Reverse engineering ohv to be more like flathead
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ezcome-ezgo
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Thepartsguy
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They did the opposite in the 90’s converting 3hp briggs with Honda cylinder heads.
Rat
Well-known member
This is a pointless endeavor that makes exactly NO sense.
WHY would you want to? This is the legitimate question nobody has asked yet.
OHV conversions is a mod first seen in the automotive realm with the Ardun kits for Flathead Ford V8's... but going the other way around is a massive step backwards.
It is mechanically possible but it would be extremely expensive and questionably reliable.
You would need to start by welding up the block to completely fill in the pushrod galley first, as well as relocating the ports. That's a just a lot of TIG filling just to get started.
After filling the galley you would have to bore it for the ports and inverted valves and their seats, as well as machine out a rockerbox in the front of the block to have valve spring access.
Thats just A whole sh!toad of work, or money for the work to be done and zero assurance it will even run right
WHY would you want to? This is the legitimate question nobody has asked yet.
OHV conversions is a mod first seen in the automotive realm with the Ardun kits for Flathead Ford V8's... but going the other way around is a massive step backwards.
It is mechanically possible but it would be extremely expensive and questionably reliable.
You would need to start by welding up the block to completely fill in the pushrod galley first, as well as relocating the ports. That's a just a lot of TIG filling just to get started.
After filling the galley you would have to bore it for the ports and inverted valves and their seats, as well as machine out a rockerbox in the front of the block to have valve spring access.
Thats just A whole sh!toad of work, or money for the work to be done and zero assurance it will even run right
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No, I wasn't talking about converting an ohv to flat head, the head pictured just reminds me of the flat head design with the head blocking the area around the valves. That's all.
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Rat
Well-known member
Oh, well by the looks of it... that's a fairly high compression head. Like if you milled any off you'd need valve reliefs in the piston crown if it doesn't already have them
I replaced it with a normal looking head off a seized 140cc engine.
The engine I'm working on is a 160cc.
Now only if I could find a thin head gasket for a vertical shaft lawnmower engine...
It does seem louder with the 140cc head on it.
BaconBitRacing
Well-known member
You might be able to make one. Look up “how to make gaskets for engine“ or some variation of that. Most auto parts stores carry gasket material. Wether or not it would survive head gasket work is another question. Might be a wild goose chase, might not.
I would probably have to cut one out of thick metal foil by hand, clean up the edges with a Dremel, ect. Hopefully a better, smaller cc head on a 160cc block, timing advance and a big muffler will make decent power.
This is going to be a lawnmower converted to something like a walk behind DR trimmer but with a big saw blade.
ezcome-ezgo
G'me sumthin to write on
Sounds dangerous 
. Keep us updated.
. Keep us updated.
Rat
Well-known member
Your best bet is going to a hobby crafts store and find a big enough piece of sheet copper (copper tooling) and make a gasket from that, should be able to get 0.4mm to 0.6mm pretty easily just don't forget to anneal it.
If you want thinner the only thing I can think of that might be thinner is roof flashing aluminum.
Stock gasket is like a graphite metallic steam gasket and appears to be at least 1mm thick.
Yeah copper will definitely work and I could reuse it like 50 times as long as I anneal it.
Aluminum will be cheaper and the whole engine is made out of it so it should work too.
For now I reused the one on the 160cc block. I loosened the head bolts and let it sit for several days before putting the head, old gasket came right off.
Rat
Well-known member
Sounds like you want what came factory on my 208... 0.03mm stainless steel
That would be kind of cool.
I have a horizontal shaft Kohler 196cc that appears to have a paper thin stainless steel head gasket too.
I was going to put a think gasket on glad I checked before ordering stuff.