How To - Renew Cylinder Head Gasket Sealing Surface

[Save Old Iron 1,566]

Unevenness or warp in the gasket sealing surface of a cylinder head may cause vacuum or pressure leaks in the combustion chamber. If left unchecked, cylinder head distortion may result in less than optimum engine performance and visible symptoms including oil leaks around the head area and possible blowout of the head gasket material. If hot combustion gases are allowed to continue to leak past the aluminum head, erosion of the aluminum gasket sealing surface can occur and render the cylinder head useless.

 

The procedure below explains how to renew a flat(ter) surface on the cylinder head gasket sealing area to prevent defects in the gasket surface from destroying additional head gaskets or the cylinder head itself.

 

Float glass is certainly not the end all argument for a perfectly flat surface but can easily provide sufficient flatness for the purpose of improving the sealing capability of a LGT tractor cylinder head.

 

In preparation for renewing the cylinder head, a few common items will need to be obtained from local suppliers. The surface of an ordinary pane of glass makes a very suitable flat surface to perform this procedure. Several sheets of Wet/Dry 220 grit waterproof paper will be required. Water in a spray bottle will be needed to wet the abrasive paper to keep aluminum debris from collecting on the abrasive paper and clogging the grit prematurely. Wetting the glass pane slightly will allow the paper to "suction cup" itself to the glass pane when the cylinder head squeegees the water from underneath the paper.

The cylinder head pictured below will be used for this process. This is a high compression head from a Cub Cadet 10HP Kohler engine.

To observe the progression of material removed from the head, I apply a very light "guide coat" of black spray paint to the gasket sealing area of the cylinder head. Complete removal of the guide coat will signal the completion of the flattening process.

 

 

 

 

 

First, establish a stable and flat surface on which to lay the glass pane. The float glass I used was 1/4" thick - pretty stout stuff. Edges of the glass were beveled for safety.

 

Make certain the glass surface is clean. Any detectable residue such a grease, dirt or stickers on the glass will cause a dimple in the abrasive paper and prevent the cylinder head from renewing perfectly flat. I usually run a single edge razor blade across the surface of the glass pane to assure no residue is present.

 

 

 

 

 

and onto the back of the abrasive paper. Allow the paper to soften somewhat so when flipped over, it will lay flat on the glass pane and hold the paper in place with "stiction"

 

 

 

 

 

Flip over the abrasive sheet and wet the top side to allow aluminum particles removed from the cylinder head to float away from the abrasive and not clog the sheet prematurely

 

 

 

 

Place the cylinder head gasket surface side down on the abrasive paper. I leave the spark plug in the head to allow for a better grip on the head throughout the process.

 

 

 

 

 

Move the head in an even figure 8 motion across the abrasive paper. Apply a slight downward pressure on the head and inspect the progress every 20 or so figure 8 rotations. The downward pressure applied to the head is approximately what you would use if you were applying polishing compound to car paint. No need for excessive pressure here, let the tools do the work.

 

 

 

 

 

 

After the first 20 swipes, inspect the head to check your progress. Notice the black guide coat is being abraded away on the "high spots" on the cylinder head.

 

 

 

 

 

Another 10 to 20 swipes on the abrasive paper and inspect the progress. The blacked areas are the guide coat still present in low spots between the areas polished by the abrasive paper.

 

 

 

 

 

 

 

 

Another 20 or so swipes and note how the shiny portion of the gasket area is increasing in size.

 

 

 

 

 

Another 20 swipes

 

 

And the final 20 swipes produces a gasket seal area without any evidence of guide coat left

 

 

 

 

 

 

 

 

 

 

 

The head material removed during the process . The slurry produced from this process is also highly abrasive. You may want to keep the slurry away from any nearby hand tools or power tools.

 

 

The final step is to gently wash away any silicon carbide material from the glass pane. Rinse the pane prior to wiping it down so as not to rub any abrasive into the glass surface.

 

 

[Mr. 856 170]

I have to do mine. Thanks for the tutorial.

[Wishin4a416 2,191]

^{Very good advice. I like the color coat of paint idea. The very few I have done, I have done on an industrial table saw top which works well too. Very flat and rigid. I have one to do real soon.}

^Thanks!

[varosd 1,185]

this would be nice moved to the Tutorial section. may need to do this in the future    

[rmaynard 15,434]

^{...The very few I have done, I have done on an industrial table saw top which works well too. Very flat and rigid...}

 

And you can be assured that the table saw top is true (flat) because it is machined. Also, you don't risk breaking the glass. Unless the glass is placed on a completely flat surface, the downward pressure that needs to be exerted on some heads while you "mil" them, can crack the glass.

Edited February 22, 2013 by rmaynard

[Save Old Iron 1,566]

Because this post has suffered from apparent "site upgrade issues". the pic of the plate glass thickness has not yet made it into the post. The plate glass used in this post is 1/4" thick with beveled edges to protect the user from cuts and scratches.

