Revisiting valve problem with pictures
 

...Continuing the saga of my Chronic tight intake valve. ( Rebuilt heads with guides and seats form RIMCO. New exhaust vavles old intakes. Problem is that number four intake valve continues to get tight.)

Details and refresh memory here:

http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/98747-chronic-tight-valve-part-2-a.html

Valve in question is number four on the left...see photos here: http://photos.yahoo.com/lsg914

The valve on the right is a bright and shinny new valve...

Both are TRW. The older has unkown mileage.

see photos here: http://photos.yahoo.com/lsg914


I lapped both valves in the number four port. Notice the elevation difference as well as the width of the seat contact...


Are the Valves are shapped differently?...Or has the older valve changed in profile from stretching or wear. What are your thoughts...BTW, this does reflect and support my earlier findings. I should have more room at the adjuster with the new valves installed...

I have bench tested the RIMCO seat by applying light taps to the slight lip on the back side. It is very solid. It also measures the same as the others as far as being reccessed or sunk into the head.

Unless I hear other wise from this post I am going to give the new valves a shot.


Thanks for your input...lsg

incase the link does not work...http://forums.pelicanparts.com/uploa...comparison.jpg

another viewhttp://forums.pelicanparts.com/uploa...omparison2.jpg

If someone put a gun to my head and forced me to guess, I'd say that the valve was starting to "tulip", which is what they do shortly before the head pops off. (This is a Very Bad Thing, as you probably know.)

This usually happens because of age or heat. It was a new valve, so that leads to the conclusion that either it was a sub-par valve or that cylinder (or rather valve) is seeing a lot of heat...

Or I'm missing something.

--DD

Clarification
 

Dave..More info to clarifyhttp://forums.pelicanparts.com/uploa...swithnotes.jpg

Valve problem not "Nsinc" has me on the "Backstreet" Boy,
 

I thought I would get a couple of views or opinions on my valve situation...

Did this stump the board? Or did I title the post incorrectly...

ie. Revisiting my "insert lame celebrity name here ie. Timberlake" valve problem...:D

...Has anyone experienced a head that is not capable of supporting a valve seat...no cracks or previous damage noticable...or is the problem the old valve picture?

No looking for any "guaranties" just making sure I have thought about and covered all of the bases..


Thanks. Scott

I'm stumped!:confused:

I'll bet it is the seat moving around in the head. We have this problem with my race engine and even though I run race gas and the head temp meter says 360 degrees during a race, the seat can change it's location due to the metal in the head getting very hot. Once the seat moves, the valve no longer has a good seat and it will start bending and flexing and very shortly beak off the valve head. A way to check this is to use a straight edge across the combusion chamber and try to get some accurate measurements from the head surface down to various points on each seat. If the heads are new then all measurements should be the same for each valve seat on each cylinder. I think the only fix is another head or to keep working and tweaking the existing head. Good luck.

John, I am leaning towards your analysis. I have another head. What are the chances RIMCO is going to redo another head...Zippo. But I will ask.

If the seat gets loose it usually works it's way out of the head, resuliting in a loose valve, not a tight one. Anything is possible though. I never thought od the situation John mentioned, I have to chew on that one for a while til it sinks in :)

Before I blamed RIMCO I would blame the old valve like Dave says. I think the valve is stretching and is getting closer to breaking off.

Another possibility could be the valve guide. If they're off they can cause the valve to bind - which is what I thought of when you mentioned "tight" valve.

When I had to pull my new engine after installing, because a seat dropped, we ended up having to redo the guides, as they were slightly off-center (considering projected height) when the new seats were installed.

Just a thought.

Not that I know that much about it,

But I lean toward the bad valve theory.

I think if the seat were sinking it would defiantly show signs of having moved on inspection.

The area of the contact on the valve seems to indicate that the valve is not cut at precisely the same angle as the seat as indicated by the width of the contact. This would not be uncommon and might actually be desirable.

I would not chance the old valves (any of them) in any case.

What has RIMCO had to say about it?

Answers

I have replaced all of the valves.
RIMCO did replace guides with the seats.

I spoke with Craig, the machinist at RIMC, He offered heavy reassurance that it is most likly not the seat...The fact that it is an intake seat and that He did the work and has never had this problem before. He points to the valve and after that ????

RIMCO offered to look at the head again and verify that there is not a problem. Unfortunatly I can't swing by there after work, rather it is another 50 bucks worth of shipping...