Cylinder Head Porting - Post Pictures Here

[KartFab]

So I've been looking into porting a few of my heads and haven't ran into any good how to guides or resources for the OHV heads. Anybody have some good advice before I start porting? I dont want to hog out the ports and lose low end torque, but want to get a little bit more flow than the stock head. Any suggestions would be greatly appreciated. Pictures would be EGG-SELENT.

Im assuming the methods would be similiar across heads e.g. predator 212, honda gx390, honda gx200 etc.

Here are a few pictures of professionally ported heads i lifted from a facebook post.

I feel like I know next to nothing about porting the OHV heads.

 

[bob58o]

If grinding the port or bowl area from the combustion chamber side, make sure to protect the valve seats with tape and be careful or be prepared to get a valve job after.

If doing a valve job anyway, do it after porting.

 

[Whitetrashrocker]

I put some pics in my dingo post, Bob has gabbed his to death, and there are a few others around here that have done it.

Not really hard just time consuming. Get your Dremel or rotary airtool, and get after it.

Basic concept it to make a smooth path. There are casting edges that can come off. Trim around the valve guide and make it aerodynamic. Round off the hard inner edge...

The exhaust should be mirror polish and the intake can be left a little rougher.

Long arbor bits are extremely helpful.

And while your doing head work take a few thousands off the head. Compression and a easy flow head really wakes up the engine.

 

[Hellion]

From what I understand, the intake ports can be substantially rough. You don't want polished, glistening surfaces in there at all.

 

[anickode]

From what I understand, the intake ports can be substantially rough. You don't want polished, glistening surfaces in there at all.

The more the air/fuel mixture gets mixed up, the better the burn.

You don't want RESTRICTION, but some turbulence can be a good thing. Rough surfaces, sharp corners, and obstructions break up the laminar flow and improve mixing, but when it comes down to trying to cram as much air as physically possible through a given size passageway, the only way to achieve that is by promoting laminar flow, which means wide bends, smooth surfaces, no obstructions, and no sharp corners.

Some auto engines have throttle plate type butterfly valves in the manifold right before the injector to make the air tumble and swirl to improve the fuel/air mixing, particularly during cold starts and cruising. They are helpful, right up till they become a hindrance, ie, when you're trying to eek out more power from the engine.

 

[bob58o]

The Harbor Freight mandrels suck if you use this kit.
https://www.harborfreight.com/sanding-cone-set-52-pc-62394.html

Get the one from Eastwood.
http://www.eastwood.com/engine-port...UHpqiOjA53EowSLTvcL7PhBxbLuTngq4aAsywEALw_wcB

It comes with (2) 4" and (2) 6" mandrels. The offer other sanding cones too. I think I picked up 80, 120, 240, 320 grit from Eastwood IIRC.

---------- Post added at 08:38 PM ---------- Previous post was at 08:35 PM ----------

And while your doing head work take a few thousands off the head. Compression and a easy flow head really wakes up the engine.

I've read that a good valve job also really helps the flow a bunch on these small engines. I'll have to take their written word on that, I'd love to see if a valve job make noticeable HP difference on a DYNO or flow difference on a Bench.

---------- Post added at 08:48 PM ---------- Previous post was at 08:38 PM ----------

Ohhhh, I really like these for finishing up the exhaust and combustion chamber. 180g, 280g, 320g abrasive finishing buffs. They start out kinda big and are tight in the port, but after a few minutes they get small enough to fit in some of tighter nooks.


https://www.dremel.com/en_US/produc...-finishing-abrasive-buffs-180-280-grit-2-pack

https://www.dremel.com/en_US/produc...lock-finishing-abrasive-buffs-320-grit-2-pack

I think I leave the intake at 80 grit, the chamber at 320 grit, and the exhaust as polished as I care to make it (which is also usually 320 grit - because I'm lazy).

Below is the exhaust port on the NR Racing Hemi Head.
I believe he bead blasts to finish???

 

[bob58o]

And the intake

 

[bob58o]

Since I took the valves out...

 

[Hellion]

Agreed, anickode, on your above post.

ALSO, you can basically go HOG WILD on porting/polishing the exhaust port as opposed to the intake if I'm following the popular consensus (and the experts) right. The exhaust gases are best dealt with swiftly so get-them-out is the order of the day. You can also have a smooth, polished port with no issues.

