PORTING HOW-TO: Subaru dog leg exhaust port!

The Subaru dog leg port is the most challenging port by hand or by cnc machine because of its complex shape! Watch Dave show you how to take on this challenge and he even shows you how to make fins in the port!

[@markgeletzke6328]

Thank you, I've never seen anyone else put a fin in an exhaust port. But it makes perfect sense.

[@headgames]

Welcome! Most people can't do it or know why to do it so they don't. Dare to be different and learn brings us to these things.

[@Jim-gs3jo]

The Subaru dog leg port is very similar to the Harley Milwaukee 8 exhaust port.The M-8 is what I do the most of these days. I also use the 3/4" super spiral ball for most of the M-8 port. It truly does a great job shaping a round port. I was looking at videos to see if anyone might have a different perspective on working this type of port. I saw a lot of videos by guys who have very poor technique, or don't seem to know what they are doing, or why they are doing it. Your approach is the same as mine. Thanks for taking the time to post your videos. As I am slowly approaching retirement from the business it is gratifying to see you helping to develop a new generation of cylinder head specialists. (I am not planning to retire, but I'm in my 70's, so it's inevitable)

[@headgames]

thanks brother!

[@papapetad]

That just looks right. I still know NOTHING but I'm working on that, one video at a time for now. Thanks for taking the time to share some of your knowledge.

[@thomasmclaughlin3863]

That is just beautiful work. Must have taken thousands of hours to develop these techniques.

[@GroovesAndLands]

I just reworked some SOHC EJ25 heads this weekend. Heads were off for leaking head gaskets (of course). Engine has 180k so no way am I putting it back together without retouching the valves/seats - which means there's no good reason on earth not to spend a few hours giving the bowls/ports a good once over. I definitely didn't work mine as much as Dave did here, but it was real nice to see the basic areas where he pays attention. I widened the port roofs where the pockets transition into the ports. On the dogleg ports I didn't grind nearly so much as Dave to the point where I was beginning to create a fin - but I did lay back short side radius of the dogleg - then blended it into the roof. The short side radii of the intake ports had a sharp edge. I laid those back and hand-sanded the final radii with 80 grit emory cloth. Anyway, thanks for showing this to us, Dave - served as a nice guide to know specifically what areas to address and what to leave alone. Hopefully mine picks up a couple horsepower; it sure could use it!

[@headgames]

That’s awesome that I could help!

[@kevinsikora6915]

Keep the Subaru content going!. In the process of rebuilding mine love the content!.

[@GroovesAndLands]

The name I've always used for my 1/4" rod with a slit in the end for holding a strip of crocus/emory cloth is "the magic finger".

[@headgames]

I like it!

[@pab3783]

Love the Subaru content.

[@goyocarreras]

Hello again, very good job, I have to tell you that I have learned with all your videos, improve my work technique. Also, thanks to his explanations, I bought a Makita machine and I have to say that I am very happy, I had a Bosch and it has no point of comparison. Thank you very much and keep uploading videos. Best regards Goyo

[@headgames]

So happy to read this! Thanks for watching and the kind words!

[@jonathoncouchey7151]

Hmm,yhamk you for all of your Greatips. For Your standard ohv 2v pushrod engines generally you don't need the 1/2 however i think I will use your flapper idea on the ssr.

[@headgames]

Thank you! We don't use a cartridge roll on a short turn ever. Ruin it quickly.

[@boostedpower5417]

Those burs are bad ass! I gotta get me some so i can screw up my stuff 😊

[@headgames]

lmao think positive

[@TheDeadMan3848]

Beautiful work!

[@headgames]

thanks!

[@jonathanhurdthe]

Awesome vid & awesome product

[@headgames]

thanks!!

[@ovalwingnut]

You R the "Port Whisperer"...

[@headgames]

hahaha thanks!

[@10awkwardpenguins]

Great video, easy to understand. This is the only channel that i trust after seeing a lot of people gouging out their ports. What are your opinions on porting Nissan's vq35de heads?

[@headgames]

thanks for the kind words! We stopped doing the VQ a few years ago, but we set world records with it from day 1 in boosted applications. It's a great head that doesn't need much to make it work great up to 2000whp

[@10awkwardpenguins]

@@headgames thank you for the reply, and that's good to know, that helps me make my decision on my build.

[@deadlife93]

Awesome video guys! Gonna have to check out you other videos. Just picked up some b25 heads and was thinking about porting the exhaust side. But im guessing its better to do both in tandem seeing as they work "together". Subscribed!

[@headgames]

yes! Thanks for becoming part of our page!

[@JaapGrootveld]

Clear and simpel, Tanks.

