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I've taken up metal polishing as a hobby in the last 8 months. I've recently finished working on an 86 Corvette TPI setup. During the entire process of finishing that manifold, I encountered several areas where tiny air bubbles in the cast had surfaced after I had gone through the initial sanding and gotten all of the rough cast removed, and had started in with the black emery compound. After these air bubbles surfaced, (and after being severely ****ed because I thought I was finally done with sanding after countless hours), I got the sandpaper back out and started to work AGAIN trying to get rid of these air bubbles. Well guess what? It STARTED out with just 3 or 4 air bubbles, but as I began sanding them out 3 turned into 10, which turned into 30, which eventually left the surface of the manifold looking like a damn piece of Swiss cheese. So I threw up my hands and gave up on that endeavor, thinking that I had maybe happened upon a badly or defectively casted manifold. I just decided to cut my losses and try and get as good of a polish on this thing as possible with what I had left. I eventually got the manifold looking halfway decent, (perfectionist), from the "5 feet away" standpoint, but if you get close enough those air bubbles are still there taunting me.
Okay now the good part. I've recently started working on an LT1 intake, with higher hopes this time. Been working on it for about the last 10 days. All was going well in other areas UNTIL I got the the rear part of the manifold down around the area where the distributor hole would be on a conventional intake. Same thing as with the TPI manifold, friggin air bubbles. So now I'm thinking maybe this is just a normal thing, seeing how it's occured on 2 different intakes. So I got ambitious and really went to town on that spot with the sandpaper. I'm now about to chuck this manifold into the street, because these damned air bubbles aren't going away; they only seem to multiply. I'm pretty sure I've gotten at least 1/32's deep into the cast, maybe even as much as 1/16's. I'm also pretty sure that it isn't my sanding technique, because if it was then I'd be seeing air bubbles in every place I'd sanded, instead of in just certain spots. So here's what I wanna know:
(A) Has anybody who's worked on intakes or other similar parts that have thick casts to them ever encountered this problem and what did they do to fix it?
(B) In other threads I've read about the copper plating process, whenever someone referred to "building and filling", was that for the purpose of getting rid of something such as air bubbles in the cast? Or is that for a different purpose?
I'm trying to figure out if I need to quit while I'm ahead with going any further with the sanding in this area and just finish sanding the rest of the manifold and hope for the best when it gets to the chroming stage, or do I need to keep going deeper because these bubbles will eventually clear up? (I'm imagining that the air bubbles would be all the way through the cast, and I'd just end up sanding till there was nothing left.) Please tell me that after all this work I'm not just gonna be stuck with something that looks like a POS. Anyway this problem's got me tied up in knots, and I'm losing sleep trying to figure it out. Any help or suggestions would be greatly appreciated.
Okay now the good part. I've recently started working on an LT1 intake, with higher hopes this time. Been working on it for about the last 10 days. All was going well in other areas UNTIL I got the the rear part of the manifold down around the area where the distributor hole would be on a conventional intake. Same thing as with the TPI manifold, friggin air bubbles. So now I'm thinking maybe this is just a normal thing, seeing how it's occured on 2 different intakes. So I got ambitious and really went to town on that spot with the sandpaper. I'm now about to chuck this manifold into the street, because these damned air bubbles aren't going away; they only seem to multiply. I'm pretty sure I've gotten at least 1/32's deep into the cast, maybe even as much as 1/16's. I'm also pretty sure that it isn't my sanding technique, because if it was then I'd be seeing air bubbles in every place I'd sanded, instead of in just certain spots. So here's what I wanna know:
(A) Has anybody who's worked on intakes or other similar parts that have thick casts to them ever encountered this problem and what did they do to fix it?
(B) In other threads I've read about the copper plating process, whenever someone referred to "building and filling", was that for the purpose of getting rid of something such as air bubbles in the cast? Or is that for a different purpose?
I'm trying to figure out if I need to quit while I'm ahead with going any further with the sanding in this area and just finish sanding the rest of the manifold and hope for the best when it gets to the chroming stage, or do I need to keep going deeper because these bubbles will eventually clear up? (I'm imagining that the air bubbles would be all the way through the cast, and I'd just end up sanding till there was nothing left.) Please tell me that after all this work I'm not just gonna be stuck with something that looks like a POS. Anyway this problem's got me tied up in knots, and I'm losing sleep trying to figure it out. Any help or suggestions would be greatly appreciated.
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