Hey everybody, it's KartFab here, and today we are going over some performance mods for
your briggs and stratton 5 horsepower flathead engine.
The two modifications we are going to do today are 1) shaving the eyebrows, and 2) porting
and polishing the intake and exhaust.
So let's go check it out.
(shave eyebrows) So what does it mean to shave the eyebrows on a briggs and stratton 5 horsepower
flathead engine?
Well, basically, all it is is removing material between the intake valve and the piston, as
well as the exhaust valve and the piston.
What that will do for you is that it will actually increase your flow so you can have
a better performing engine.
The downside of that is that it actually decreases your compression a little bit.
You can overcome that through some things we are going to look at in another video later
down the line.
The first step is to put on your head gasket and mark where you want to have your eyebrows
shaved.
It is very important to shave only where the headgasket does not touch, and that you just
do a gradual slope.
Your tools that you need to have is a rotary grinder.
I just have a dremel with a sanding disc, and a polishing disc.
Go very slow, just making a side to side motion, and you only want to slope up to the top of
the cylinder.
You do not want to cut out where the cylinder is or you might ruin your block.
You do all the grinding first, vacuum it up.
That is the initial grind with the heavy grit.
Then you put on a finer grit or a higher number grit sanding drum.
You just do the same thing.
Smooth it all out.
The idea here is just making sure everything is smooth.
The final step is taking the polishing disc, and making sure everything is super smooth.
You can do this with or without the valves in it.
I did it with the valves in place because I am going to be replacing them.
You don't want to run into the valve seats.
That is it for shaving the eyebrows.
When we are talking about porting and polishing, we are talking about intake and exhaust.
The engine, when it is built, has castings in it that need to be knocked down.
I am not going to do a very strong port and polish job.
It is going to be very mild just to knock down the castings.
The tools I used to port and polish the intake and exhaust were basically some bits for carving
wood.
A sanding drum, and a polishing drum.
I also used tape to tape everything off so you don't have all this junk going into the
engine.
So this is the exhaust.
It has all the junk (castings) in it.
The intake.
All these little bits of casting and sharp edges are protruding.
As I mentioned, you don't want to have stuff go into the engine.
I just broke some q-tips in half and shoved them down the valve guides, and put a rag
in there as well.
I used this bit here to grind out the casting . I roughened up the intake, polished up the
exhaust here.
This is just for demonstration purposes.
I used this bit mainly to rough out those sharp edges there.
Just remove the casting burrs and edges.
This is the exhaust before and after.
This is the intake, before and after.
You notice I removed just a little bit of the burrs.
Kinda filed that down.
You don't want to run into the valve seats when you are grinding.
That is very important.
This is the intake here, make sure it is not super smooth.
That is it for porting, polishing, and shaving the eyebrows.
Hey everybody, thanks for watching this video.
If you like it, please give it a thumbs up.
Comment below.
Let me know in the comments if I did a pretty good job.
This is the first time I have actually ported and polished a small engine, as well as shaved
the eyebrows.
I have seen a lot of different pictures on it, and I wanted to make sure I am doing it
right.
The next video we are going to look at is tearing this engine apart, and putting all
of these awesome performance parts in it.
We are going to go over the flywheel installation, arc billet rod installation.
We are going to look at cams, as well as installing valves with higher tension valve springs,
and putting on a thinner head gasket.
Please subscribe if you haven't already, and we will catch you next time.