SOHC Neon Head Porting

By Matt Beazer and Craig Grass
Last Updated 08/09/07

Originally, I had planned on swapping in a Crane #12 cam for the Neon with some valve springs from a Magnum-head 2001-up Neon R/T. That was going to be a nice upgrade, 12 horsepower as seen on the dyno. Then I ran across a '95 Neon in the u-pick-it boneyard and purchased the head from it for $28. Then I decided to put all the cam, etc. on that head after having it hot tanked and resurfaced, then do a complete swap of the head so I'd not have to worry about dropping a valve by accident while replacing the springs on-car.

I got it into my head that I should use some sanding rolls on a drill to smooth out the ports a little, take out the casting flash, etc. This way I'd not take the risk of messing up the head by hitting a water jacket or oil passage I didn't know about.

Then I disassembled the head, taking off the exhaust manifold, and was shocked at the size and design of the exhaust ports - they were tiny with a huge "hump" in the floor of the port, making it even smaller! I decided I'd like to get rid of that hump a bit to improve flow on the exhaust side of the head.

One day, bored at work, I found a page on SOHC head porting on the Fierro Racing site (the web site has since gone missing). This gave me pictures and a drawing of where the major coolant/oil passages were, some basic instructions, and pictures of the end result. Then I decided "hell, it's only 28 bucks" and I decided to take a gamble on the junkyard head. The results are here for you to see, and copy, if you so choose. This takes a little courage, a steady hand, and a lot of time. If you are inexperienced, I would recommend that you only perform this work on a spare head. You will not have a running car if you hit a coolant passage on your only head. Considering the number of Neons showing up in u-pull-it yards these days, it shouldn't be hard to find one unless you're looking for a DOHC head.

Note that these porting tips should work on a DOHC head, though the exhaust ports on a DOHC head are much more free-flow compared to the non-Magnum SOHC head. I've never worked with a Magnum head before, but considering the size of the exhaust ports on it, it's very likely that the "hump" is much thinner than it is on the non-Magnum heads, so be careful!

NOTE THAT I ACCEPT NO RESPONSIBILITY FOR ANYTHING THAT HAPPENS AS A RESULT OF YOU USING THE INFORMATION ON THIS PAGE. IT IS HERE FOR REFERENCE PURPOSES ONLY!

USE THIS INFORMATION AT YOUR OWN RISK!

Preliminary Considerations

In the process of porting this head we took a lot of material out of the ports, especially the exhaust ports. Note that this is somewhat detrimental to the low end torque abilities of the SOHC head. The effect in my car was to lose a small amount of low end torque (below 2000rpm), but not enough to make a difference in my 5-speed car. A car with an automatic transmission would likely have more issues, especially since the stock ECU will not allow it to rev over 6500rpm to save the torque converter. Also realize I installed this with oversize valves and a #12 crane cam, which I'm sure likely mitigated the loss of velocity in the exhaust ports on the low end. I don't think I'd attempt this if you intend to use a stock cam and springs, much less a stock ECU/PCM that limits the 5-speed SOHC to around 6700rpm. (I use an AFX Race unit in mine, which limits me to 7800rpm, not that the bottom end of the engine in it's stock form could take this safely.)

Also realize that the stock SOHC intake manifold is tuned for low and midrange power, though not as bad as the '00 up Non-Magnum SOHC intake is. My experience with this head with my mods resulted in the bulk of the power band being between 4000-7000rpm. This would be extended further I think if I had a better intake manifold (stock currently) and a header. The stock intake becomes a large bottleneck at higher (5600+) rpm. If you intend to do this, you might also plan on changing to a better intake manifold (such as the Indy or a modified Magnum intake with functioning butterflies) in the near future, as well as a good exhaust header. I don't have these since I've not had the money or time to install them, though I'm working on a ported aluminum SOHC intake which will hopefully help somewhat.

The car in it's form prior to the installation of the head and AFX PCM was a 15.9@87 (2.4 second 60ft and shifting at 7,000rpm). At that time it had an Iceman air intake, 56mm TB, DOHC PCM, and DOHC Muffler. This was in 90 degree heat at 2,315ft above sea level. I'm learning how to launch the car still, I'm used to a 2.5L Turbo car that ran 14.0@102, and the Neon is completely different to get off the line.

Realize this won't be a true comparison over a stock casting since I'm changing too many big things to truly evaluate the overall power gain of this head porting work. The #12 Crane cam I have is known to add 12hp to a stock headed car with a larger throttle body, DOHC PCM, and a header. I'm hoping this head work will just accentuate the effect of the Crane cam on the overall flow of the head.

