fresh rebuild is blowing head gaskets, help!

[Gregor 4,846]

You DO have all the motor shrouds on? Right?  Sounds like it's getting hot. No mouse nests, grass build up anywhere?

[tunahead72 2,424]

37 minutes ago, ol550 said:

 

One thing I did notice each time is the smell of hot oil and fumes from the crankcase vent.

 

 

Are you certain the breather is assembled correctly, in the right order?

 

[squonk 41,155]

Was the piston fitted by the machine shop? Or did the engine get bored and then you bought a.010 piston and install it. Sounds like the engine is not breathing and pressure is building up and coming out where ever it can

[Gregor 4,846]

9 hours ago, ol550 said:

Hurry up and get this figured out. I've got a 12 horse with very similar problem.

I know these are similar problems, but I for one, am getting confused as to just what engine we are talking about. Maybe you should start another thread, describing your entire sequence of events, and what is happening now.

[Shrek 12]

1 hour ago, squonk said:

Was the piston fitted by the machine shop? Or did the engine get bored and then you bought a.010 piston and install it. Sounds like the engine is not breathing and pressure is building up and coming out where ever it can

Yes. The machinist checked the new piston in the cylinder.  I'll double check the orientation of the breather components today.  It's a K181, with the timing sight hole on the side of the  shroud..

[Gregor 4,846]

14 minutes ago, Shrek said:

I'll double check the orientation of the breather components today

While your doing that, I would check valve clearance. You will be in there anyway.

 

Intake  .006 / .008

Exhaust   .017 / .019

 

Piston MUST be at TDC

Edited April 27, 2021 by Gregor

[953 nut 55,320]

34 minutes ago, Shrek said:

The machinist checked the new piston in the cylinder.

Were the end gaps of the piston rings checked prior to installation?      I don't think any Kohler engine will develop enough compression to blow the head gasket. Are you certain that the head torque sequence and setting were correct? I generally stage the torque in two steps, first round at 20 ft/lbs then a second round at 30 ft/lbs. After the engine has run long enough to come up to operating temperature and has cooled down a bit I do another round at 30 ft/lbs.

Static timing of your ignition points will work because yours is the later model with a ring gear flywheel. I suspect that the carburetor is a bit on the lean side which can cause the engine to run a bit hot.

[ranger 1,750]

You said you cleaned the threads in the block for the head bolts? Are the bolts going far enough into the block to clamp the head fully? Head / block been skimmed / surfaced? I’ve seen auto blocks cracked because oil or water, (or “gunge”) from disassembly had not been cleaned out properly, head bolts when torqued down would,  “ Hydraulic”, and crack the block, 1.6 and 1.9ltr VW diesels. I always run an appropriately sized drill bit, (using my fingers), into each threaded hole It’s surprising what you can sometimes get out of the bottom of a “clean” hole! Have the gaskets failed in the same place each time? Does the rattle sound mechanical? Or could it be the failing gasket acting as a “Reed”, and vibrating? This would point towards block / head surfaces not clamping gasket sufficiently in places. I’ve also come across “Rattling” noises and clouds of smoke from Diesel engines that have been over filled with oil, this would pass through the breather / oil separator and feed the engine through the air filter/ manifold connection. “SCARY” when this happens, as engine runs away uncontrollably! With the very high compression ratios diesel engines have, compared to the Kohlers, I wouldn’t think this is the cause, unless, when it fails, there is oil all over everywhere. Nothing to do with this post, but I thought I would add it. I had one piece of equipment that kept running away on it’s own oil, only at max rpm, everything ok, oil level, breather etc. It turned out to be, A vacuum pump mounted on the alternator, which was lubricated from the engine, the drain went back to crankcase. This pump was connected to the brake servo, (diesel engine, no manifold depression for brake servo). The vacuum line non return valve had a small leak, this meant instead of pulling a vacuum in a closed circuit, the pump acted as an air compressor and pumped air into the crankcase via the oil return, this was a “Vane” pump, not diaphragm. The volume of air at high engine rpm’s completely overwhelmed the breather system!

 

Doug.

[Shrek 12]

7 hours ago, 953 nut said:

Were the end gaps of the piston rings checked prior to installation?      I don't think any Kohler engine will develop enough compression to blow the head gasket. Are you certain that the head torque sequence and setting were correct? I generally stage the torque in two steps, first round at 20 ft/lbs then a second round at 30 ft/lbs. After the engine has run long enough to come up to operating temperature and has cooled down a bit I do another round at 30 ft/lbs.

Static timing of your ignition points will work because yours is the later model with a ring gear flywheel. I suspect that the carburetor is a bit on the lean side which can cause the engine to run a bit hot.

the piston ring gaps were checked. I followed the torque sequence pictured in the manual, two rounds. 

