Potential NF Piston Option??? Engine Experts Help.

[Bruce Bell]

By my calculations, you can get to 11.3 by decking the block 1 mm. I did
this with good success on an earlier block (there was enough deck height).
I'd use some clay and check valve clearance before cutting. That's a big CR
for a 10v. Without knock sensor I found 10:1 to be marginal without good gas
and I was running a big (for cis) cam at altitude. I wonder if the knock
sensor might run the ignition in a perpetually retarded state (pure
speculation on my part).

Bruce
"measure twice cut once"

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
Behalf Of passat TS
Sent: Friday, October 04, 2002 7:26 AM
To: quattro at audifans.com
Subject: Potential NF Piston Option??? Engine Experts Help.


[ Converted text/html to text/plain ]
I want to raise the CR of a NF Engine as much as possible. The target is
11.5:1 but
anything better than the 10:1 I have today will be welcome.

The ideal situation would be custom pistons, but all the places I contacted
want a
minimum of 2 sets ordered.

Here are the options I found so far:

1. Find someone interested in split the custom run at around $500 for each
set.
Pistons anyone?

2. Stock 7A pistons. They will raise the CR to 11.2:1, but the ones I
founded
are
too expensive. Can anyone find a set for under $600.

3. I found at the Wiseco catalog a set for VW 1.8l that has several ideal
measurements. I called them yesterday and the tech person seems to agree
that
it
would work. It will raise the CR to 10:8:1. The good thing is that it will
cost under
$400/set, the bad thing is that it has flat top. It has enough material to
machine the
pockets, but that would reduce the compression to 10.3:1. This is the same
as
deck
the cyl head at $40.
Questions:
   3.1 Can I use flat tops? (valve clearance, combustion problems)
   3.2 Can I use flat tops and deck the cyl head to achieve a higher
compression
without the above problems?

I really appreciate any help, I'm about to finish the head work(last
polishing
phase)
and need to make this decision.

Carlos.

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