Porting a Flathead 5hp, Input appreciated

[gunsup0331]

got started on porting the combustion chamber area, still need to clean up around the valves and polish her up. I will post more pics and updates as i go. The ports themselves will be fun :/ How does JB Weld hold up to gasoline?

my dremel is a single speed, was in a hurry when i bought it, a variable would be infinitely better. those little flat sandpaper discs are BOMB for little detail spots like around the valves. I was able to unshroud them quite well imo, just cut out the step and blended a radius leading to the steel seat area. i nicked the seat a few times due to misjudgement of light when the sun got in my eyes not too bad hopefully it will come out when i grind the valves.

I dinked the HG area in a place or two as well, im gonna dab some JB on there and glass deck it flat when im done. I think im gonna leave the head alone entirely except for decking.

If i dick up this block too bad im gonna search for a steel bore block. the flywheel side bushing area for the crank isnt even a bronze insert on this one although the cover has a bearing in it. Anyone know if they sell a bronze bearing sleeve for the flywheel side of the block?

 

[MotorMind69]

i use the 24 hour jb weld, holds up fine. and i stuff a napkin through the valve guide put the epoxy in there and then put it the freezer for an hour, pull the napkin out and let it sit over night in a cool room.

 

[roccosbike]

The bushing you want is a DU bushing. Nothing but the best

 

[gunsup0331]

The bushing you want is a DU bushing. Nothing but the best

link? google doesnt care about flatheads, unless you are just talking about a generic bushing i can size, which is also fine..

 

[roccosbike]

American Power Sports - Karting Parts & Accessories anything you'll need

 

[middleoftheroad]

Hate to be the bearer of bad news,but you seriously comprimized those valve seats.Decking the block is one thing,digging a valley is another.Most guys just shave the head down,decreasing the cumbustion area buying you a couple of horse power.You've increased it.I dont know the modifications you plann for this motor but im afraid you might need to start with a new block.

 

[5 Horse Fan]

When porting and shaving eyebrows,
the idea is to remove the least amount of metal from the block.

This will help you maintain a healthy compression ratio, which leads to an increase in power.

 

[gunsup0331]

yeah i was thinking the same thing about the seats, if nothing else this will be a practice motor. Phoenix Craiglist has aother 5hp for sale every day.

As far as the combustion chamber goes...the stock design is total shit for flow so i will need to find the compression elsewhere.

All things considered if I cant get the compression back up I will shelve this block for the time being, then sleeve and supercharge it later.

Orrr maybe just not take so much off next time

 

[5 Horse Fan]

It might make a decent SC or Turbo engine block.:shrug:
A thin headgasket helps bump compression back up a little.

 

[gunsup0331]

ok i just went out and took another look...
The picture makes it look like there was a TON of material removed but im thinkin I lost maybe 1cc...Looking at the head i think i can deck enough out that when combined with a thinner HG will be able to get me adequate compression. Then i will need to clay the motor once i get the cam and piston installed. Im gonna CC the whole deal when im done for reference as well, so i can have a better idea of the actual compression ratio.

Anyone know the stock CC for the combustion chamber? Total including oem HG, assembled?

 

[middleoftheroad]

As far as the cumbustion,its perfect..for a 5hp motor.The Briggs 5 horse is a great little motor.The only weak area's on the motor in my opinion are the stock rod and strangely enough,the valve area.

 

[Phantom]

got started on porting the combustion chamber area, still need to clean up around the valves and polish her up. I will post more pics and updates as i go. The ports themselves will be fun :/ How does JB Weld hold up to gasoline?

my dremel is a single speed, was in a hurry when i bought it, a variable would be infinitely better. those little flat sandpaper discs are BOMB for little detail spots like around the valves. I was able to unshroud them quite well imo, just cut out the step and blended a radius leading to the steel seat area. i nicked the seat a few times due to misjudgement of light when the sun got in my eyes not too bad hopefully it will come out when i grind the valves.

I dinked the HG area in a place or two as well, im gonna dab some JB on there and glass deck it flat when im done. I think im gonna leave the head alone entirely except for decking.

