7A to 3B conversion using 7A head and MC2 block?

[Ben Swann]

Goal - 300 HP upwards, but within reasonable budget - engine to be installed
into '83 UrQuattro.  Basically a nice well balance powerplant, not
necessarily trying to win drag races, but will at least keep the car from
getting skunked by the latest WRX or EVO.

Some sort of EFI conversion could be incorporated, but looking at starting
with the original solution as parts on hand - MC-2 bottom, MC-1 head ported
with larger exhaust valves, cam, etc.  MAC-11 ECU with QLCC chip augmented
by supplementary EFI for start is the most straightforward, tried and
tested, as in I know I have the stuff and I know what it will do.

At some point would probably integrate Full EFI - constraints being time and
money of course.

I was contemplating the 20V engine, as it is available for a reasonable
price and I can get the full 3B Motronic setup - all for under 1k.  But if
getting it to be nearly identical to the 3B will cost too much, then I might
as well forget it.   As I'd need to source manifolds, etc. I probably would
be better finding a wrecked 200 20vtq or complete engine.  This starts to go
beyond my objective of using what is on hand - I have several engines in my
garage - 2 or more MC-1, 1 MC-2, Complete MC setup that is in the pearl
avant that got smashed, NF, at least 3 KX/JTs, etc.  So I think I need
another engine like a hole in the head.

Ben
----- Original Message ----- 
From: "Jim Green" <jeg1976 at yahoo.com>
To: "Ben Swann" <benswann at comcast.net>
Cc: "Quattro list" <quattro at audifans.com>
Sent: Friday, January 09, 2004 2:48 PM
Subject: Re: 7A to 3B conversion using 7A head and MC2 block?


>
> --- Ben Swann <benswann at comcast.net> wrote:
> > Could I use the MC-2 Pistons and NG/NF crank and
> > rods or???
>
> Nope, MC-2 rods are 136mm long, 46 mm journals, NG
> rods are 144mm long 48 mm journals.
>
>
> > I'm trying to understand the differences more
> > clearly.
> >
> > I thought the 3B bottom end was nearly identical to
> > the MC-2.  Where is the
> > compression difference?
>
> Ben, the compression is always changed with the
> pistons if you stay in the same familly.  Now, the
> volume in the heads is different between the 10v and
> 20v, so when you start swapping heads between the 10v
> and 20v blocks, things change.  Putting a 20v head on
> a 10v block will always lower compression.  That's why
> if you put a 20v head on a high CR 10v block like the
> NG, it drops to ~8.5:1
>
> > Is there a major difference in the 7A head and 3B.
>
> The turbo heads have extra cooling jackets.
> http://audi.newtsplace.com/forum/viewtopic.php?t=69
>
> > I take it the cams are
> > way different, or can compensation be made by
> > sprocket
>
> Probably not, one tooth on a 20v sprocket is a pretty
> large change in cam angle.
>
> > I have the feeling I may be better off dealing with
> > the MC-2 bottom and MC-1
> > head and FI that I was going for originally. Then I
> > can implement EFI
> > solution.
>
> See that thread Marc pointed you to.
>
http://audi.newtsplace.com/forum/viewtopic.php?t=84&postdays=0&postorder=asc&start=0
>
> Dig through the three pages that are there, there's
> some really good info.
>
> With either of these you need to bolt on big power
> parts.  450 hp on a 10v is entirely possible, on an MC
> bottom end, maybe more.  The 20v is less limited
> because of head flow, but the lower has to be beefed
> up at some point.  So what's your goal?
> =====
> Jim Green
> '89 90tq
> '89 80q
> http://www.mswanson.com/~jgreen/car_home.html
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Hotjobs: Enter the "Signing Bonus" Sweepstakes
> http://hotjobs.sweepstakes.yahoo.com/signingbonus