Acid porting intake

[Dirk37]

I had my car all apart this weekend to put in some BBB's and 48lb injectors and decided I'd give acid porting a shot. Unfortunately I had to stop half way through because I needed to get my car back together, but the results from about 3 minutes of acid were pretty impressive and I intend to try it again when I have more time.

For plugging up the end, I used a piece of wood, a piece of cardboard, then some super thin plastic wrap. It worked quite well and didn't leak even when pressurized by blowing on it.

I set it up outside because the fumes this stuff puts of are nasty. It also produces hydrogen gas which can be explosive if confined, if you try this yourself the bubbles are fun to light on fire

After adding the acid, it bubbles up black nastyness that rains all over the place, the intake also gets quite warm. Wear gloves because chemical burns are no fun. You must keep periodically adding acid to keep it topped off, even if it looks like it's full it's just a fine foam. Something I was a bit worried about was damaging the gasket mating surface since acid pooled up on it, it did rough it up a bit but it doesn't leak as far as I can tell. I think I'm going to paint it next time to be sure it stays flat.

After it was all over and hosed out, here's what was left. There was a layer of gray aluminum oxide all over any part that was touched with acid, I just wiped as much as I could off with paper towels and it seemed to be fine. The other guy who tried this said acetone works well, I'll have to try that next time.

It was quite a bit smoother than before the acid treatment (it looks kind of rough in this picture but there's significantly less texture and it feels much smoother), I couldn't see a size difference with my eye but next time I'll measure with a micrometer and see for sure. Here's a picture of the other one that wasn't acid ported.

Something else to know if you try this is the acid overflow will discolor the outside of the intake, mine now has several big gray spots that don't look that great. I'd recommend painting it afterwards to cover up the discoloration, plus painted intakes are cool :woo-hoo:

Had I not had to quit early I think this would have been much more successful and I'm eager to give it a shot again, stay tuned!

 

[intimdatr]

Looks like you could have left it in there for a fair bit longer.

 

[Dirk37]

I'm thinking I'll try 15-30 minutes next time, that should really open it up and get rid of all the texture

 

[Off Road SHO]

Acid will not eat out aluminum so that it is smoother. It doesn't work that way.

Tom

 

[Dirk37]

I think it will up to a point. If it's perfectly smooth to start, the resulting texture is going to be dependent on variations of the thickness of the inital oxidation layer and metal purity and will definitely come out rough.

On the other hand if it's pretty rough to start like our intakes, the little bumps are going to have much more surface area per mass and be consumed faster than the flat areas, up until a certain threshold. That threshold seems to be enough so that most of the large casting marks and big bumps are removed and it is overall a little smoother.

It's not clear between the two pictures I posted earlier, but they look at the intake from very different angles. If you match up the corresponding areas, you'll see the acid ported one is way less bumpy than the non-acid ported one.

 

[intimdatr]

Are the bumps casting imperfections or are they carbon build up?

 

[Dirk37]

All the little bumps are casting imperfections, I had to clean all the carbon out before acid porting because the acid won't eat the metal if there's carbon on it.

I did a little test to show how acid will actually smooth out aluminum. Here's a piece of metal I (very crappily) casted from some melted down pop cans. Notice all the ridges and valleys in it.

Now here's the same corner after about 2 minutes in an HCl bath. All the little holes are because I suck ass at casting metal and it was full of bubbles.

If you look on the left corner you can see most of the ridges have either disappeared or are just barely present now (compared to the right where they're clearly visible) and if you disregard the air pockets the metal overall is much smoother.

 

[gmail]

Speaking from experience you better oil up the intake.. After the porting the aluminum will oxidized or rust if you will..

I ported 5 parts water to 1 part water and did 15 series after every 2 acid baths I did lye which was a great combo and the intake was ported to the extreme lol. .

The switching back and forth between lye and acid works better then cleaning the intake out all the time from the acid

 

[Dirk37]

What did you do to protect the gasket mating surfaces?

 

[zak]

Anyone ever try this starting with an unused Extrude Honed surface?

 

[gmail]

When I ported I used petroleum jelly since the acid does not effect it .. like a barrier. .. I didnt have to do anything further to the gasket sides...

Also extrude honing after acid porting would be a better idea as the acid would eat any soft spots where air bubbles might be and cause pits..

Dont get mistaken acid porting actually smoothes surfaces more then you might think so after several sessions its quite smooth

 

[waffles]

Are you going to port the heads as well?

 

[gmail]

Actually I did a port on a head a few years back... works very well just use petroleum jelly on the valve and put a old valve in.. dont appear to hurt the valves at all tho

 

[Dirk37]

When I ported I used petroleum jelly since the acid does not effect it

I will definitely use that next time, the gasket surface of the one I ported is much rougher now lol

Are you going to port the heads as well?

I'll probably leave the heads alone, they look like they flow pretty well and removing them is a lot of work