This is something I would like to do but can not afford to pay a shop. Does any one know a good how-to website for this topic? Can you do it with a basic tool that the average person has in thier garage?

I could post questions all day but if someone can explain how. Then that should explain most of my questions.

 

A die grinder, templet and a steady hand. i wouldn't do it by your self your first time....

 

Hold on, I am uploading some pictures...

 

find someone that has the templet, and that has done it before, I praticed on a bad set of housings then I did the good set. just take your time.

 

Many people have a Dremel tool, but it takes a long time. A die grinder is faster but takes more experience.

 

Air tools are great...

 

Ok, so porting a motor is pretty hard, the first time. You get nervous, the shakes, the "what-if's".

In all actuality it isn't terribly hard.

In this picture we have the stock 12a port. Specifically, this is the rear iron.



It is a nicely shaped port. The shape of the port determines the timing. From the bottom small end to the top end is similar to a piston's valve. As the rotor sweeps past the port, it is opened, as when a piston is moving down and a valve opens up. You do not want to port too high, as you will begin to cut into the compression cycle, which is bad unless you have it tuned to take advantage of it (6 port motors). Do you see the grooves, or lines in the shiney surface? Those are from the seals. When porting, DO NOT port into the oil seal land area. You will end up sucking in oil, and you know that is bad, right? More on porting limits later.

Streetports are just an enlarged stockport.



The port on the left is a stock port, the one on the right is a street port. I ripped this picture off the internet, so this is not a 12a port. These ports are called "Streetports" because they are a streetable way to add more power without sacrificing too much. The only thing you MAY notice is a drop in gas mileage.



This is a bridgeport. I cracked open an engine I got from a guy and found this. First thing you notice is the long parenthesis shape over the port. Why is that there? This adds more airflow... at the expense of overlap. Overlap is when the exhaust and intake are open in the same chamber at the same time. Not good. You want clean air and fuel going in the engine, not dirty exhaust air coming back in. It is kind of like breathing into a paper bag. Still get some oxygen but you can tell if you brushed your teeth lately or not.

This bridgeport is no good. Why is that? Well, that little eyebrow (or... a bridge) is too skinny. The bridge is there to keep the circular corner seal and slender side seals from falling into the port. Bad news when that happens. Well, you would want enough of a bridge to keep the corner seal in, but you don't want it skinny enough to where you run it for a few thousand miles and the bridge cracks. There is a way you can keep the corner seal in the rotor, but that is a secret

This port differs from the streetport, as it will raise the idle up a lot. Instead of the smooth 750rpm, you are looking at double that. ATLEAST. This is due to the larger port shape making the air move slower. Speed that air up (by raising the idle) and it will hold its idle. Bridgeports are fun, and are somewhat compared to 2 stroke motors. Once the rev's begin to rise, you will feel a surge of power (3500-5000+), depending on the port timing) as the port scavenging begins to work in your favor. Redline will rise as well, depending on your porting. You WILL need modifications to the engine to handle the increased RPMs.

Next up is a J-port. This is a work in progress, and I have already semi-screwed myself on this one.



A J-port is basically a HUGE bridgeport. The J-port was invented because at one time or another, Peripherial ports were banned in the racing league (ITA or IT7, someone can correct me on that) and teh rotary had to be side port fed. Enter the J-port. This is one big #$%&ing port. Idle is generally higher than a bridgeport, as well as the power and RPM band. Imagine all the characteristics of a bridgeport, only more.

With doing a J-port, you cut past the inner coolant seal. Read up on how to get around that, it will be a lot more typing for me.

Finally, a peripheral port.

This one was done with a hole saw. Literally.



It looks ugly, but I will still need to clean it up a bit and get a sleeve in it. With a Peripherial port, this is maximum power. Big hole going straight into the rotor. No 90* turns or anything. This is generally made for pure racing applications. This is a loud and fast port with a lot of overlap. Again, depending on the size you can have an almost streetable idle or 2000rpm idle. With this port, it gets cut into the housing, a tube is then inserted and fitted and the water passage sealed along with the side ports. Some people even use the side ports in conjunction with the PP.

The one shown will be a loud motor (PP's require very little to no muffling to get the power out of it) with a high idle. Search up the ports on a Suzuki RE-5 or the original cosmo, and you will find a more streetable port.




Now, how do you port? Well, I do it with this:



A Dremel. Found at your local hardware shop at varying prices. Word to the wise: You will be porting IRON. I bought a cheapo $30 dremel, which got me through a port and a half before burning up. The one pictured set me back around $80, and have not had a problem with it. Now you need the dremel bit to port.



This is a carbide bit. Generally expensive, but cuts like no other and lasts a while. These will generally port a motor, and depending on how nice you were to it, may do another. When I use it, I spray a little WD-40 on it every once in a while to keep it cleaned and semi-lubed. This will keep it in a little better shape and longer usage.

