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Acid porting

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Acid porting

Postby e-tach » Sat Oct 11, 2008 3:48 am

I did a search - didnt find anything.

I was just curious about acid porting - and how it is done, and how much improvement it really makes on "stock" heads.
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Postby supergass » Sat Oct 11, 2008 8:45 am

It is a old stock and superstock eliminator way to get a little more air into the engine without evidence of grinding marks into the port. It was done with Sulfuric Acid and the head was put into a position so that the bowl would hold a small amount of acid and then they would let it work on the cast to dissolve. When the heads were a choke point, it was a clever little trick when there was teardowns if you won!
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Postby Rod » Sat Oct 11, 2008 9:13 am

this sound like the same principal as Spark Erosion

just dont get caught out

i think the heads were called cheater heads

have a look here you may find something that interests you

http://www.castheads.com/acid_porting.php

regards
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Postby ZIGGY » Sat Oct 11, 2008 9:56 am

I had a circle track tech man claim that NHRA had a (chemical?) test
that would detect the presence or absence of casting sand residue
in the port walls and thereby expose acid porting. Or maybe it was
a test for acid residue. Fact or fiction???
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Postby robert1 » Sat Oct 11, 2008 10:57 am

I had a customer that had a set of 186s that fit 1206 gaskets pretty good.
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Postby mtkawboy » Sat Oct 11, 2008 12:39 pm

Youre joking about the tech men finding acid porting right ?
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Postby panic » Sat Oct 11, 2008 2:17 pm

The actual acid can be easily neutralized (baking soda is fine), but I'm not sure if the sulfuric may not interact with minor inclusions (i.e., non-ferrous particles in the surface), carbon, etc. and leave a salt of sulfur (sulfate, sulfite, sulfide, blah) as a detectable residue.
Good: easy to do.
Not so good: if not completely flushed the head will continue to decay until it cracks.
Worse: a minor splash can blind you - close fitting goggles, gauntlets, disposable clothing, instant access to running water
Bad: it removes material evenly over the entire surface - SSR to the same degree as anywhere else, which isn't exactly best for all port shapes. At least Extrude-Hone removes material in the flow direction, and obstructive bits (flashing, casting lines, tool marks) more aggressively than the parent wall surface. Too bad it's about the same price as breast enlargement...
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Postby panic » Sat Oct 11, 2008 2:24 pm

BTW: any old-time Harley mechanic can tell you that you can tell an acid-cleaned surface from an as-cast surface very quickly (if you've seen both - the average surface irregularity is lower, more rounded, and very few small ones remain), and there are many methods (shhhh!!) of how to re-texture the casting to get back the grain roughness to prevent arrest.
A suspicious techie with a Bore-Scope will catch this.
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Postby Ron E » Sat Oct 11, 2008 3:47 pm

panic wrote:A suspicious techie with a Bore-Scope will catch this.


I don't think we should be mentioning and therefore encouraging such procedures, sir.
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Postby panic » Sat Oct 11, 2008 4:25 pm

...which is why I did not identify them.

Of course, following your comment a bit farther: does failure to remark that crimes occur prevent future crimes?
Of course not.
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Postby e-tach » Sat Oct 11, 2008 5:10 pm

Ron E wrote:
I don't think we should be mentioning and therefore encouraging such procedures, sir.


I don't see why not!
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Postby jfholm » Sat Oct 11, 2008 5:13 pm

Having an interest in how this was done I had ordered an electronic book from the internet on "Acid Porting". To poor acid in the port and hope the whole port gets bigger may help a little but is not the way to go. I will give a quick little synopsis on how it was done. You port the head in certain areas you want to improve. As we all know you want a CSA larger to prevent "choke". After you get your port improved you take a carbide burr that has a slightly bent shaft so it bounces and leaves a roughened surface preferreably with sharp little peaks. Then you paint the inside of the port where you do not want the acid to touch with a special shellac/varnish that is not affected by the acid then you pour your acid in the port. We, uh, I mean the guys I heard of that did this used Nitric acid which is really killer stuff so you have to be very very careful, then after it was done it disguised the ground areas. When the heads were neutralized then you would give them a light glass bead with broken up used glass bead. When in that state put outside your shop and squirt down with water and let stand a couple of days to rust up. Then bring back in and sand or machine the gasket surfaces and Walla you have you fresh "Stock" junk yard heads. But I don't think anybody would really cheat in NHRA Stock Eliminator. Stock 186 heads will normally go to 8200 rpm without any help with a stock manifold and carb.

John
one of these days I will have my web site done ;-)
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Postby Metrobilly » Sat Oct 11, 2008 6:12 pm

Some stock parts are just more stock than others.

An engine builder I know refers to some special heads as "Really goooood castings". This is spoken in his southern accent very slowly and quietly.
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Postby TheEngineWorks.com » Sat Oct 11, 2008 6:34 pm

I believe I may have a few glass jugs of ************ acid hanging around from a time when I got into some of that stuff.. :wink:

I found the highest % of ************ that was available, that stuff would choke you unconscious if you got more then a little whiff of it.. :shock:
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Postby airflowdevelop » Sat Oct 11, 2008 7:45 pm

Acid is not used too much anymore. Acid CAN be detected.

Some newer cover up procedures exist. These procedures are undetectable unless a go-no-go guage or template is used. As far as I know only 3 guys exist that can do this procedure. They are VERY backed up...and of course the procedure is expensive (about $750 for a set of SBC heads). The procedure works as well on cast iron as it does on aluminum. Only one problem.... NHRA is VERY aware of this procedure...and of course they are working on countermeasures.

Dennis
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