[@jmoemorris4133]

I have a question? My Yamaha FJ 1100 1985 has this exact port shape and I am going to use your method to port the head my question is that I am welding the intake ports on the top and sides to raise the ports up about .500-.700 of a inch so would you suggest I stay on your path with the porting and stay inline with the stock port size to start? I will be going from stock 36mm carbs to aftermarket 41mm carbs. (Note) This vid was kickass as I was wondering about this particular port design and how to address it, so thank you very much for this lesson.

[@bluegizmo1983]

What kind of flow improvement do you get with the dog leg ported like this? Has that been measured vs stock dog leg port?

[@headgames]

picks up 20-30cfm throughout the range

[@Kyrazlan]

I don't see how adding a fin in the exhaust helps with air speed. If you wanted airspeed you would have just kept the cross sectional area of the port constricted. That fin just looks like it follows the casting and not how the air would want to flow through the port.

[@timjenkins6049]

I've yet to see you do a pre / post velocity video, as well as CSA pre / post showing symmetry and actual gains. When will that happen ?

[@headgames]

I don’t see that in the future of this channel. Here to educate and showcase. The dyno and the world records can be the proof it works.

[@timjenkins6049]

@@headgames Awesome, which Subaru powered record do you currently hold ?

[@headgames]

@@timjenkins6049 we have been involved with many records on many different platforms. Not just Subaru. I believe this record still stands. kzbin.info/www/bejne/iKOzoYasarCVfpYfeature=shared

[@SubieMayhem]

Hey, on the dogleg port do you get the very back to the right of the bowl from the dogleg port. It seems to be very hard to get with out deflection. I kinda skipped that spot about the size of a quarter. I know this is an old post maybe someone else can answer.

[@CneyTMS]

So port matching is inadvisable. But what about the big port heads? They have a couple MM bigger ports. Are those bigger all the way in? Can't you get a regular port EJ to that degree?

[@CneyTMS]

I see that this is the USDM ej25 head which already has similar ports to the bigport.

[@jmoore9806]

Oh crap.....i made my exhaust header port 1mm bigger 😔.....is the performance loss really that bad ?

[@headgames]

The header? I don't think .020 a side is going to hurt you.

[@saki10man]

@headgames what are the advantages of this porting? What would this do for head heads for up to 600hp?

[@headgames]

It would hurt torque under 800whp. Not recommended. Only a pocket port for 600whp.

[@XtremeBoomer2007]

the fins confuse me because I think of air like water..without a wall being there dividing the air into each valve from the start through the exit isn't it just acting like a ramp? If you could put colored smoke and send it through I imagine it's a chaotic mess anyway but in my mind I just picture the two sides converging into turbulence...no? Have you ever experimented with a spiral....same way you make your fin but making 4 or 5 like a gun barrel?

[@deadlife93]

The spiral idea was going through my mind while watching this. Like what if you start a spiral or however many on the right side and send it up and around, which send the air spiraling into the left side port after the divider and vise versa starting from the left side going down and around into the right side port after the divider. That'd probably take alot of work for the same or slightly better performance/flow...so maybe not worth it?

[@headgames]

That spiral idea would be cool to try but hard to execute.

[@victorsabala2108]

Is possible 🤔 to just use sand paper with out using a burr and finish up 320 or 450 sand paper 📃

[@headgames]

I think that is a total waste of time and effort. There is no gains unless you are moving material. And even less gains or possible losses doing it to 450 grit and spending your life doing it by hand.

[@jonathoncouchey7151]

There's a reason why professionals call it port matching.not gasket matching.

[@chief8269]

Do you have to flow bench every port once you are done to balance everything?

[@headgames]

Hey Chief! No sir. Jesus could come back and he wouldn't be able to get the ports to flow the same. They don't flow close to each other from OEM either.

[@chief8269]

Thank you, I’ll be reaching out regarding my old 02 wrx ej205 heads. I would like them freshened up, hopefully they aren’t cracked. Is there a huge flow difference between these and the Sti heads?

[@moonchildsixsixsix]

do you hit the intakes with scotch brite or leave it with the 60?

[@headgames]

Scotchbright the intake too. Just removes the glue from the cartridge roll.

[@classicb100p]

Where to get the tools used in this video

[@headgames]

Www.headgamesmotorworks.com

[@syukrimusa1850]

can I polish mirror shine in the intake port?

[@headgames]

Never mirror shine kzbin.info/www/bejne/eZXLhIKBj7WMqM0

[@XtremeBoomer2007]

I always assumed you wanted the intake a little rough to help mix the fuel and keep it off the walls, but maybe doing the exhaust would help keep carbon buildup off. Polish the combustion chamber maybe for the same reason.

[@trxtech3010]

Ohh man.. Idk, I have ported a few 2019-2021 CRF450R dirtbike Heads and the exhaust port is a pain in the a$$. I think they might have this one beat when it comes to pain in the A$$ lol!

[@headgames]

this is the toughest in all of the import heads in my opinion.

[@trxtech3010]

@@headgames It looks like a pain in the arse for sure.