Well some times I wish I wasn't such a perfectionist. Maybe it is a good thing I didn't build one from a kit.
Not only was the intake ports narrow and miss-aligned, they were a good 1/8" short on the height. While grinding the ports out (which is quite easy) I noticed the fuel injector bungs were sticking into the air flow. They were all different lengths the worst was 1/4" into the air flow and two were flush. Since the bungs are all straight and level on top, I guess the manifold port heights are all different. So while I was at it I ground them all flush to the port wall. Then I noticed that where the fuel injector bungs were welded, the metal swelled in blocking the path of the fuel flow. A couple ports were nearly 1/3 blocked. So I rounded the diameters out. That wasn't too bad to do either.
While smoothing out the grinding with a small wheel of sand paper flaps in the die grinder, I was amazed at how easy it was to polish away the rough casting. After getting the center four ports done, I realized I couldn't reach all the way through the 4 end ports. It's always a dad time to figure this out - after you are committed. Well 8 hrs later after using a dial rod and sand paper I had the entire inside of the manifold polished. And the bad thing is I fully understood that this polishing would do next to nothing at the rpms I run in, but I just couldn't stop my self. The cleaning was a horrible job. Even mildly polished this thing is porous. Another 2 hr job. All in all I must have 20-30 hours in intake.
I do feel that matching the intake ports to the gaskets and getting the bungs out of the air flow has to help on the power. Rounding out the bung holes may have helped on atomizing fuel better, at least it should have.
While I had the
oil pan off I put in a windage tray, so it would be impossible to separate out what did what in terms of Hp gains. It definitely has more torque down low and I haven’t a clue how this work would have done that. The intake was leaking vacuum when cold before maybe some hot too. The idle speed is same as before with out any adjustments, so I don’t think is was leaking much vacuum when hot. Power wise it is too loose in 1st gear to tell anything, but second gear seems to wind out much quicker. It’s been seven months since I drove it, so how can I say for sure. I want to believe it did something for top end Hp, but honestly I cannot say for sure.
The one thing all this work definitely did was help fifth gear a bunch. Before I had to stay above 1800 rpm to keep it from surging and it didn’t have much guts down there. Now, I can drop it down to 1400 rpm in fifth, and it pulls much stronger. Before, the torque didn’t come in strong until 3500 rpm and now its pulling pretty hard bellow 3000 rpm.
In the end I’m not sorry I did all this, but I sure would like to understand how this helped the low end torque so much. That was the last thing I expected. Makes no sense to me.