If i dick up this block too bad im gonna search for a steel bore block. the flywheel side bushing area for the crank isnt even a bronze insert on this one although the cover has a bearing in it. Anyone know if they sell a bronze bearing sleeve for the flywheel side of the block?

Ima tell you a secret recipe i use to juice up flatheads. 68.9hp aprox

1st make the intake port 4" wide and ram a pvc tube in there.
2nd dont forget the velocity stack without it you will lose rice points.
3rd instead of running gas, go to a local fast food and grab as many chicken fat as you can thats a 15hp increase over gas. BOOM!!! Head Shot
4th if you want more street rep put some honda stikers in it that says vtak yo.
5th when you ridin don't forget to shout " Ima Firin Ma Lazer" that will give you .002 mph alone.

Good Luck. LOL :001_tt2:ut:

 

[Ibanez616]

If not already mentioned, you need a DU bushing, or Depleted Uranium, much better than brass. If you wants to increase compression you could always use a 4hp head.

 

[gunsup0331]

????????????

i dont know where you are going with that but thx for the constructive commentary. fwiw every high performance engine i have dynoed has performed better with a velocity stack when applicable, its hardly ever a BAD idea......The last Honda engine I built was around 120hp per liter naturally aspirated so "vtak" ftw definitely lol

If not already mentioned, you need a DU bushing, or Depleted Uranium, much better than brass. If you wants to increase compression you could always use a 4hp head.

Im having a hard time telling if youre joking or not, obviously the depleted uranium is total shit and from my thus far limited research ppl are saying the 4hp head kills flow...Bronze is used in bushings, not brass...where you going with this?

 

[gunsup0331]

The bushing you want is a DU bushing. Nothing but the best

oh i take it youre joking. i guess if you dont know what the hahahaha youre talking about you can just invent a snarky response to cover your incompetence?

that website blows btw

EDIT: thanks to the people who have not been choads so far, I didnt think this would turn out like the car forums but apparently theres douchenozzles everywhere you turn. I dont mind constructive criticism. So lets keep it constructive

 

[middleoftheroad]

Using a 4 hp head was a pretty common swap to gain compression.So,that's no joke.Making one BIG modification that doesn't work with the motor(cam,valve,valve springs,carb,etc.) is not the way to go in my opinion.You want the modifications to work together for best result.

 

[Ibanez616]

Wow dude, easy. We are all just trying to help. I have heard that the DU bushings are the best, so that what i would reccomend, and yes i meant bronze, not brass. The 4hp head will limit flow, but you will gain compression.

 

[roccosbike]

Sounds like your the kind of guy that really appreciates input and by the looks of your amazing talent that engine will be screaming in no time.Maybe you should research things a little more before you throw your mouth in gear.Have a good time on your build.

 

[rebelyell]

Dual bearing > DU, IMO, but, DU > standard bushing for sure.

Pssssst........ 4 horse heads kill flow. :hammer:

 

[gunsup0331]

Sounds like your the kind of guy that really appreciates input and by the looks of your amazing talent that engine will be screaming in no time.Maybe you should research things a little more before you throw your mouth in gear.Have a good time on your build.

okie dokie. So do you even know what depleted uranium is? It is an extremely dense radioactive material used in armor piercing rounds and also a controlled materiel. I hardly believe it is being used in wide ranging bushing applications for the general public.

Ive found "DU" bushings but i can guarantee there is no depleted uranium in there, and im still looking for a Briggs application or at least a vendor that will sell a suitable bushing of a specific dimension. I came on here as part of that "research" you mentioned and got a bunch of half-answers and sarcasm. Its difficult for me to weed out a real answer from sarcasm when im not familiar with the specific nuances of these engines. Sooo input IS appreciated, as long as i can use it and it is specific. IE: "go to this website xxxxxxxxx.com and they have these DU bushings you can press into your crankcase."

anywho, im still open to real suggestions and guidance, links, etc. Once again thx to those who have contributed thus far with the exception of "phantom" whos post was entirely facetious.