Did you notice all that green tape on the Iron of the J-port? That is a good idea! Tape up around the stock port and around it a good bit, then lay your template on it. The tape will keep your bit from gougeing the iron. You can be a pro porter, and you will still have a dremel bit pop out of the port and dance across your now-paperweight iron. A little insurance goes a long way.

This is a bridgeport template.



The circle holes on the top and bottom are where you slip the template over the dowel pins. This will keep the template from moving. Now with the template on the port, you can mark where you are going to cut. I generally use some cheapo spray paint and spray the template ports on the tape, then cut them. You could also go straight to an exacto knife. Either way, get that shape down perfect.




I have finished the rough porting on the main port. The main port looks somewhat like a streetport, but most Bridgeport/J-port will not go into the corner seal as much as a street port will. When you are doing a BP or JP, you begin on the 2nd port with a punch (I believe it is called that, it is a screwdriver with a point on the end), and lightly tap it inside the port area a few times to get a pilot point made. Then grab a drill and bit (preferably bigger than your dremel bit... for obvious reasons) and begin slowly drilling into the port. It will go through, then just back out and do it again. I generally like to do about 5-6 on a bridge. This was the first time I did a J-port, and I drilled a hole too close to the top of the port. You would want to make the last hole about 3/8ths inch or more from the very top of the port to avoid missing the intake runner. Now use your dremel and go to town. When you are porting, a good rule of thumb is to stick a finger into the adjcent water port and put your finger near where your port is. When you feel it getting warm, stop. You are close enough. Last thing you want to do is poke through the water jacket!

Hope this helps you a little bit. It is a very general, very brief description of the ports and how to make them. For more detailed info, go to the NA section and read up in there.

 

Thanks this has been very informative... You only port the intake right?... There's no reason to port the exhaust

 

No, when you port the intake you also port the exhaust. I wasn't sure you were asking about the intake or exhaust. Exhaust porting is a little easier than intake porting. You can port it down a little bit (opening earlier) and up a little bit (closing later), but the main difference is porting from side to side. You do not want to port it down too much, because then you will be cutting into the power stroke of the car. Going up tends to have a little more leeway, but remember that the higher you port, the more overlap you will have. The 12a exhaust port is itty bitty.



The 12a is on the right, and 13b is on the left. The baffles in the 13b are there to help quiet the exhaust down (13b is from a 2nd gen NA car).

I wish I had an exhaust housing that has been ported to show you, so I yoinked this from Paul Yaw (his website is down right now):



That is a ported exhaust, pretty much to the max. Porting the exhaust is pretty much the same as porting an intake, but instead of iron, you are porting aluminum, so it will cut faster.

 

nice info Jeezus!!!

 

Thanks The things I do when I am bored at night.

 

Im gonna send my **** to you next time, that was really good man mega kudos!

 

Hey Jeezus, where can i get some 12a templates? I saw that some of the vendors sell 13b... I wanna keep my 12a on one of my cars.

Thanks and your article was very informative!

 

You can use 13b templates on 12a engines. Only difference between the 2 is if you get 13b 6 port templates, which obviously will not work

The exhaust templates are different between the 2. The housings are wider between 13b and 12a.

 

You know i have never seen a peripheral porting job in person before... i had no freaking idea that it consisted of drilling a big *** hole into the housing LOL...crazy ****

 

Excellant write up Jesus. One of the better informative ones I've seen here. Mazdatrix or Racing Beat has a porting video which is overall pretty decent. Well worth the purchase price. Before one even begins porting or buying templates, they need to decide what they want pefomance/driving wise from the engine, how much they are willing to spend and how much of the downside they are willing to tolerate.

A streetport won't make any major difference in driving or low end torque. Once one goes to a bridgeport or larger, that changes a great deal. Low end is gone, idle goes up to 1200 rpm+ and the higher powerband exceeds the stock build parts, increasing the build costs. Read/study everything you can before deciding. Not only on this forum but also on nopistons.com. Increasing air flow and rpm range not only requires upgrading internal parts, the fuel system and carb/injectors/pump, (oil and fuel), also need upgrading. Exhaust system also needs needs upgraded to handle the increased flow rates. db levels also increase so as to not choke off the exhaust flow. In the end, the rebuild costs can double, triple or quadruple to support the needed mods for a bridgeport and larger.

 

Thanks...that makes sense. I have been thinking about either a large streetport or a bridgeport on my 12a (Black 1980 car).

I will probably use a sidedraft webber.. (trying to keep it oldschool).. I have a RB streetport header and dual pipe exhaust system. According to the Mazda Competition manual, they state, basically any exhaust system other than a header and megaphone pipe will negate the gains from going bridgeport.

