Head Work $?

[Ecomike]

FTP means

http://www.acronymfinder.com/FTP.html

 

[Ecomike]

NEVER do a valve job and knurl the guides. Always have the guides sleeved, otherwise you will be sucking oil past the guides and smoking like mad within 20k miles.

What does "knurl" mean?

 

[SpartyKrunk]

FTP means

http://www.acronymfinder.com/FTP.html

To break it to ya, all those acronyms are wrong. lol.
Wanna know what it means?

http://www.youtube.com/watch?v=gNdR...4F5CFE25&playnext=1&playnext_from=PL&index=21

 

[SpartyKrunk]

http://naxja.org/forum/showthread.php?t=968180

 

[old_man]

What does "knurl" mean?

As the valves open and close, the stem of the valve moves up and down within a long cylindrical hole drilled in the head called the valve guide. The tolerances are quite tight. On the intake valve, the vacuum tries to suck oil from the top of the head where the springs and rockers reside. Most modern engines use what is called a valve seal to reduce the oil being sucked into the intake and ultimately taken into the cylinder where it is burned and turned into the blue smoke we sometimes see on cars.

There are two basic types of valve seals. The most common looks almost like an umbrella that the valve stem sticks up through. It actually goes up and down with the valve. It keeps oil splash from directly hitting the area where the valve stem exits the head. The second is what is called a positive seal. A positive seal is attached to the head and the valve stem slides up and down through the seal. Positive seals require a particular profile to be machined into the head that the seal snaps onto.

As an engine wears, the clearance between the valve stem and the head gets larger. This allows more oil to be sucked into the engine. Positive seals tend to help minimize this but are not 100% efficient.

So how do you get rid of this oil burning. In the old days you could actually buy valves that had a larger diameter valve stem. You would then simply run a precision reamer though the valve guide to make it match the new valve stem diameter. The problem is that these valves are getting hard to find, not to mention more expensive.

The cheap method used today is called knurling. A tool that looks similar to a tap is threaded down though the valve guide. The thing that seperates this tool from a tap is that it does not have a cutting edge. As it is screwed in, it displaces some of the metal, pushing it up. It is then followed by a reamer to cut the tops of the displaced material down to the correct clearance for the valve stem. If you think about it, the valve will not wiggle in the guide any more, but you end up with what looks like a set of screw threads down though the guide. They count on the fact that the length of the thread is long enough that the suction can't pull much oil. That is all fine and good, but think....the amount of metal that is supporting the valve stem is less due to the spiral groove. That means that the smaller amount of metal will wear faster. This is why buying an off the shelf "rebuilt" head many times works fine for 15-20k miles, then the smoking starts.

Other than going to a larger valve stem, there is really only one way to make a head as good as new...or even better. It is called sleeving the guide. The last time I had it done it cost about $5 per valve. The machinist actually drills out the valve guide significantly larger. A bronze tubular insert is then driven into the guide. The insert is then reamed back to the correct size. As it turns out, the bronze is actually a better material than the original iron of the head. It isn't done to new heads for one reason, cost.

 

[Ecomike]

Thanks, old_man. That might explain a problem that is developing with my sons Vulcan, 3.0 engine, 96 Ford Taurus. Did the head gaskets last Christmas, heads had hairline cracks (instant coolant dump on the freeway damage) so the machine shop got us some cores, replaced the valve stem seals, cleaned, and made sure the heads were flat. He used about 3.5 quarts of oil (10W40), a few weeks ago mostly on about 500 to 600 mile road trip (ODO is down, so not sure of miles before the road trip, or total miles, but guessing it was no more than 1000 miles total. Moved him up to 20W50 for the top off, and watching it closely. Also added Restore to the oil. So far so, good, but at least now I know what to look for and why!

That Restore product may be just the ticket for fixing the knurled valve guide leaks. It has colloidal particles of a silver-lead-copper alloy, that plate out on wear areas, to reduce leaks like these. IN fact it might be smart to use the stuff at the start up after having head guides knurled. It just might fill in the gaps left by the knurling.

I got 12 months and about 20,000 miles out of my sons old heads after they cracked, just by using Restore. One valve guide completely gave up finally, but the engine had 220,000 miles on it to.

Thanks.

 

[magimerlin]

File Transfer Protocol?

Midian and I both have AMC XJ's (as opposed to Chrysler ones like yours). Ours are "powered" by 2.8L V6 motors.

As for smarter? Ummm....ours don't need all the computer dudas that the rest of you have, so, sure, they are smarter.

I met this chick who hangs out by some payphones that apparently does head work for $25.00. I'm not sure that will help the XJ though. :eeks1:

ya but what it lacks in a computer it makes up for in miles of vacuum linesuke:to vacuum lines

 

[MischiefMan]

Are AMC engines like the old Chevy small/big blocks? Just the block, filter, and throttle? lol

Not that this has ANYTHING to do with where to get head work done, but the '84-'86 V6 is actually a GM 2.8L motor. Yes, just a block, filter, throttle and enough vacuum lines to make make the Trojan company envious because of all the rubber we have.

 

[SpartyKrunk]

lol.

 

[bdiamond]

I'm hoping to just find a set of aluminum headS for mine ).

I think Flores had a set. I don't know where they are now though. I'm pretty sure a pair of 3.1 heads off a beretta or lumina or similar would be a pretty good power boost. You will probably need a different intake as these are raised port and splayed valve heads. A few years ago I was thinking putting a set on an old camaro to road race. The GM performance parts catalog has alot of info on JYable 60 degree parts.

 

[bdiamond]

Sorry about getting off topic. I called last week about rebuilding a 4.0 head. My guy shot me $95 for the valve job and $50 to have it surfaced.