122 Head Bolts?

Sun Feb 05, 2012 12:06 am

I am replacing a blown head gasket on my 122 and following a “how to” that has thing pretty well covered including how to “true” the head. It notes to pay attention to the bolt and washers placement. Well, the bolt heads were pretty shot; it took 3 different sized sockets to remove them. There are two lengths currently (2 ¼ “and 2 ½”) and I plan on replacing them with new grade 8 bolts. The shorter bolts had washers with a bevel on them (facing up).

Does anyone know the correct placement of the long and short bolts? Assuming they were in the correct places I will just put them back where they were, but if they were not??? The depth of the bolt holes in the block don’t correspond with the lengths I took out (some long bolts were in shorter holes :shock: ) Parts manual shows 4 bolts and 5 studs?? (….and I can’t find any reference to what goes where)?? To further confuse me there are 6 “shorter” holes and 3 deeper in the block. :? Logic would say get 6 shorter and 3 longer. Previous owner putting longer bolts in shorter holes may have contributed to the gasket failure if they bottomed out and it didn’t seal uniformly.

And, does anyone know if that unique washer is critical, or will a flat washer, like the others are work? (any reason for the beveled top?)

Thanks for any guidance,

Re: 122 Head Bolts?

Sun Feb 05, 2012 10:37 am

Here's the location of the studs in my 122
click for bigger pic

My K301 does have a newer head ( low boss )and required spacers for correcting the mounting height of the heat shield and gas tank mount.

As far as thread depth and washers, I highly suggest cleaning the threads with a tap. Use 2-1/2" bolts were ever possible to maximize thread engagement. Make sure you use a heavy washer that won't distort under the correct head torque.

Here's the correct tightening sequence and torque values

I retorque after 15-30 minutes of run time, again after one hour run time, once again after 5 hours and finally after 15 hours.


Re: 122 Head Bolts?

Sun Feb 05, 2012 11:17 pm

Thanks for the reply Jeff!

I went to TSC and picked up some grade 8 bolts but they only had 2 ½ inch length. So, unless I get to Fastenal or another source I will have to cut a few. They had grade 8 washers but they were thinner than the ones that were on it. The studs on yours have no correlation to the hole depth on mine, so I guess it is a mixed bag.

I made the jig to wet sand the head flat this afternoon, and after a couple passes I see the head needs some work, definitely not flat.

The plans is to clean the threads and measure depth and cut a few bolts as needed, put it back and see if it will fire up! The previous owner said it had been setting in a shed for over 5 years and I got the “it ran when parked”???? I have changed fluids, cleaned and rebuilt the carb, strainer, all wiring connections and checked the points. I got a good spark before I found out the head gasket was blown.

Thanks again,

Re: 122 Head Bolts?

Mon Feb 06, 2012 10:00 am

I may be wrong here, but I think the depth of the bolts in the head are all the same. I believe that the different length bolts were along the PTO side of the engine to allow for mounting of the muffler, and along the flywheel side of the engine to allow for mounting of the gas tank. They should all thread into the block the same length.