[email protected] (Dave Williams)
racefab  1 May 93
- -> I recently heard a rumor about TRW or someone working on ceramic
  -> valves for various engines (a small block V8 of some sort was
  -> mentioned...).
- The first group to work on this (that I know of) was called Polimotor.
  Ford pumped a lot of money into them during the '80s, and connected them
  up with their factory racing team, which was Zakspeed-Roush at the time.
- Ford was basically paying Polimotor and Roush to do research.  They
  experimented with composite conrods, blocks, heads, cams, and valves
  among other things.  The problem is, though ceramics have nearly ideal
  thermal properties for valves, they practically fall off the other end
  of the scale for mechanical properties.  You need something that's
  tough, can withstand repeated heavy shock, vibration, etc.  These are
  all weak points for ceramics.  Last I heard, composite ceramics were
  being tried.  A composite ceramic uses an inner core of carbon or metal
  fiber, which is then baked inside a ceramic shell.  I dunno what
  happened to that idea.
- One of the major reasons for the continual assault on the valve problem
  was, the valves are the WORST application for ceramics.  Polimotor felt
  if they could build a workable poppet valve, they could adapt ceramics
  for any purpose.
- Pistons, valvespring retainers, and camshafts are more suited to
  duplication in ceramic materials.  Isuzu's small Diesels use a ceramic
  top on an aluminum piston; this idea will probably spread.  As for other
  applications, ceramics don't seem to show any cost or performance
  advantages over the usual materials.  The same thing basically applies
  to the group of materials we commonly call "plastics".  The people who
  make them like to call them "engineering resins" or "alloys", but so far
  valve covers, oil pans, and some intake manifolds seem to be their
  limits for automobiles.  In these cases, they're usually used more for
  their sound-deadening properties than any mechanical or cost advantage.

[email protected] (Dave Williams)
fords  31 Jan 1994
- -> Yes they do exist.  1968-1/2 thru 71 exhaust valves used hardened
  -> caps along with the rail rocker arms to minimize wear.
  -> I'm sure the absence of the caps would lead to premature valve tip
  -> wear and metal fragments/valves in the engine
- Normal valve tips are either heat treated to hardness, or (more
  commonly) harder metal welded to the end, then ground down to stem
  diameter.  The valves with the hardened caps are soft, plus the ends are
  turned down to a smaller diameter to get the caps on.  They wouldn't
  last long at all without the caps, and frankly I'm surprised the
  rebuilder could get enough adjustment to set the valves if the engine
  had the usual stepped studs.

[email protected] (Dave Williams)
asedan  30 Mar 1997
- -> .040 to .050 now days.  The flow can increase as much as 30% in some
  -> engines at lower lifts (below .350) and provides a notable increase
  -> in both horsepower and torque in the miid-range (coincidently where
  -> A-Sedan cars like it).
- I have been running a set of reduced-stem-diameter valves in my Capri for 
  ten years.  The stems are cut down to .200.  The intakes are ditch cut on 
  the face, the exhausts are ditch cut on the back.  Though many prominent 
  authorities claim the ditch cuts will fill with carbon, they were still 
  clean at 30,000 miles when I had to go back in for valve guides. 
- The reduced-stem-diameter trick lightens the valve, which is always a good 
  thing.  The just-rediscovered trick of drilling the stems results in a 
  stronger valve for the same weight.  Typically a "good" head will have a 
  steep approach angle to the valve, that is, a large shortside radius.  This 
  type of port generally doesn't respond much to reduced stem diameters.  
  Ports with a shallow approach angle tend to like them. 

[email protected] (Dave Williams)
Fangle  03 Sep 1998
- -> Check out the concentric circle wear pattern on the tip of the
  -> valve stem and ask yourself "How did that get there?"
- A *proper* wear pattern is a concentric circle.  It's not uncommon to see a 
  line, though.  Ford V8s are particularly bad about this, as Ford uses some 
  of the cheapest crap for valve steel they can get away with. The tips 
  evidently dent early in the engine's life, forcing the valve to stay in the 
  same orientation from then-on.  I've seen it happen on other motors too, but 
  for the Fords it seems to be the rule rather than the exception. 
- If you have everything set up right, the valve *should* rotate.