Don't let this process scare you away. You are not "milling" the head, the last time I looked, 220 grit paper is not a good substitute for a Bridgeport milling machine. The process I described abrades off less than 0.002 inch in most cases. The pressure needed to accomplish this is equivalent to compounding a new paint job. Don't rush, let the tools do the work. Just use the common sense any first year 9th grade shop class noob would use. If you do attempt to gorilla the process, the abrasive paper would simply push off the glass before the glass plate would crack. If you trip and fall on any tools laying around your shop, that one's on you!!

A table saw surface is certainly an option. For those who believe all table saw surfaces are flat because they are "machined" probably have never checked theirs. Most manufacturers find it "acceptable" if their machined tops are within 0.003 inches these days (less than what we are trying to achieve on the finished cylinder head).

I included a picture of the residue from this procedure to confirm this is a very "dirty" process with abrasive material released from the wet dry paper. I personally will not take responsibility to recommend using a fine tablesaw to accept the residue off this process. Right tool for the right job, etc. In the end, your tools, your choice.

Finally, a piece of plate glass is much easier than a table saw to carry to a neighbor's house to help with an engine. And all said and done, plate glass is squirrel proof and after your are finished, it can be easily stored in your shop. I'll be happy to address any further concerns about this process.

Chuck

[Duff 206]

I agree - this is definitely "Tutorial" material!

 

Thanks, Chuck! 

 

Duff

[Mr. 856 170]

question.............Are K181 and K181S heads the same? Mine has a few broken fins. I got my hands on a used K181 but I have a K181S. The fins are differant on the two heads but the insides look the same. My old one is stamped and this other one is not. Wondering if I can use the better one with the non broken fins off the K181 on the K181S?

[Save Old Iron 1,566]

question.............Are K181 and K181S heads the same? Mine has a few broken fins. I got my hands on a used K181 but I have a K181S. The fins are differant on the two heads but the insides look the same. My old one is stamped and this other one is not. Wondering if I can use the better one with the non broken fins off the K181 on the K181S?

The "S" head is probably drilled to support a starter generator mount.

[Save Old Iron 1,566]

My apologies to all regarding the initial post. Karl and I are working out an issue on why the images and text get corrupted when updates are performed to the text.

Please be patient, this post will be back soon.

[Save Old Iron 1,566]

For the time being, anyone wishing to view this post in its entirety,

please feel free to stop by at SOI University and check out

http://saveoldiron.47.forumer.com/how-to-renew-a-cyclinder-head-gasket-sealing-area-t2321642.html

[Mr. 856 170]

question.............Are K181 and K181S heads the same? Mine has a few broken fins. I got my hands on a used K181 but I have a K181S. The fins are differant on the two heads but the insides look the same. My old one is stamped and this other one is not. Wondering if I can use the better one with the non broken fins off the K181 on the K181S?

The "S" head is probably drilled to support a starter generator mount.

I will get pictures of the two heads. they look almost identical. The block holds the genrater bracket not the head. although I believe there are a few other brackets to hold it in place.

[rmaynard 15,434]

There is a steel support that attached from the head to the generator for the belt adjustment, and the belt cover attachment tab. The additional fins may have been to help support that bracket.

[WheelHorseSteve 56]

This is wonderful! (excellent tutorial!)  Question -- what do you guys do about the block side of things?  (how do you clean the surface there)  I see marks from the head gasket... leftover gasket material, I believe.

 

Your advice is appreciated, as always!

[Mr. 856 170]

I was wondering the same thing........wondering if this is when a milling machine would be sweet to have?

 

 

 

Alrighty here are the two heads in question. The clean one is off my engine. Has a few broken fins, should sand out ok. The dirty one was taken of a parts motor I picked up.

Has no broken fins but has a few small differnces in fins placement and the head bolt hole area around the hole is larger. Other then that is there any reason I couldnt clean up the dirty one, sand it smooth and use it on my engine? Why would I want to swap? really no other reason then the broken fins. I can make that dirty head look brand new in approx 10 minutes. I have the brackets etc, for the generator.

[Save Old Iron 1,566]

I'm reading your last post as the original head is the one with the bolts used on the SG based engine. If the damaged head finsa are just the small pieces seen in the "fins" pic, I would take a dremel tool with a fine stone and remove the sharp edges from the broken fins and call it a day. If the "dirty" replacement head can be drilled and tapped to accept the 2 bolts seen on the clean original head, renew and use the dirty head.

[Save Old Iron 1,566]

This is wonderful! (excellent tutorial!)  Question -- what do you guys do about the block side of things?  (how do you clean the surface there)  I see marks from the head gasket... leftover gasket material, I believe.

 

Your advice is appreciated, as always!

Start by placing an oily rag down in the cylinder bore so any residue scrapped from the gasket area doesn't end up in the piston ring area. I start with a plastic razor blade to remove most of the rough material and then change over to a single edge metal razor blade to VERY LIGHTLY plane off any residue left behind. I finish with a red scotchbrite pad. This process usually achieves the desired finish.

Checking the block gasket area for flatness is easy with the proper tools. Its a good question tho as I don't think I have ever had the need to check it due to repeated head gasket failures. Once the head is flattened, all my issues had disappeared. A good flat edge or granite surface block designed specifically for this purpose can be used with feeler gauges to check the block warps. I wouldn't attempt to flatten a block using the method described above.