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Cylinder Heads: Crack around the valve guides

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ProjectAbby:
Hey guys, so after taking apart the cylinder heads and cleaning it, I noticed the area around the valve guides are cracked.  This is towards the top part on all of them.  What's the main cause of this?  Is it something I can easily replace?

Soaring:
Obviously those valve guides need to be replaced, and while the machine shop is doing that, ask them if there is a clearance issue with your heads.  Something is not within tolerance here. 

5.0gt:
i could be wrong im not a machinist  but it looks like the guides were replaced and the cracks are whats left of the old guides as the pressed the new ones in though the buttom

Soaring:
After looking at those valve guides carefully, it appears that they have been sleeved.  Here is some reading you need to read to see if this is what you have from a previous owner, and it was a botched re-sleeving. 
VALVE GUIDE LINERS

Boring out the original guides and installing thin wall bronze liners to restore proper clearances is not only a fast and economical guide repair option, it also provides the benefits of a phosphor/bronze guide surface (better lubricity, scuff resistance and wear characteristics than cast iron).

Though liners are most often used to repair integral guides in cast iron heads, they are also a very effective way to repair replaceable guides in cast iron or aluminum heads, which saves time and eliminates the risks associated with driving out the old guides and pressing in new ones.

Liners also save the cost of having to replace the valves. If the original valves are not worn, standard sized liners can be used to restore the inside diameter dimensions of the guides. If the valves are worn, the stems can be turned down .0050 in. to accommodate liners with slightly undersized inside diameters.

Jerry Qualiana, vice president of aftermarket sales at K-Line Industries, Holland, MI, says their K-Line Bronze Bullet Guide Liner system has been authorized by Ford Motor Company and meets Ford Q-1 quality standards.

According to Qualiana, the Bronze Bullet Guide Liner design is an enhanced design over previous bronze liners, incorporating an "Interrupted Spiral" which assists in retaining oil in the guide, while eliminating oil flow through the guide. In conjunction with the previously mentioned lubricity characteristics of phosphor bronze, Bronze Bullet Guide Liners offer improved guide life in today's oil starved valve guide environment. Also, Qualiana points out that because of the lubricity in the phosphor bronze, K-Line has always advocated valve to stem clearance at the low side of the manufacturer recommended specifications.

Mike McElmurry, vice president of production at Sequal Corp.,Willow Springs, MO, says regarding K-Line's Bronze Bullet Guide Liner, "Because the final size is so easy to control, we have been able to tighten all of our valve to guide tolerances by at least .001 inch. This, along with the liner's ability to resist

galling has reduced our warranty claims by as much as 75% "I have looked at other methods of valve guide repair, .015 inch overised valves, new and rechromed, .003 in undersize valves with replacement cast iron guides, but have found nothing that was cheaper to use than K-Line with .003 in. undersize valves. We grind our own valves and enjoy over $0.80 per guide savings over any of the combinations listed above."

The key to using the Bronze Bullet Guide Liners successfully is proper installation. Qualiana says if the original guides are not worn more than .030 in. or cracked, they can be lined. Otherwise, replacement would be recommended.

Installation of the Bronze Bullet Guide Liners is a five step process:




1. First, the old guides have to be bored out to accept the liners. Qualiana recommends using a KL1725CB Black Beauty carbide reamer in an air drill with a no load speed of 2100 to 3000 rpm. K-Line's KL9900 Boring Fixture has centering pilots that center the reamer off the valve seat (which maintains seat concentricity), and an air clamping fixture that holds the head securely in place while the guides are being bored. The guides should be bored dry with no lubricant, using steady consistent pressure.

Once the guides have been bored out, they should be blown out and checked with a go-no go gauge to make sure they are the proper size.

2. The liners should then be pressed in from the top side of the head using an air hammer and K-Line's Auto Installer tool. The liners go in with the tapered side facing the guide hole. The liners are then driven in flush with the top of the guide boss.




3. Next, the liners are sized. Any of three different techniques may be used: roller burnishing (use with lubrication), broaching (driving a calibrated ball through the liner with an air hammer), or using K-Line's ball broach tool in an air hammer.

Sizing the liners is a critical step because it accomplishes two things: it provides the proper clearances between valve stem and liner for proper lubrication and oil control, and it locks the liner in place so it will transfer heat efficiently to the surrounding metal for proper valve cooling. Bronze actually conducts heat more efficiently than cast iron, but requires a tight fit and metal-to-metal contact with the surrounding guide for good heat transfer. If the liner isnot sized properly, it may cause the valve to run hot, or worse yet, come loose.




4. After the liners have been sized, turn the head over an trim the liner to length. The liner should be cut flush with the guide boss in the port. This step is not necessary if precut liners are being used that have the correct length for the application.

5. The final step is to Flex Hone the liner after any seat work that is necessary has been completed. The Flex honing step removes any burrs left from trimming the liner to length, and leaves a nice crosshatch finish that improves oil retention. One pass in and out is all that is recommended to hone the liner. A flexible nylon brush should then be passed through the liner to clean the hole.

Though the just described procedure sounds more complicated than it really is, a typical four cylinder or V8 can be relined in six to seven minutes says Qualiana. Also, the majority of the detailed steps listed regarding cleanliness and accuracy in the guide area are requirements no matter which method of guide repair the rebuilder chooses.

Ron Bernstein, vice president of Precision Engine Parts in Las Vegas, NV, says his company sells a solid one-piece smooth bore .030 in. oversize phosphor bronze valve guide liner.

"Ours is not a split design, so all you do is ream out the guide and press it in. You do not have to broach it afterwards because the liner is installed with an interference press fit of about .001 to .0015 inch. This saves a step and prevents the liner from falling out. But the guide must be bored to exact dimensions, which means you have to use the proper boring tool and replace it when it becomes worn.

"Our liner restores the guide back to stock dimensions so a reclaimed or new valve can be installed. It is a very popular liner with Mexican rebuilders," said Bernstein.

Ertel Manufacturing Corp. in Indianapolis, IN, makes cast iron liners as well as guides. Engineer Bob Leszcynski says many people have a love/hate relationship with bronze liners. "They love the fact that anybody with a Black & Decker hand drill can install the liners, but they hate the fact that if they are not installed correctly the head will come back with loose or worn liners.

"We say rebuilders should use always some type of piloted installation equipment that centers off the valve seat so the liner will be centered properly in the guide. With a hand drill and no fixturing, you have no control. Lean this way or that way on the drill a little bit and your hole will be off.

"We also say you must always broach the liners once they have been installed to seat them, which is something we also require for our cast iron liners. Most people do not think cast iron will stretch, but it does when you broach the liner to seat it."

Leszcynski said cast iron liners cost about the same as bronze liners. "Bronze has good anti-seize properties and is popular for that reason. But cast iron wears better and performs more like an integral valve guide in a cast iron head. Cast iron is also a good replacement choice for aluminum heads. In fact, you can use cast iron guides or liners in virtually any application where bronze might be used. We also have cast iron guides for the 1993 and newer engines that have powder metal guides."

OVERSIZED VALVES

ProjectAbby:
Thanks a lot for the imput everyone.  Im bringing all my parts to a machine shop tomorrow, so i'll get back to you with more details on the head and everything done to the engine

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