5-h.p. b&s head work

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ironman

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wanted to know has any one ever ported out one of these heads before and what kind of gain did they get out of it was thinking about trying to do this myself i have a extra L-head laying around the garage and was woundering how much to port out of it.
 

Kenny_McCormic

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Most of the head work i have seen was just milling out the pockets for a higher lift cam, you could check clearances and shave it down for higher compression.
 

ironman

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never ported head on my briggs just went ahead and had them milled down .40 didnt see any more top speed out of it.did feel alittle more mid range power but can not prove it.
 

oscaryu1

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never ported head on my briggs just went ahead and had them milled down .40 didnt see any more top speed out of it.did feel alittle more mid range power but can not prove it.

Hey ironman! I'm interested in doing that for one of my heads also, where can you get this done? Are they called "milling shops" or something?

Thanks alot!
 

ironman

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local kart shop did mine 30.00 for two heads and the gaskets gave me a good deal i think its about 15.00 a head at a machine shop.
 

oscaryu1

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Hmm... I was lookin on a flathead forum the other day, and one guy said that if you were to mill the head, you were going to sacrifice head flow bigtime... and he wouldn't recommend it...

Maybe that's why you don't see much of a performance gain?
 

kibble

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Yes! That's right Russ, it is a bull! Good, now on to the ABC's

 

Russ2251

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just went ahead and had them milled down .40
Don't you mean .040. You would have almost nothing but cooling fins left if you went to .40.
didnt see any more top speed out of it.did feel alittle more mid range power
This would be correct.
I'm interested in doing that for one of my heads also, where can you get this done?
Any reputable machine shop. If you don't know of one, check with an auto parts shop or automotive repair shop for someone they can recommend.
one guy said that if you were to mill the head, you were going to sacrifice head flow bigtime
True enough. For the small amounts you guys are dealing with, sacrifice would be minimal. I personally would not go beyond .030, only because I like wiggle room and don't want to over stress internals. Gasket thickness can be played with (or eliminated) also. Which reminds me...I have to post an update on another related thread...and maybe some SPAM for dinner.
 

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oscaryu1

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Hey Russ - You said that gaskets were more important on 2 strokes than 4 strokes, correct?

And you could use gasket sealant (the type pictured) as a head gasket... right?

How much PSI can that hold?
 

enel1221

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i have ported the intake and exhaust on my 5hp brigg. on the exhaust i took the threads out. i also took alot of metal away so that its a straight shot from carb to piston/spark plug (same with exhaust). this isn't related to the head but i made a custom intake, and bolted 2 chainsaw carbs on, along with a custom straight pipe exhaust. o an also put dual springs on valves, got a aluminum flywheel off a 3.5 hp briggs hoping to get that on there sometime this summer. i'll let you know if it even runs :worried2:

was going to put pic on here but its too big, i'll get it later
 

Russ2251

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You said that gaskets were more important on 2 strokes than 4 strokes, correct?
For simple reason that 2 cycle engines are dependent on a tight seal for processing of fuel/air mixture. If reed plate gasket (for example) were to leak, it would lead to a lean condition and therefore a lack of lubrication as well as a loss of volumetric efficiency.
Other questions refer to another thread which I will address within the next few days.
 

oscaryu1

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I see... (not really)... so would using sealant on all of my engines work good? Or would they blow on my performance one? (lots of compression mods)
 

I like karts

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i have ported the intake and exhaust on my 5hp brigg. on the exhaust i took the threads out. i also took alot of metal away so that its a straight shot from carb to piston/spark plug (same with exhaust). this isn't related to the head but i made a custom intake, and bolted 2 chainsaw carbs on, along with a custom straight pipe exhaust. o an also put dual springs on valves, got a aluminum flywheel off a 3.5 hp briggs hoping to get that on there sometime this summer. i'll let you know if it even runs :worried2:

was going to put pic on here but its too big, i'll get it later


You took my double carb Idea!!

Sounds awesome though, youre going to have to run both carbs really lean, and get a video of ith when you run it. I must see it!
 

enel1221

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me again, last night i tested out the dual carb 5hp briggs, it ran!! one of the carbs is leaking so i'll fix that and then get a video hopefully tomorrow
 
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