of the heat of the exhaust. > > An informal survey a few months back seems to indicate that this >statement is wrong. (Which is odd, because it makes sense that the >exhaust would be the problematical ones.) > With you, that makes five people who have dropped a total of eight >or nine valve seats so far. Two of them have been exhaust seats. All >three of mine were intakes, as were at least three others. > Why? I don't know. In my case, I am prepared to believe that it >was crappy work on the part of the people who did the job the first (and >second) time. Perhaps the intakes can have problems because the incoming >charge cools the seat faster than the head? (That would cause the seat >to shrink...) > > A dropped valve seat is usually obvious when you look at the tips >of the valves. The one that has dropped out will, even when fully closed, >be 1/8" to 1/4" closer to the head than the other fully-closed valves. > > I would recommend that the original poster use a high-quality box- >end wrench to tighten down on the jam nut. I try to put some effort into >it. I use a Snap-On deep offset 12-point box-end wrench. I found that >my other wrenches were slipping off the nut and rounding the corners. Be >prepared for sticker shock when you see the price of new jam nuts, BTW! >Not quite in the range of exhaust nuts, but still... > And don't go very far on the test drive. > >--DD > Dave Darling 74 914 2.0 (decapitated) darling@simlab.arc.nasa.gov "OFF WITH ITS HEADS!"