Of course you don't want the exhaust port hogged-out in such a way that the inside diameter or dimensions are larger than the exhaust pipe, for example, and you create a bottle neck or other flow issues where the pipe is joined to the head...
Be interesting to see some examples of a Cylinder Head Porting "Hall Of Shame".

Anyone paying extra special attention to the exhaust porting?

 

[bob58o]

Seems to make sense. The exhaust is much more "hogged out" than the the intake on the head from NR.

 

[KartFab]

Okay, so the more I am learning about this, the more reserved I am going to be with material removal. A mild port job on the clone engines - according to ARC Racing video here: https://www.youtube.com/watch?v=rj8V9wiOh40

Expected Gains:
Should give a 200 rpm gain and .3-.5 hp increase in HP for the honda gx200 clone engines, or about a 7.6% increase is awesomeness, mainly found in the mid to high RPM range.

Port to Bowl
Now from what I get in the video where the port transitions to the bowl, there are sharp edges that need to be blended into the bowl. AKRA (racing) rules don't let you jack with it too much, hence the talk about dont touch the guide etc.... but we dont care about that.

Roof/Floor Allusions
Seems like he spends about 3-5 seconds talking about "lowering the floor on the intake and raising the roof on the exhaust" but doesn't elaborate on it sadly.

Port Cleanup
Video also talked about cleaning up the port but not so much changing the size, because port size is equally as important as these CFM numbers, because intake and exhaust velocity are crucial to efficient operation, and if you hog out a port, it kills velocity, which kills low end torque (but can see improvements on the high end).

My Thoughts So Far...
Was a great video, ill clean up the ports without enlarging them, keeping a somewhat rough texture on intake, will polish up the exhaust port. Transitions to the bowl will be rounded off to get rid of the sharp corners. This will be a bit different from that NR racing head because I want to retain all of the low end torque with a compromise to not get the 'max flow" but enough flow for improvement at mid to high without the sacrifice of torque loss on the low end. Also will need to revisit jetting once the port job is done.

Im feeling a tiny bit more confident about this now that I think i can actually do it without screwing anything up.

 

[Whitetrashrocker]

Next step. Grab the Dremel!

The reason you can go a little larger on the exhaust side is the air had expanded! There more of it.

 

[Mammoth]

Filling in the inside turn of the exhaust port can increase flow. Weld it up or use high temp epoxy.
Here is a gx390 head I welded.
The port ends up smaller. but it flows better.

 

[bob58o]

Filling in the inside turn of the exhaust port can increase flow. Weld it up or use high temp epoxy.
Here is a gx390 head I welded.
The port ends up smaller. but it flows better.

Just curious. How do you know it flows better?

Jody from ARC says he thinks the ports are too big on some of these heads, but I never seen something like that done.

 

[big-d]

If this does not belong here because it is not really "Head Porting" feel free to delete.

Here is an 11hp flat head briggs and stratton engine I cleaned up the ports on. (just knocked down the rough edges and sharp angles. I cleaned it up a little more after the pictures were taken as well.

 

[big-d]

Again, these were detailed a little more after the pics were taken.

 

[Mammoth]

I spent a little time with a few gx390 heads on the flow bench.

[/url][/IMG]

Here are some numbers comparing a stock head verses the ported head.
It shows the exhaust port had a pretty good increase in cfm.

The intake had an increase, but it started to taper off like there was some turbulence happening. It looks like it could be improved on.

[/url][/IMG]

What I did was try to straighten out the exhaust port by grinding the top side of the port as far as it would go.
Then in steps I would add a little material to the bottom side of the port and test for a increase in cfm. Kept repeating until the cfm starts to reverse, and that tells where to stop.

In the end the port looks like it does.

[/url][/IMG]

 

[KartFab]

More Pictures of porting cylinder head

Found a few more head porting pictures from brad hill, an engine builder on facebook.

 

[KartFab]

JPRW Racing, Inc

 

[zogthegreat]

Then in steps I would add a little material to the bottom side of the port and test for a increase in cfm. Kept repeating until the cfm starts to reverse, and that tells where to stop.

Hi Mammoth,

Stupid noob question. Could you use something like JB Weld to achive the same results?

Thanks!

zog