[audi20v] Re: [20v] 7A vs 3B C/R

Bernie Benz b.benz at charter.net
Wed May 7 11:59:56 EDT 2003

Hi Alex,

Here's an idea for your consideration.

Talk your friend into doing, and publishing to the 20V lists, what I've been
threatening to do, but I can't find the loan of a loose and stripped down 3B
or AAN head near by.  That is to generate a H2O manifold machining drawing
for converting 7A heads to accept the 3B/AAN manifold.  Apparently he has
the old 3B head and a digital readout mill, so just needs to fixture the
head on the table and measure the centers of the needed holes relative to
the identical 7A and 3B main large water outlet and associated hold down
bolt holes.  With this info available, the shortage of 3B and AAN
replacement heads will be eased.

Keep me posted.


> From: "Alexander van Gerbig" <avangerb at zoo.uvm.edu>
> Date: Wed, 7 May 2003 13:39:32 -0400
> To: <b.benz at charter.net>, "Audi 20V" <audi20v at rennlist.org>
> Subject: Re: [audi20v] Re: [20v] 7A vs 3B C/R
> Howdy!  Was just chatting about this whole 7A/3B/AAN subject with the
> fellow who bought my 200q20v.  He's got a monster 200q20v that tossed a
> valve and put a hole through a piston, so he's slowly been contemplating
> what to do.  He's got a brand new 3B block all built up and this and that.
> Though he popped a 7A head next to a 3B and found them to be identical in
> every respect, obviously the only difference is the lack of a water manifold
> on the 7A head.  I did a quick check and found the exhaust valves are the
> same 98.2mm, but they 7A and 20vt engines list different part numbers.  I
> was surprised, both are sodium filled, anyone know the difference?
> I'm not sure about the piston tops though, I am fairly certain the 7A
> will have less of a pocket than the 20vt piston.  I may ask this guy to snap
> shots of stock engine internals while he figures out what he wants to do.
> He's contemplating all sorts of different engine options, 7A head 10v block,
> 3B block 7A head, and so on.  Another thought he had was to take a stock 7A,
> CNC the pistons down to 9.5-9.2:1 and go with that, larger bore, slightly
> higher comp, huge intercooler, and a standalone fueling system, he's really
> interested in the new 034EFI box.  When he's got all the parts laid out it
> would be great if he took pictures and did measurements, he's a machinist so
> he's got all the fun tools for measuring and machining.
> Cheers,
> Alexander van Gerbig
> Europrice
> Waitsfield, VT 05673

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