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5-09-05 - Intake Manifold Porting
I found a pretty neat DIY article on porting/polishing that inspired me [Standard Abrasives DIY cylinder head porting guide]. I originally wanted to get some flow work done on the n9t head but that just doesn't look possible. So the best i can do for now is to do some minor 'adjustments' by myself. It's more fun that way anyway.. right?
I started on the intake manifold. This was the most blatent bottleneck i could find. The ports on the head actually look pretty impressive. They may need some minor work but we'll get to that later. When i originally took off the intake manifold, i remember noticing the seal marks where the headports met up with the gaskets and comparing them to the intake manifold inlet and thinking angry thoughts. The ports were... just plain WAY off. It was really a hilarious site to see. It's almost as if the head and manifold weren't even meant to be together. The head ports were uniformly shaped and even, while the manifold ports had an odd non-circular shape to them (apparently due partly to the location of the fuel injector bungs on the manifold), and were much smaller in 'diameter.'
Below is a picture of the original manifold before any work was done. You can see some markings around the ports. From looking at them you can get an idea of where the head matches up to the port. The head ports were a bit larger
An original port is pictured below. You can see lots of sharp edges around the injector nozzle, as well as the permanent ink that marks where the port "should" line up with the head.
The goal is to match the ports to the head and to smooth out all the sharp edges that create negative pressure areas and hinder airflow. I tried several different methods of marking the ports. The one that worked best turned out to be the most obvious one. I first took my new intake manifold gaskets that i was lucky enough to find on ebay, and i secured it to the head. I then port matched the gasket perfectly to the head using an exacto knife. Aligning the gasket with the manifold and marking the ports will give a good baseline of where to grind. I originally tried the same thing with a paper tracing of the gasket, tried some light paint to mark the ports, but really, the gasket matching is the easiest in my opinion.
Grinding can be done with an air grinder or an electric grinder. The air grinder worked way better for removing large amounts of material. I went through WAY too many bits with the electric "dremel" type grinder while trying to remove bulk material. I would suggest using an air grinder to enlarge the parts to the approximate size, and then switching to the electric grinder. The electric grinder is much easier to control. I used it to shape the injector spray ports, and to put the finishing touches on the port shape. I tried to make the enlargement of the manifold runner as gradual as possible (realistically) with the tools i had. I was only able to get a few inches down the runner, but for my purposes it will work just fine. It's totally possible to use only the electric grinder for the job, it will simply take longer and you'll need quite a few packs of sanding drums.
I actually started the job with just the electric grinder. Below is a picture of the first port underway.
After realizing that this would take quite a while i stopped and waited until i could take it to my place of work and use the air grinder there to enlarge the ports. I then continued work with the electric grinder to finish the ports off. Below are a couple pics of the finished product.
The manifold ports now match those on the head, and i can rest assured that all that nicely compressed air is flowing through a smooth transition instead of taking the stair-step route into the combustion chamber.
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