Grinding and polishing cast large(ish) aluminium air intake?

[kherseth]

Hi again folks.

I`m in the process of giving one of my car engines a little cleanup and shining. The one I am working on is a 2.0L Opel engine. It used to sit in a car i bought for trackday purpose, and i decided to shine up the engine before selling it. I did just get started on grinding down the intake manifold before i got a decent job offer, you know how beauty sells right? Got free access to both a lathe and a mill on the spare time there

I have ground down roughly half of the intake, but i cant get to the rest with the angel grinder using a flappy-disk, it is kind of "U" shaped, so the internal area of the "U" is unaccessible. I tried using the dremel but that would take more time than i have before starting in the new job(500km away), and i really want to get done before moving. I got two weeks, but i was hoping to also have mounted a 3L straight-6 into the car before that time too :S

Any tips/hints will be very much appreciated.

Regards
Kim

 

[bearcar1]

Hello Kim, various grits of emery cloth in one inch wide strips should do what you want to do on the casting. Secure the manifold in a vise and apply the emery cloth using a "shoe shiner's" action of pulling the strip in alternate directions over the surface. You will find that it won't take too long to get the surface cut down smooth at which point you could then polish it up on a flannel buff and the appropriate compound for Aluminum.

BC1
Jim

 

[kherseth]

Thanks Jim,

I do actually have some emery cloth, just that my experience with regular sanding paper is that it took too long, but i`ll give it a go and see, maybe the emery cloth will grind better

I did give it a go with a steel brush on the angle grinder, but that cheap tool was so unbalanced i nearly dropped the tool :S

 

[ShedBoy]

Polishing cast ali, just be ready for sore fingers. Start with rough stuff and work to the fine stuff. I did some motorcycle casing once and NEVER again. I had the engine apart and all and it was still hard. Mu hat goes off to anyone who has the patience to do anything large. I stick to small things that will fit in a mates rock tumbler but you don't get to choose what gets polished with that. Little tight corners were no match for my stubby fingers, I sinck to sandblast finish now. On a side note if you polish anything finish with ZOOPSEAL, clean with water and detergent after that.
Just my two cents

 

[kherseth]

I`m far from done still, got to borrow some other sanding tools, but I do agree with you shedboy, never again. I don`t think i will finish this the way i planned due to too much work. I think I`ll grind away the casting surface, give it a rough sanding and paint it with rim paint.
Maybe on the other intake which i am going to keep, but not really sure on that one either, roughly same design but it feeds a straight-6 instead so it is MUCH larger

Never the less, it has at least been a small learning experience, so i`m pleased no matter how i decide to finish it up

 

[jpaul]

Kim,
Some years ago I had a plating company polish an aluminium intake manifold for me. They offer and I accepted their cheaper price that didn't detail the nooks and crannys. I was very pleased with the result. The difficult to reach areas are a mat finish and blend reasonably well with the polished area. You could consider this approach, maybe bead blast the nooks.