What are your thoughts on this? I heard a 13b BP last night going through an RB muffler...it sure sounded great!

 

As far as the Mazda comp book goes, yes that is true, for competition.

Then again, I have seen bridgeports with small carbs and restrictive exhausts put out over 170whp.

Racing beat does make some good exhausts. If I had the money I would spring for their stainless steel 3" muffler (not in the website, you have to call and ask, $500ish). In general if you have a good road race header and long primaries/SDJ header/RotaryShack MaxPower header and good 2.5-3" high flow exhaust you will be good.

Best part about the bridgeport template, is you can use just the main port as a smallish Streetport. If you don't like it, break her back open and put the eyebrow on it. You can call mazda and get a soft seal kit for about $120, or less if you know the guys ;-). Replace the coolant seals and you should be dandy.

Using a bridge's main port for a streetport is a great way to see if you like the streetabiliy and power of it. A standard streetport will go into the corner seal land area about 40% max, some have even gone 60%, but I begin to fear the side seals at that point. The bridge ports generally do not go into the corner seal area, and again some people have gone a little into it. I would worry about a thin bridge cracking from heat cycling and boost. I will see if I can find the picture of a cracked bridgeport I have somewhere stashed away.

 

Cool Jeezus...keep the great info coming. What are your thoughts on 1/2 bridge?

 

i personally haven't done any porting but from some buddies that have done both 1/2 bridge and full bridge in a 12a they say just go full bridge, their thoughts are "with the half bridge you have all the tunning problems and drivability issues that you do with a full bridge, and none of the fun"....i personally plan on sticking with a streetport simply because my car is a DD.

 

I'm running a 1/2sp-1/2bp in the widebody. When I first put it on the street I was using a Mikuni wrap around carb/intake. No low end at all, often killed the engine from a dead stop, couldn't cruise below 3k without doing the herky jerky and usually had to run in 4th gear on the highway if I was below 80 mph. I'm also running 15" tires that has the net effect of running a 3.60-3.70 diff gears. Speedo was off by 10-11%. Got a warning ticket for doing 87 in a 75 even though I had the speed set at 78-79 mph. Only reason I didn't get a speeding ticket is it was Christmas Eve so the State Trooper was giving out Holiday warnings instead of tickets.

Since I knew the Mikuni was too small for for the porting, I picked up a Rotary Engineering dual DCD Weber set up. This is one of the very few carb/intake setups that has completely seperate primary and secondary runners/ports from the throttle plates to the engine. Net effect of this setup is as long as only the primaries are open, the engine performs as a streetport. Most other carb/intake setups are either 2 barrel and/or have a crossover port between the primary and secondary ports or the front/rear rotors. Once the secondaries open up the rpms are up enough that between 4-5k the car takes off when the 1/2 bp kicks in. I can now cruise at 1500 rpm as smooth as a stock engine, even though my idle is set at 1600 rpm. I can also use 5th gear at 45+ where before I had to use 2nd for anything below 30 mph. I can also get 22-23 mpg on the highway.

The fun part is the brap. With the stiff suspension, the body rocks side to side and sounds like a V8 with big *** cam. I'm also running a full 3" exhaust so it's not quiet, at any rpm.

 

Trochoid nailed it on the head. 1/2 sp/bp are great, as long as each port style has their own runners. When you throw on a 2 barrel, you end up having it cater more towards a BP engine's characteristics (high idle, rich near the top) that you end up with nothing on the bottom end. It could work with a 4 barrel, but you would need a flush manifold with no spacers. Only problem with that is that most brake booster lines are attached to the secondaries and you have very little brake power. Dedicated runners like Trochoids set up or and of the EFI manifolds would truely bring the low end running back.

EDIT: But as for my personal opinion, I would go big or go home

 

wow, I never knew about j ports or peripheral ports. My FC is a daily/soon to be drifter as well so that 1/2sp 1/2bp idea sounds like the best of both worlds. I have to rebuild a T2 engine I inherited from when my brother got his 7 plus a bunch of extra stuff so I am swapping my N/A.

Could you go into more info on the fuel setup? I am a noob on that part, you have to get rid of the EFI and go carb right? I don't know about that aspect. Is there a way to keep the EFI or would it not be able to run like the streetport daily, bridge performance driving and run bridge all the time.

I was thinking medium streetport because I could use OEM rotor seals. with 1/2sp 1/2bp I would have to upgrade the rotor seals to what, ceramic which are like $1000 or more for just apex seals? can't afford that right now. Like I said, more info would be a great help, thanks.

 

When you port the exhaust you get rid on the little sleeve that is in the exhaust port right?

 

The little sleeve is there to keep the exhaust temps from heatsoaking the engine. You can remove the if you like, I have even heard of people making them to fit their port shape, then weld them on the back side of the header.