40fp head gasket

**RknRusty** Tue Oct 06, 2015 10:41 pm

I started laying the silkspan on my Oriental fuse tonight, and while it was drying I decided to disassemble the OS 40fp to make sure it was clean of any dirt it may have ingested. I used a magnet to confirm that it is indeed an ABN, it is. But there was no head gasket. It's not hiding in the groove of the head, and nowhere to be seen. My floor is clean since the flood, so I know it's not down there. I tried one from my Thunder Tiger 25 and it's too small. I'll see if the one from my 35fp fits. Maybe that's why it's always hard to hand start. Anybody ever ran an fp with no head gasket? It apparently runs fine, but I worry about it leaking. I'm going to order one on the Bay tonight. I'll probably have to do my trim flights without it. I'm guessing it's about .015" thick.
Rusty

Ken Cook Wed Oct 07, 2015 4:37 am

The gasket fits so tightly inside the head, you probably don't recognize it's there. If your that confident that it's missing, put it back together and run it the way it is. A head gasket will significantly change the run that you were experiencing. Head gaskets from OS vs vendors are usually different. OS gaskets I believe are .015". Tower .40 gaskets were slightly thinner about .010". When the head gasket is added, it lowers the compression reducing the power of the engine. This will change the break in power transition from level going into a maneuver and over the top of the maneuver. May not be a bad thing, but the run time will also increase due to you requiring to lean the engine in for more power. Ken

**RknRusty** Wed Oct 07, 2015 11:41 am

Okay thanks, I won't sweat it. I will go spelunking under the table just to make sure too.
Rusty

**RknRusty** Wed Oct 07, 2015 11:17 pm

RknRusty wrote:Okay thanks, I won't sweat it. I will go spelunking under the table just to make sure too.
Rusty

You're right, Ken, it's in there. I knew they could hide but this one is doing a really good job. It's pressed into the groove so tightly, it looks like part of the head. If I wanted to get it out I would ruin it. The only way I can tell it's there is it scratches too easily to be the metal of the head. Anyway the engine is nice and clean, oiled up with a new backplate gasket and a fresh Enya #3 plug.

I'll conclude in the Oriental Repair thread.
https://www.coxengineforum.com/t8667p80-broken-nose-all-fixed-silkspan-time#112672

Rusty

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