NAA and 860 head gaskets

[Jamie in NC]

Well, I guess the stars aligned just right and I need to go get a lottery ticket, but both of my tractors head gaskets seem to need replacing. My NAA lost power and seemed to be missing after I was moving dirt with the box blade. I checked ignition and had spark on all 4. I thought the valves needed adjusting, but did a compression test first and came up 120/30/30/115 and heard a whoosing sound from 2 and 3 spark plug holes. I guess the gasket is blown between 2 and 3.
My 860 is leaking antifreeze down behind the coil from the gasket between 2 and 3.
I guess my question is, that is this a common problem for head gaskets to blow or is this an anomaly? I have had the NAA for 22 years and other than normal maintenance, no real issues except the leaking rear wheel seal that I cant get stopped.
Is there a good gasket to get so I dont make this a yearly item?

 

[Royse]

In my experiece, it is not common for either engine to blow a head gasket.
I have replaced them in the past during rebuilds, etc. and prefer to use the soft material head gaskets.
Follow the manufacturer's instructions on whether or not you should use anything on them.
Check the head carefully for cracks while you have it off.
Especially if it has overheated and make sure you have a working thermostat.
You'll already have it off, so a thermostat, hoses and belt are cheap and easy.

 

[pomester]

I had (have) a 960 which would blow the head gasket between 2 and 3 if it were put to hard work. I replaced it a couple of times, using various tricks, flattening the head, copper gasket compound, staking the deck/head, light gauge copper wire between the cylinders - finally had to bite the bullet and get the block decked/flattened. Using a straight edge I could tell the block was slightly low in that narrow area.

Since you'll have to pull the head, it's time to evaluate whether it needs machine shop work. Maybe a valve job? And evaluate it carefully for flatness. If you have a good straightedge you can tell quite a bit.

One thing I've started doing the past few years is replacing the 60+ year old head bolts ,which have likely been torqued a number of times, with studs, washers, and nuts from ARP. If you choose to reuse the head bolts be sure to clean the threads of both the bolts and the block thoroughly so they can be accurately torqued.

Probably should have the head leaking antifreeze leak tested for cracks...

This post was edited by pomester on 12/20/2021 at 08:36 pm.

 

[Jamie in NC]

I was working the NAA pretty hard. I was moving dirt for about 4 hours, so I guess it needed a break. I will look into the head bolts. Have you had any further issues since using the studs? Do you torque the studs the same?

 

[showcrop]

I suggest Felpro gasket and follow their instructions. 2X ARPS studs. I had a 901 for fifteen years and have had a 960 for twenty. I have replaced the head gasket in both. As pomester said check for the deck being low. Sometimes you can see that it has eroded a little. Before starting the job check the compression of the 860 to ensure that you are not doing a major repair on a motor that will need rings in another 100 hours. Get the heads surfaced. They will want you to spring for a valve job but you can say no.

 

[Jamie in NC]

What is the part number for the arp studs?

 

[showcrop]

(quoted from post at 12:11:14 01/03/22) What is the part number for the arp studs?

It is unlikely that you will find any listing for NAA or 860 but just go to the ARP website and order by diam. and length or better yet ask the shop that you take the head to to order them for you. That is how I do it.

 

[pomester]

I have that information, but this website won't let me post the details because of 'advertising' I guess.

My email is open in modern view, shoot me a PM and I'll send the numbers to you.

Be aware that some 172ci engines had 7/16" bolts and later ones had 1/2". I don't know about the NAA, but I'd guess they have 7/16".

By using the calculator at the ARP website, I determined that for my situation, 5" long studs were the appropriate length.