Should I replace head bolts when replacing head gaskets?

[grumpyunk]

I would just put it back together. You can get white smoke from the exhaust if oil got into the muffler. It will produce smoke until it all has been evaporated and shoved out of the muffler.
Engines are not clean and will get deposits no matter what you do to prevent them - in almost all cases. It is not something to worry about unless the deposits interfere with valves seating properly, or the deposits get hot and start to cause pre-ignition(glowing carbon deposits cause the fuel:air mix to light off too early)
One way to keep them minimized it to NOT run the engine at idle. The mixture is likely not well distributed, leaving more carbon to deposit, and the splash of the oil in the sump is diminished, reducing lube to splash lubed parts such as the cam, followers, and cylinder wall. Rod and main journals in some cases. Also the airflow over the cylinder is reduced, causing higher than normal temperatures if idled long enough. Run it like you stole it, at the indicated throttle lever position, and shut down when you are ready to quit. Idling is a waste of fuel.
tom

 

[Johner]

I'm at 300 hours and took the heads off to clean the carbon from the pistons and check the valves. Should I replace the head bolts or re-use the original bolts?
Where should I use Loctite, I was told that the blue loctite needed a primer when steel bolts go into aluminum?

Retap the holes, clean bolt threads, use a anti seeze compand when installing, use new gaskets. Remember some day you might ave to take apart, think twice before using thread lock.

 

[Gym123]

Kohler doesn't call them that, but basically they are a torque to yield style bolt. The only ones I alway replaced were on the old K-series, because they had issue of heat related head gasket failure if the bolts were reused.

Are those bolts steel?

 

[ILENGINE]

Are those bolts steel?

Kohler referred to them as elasto-head. Basically they were "according to them" made in such a way that the would match the expansion and contraction of the aluminum head with the cast iron interface of the block. The issue was if the head bolts were reused they engine would run fine until reaching operating temps and then the head gasket would no longer seal causing loss of compression and in some cases the engine would die and not restart until cooled.

 

[Gord Baker]

I'm at 300 hours and took the heads off to clean the carbon from the pistons and check the valves. Should I replace the head bolts or re-use the original bolts?
Where should I use Loctite, I was told that the blue loctite needed a primer when steel bolts go into aluminum?

A total waste of time to clean Carbon from Pistons. You only had to remove the Valve Cover and check valves with Feeler gauges. 0.004. 0.006. Done. Original head bolts should be fine. Lightly lube and Torque per Specs.

 

[john in ohio]

My suspicion is since the bolt hole is there, dark area could be caused by different heat dissipation cause heat warpage of the cylinder walls causing that area to wear more. Can be cause by not using a torque plate when the cylinder is honed leading to out of round when the cylinder gets hot. Or the bolt threads could be heat treated and the heat treatment bleed through to the cylinder walls.

That is good info! Some one has been around the block a few times. Stuff the average person wouldn't think about. Thanks

 

[tcpuccio1]

either a hot spot or it's piston scuffing the cylinder wall. you can still clearly see the hone pattern. if you feel like digging deeper pull the piston out and taker a look at it. to your original question if the bolts are not TTY then I would reuse them. That's just me.

 

[Boit4866]

on a mower engine I would resuse the bolts unless they are damaged or heavily rusted/corroded. Alumium is considered a passive metal. A primer is needed for Loctite to properly cure on an aluminum to aluminum surface, however, you are using steel bolts and that is an active metal. Personally, while I use Loctite and have since the 1970's, I would not use it on a head bolt. When oil, grease, anti-seize is used etc., it causes the torque the bolt actually get to be exceeded by a significant amount. Head bolts already get quite a bit of torque and don't need excess. Sometimes as an engine breaks-in or has high hours, you may want to retorque the head(s), and Loctite may prevent that.

Right. When using an anti seize, it is recommended to reduce the torque setting by 30%. So, as an example 30lbs/ft would be 21ft/lbs. There are different anti seize compounds such as graphite, copper, nickel etc. so it’s advisable to choose the correct compound for the application.