Briggs high hour 11 build

Hey fellas (and any girls on here too!), I am currently building an engine with my best friend/partner in crime that I think you guys will be interested in.
So the engine is an 80's Briggs 11 horse flathead. Nothing too special about it. But it was used on a DIXON zero turn in a lawn business 8 hours a day for its first 13 years, then was given to my friends grandpa who used it on a pull behind mower until last year. The total hand calculated hours are a staggering 31,000 hours without a rebuild (+/- 1000). This thing is TIRED!!
But, we had a worthless (to us) 14.5 ohv Briggs just kinda kicking around. We took the piston and rings out of the 14.5 so we have compression back, a stronger rod that he picked up in shop class, and the higher lift cam out of the 14.5

So now I'm in the middle of eyebrows and porting. Once that's done, we're pulling it apart to clean everything and hone the cylinder and it will be going in his mud mower.

Cool!

Nice! Keeping the governor?

No, I forgot to mention that. We yanked the gov. out while it was open. as long as we're fairly responsible drivers i think it'll be fine. I have an identical 11 on my mower with way less hours, so we call this the hh11 and mine the lh11. Thats just clarification for if I say hh11 in the future, you guys aren't like WTF??

Yeah I think it'll be okay. Got any pics?

Not right now, I'll have to take some when I get home.

Okay. Looking forward to see it. Any idea of what age it is?

Pretty sure its an '83, but I don't remember exactly. Pics late tonight or this weekend.

nice. At least it dont have points. Stock carb setup?

Yeah, for now. We're thinking about maybe a ATV slider carb or even efi from a scooter or something. Possibly even a homemade supercharger made from a weedeater leafblower attachment. air filtration would be the biggest concern though. This is my friend's engine though, so he will do with it what he may

Does anyone know the easiest way to post pics from a mac that were taken by an iPhone?

so intake is done, still need to do the exhaust

I don't think the pics made it. I don't know anything about phones or macs.... I put all my pics on photobucket these days and then link from there. You can hit preview to see if it worked or not before posting if you want to mess around trying to figure it out.

I think you just linked the name of the file, what you gotta do is upload the image to an image hosting website, like photobucket or you could just use servimg that is tied in with the forum.

So images are linked to photobucket. I'm trying to figure out how to link them here.



this is the intake valve. Not perfect, but better than it was.



And the eyebrows. Bad pictures I know, but I took more off than it seems.

Pics still arent working for me?

aargh. ill just paste the link to photobucket

http://illiweb.com/fa/pbucket.gif?o=0

http://illiweb.com/fa/pbucket.gif?o=1

Try this guide here,
https://www.atltf.com/t1525-image-posting-for-new-members Should help ya!

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Ah, can see them now. Looks good

Thanks for the compliment and thanks for the link. That helped a bunch!

Exhaust is done. I took quite a bit out. The valve guide sticks into the port quite a ways but I didn't feel like jacking with that, so I took out some material on the opposite side of the port. Neither the intake or exhaust are perfect, but they are a heck of a lot better than they were.

So quick recap: Ported intake and exhaust, shaved the eyebrows down, cam from an OHV, heavier duty connecting rod, fresh rings/piston, and a carb off of a 12.5 flathead (yet to be done).

We'll compare this engines performance to my stock 25 cubic inch flathead and see just how big of a difference this made. The engine itself belongs to TheGreenHornet, whose account wasn't activated when I started this thread.

Any tips, questions, or comments welcome!

Did you grind on the short radius side of the runners when porting the intake and exhaust? This is the best spot to remove metal for best performance. I made a few vids on small engine mods on my You Tube channel if interested.

I'll check out the vids. What do you mean by short radius side? Is that the side of the port farthest away from the valve guide?

A short radius side of the intake pathway- the pathway goes into the engine and turns up 90 degrees into the combustion chamber. The side of the pathway with the shortest distance on the 90 degree turn is the short radius side.

Drew a quick pic. Pic is of engine block and is the black lines. The pathway or intake runner is blue. The short radius side is orange which is where you want to grind off metal. The purple line represents the original path of fuel/air going into the engine before porting the short radius side. The red line represents the new path taken after you grind away on the short radius side.


How you need to think of it when you are porting is that the fuel/air charge is being sucked in and the suction starts at the piston when moving down. For the flat head engine, has a couple nasty sharp turns. These turns slow down the fuel/air charge moving into the engine. Your goal is to make these turns as less sharp as possible so the fuel/air charge keeps its speed moving through the pathway. When comparing the purple line to the red line, the red line has less of a bend in it compared to the purple line, so the red line will be faster moving going through the pathway. This can be done to the exhaust pathway also.

Flathead engines, OHV engines, OHC engines, have different pathway designs but the principle is the same, you just need to identify and evaluate the sections to do the porting. So the short radius side of the intake pathway will be in different spots on these 3 engines mentioned. My videos cover this and is done on a 5 hp Briggs and Stratton flattie engine. With other mods too, I made a couple vids on different parts of this engine.

Hope it helps