Hi, as the title states I purchased a semi polished (outside) upper plenum. I started the process of sanding down the outside to just have it powder coated. I noticed how rough the inside is. I started thinking if I could smooth the inside up a bit to help the air move faster/better? Has anyone every done this? I did slightly sand a little of the inside. Not to a polish but just a little smoother than factory. I don't want to do anything to mess up the plenum. Any advice would be appreciated. Thanks

 

Hey man! Is it Chris??? Sorry I forgot your name buddy, but I met you at Import Face-off at Capitol. Anyways, I've been working on doing my upper plenum, lower plenum, and lower manifold. I'm sure the difference (if any) will be very negligible but I did it anyway for my own peace of mind. Check it out:

It's not completely finished in this picture, but you get the idea...




This was during the process of:





-Paul

 

^^ Can't see the pics...

 

Sorry about that, here we go:

 

^ Sorry I'm not Chris. I was thinking of doing exactly what you are doing. I started to do it (not even close to that though) and stopped. I wanted to ask around to see if this could possibly hurt the air flow. I emailed Frank Hill and he wasn't sure and told me to ask around. I have to ask what you used to get it to that point in the pics? I stated with 80 grit paper. I have 1000 and 2000 for the finish. To this point I was doing it by hand. I would love to have the look of yours for flow!!! What you have done so far looks awesome. These are the little things I love, a little time and effort for maybe not much gain. But we know what we have put into that car. Thanks for the pics, please let me know what you are using? Robert

 

Hey Robert,

Sorry for the mixup man! So far I have basically used 60 grit dremel bits, 120 dremel bits, 150, 200, 320, and 400 grit sandpaper. All done by hand. After the 400 grit I used some metal polsih (iBiz) or you could use mothers mag polish or something similar and you can get it to look just like that! I plan on going back and doing some 800 grit to smooth it out a little more!!

 

^ so all but the 400 grit is done by hand? I need to get a dremmel. I was more scared of thinning the plenum or if using power gouging it. But what you have done looks awesome. I was hoping some of the experts would chime in and say that Nissan didn't leave it rough for a reason. I can't imagine it ever hurting air flow to make everything smooth. Thanks for all the info. This is one of my winter projects since my car is already away for the winter. Robert

Ok, I see the dremmel was 60 and 120. My mistake.

 

I was chatting with Eddie (mynismo) and he said that the only thing about the textured inside is that it may help with cooling. He said its well known that a polished surfaced wont dessipate the heat as well as the textured surface. Its not about air flow. Its about heat soak. Robert

 

I also bought the Cosworth Phenolic gasket that sits between the lower plenum and the lower manifold, and I also got the P2R Phenolic gaskets that go between the heads and the lower manifold. So I'm hoping that those in conjunction will kind of help with heat soak. I also plan to do the throttle body coolant line bypass that came with my powerlab plenum spacer kit. So I will def give some feedback after it is all on, etc.

In regards to the dremel, YES BE CAREFUL!!! If you are new to using it, etc, it can easily take away more than you want and from places you don't want it to. So you need to have a steady hand. I have an extender that lets me use the dremel bit free from the actual dremel piece. That also helps get into awkward spots. But you do need to be careful with the bits because you will put lines in the surface that will take A LOT of work by hand to get out if you make the mistake of letting it happen.

 

https://my350z.com/forum/engine-driv...m-porting.html

[/thread]

 

not worth it imo

 

It's really not that much work. But I already have mine off since I'm polishing the outside of it and just did it (like I said) for my own peace of mind. It makes me happy knowing that it will be that condition, whether it makes any difference or not.