TIG Welding an Open Chamber Head

[JumboFett]

Hey y’all,

Just pondering an abstract thought… Has anyone ever tried TIG welding the chamber of an open head and machining it into a closed chamber? 
Like, someone has to have tried that… right?

[datzenmike]

I've thought of it. Unless you have flattop pistons a closed chamber head doesn't benefit you all that much other than compression increase. The L16SSS and L18SSS that came with 219 closed chamber heads all had flattop pistons. This maximizes the pinch between piston top and the underside of the head as it's only separated by the thickness of the head gasket.

 

I guess just two crescent shapes, one above the spark plug and one at the bottom. Doesn't have to be exact

 

[JumboFett]

1 hour ago, datzenmike said:

I've thought of it. Unless you have flattop pistons a closed chamber head doesn't benefit you all that much other than compression increase. The L16SSS and L18SSS that came with 219 closed chamber heads all had flattop pistons. This maximizes the pinch between piston top and the underside of the head as it's only separated by the thickness of the head gasket.

 

I guess just two crescent shapes, one above the spark plug and one at the bottom. Doesn't have to be exact

 

Yes, I believe the idea would be to turn a low-performance head into a high-performance variant; taking advantage of the large ports and valves while reducing the pre-ignition issues, so a flat top piston is part of the thought exercise. It’s an especially curious notion given how rare those SSS heads are, and the overall lack of aftermarket head options.
Honestly, if it’s a viable solution it would’ve saved me the trouble of tracking down a 219 head, and it may help future Datsun engine enthusiasts. Nonetheless, it’s a fun thought.

[datzenmike]

Yup it sure is. I had a W58 closed chamber head once. It was in poor condition but got it just to look at. No idea what they were on in Japan, we sure didn't get them. Said 200sx on the tag so '78-'79 Silvia import engine?.

[JumboFett]

5 hours ago, datzenmike said:

Yup it sure is. I had a W58 closed chamber head once. It was in poor condition but got it just to look at. No idea what they were on in Japan, we sure didn't get them. Said 200sx on the tag so '78-'79 Silvia import engine?.

Was that the head with the round exhaust ports and the weird steel insert?

[datzenmike]

Indeed it was. Used on all '78-80 L20B engines. The exhaust ports had strategically placed bumps that supported the steel liner away from the port walls so it wouldn't be cooled by contact with it. The liners would become glowing hot and with the added air (oxygen source) from the air pump it would ignite and burn any unburned hydrocarbons. I was curious and removed the liners while the exhaust valve was out. The first took 45 min to figure out and the last was 15. For a performance build I would remove, for general use they don't affect it much.  

[Stoffregen Motorsports]

18 hours ago, JumboFett said:

Hey y’all,

Just pondering an abstract thought… Has anyone ever tried TIG welding the chamber of an open head and machining it into a closed chamber? 
Like, someone has to have tried that… right?

Yes, many race shops do this. When I was at Rebello, this was done on quite a few GT racing heads, and even some street heads. The head can warp in the process, so be prepared to have it machined on both sides, or figure out how to slow down the cooling process. Some welding shops have a box full of kittly litter which they will put the head (or other part) into and completely submerge the head and let it cool overnight.

[Stoffregen Motorsports]

But...

 

There's also another way to get the chamber to better fit the cylinder bore. Eyebrow the top of the bore to help unshroud the valves. Just don't go deeper than the height of the top ring.

[datzenmike]

What about sealing the thermostat housing and coolant holes for the intake runners (if equipped) and fill with water? Then TIG it.

 

 

[Stoffregen Motorsports]

That would be neat if it worked.  I'm sure on some level it could be done.

[JumboFett]

On 9/28/2024 at 1:26 PM, Stoffregen Motorsports said:

Yes, many race shops do this. When I was at Rebello, this was done on quite a few GT racing heads, and even some street heads. The head can warp in the process, so be prepared to have it machined on both sides, or figure out how to slow down the cooling process. Some welding shops have a box full of kittly litter which they will put the head (or other part) into and completely submerge the head and let it cool overnight.

By “machined on both sides” what exactly do you mean? Like, the top and bottom? (the chamber side and the valve cover side?)

[datzenmike]

Cam towers. If they are not level the cam will be bent while turning. Metal fatigue will make them snap and that's not good for the valves and piston tops.

[JumboFett]

1 hour ago, datzenmike said:

Cam towers. If they are not level the cam will be bent while turning. Metal fatigue will make them snap and that's not good for the valves and piston tops.

Aha… I’d like to think any machinist/welder would be aware of this fact and prepared to deal with it, but it’s good to be armed with the knowledge to ask beforehand.

[gh0stwerx76]

2 hours ago, JumboFett said:

Aha… I’d like to think any machinist/welder would be aware of this fact and prepared to deal with it, but it’s good to be armed with the knowledge to ask beforehand.

Ive done it atleast 5-6  times, I had a 1/2" steel plate cut using a head gasket as a template, they cut the cylinder holes to the outside diameter of the fire rings.head bolt holes get tapped ( I use studs not head bolts) the plate is extended toward the the manifold side about 6" so I could weld a vertical 1/2" plate ( think upside down L) which allows me to mount it in a bench vice. I dont do the machining however, just the welding. None have warped or distorted. first I use clay in one cylinder to establish desired combustion area and shape, then I use this ( https://www.lowes.com/pd/Alumilite-Amazing-Mold-Maker-16Oz/5014914385?user=shopping&feed=yes&srsltid=AfmBOorD0QeRAjWKfc7IUaHPIaSyINjApg2QrsKmH02hZoXMgGWmi6Xa07A ) to make my combustion chamber impression. then I weld it up. once back from machine I use an air motor in each chamber  so that my impression fits each quench area the same. Warping isn't an issue however it's HIGHLY recommended you do a valve job after, including NEW seats. 

Edited September 30, 2024 by gh0stwerx76

[JumboFett]

12 hours ago, gh0stwerx76 said:

Ive done it atleast 5-6  times, I had a 1/2" steel plate cut using a head gasket as a template, they cut the cylinder holes to the outside diameter of the fire rings.head bolt holes get tapped ( I use studs not head bolts) the plate is extended toward the the manifold side about 6" so I could weld a vertical 1/2" plate ( think upside down L) which allows me to mount it in a bench vice. I dont do the machining however, just the welding. None have warped or distorted. first I use clay in one cylinder to establish desired combustion area and shape, then I use this ( https://www.lowes.com/pd/Alumilite-Amazing-Mold-Maker-16Oz/5014914385?user=shopping&feed=yes&srsltid=AfmBOorD0QeRAjWKfc7IUaHPIaSyINjApg2QrsKmH02hZoXMgGWmi6Xa07A ) to make my combustion chamber impression. then I weld it up. once back from machine I use an air motor in each chamber  so that my impression fits each quench area the same. Warping isn't an issue however it's HIGHLY recommended you do a valve job after, including NEW seats. 

Very cool detailed description. Re the valve seats, could they be removed before welding and replaced after?

[gh0stwerx76]

4 minutes ago, JumboFett said:

Very cool detailed description. Re the valve seats, could they be removed before welding and replaced after?

Not sure, im just passing on the machinists advice. I dont mind the extra cost because now I have a brand new competition cylinder head.

[datzenmike]

Might be a good idea to weld before replacing the valve seats if doing so. The seats are frozen and the head heated (300F to 400F) to expand the seat mounting holes before installation for an interference fit after cooling. Heat, any heat near the seats should be avoided if possible.