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 Briggs Flat Head Build

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gearheadmike
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gearheadmike
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PostSubject: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 1:14 pm

ok so i got an old 11hp flat head engine i was woundering if theres anything i could do to make it run better prot it?/head work? with out spending lots of $$ id rather have the i/c but i dont.
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AcreFarm
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 1:55 pm

Is the engine a 25 or a 28 ci? The first 2 numbers of the model # will tell you.
If you have a 28 you can bolt a 25 head on it & raise the compression a bit.
You can clean up the intake port, but don't over-size it or polish it. Just clean up the rough castings.
The exhaust port can be cleaned & polished, but again don't go bigger.
You can smooth out the "eyebrows" between the valves & the cylinder
You can help oiling some by slightly enlarging the oil return hole (behind the breather)
Some people swear that fire-slotting the head can help, but I've got no input on that one... never tried it.
If the engine is old enough to have points you could eliminate them by fitting it with a newer coil.
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gearheadmike
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gearheadmike
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 3:40 pm

The engine is a 11hp
Model # 252707
Type # 0652-01
Code #83040811

I have a 12hp I/C but has a hole through the block,Unknown condition for the rest as head/pistion/crank/cam/valves/ect ill have to wait and tare it down to find out but that engines numbers are these.
Model # 281707
Type #0415-01
Code #90071911

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blanket80
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 3:51 pm

It all depends on what you want to do with it. It's helps to know that flatheads love flow, even more than compression. When I built my 8hp flatty I removed the governor completely and plugged the hole with a bolt. Then I polished the castings off of the connecting rod to allow oil to flow down it quicker, to keep it cooler. I also opened the intake port up to the size of the new gasket for it, AKA gasket matching. I also removed the rough castings up near the valves. Then I ran a small hone through the intake port to give the fuel a place to lay. And as Acre said I did shave the eye brows off, and then polished the block. As for the head, I had it milled so that it was even and not warped. Then had it fire slotted. I also put an exhaust valve spring on the intake valve, to keep it from floating at high RPMs. You can also advance your timing, by getting an advanced flywheel key.

I know that may be alot to take in, but I hope it helps. Feel free to ask me if you have any other questions.

P.S. Acre, I'm not sure if the fire slot helped or not. But everything combined woke that little 8hp up tremendously!
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gearheadmike
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gearheadmike
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 4:08 pm

honestly i just want to kinda build one up, maybe down the road go on a pulley swaped tractor for just mostly like stright aways
is there any other briggs engine i should keep an eye out for to snag parts off? like heads/carbs/that stuff?
ik alot of guys like the ohv but these remind me sorta of the old flathead car engines and i like them lol
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blanket80
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blanket80
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 4:10 pm

The 12hp briggs are one of the best flathead engines to build.
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gearheadmike
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gearheadmike
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Age : 33
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 4:28 pm

yea ill prob look for a 12hp I/C i got one just dont to pull it of a compleat lawn mower.
interested in getting better oil flow,and what gasket matching and porting can be done to these?
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blanket80
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blanket80
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitimeJanuary 11th 2012, 6:54 pm

I just cut my intake port to the inner diameter size of the gasket.

Here is a subforum all about building briggs flatheads for racing applications.. http://www.heymow.com/index.php?board=5.0
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PostSubject: Re: Briggs Flat Head Build    Briggs Flat Head Build  Icon_minitime

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