[email protected] (Dave Williams)
fordnatics  06 Jun 2000
-> eventually burn up.  How many miles am I talking about
- > here?  I've been very honest with him about his motor
- > needing a valve job and I want to give him a worst
- If you're concentric and the guides aren't worn out, heck, 20,000 or 30,000 
  miles.  I've seen OEM heads with exhaust seats 1/8 inch wide, and close to 
  it on rebuilt heads. 
- The major consideration is guide wear.  Lift the valve about 1/2 inch off 
  the seat.  Wiggle it lengthwise (front of head to back of head). Then wiggle 
  it crosswise (intake face to exhaust face).  If it wiggles about the same 
  each way, the guides are fine.  If it wiggles more... you can figure the OEM 
  guide clearance was probably on the order of .002. If it wiggles twice as 
  far crosswise, you're looking at around .004, which is technically way out 
  of bounds, but in practice it will usually last many thousands of miles.  If 
  it's .005 or .006 it will usually pump so much oil through that the wear 
  isn't really an issue. 
- How are the valve tips?  If they're beaten up, they can be refinished with a 
  belt sander or similar tool; spin the valve to keep from cocking the 
  finished surface to the side too much.  If the tips are dented the valve 
  will rotate to that position shortly after you fire it back up and then 
  it'll proceed to beat the seat do death again.  You can't get it properly 
  perpendicular doing it by hand, but you can make it better than it was to 
  start with.   Don't take off any more than you absolutely have to, 
  particularly if it's a nonadjustable valvetrain. 
- > compression between each other (V6 mustang).
- Buy new umbrella seals; they should cost less than $10.  Tell him to skip 
  lunch if that's what it takes. 
- > was oil in the water and water in the oil.
- Clean the heads and the block as best as you can and give them the hairy 
  eyeball - make sure the problem was just a blown head gasket and not a crack 
  too.  Be *very* careful cleaning the thin sections between the bores; you 
  don't want to remove any metal or scratch that area. 
- > enough money for gaskets and that's about it.
- Borrow a carpenter's square or steel rule.  A machinist's flat is guaranteed 
  true, but you don't *have* to have a true surface to measure from - if you 
  check several parts and they all show the same amount of warp, then that's 
  most likely the error in your rule.  I have a fancy machinist's flat, but my 
  cheap Craftsman 24" carpenter's square is straight within .001".  Most 
  engines allow .003ish warp before calling for refinishing.  In practice you 
  can get away with a little more without worrying about gasket failure, at 
  least with most engines, but considering the thing has *already* blown a 
  gasket, if it's warped more than .003 putting it back together without 
  refinishing the head might be a waste of money. 
- The first rule of jerry-rigging is, if you can't afford to do it right, you 
  probably can't afford to do it twice.  So be paranoid and check everything 
  you can! 

[email protected] (Dave Williams)
fordnatics  12 Jul 2000
- -> The machine shop quoted me $3 bucks each for Bronze guides and 28
  -> bucks for an entire set of iron guides.  So am I missing something or
  -> getting screwed? There's 16 guides right?
- Beats me.  I can buy 11/32 x 1/2" bronze guides for 78 cents each; iron 
  guides the same size are $1.35. 
- Some of the price difference may be in the tooling and labor.  You have to 
  have special reamers to size bronze guides, and they're expensive, and the 
  bronze wears them out quickly, *and* they take enough torque to stall light-
  duty equipment.  The thinwall bronze liners aren't reamed, they're swaged 
  into place, so that doesn't apply to them. 

[email protected] (Dave Williams)
fangle  22 Nov 2000
- Valve guides are either cast iron or bronze.  Iron ones are often just holes 
  drilled in an iron head.  Bronze are always inserts. 
- It occurs to me I've never seen an aluminum valve guide.  Wear might be a 
  little higher than with iron or bronze, but heat transfer ought to be pretty 
  good.  On the exhaust side stem temps can go over 500F, but hell, the 
  pistons are aluminum and they don't seem to have any problem, and they're 
  moving a hell of a lot faster than a valve stem. 
- Anyone want to be a guinea pig?

[email protected] (Dave Williams)
fangle  22 Nov 2000
- -> Seems to me, that with the expansion rate of aluminum versus iron,
  -> that the aluminum would try to expand and get "squashed" by the iron.
  -> After some odd number of cycles the aluminum would just fall out.
- Possibly.  On the other hand, it could be tried with an aluminum head.   
  Going the other way, with iron seats and guides in an aluminum head, doesn't 
  seem to be a problem. 
- I've been predicting plasma-sprayed integral valve seats in aluminum heads 
  for years, but I haven't heard of anyone doing it yet.  Besides eliminating 
  some production steps it'd sure help heat transfer out of the valve head... 
  nonregrindeable, but many of those late model heads are Dixie cups anyway; 
  you're lucky if you can weld up the cracks even if you can straighten the 
  warps.  It must take one hell of a CAE program to design an aluminum head 
  that cracks irremediably after 100,000 miles. 

[email protected] (Dave Williams)
fangle  22 Nov 2000
- -> If the valves didn't all stick first!
- Why should they stick?  One point of an aluminum guide would be to transfer 
  heat away from the valve faster. 
- I normally size thinwall bronze liners in iron heads to .0015" or so, but 
  brand-new Chevy Vortec 350 heads are .004".  It's going to take one hell of 
  a lot of heat to swell something .004".  Hell, the pistons are only .0015-
  .002 in an ordinary 4 inch bore with cast pistons, and they're getting a 
  hell of a lot more heat than the valves are!