Re: intake manifold polishing

[Big Al <awpresley@autographica.com>]

>On  4 Mar 98 at 19:06, Big Al wrote:
>
>> "...a rough intake manifold promotes turbulence which
>> >is a good thing. "
>>
>> I'm not so sure about this.  If this is so then why do racers want the
>> intakes, valves, and even the interior throats of carbs polished???
>
>The fact that someone wants something doesn't mean that there's an
>advantage to it.  Consider the fact that airplane designers have been
>trying to design airfoil surfaces with just the right degree of
>roughness for years because it actually reduces drag.  The problem is
>that it causes problems in bad weather with icing.

Well, I figure that since most race teams have just as much research behind
them as Gene Berg, and they race to put bread on the table (kind of a "no
win, no eat" situation), and they stive to polish intakes and ports to
improve these odds, there is probably something to it.

I am far from an expert from performance VW engines (my current restored
engine is a '56 T-1 36hp).

The question is, would there be an advantage?  Our 54hp (or some odd with
modifications) engines probably would not have much effect. Am I right Jim?


>
>> Air volume at a higher rate!
>
>Just because something is obvious doesn't mean that it is true.
>Actually, I'm not sure of this either, I don't own a flow bench and
>have no experience with one, but I got this information from someone
>who owns and uses one.   His feel for these things is usually good.
>I don't recall if Gene Berg had any comments on this.  He's usually
>done his homework, too.
>

And I thought he offered ported and polished VW heads...

Air (and fuel) volume is a contributing factor to HP's.  This is fact, not
just conjecture.



>> Rough pipes decrease the flow velocity of the air which makes the engine
>> starve for fuel mixture right?  I can see the "rough causes mixture" in
>> theory, but if this is so, wouldn't VW have added a texture to the pipe?

VW did their research too.

>>
>> And for polishing the exhaust manifold... Where?  Do you mean the interior
>> of the heater boxes? I am unclear as to the location you mean.
>
>This comment was general.  In our VWs I agree that there is no need
>for any polishing in the heater boxes because the pipe ID is already
>smooth, but there is some advantage to smoothing the interior of the
>exhaust ports in the heads.

Now this is an interesting idea. How much lower head temp (ballpark) could
one acheive by doing this, and as you stated "The fact that someone wants
something doesn't mean that there's an advantage to it. "  is there an
advantage?

I would suggest to John that if he wants to clean the interior of the
intake, use a bottle brush attached to a flexible extension shaft on a
power drill and (although somewhat blindly) work it through the intake to
remove corrosion and or debris.

Big Al