imported post
newday777 wrote:
newbiker wrote:
What will that have to do with the temp or head gasket failure. Its been less than 10k since I adjusted them last.
Part of the design depends on the valves correctly transferring retained heat to the head when they fully close. A tight exhaust valve will get hot, to the point where the edges can cause preignition, and that will cause your engine to run hot.
Other things.........poor mans plane. Clean inside of head thouroughly with solvent. Color it with a thick black magic marker. Take a sheet of glass or use your shop window. Tape a sheet of fine grit sandpaper and plane the head against it in a slow figure 8 motion. Flip the head and change direction regularly to ensure eveness. The black will show the low sections, plane until no more black. I've had 'em back from the machine shop and still need this.
Stud stretching. Old studs stretch. Cheep inferior and improper grade studs do as well. The more the heads have been off, the more they stretch, and the more they will stretch after torquing. Replace with Honda OEM bolts if possible, otherwise get new studs from some place like NAPA that sells high quality American made bolts......not cruddy chinese stuff.
Moly paste/lube on head studs. DO NOT DO THIS UNLESS THE MANUAL CALLS FOR IT!!!! Unless specified, it is understood that all torque values are on a dry bolt as torqueis a value derived by friction.....a dry bolt provides a certain amount of friction, while a lubed bolt will require more force and tension to achieve that same level of friction (resistance) as read by the torquewrench. Lubing them changes that value dramatically. If the manual calls for moly paste......then the studs MUST be torqued with moly paste to be correct, and vice versa. Remember, just as many bad head gasket installs are caused by overtightening as undertightening, especially when dealing with aluminum.
Pattern.....follow the sequence for tightening as outlined in the manual. I always recomend when dealing with aluminum, to torque in the proper sequence in small increments, maybe 5-7 lbs at a time until you hit the target value.
I've found the most common reason for "mystery" leaking head gaskets to be improper torque caused by old/corroded studs and threads. Why? Remember, the torque wrench does not measure the force the bolt itself excerts, it measures the friction of the bolt against the threads. A corroded bolt and threads will result in more friction, and therefor an inaccurate reading on the torque wrench. This is where folks get the idea to "lube" head studs when the manual doesn't call for it......put a little grease or moly paste on the old corroded stud, and it will torque closer to the real value.......you in essence make a right with two wrongs;-) Of course........this is a setup for a future broken head stud.......and those are loads of fun to extract.
The"best" (everybody has opinions)way to do this is to use new studs every time. I also clean the threads out using an appropriately sized gun cleaning bore brush hooked to a drill, and if they are too corroded, I'll run a cleanout through them. Don't replace one stud and not the others either. Also, if your application uses alignment pins, make sure they are clean and move freely. You don't want to be torqueing against a stuck pin.