I think I'm going to clean up and sand flat the original head,

get new head bolts.

Check the valve gaps again

put it back together and run it toward the rich side.

[Greentored 3,214]

Make sure you caught the reply from @WHX24. I had a similar issue with a 14hp and all was fine til I hooked up a plow and loaded it good. Lasted 2 passes. In a pinch, I grabbed the old oem Kohler gasket with fire ring out of the trash can and swapped it in. That was a year and at least 40 hours ago and its still perfect.

If you are using one of the aftermarket rebuild kits, they normally come with the non fire ring gasket. Stens does offer the fire ring gasket but you have to ask the counter guy to specifically look it up and verify the pic.

The next thing to do is to make sure none of your head bolts are bottoming out in the block and not actually pulling the head down. Seen that happen too.

[Achto 27,604]

On 4/26/2021 at 4:16 PM, squonk said:

I just looked at some pictures of a Kohler OEM 8 HP head gasket #41-041-10. No fire ring on them.

 

They must have changed them. Hate it when the cost analysis department gets involved and ruin perfectly good parts.  I have a few Kohler NOS small block gaskets that do have the fire ring on them.

Edited April 29, 2021 by Achto

[Achto 27,604]

20 minutes ago, Greentored said:

The next thing to do is to make sure none of your head bolts are bottoming out in the block and not actually pulling the head down. Seen that happen too.

 

Very good point. Seen this issue with new bolts and also when the thick washers on the head bolt were replaced with thinner ones.

[Gregor 4,846]

My small engine guy once told me to run a thread chaser into the holes. "Don't use a tap, use a Thread Chaser" Well I have googled thread chaser, and all I come up with is taps. Is  thread chase simply a bolt, with a slot cut down the threads?

[Gregor 4,846]

The pic in the Parts Tree blow up, shows the head gasket with a fire ring. From what I can tell, you have to be a Stens dealer to order from them. At least that's what it says.

[Achto 27,604]

9 minutes ago, Gregor said:

From what I can tell, you have to be a Stens dealer to order from them.

 

This is true. You can not order directly from Stens. Many small engine shops have a Stens account so it should not be hard to find a supplier near by. Or if all else fails, Google will find it for you.

[Greentored 3,214]

26 minutes ago, Gregor said:

My small engine guy once told me to run a thread chaser into the holes. "Don't use a tap, use a Thread Chaser" Well I have googled thread chaser, and all I come up with is taps. Is  thread chase simply a bolt, with a slot cut down the threads?

Pretty much!  For thread cleaning, not cutting, you can take a bolt of the correct size and grind 3 flats on it. Will work just fine.

[WHX?? 48,828]

The past couple of builds on large blocks I used after market gaskets and not sure if they had a fire ring or not but they don't leak so they are not going to get torn down to check! I also did not glass the heads which I probably should have done. The one I have on the bench now, a 161, I did glass the head and was surprised at how much I had to work it to get it flat. 

1 hour ago, Greentored said:

old oem Kohler gasket with fire ring out of the trash can and swapped it in.

While I don't promote using them over I have done this also with no problems. Heat of the battle thing and the urge to get it running again. 

 

On the bolts I have also pulled them out in an engine with all different lengths. Ok which one went where they all just got thrown in the parts box. Hence my reason for just using new ones WITH the thick washer as Dan mentioned. Find the thick washers in the drawers at TSC or MMC.  All threads get chased with a standard bottom style tap and depth measured. 

[squonk 41,155]

Brand new Kohler OEM still in the bag No fire ring.

 

Edited April 29, 2021 by squonk

[Howie 886]

At least part of the time the longer bolts go around the exhaust valve. Unless some other

spacer or something. 

I think the gasket set I get from my supplier does not have the head gasket with the fire

ring in but the one you buy seperately does have, So I buy those, but ALWAYS run the 

engine thru a heat cycle and retorque. Gaskets without it require the retorque no exceptions

in my opinion.

[953 nut 55,320]

21 hours ago, squonk said:

Brand new Kohler OEM still in the bag No fire ring.

 

    I bought a bunch of NOS Kohler parts a few years back and most of the head gaskets had no ring.

[Greentored 3,214]

On 4/29/2021 at 9:52 AM, squonk said:

Brand new Kohler OEM still in the bag No fire ring.

 

That is so odd. Perhaps a later, running change or supplier change?  Granted Im still a bit new to the Kohlers, but have torn at least 15-20 apart and have never seen one without the fire ring. How about you guys?

[squonk 41,155]

I have seen the fire rings on only the 10 HP and up.

[Greentored 3,214]

3 hours ago, squonk said:

I have seen the fire rings on only the 10 HP and up.

Aah!  Im a dummy- keep thinking we're talking big block here haha.  Sorry