Consider yourself warned!

Also note that I also have these images available in 1984x1488 resolution from the original camera shots. If you want them (to print out a good, large color copy to put on the wall to compare your work to) let me know.

What You Need

I got the following at Eastwood Co., other than the Chrysler parts.

Needed:

46060 - Carbide Bead Burr (Aluminum Cutting) 6" shank
13119 - Grinders Grease (helps to remove material quickly and helps keep the sanding rolls from loading up)
46076 - Manifold Smoothing Kit Don't get the Deluxe kit, the burr that comes with it is only 3" long, you need 6"! You can also purchase sanding tolls (tapered and normal) separately in 80 and 120 grit styles if you prefer.
High speed drill, air powered die grinder, or similar tool. MUST SUPPORT 1/4" SHANKS! A normal dremel won't work for the above tools since the shank size is too large on the bits. I used a 3,000rpm Hitachi Drill to do most of my work. If you have an air compressor, a die grinder will make the work faster (but makes it easier to goof up). If you do use a drill, avoid the kind with the hand-tightening chuck. It can make the bit slip out easier than if you have a good old fashioned chuck with a key. Don't use anything rated for less than 1350rpm, RPM is what matters here.
Get some kind of ear plugs, goggles and a face mask. You're going to be dealing with a lot of noise, dust and aluminum flakes, so protect your ears, eyes and lungs, especially while polishing!
A clear workbench in a well ventilated area. I set up a box fan next to my work area, blowing across it to help clear the dust and keep me cool. Be careful that the fan does not blow debris into your face.

Recommended:

46029 - Carbide Bead Burr (Aluminum Cutting) 3" shank - Makes porting a tad easier when you're not working deep in the ports
46059 - Carbide Bead Burr (Cast Iron/Steel Cutting) 6" shank (To grind away the valve guides without destroying your aluminum cutting bit)
13087A - 240 grit and 13085A - 320 grit sanding rolls (To polish up the exhaust side to a glassy sheen to promote better flow)
13141 - 6" High Speed mandrel for Sanding Rolls (The Manifold Smoothing kit comes with 4" ones)
P4876113 - SOHC Street Exhaust Manifold Gasket or the stock exhaust manifold gasket (a good guide to make sure you don't go too big)
P4648623 - 95-96 SOHC Aluminum intake manifold gasket (To allow you to gasket/port match the head to the intake manifold)
Crank pulley puller. Autozone has it under part number 27139, Snap-On makes one under part number YA9740B, OTC Tools has one under part # 6727. Any of the above should work. Miller/SPX makes one but all they sent me was a generic 3-jaw puller that didn't even fit the pulley right. I'd get the Autozone part or rent it from them if you want to save money.
Crank pulley insert, OTC Part Number OTC6013 or Miller/SPX part number 6827A. The inserts with the Autozone kit aren't long enough supposedly. I used the Miller insert.
Crank pulley installer, this is essentially a longer bolt with the same threads as the crank pulley bolt, a nut, and a thrust washer. Miller makes a tool specifically for this purpose. Some people say heating the pulley in an oven to 450F will help, I've never had to with the correct installer.

If you have a drill/die grinder, this will run you about $55 before shipping. If you go for the whole shebang with the recommended stuff, it'll be more like $150. The extra cost will make your job a lot easier, you can match up the exhaust manifold and intake manifolds to the head properly, and you'll still have stuff left over for other porting jobs, like on that exhaust manifold if you're not going for a header, though in my personal opinion porting the exhaust manifold is a waste of time (and I've tried it!). I would recommend a die grinder with a good sized air compressor, as material will come out a lot faster with the higher RPM a die grinder offers. Just make sure you use grinders grease with it for an optimal cut.

The Process

Start by positioning the head at a level that is comfortable to work at. Some kind of hand held light is also nice for looking into the ports to check on your work. Realize the workbench, the floor, and everything else is going to be covered in aluminum shavings, so prepare your wife/girlfriend for the mess. Don't let anyone go barefoot in the area where the work is being performed, the aluminum comes off in small splinters, which easily embed themselves in your feet if you don't protect them.

I started with the exhaust side. The intake side is quite good stock, it just needs some valve bowl work and a bit of polishing. The exhaust side is by far the most time consuming. Select a link below to get started.

Exhaust Ports and Bowls
Intake Ports and Bowls
Finishing Touches and Ideas
After Installation Conclusions