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how long would it take to polish the plenum?

Well you'd have to grind the cast roughness down, then sand it fairly smooth, then get out a buffing/polishing wheel and use something like Flitz on it. It has grooves in the top so it might be hard getting inbetween them, or you could leave those un-polished for some contrast, maybe even fill them with paint. If you don't have power tools to do it, I wouldn't attempt it. That's why I'm not going to, I dont have the right tools. bonecrusher is polishing his, so once he gets done with that we can see what it would look like.

25 hrs, and still NO WHERE NEAR DONE!

lol you're actually keeping track of the hours? That is a lot BTW.. Updated pic?

I didn't keep track of my intake and cam towers, but I can assure you that you will be sick of having grey/black on everythign and the dust goes everywhere....

If you do it by hand you will have some bloody stumps and then some serious calluses.  That and your arms will eventually just fall off.  

Yeah it doesn't sound like fun. I've ground aluminum before for heatsinks for power led flashlights, it sucks. I never thought to polish my cam tower though. Good idea.!!! lol    

Got in a die grinder from harbor freight. My punny air compressor only powers it for about 5secs at full power before falling on its face. So I spent several hours, but I got the whole thing mirror POLISHED!!!  ..... just kidding!! haha. I did spend several hours, and removed the side tab, 2 front tabs, and the square on the right side. I also cleand up all the casting seams, and now the manifold is all pretty and un-cluttered.

I really need a better compressor, as I still have to gasket match the upper and lower manifolds, and then grind on the TB neck of the 3500, and grind on the rockers and 3400 lower runners to clear them... Ugh!!

Oh and BTW, I cut off the tabs/square protrusions with a hacks saw first. I didn't dare try to grind those with just the die grinder!!

(IsaacHayes @ Jun. 07 2006,00:23)Q
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EOh and BTW, I cut off the tabs/square protrusions with a hacks saw first. I didn't dare try to grind those with just the die grinder!!
Sounds good... that's what cutoff wheels are for

Hey Geoff, good to see ya posting here again! I don't have cut-off wheels, nor the paitience to wait for the compressor to charge up for 5 secs of cutting. Besides, the hax saw actually cut it off cleaner than a wheel could have. The blade flexed and followed the countours of the manifold. I had to do *very* little clean up on the things I cut off. The casting seams and casting areas on the front is what took the longest!

Angle grinders work just as well....

I have very limited tools guys. Very limited. I have to borrow a torque wrench when I work on engines. Just a few basic hand tools mainly. I do have a drill, but no attachments or anything for it. Hmm, I may try chucking up one of the grinding wheels though when I go to grind the TB neck and LIM runners for clearance. Gasket matching I will stick to the slow air grinder.

I have a die grinder and run it at 80 psi with a water trap in teh line.  I have a 80 gallon tank with an older 5 hp I think    compressor and I run the compressor at a 100% duty cycle and I still can only run it for 30 minutes or so before I drop it below 80 psi.  I have a friend who wanted to see how his new compressor would work with one so I hooked mine up to it, it ran for 5 minutes, then seized the piston in the compressor    .

UPDATE incase anyone still reads this thread.

Ported and polished the 3500 and 3400 manifolds. Gasket matched them, and bellmouthed the inside of the 3500 ports. Should flow exceeeeelent. I left the bottom of the 3400 alone where it goes to the heads, as I'm not sure how exact it aligns with the 96-99 3100 heads, so best to just leave it since I won't be porting the heads. I also clearaned the 3500 TB neck for the FPR. Not sure if it will need more, I'll find out when I go to bolt things up, I can always touch up some black paint there. I also sanded the area where my bowtie and chevrolet text will go, so when I paint the lettering on, it won't bleed/look fuzzy on a rough surface. The area now there is smooth and shiny. IMO if you had the right tools you could polish the top of this plenum in no time. I used a tiny sand paper disc on my dremel clone, and it didn't take long at all for this little area. A large pad an angle air die grinder would work wonders. I could use some flitz polishing and get a mirror shine where I'm at, but I'm just painting a logo there...

So hopefully all the grinding is done on the 3500 part, and if more it won't be much. I still have to grind the 3400 lower for the rockers, and perhaps some off the rockers themselves. I think I'll take a break from grinding and paint the intakes, TB, and adapter first.

Getting there. After above is done, I just have to tear the motor down to the heads, and assemble and check for clearances. Oh and take my EGR tubes to be welded by a friend so the home made adapter works.

I'll try to get pics, as I know a thread is a lot more interesting with them.  

Sidenotes: My air compressor is 1/2 horsepower, probably 3 gallons. My dremel is a craftsman two speed, 15k rpm, and 35k rpm. Spent about 1 hr on each 3500 port = 6hrs. Took maybe 2 hours to do the whole 3400, as it was not as far off from the gasket as the 3500 is. 3500 has smaller ports than a stock 3400, but gasket matching solves this. Even unported it makes more power even though it flows less stock than a 3400. Ported it out flows it. The 3400 I didn't have to bellmouth so that cut down on the time as well (bellmouthing would hinder flow going down from larger opening to a taper.) I just port matched it and smoothed the transition to the stock taper down about 1".

I'm getting excited about painting it.   I gotta clean it first though. Make sure I get out all the aluminum. That will be fun...  

Hey guys, update. I'm going to try to get photos soon!! But the plenum is painted, tapped, and ready to go. It turned out beautiful!!!! Looks just like my avatar, only it doesn't have all the tabs/etc, I ground those off.

For all of those that say the 3500 is ugly, you are correct. But if you say you can't make it look good you are wrong. Mine looks great. All black would be too much, and adding the logo gives it just enough "flair" with the rest being black looks really sexy. It looks like it belongs factory in a corvette or something. Like their engine covers. Only this is the actual manifold itself!!

I think I'm more excited how my engine will look after the install than the HP I'll be gaining!!    

Ok pics as promised! All casting seams and 4 tabs/protrusions were ground off and smoothed down. It looks really clean!!