Port Matching Intake Manifold to Throttle Body?

[Wraith]

Hey guys, I will be dropping in a DOHC engine into my car in the next few months thanks to Joey at 6thplanet, and I'm researching little things I can do to give it a bit more pep.

I will be getting an engine from the same model year so I can retain most if not all of my current bolt ons (excluding plugs and wire obviously). So my question is, do ya'll think it would be worth it to port match the intake manifold to my SPS throttle body?

It seems like there would be some gains to be had there, since I would think the manifold in it's stock configuration would be a bottleneck. By having it matched to be the same size as the diameter of my throttle body I would gain some airflow, and therefore power.

I am by no means experienced at this kind of thing, so what do ya'll think?

p.s. I've tried looking on the internet, but all I can find on port matching relates to engines much larger than ours, although they do seem to get good results from it.

[Applefool]

Yes, you want to match the TB to the Intake Manifold in order to get any benefit out of it. I also removed the ridge on TB where it connects to the intake manifold to smooth the flow a bit more.

Could you give some more detail as to how to port match the TB to the intake manifold?

Thanks,
-Rob

[Twin_Cam]

Yea, details would be good. This is something I've wanted to do, and I know it involves a Dremel. But that's it. I imagine you'd need a vacuum cleaner so the little shavings of metal don't end up in the intake runners....

[eRic 02sc2]

stuff a rag soaked in CLEAN oil into the intake manifold first to catch the shavings. then you can use a dremel or one of those kits that have the specific bit to grind away aluminum. use the throttle body gasket as a template. that's how big the hole needs to be inside for maximum effect. use the bolts to hold the gasket in place while you're grinding away. when you're done pull out the oily rag and that should bring the shaving with it.

[Wraith]

So... can this be done with the manifold still bolted onto the engine? If so I may use my current engine (and manifold) as a guinea pig. Because if I can feel a difference with a SOHC, I'll definately notice with a DOHC.

[eRic 02sc2]

yes, you can do it on the car. that's why i suggested stuffing the oiled rag inside. if you did it off the car you'd just vacuum or rinse it out afterwards. dunno that you will "feel" a difference really. *maybe* you *might* feel throttle response is quicker.

[Twin_Cam]

I'm worried I'll deep-six the rag into the manifold and never get it back. I'll figure something out.

[Sp00nSaturn]

I would NOT try porting the intake manifold with it attached to the car still. Is it really worth the rise for the 2-3 horsepower you're going to gain?? Also, porting an intake is only effective if you know exactly what shape to hone out. It's not as simple as matching the holes, every where that the runners curve could use a little modification. Hence the reason you find manifolds polished by cramming clay through them, it curves in the same directions as the incoming air charge. Porting the head to manifold entrances are also needed to maximize the gain from porting.
I have a 322 cu V-8 that has been built for my Camaro, when I inquired at the machine shop about porting, he told me not to even bother. I was told that the most I could expect from that engine was 5-10 horsepower, and that was an optimistic guess. I imagine on a Saturn with no other mods, or even mild street mods, you could hope for 2? And if you do want to port the intake, remove it, take it to a machine shop, let them port it and polish it, and then reinstall it.

[wingnut]

Matching the manifold inlet to the TB outlet will be helpful---only if they don't already match. I removed my TB a year ago with the intention of doing just that and discovered they were already a perfect match, both to each other and to the gasket. That was easy! So check it out before you do anything drastic.

Like Applefool said, however, there is something to be gained by smoothing out the back of the TB (after the plate). There is a quick diameter change there. Next to changing my muffler, smoothing out that ridge made the biggest performance difference so far. Just make sure you get it really really clean before you put it back on the car!

Good luck with the swap.